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Chapter 4 Continued
 
K. FIRST INNER TUBE SECTION ASSEMBLY
 
4K1. Description of the first inner tube section assembly. The first inner tube section assembly is part of the lower telescope system. It provides the necessary parts and distance between the objective operating mechanism assembly (Figure 4-23) and the eyepiece skeleton assembly (Figure 4-28). This distance is necessary for the focal length of the lower (split) objective lens with the eyepiece prism and the eyepiece lens. Figure 4-27 shows the first inner tube section assembly. All bubble numbers for. Sections 4K1, 2, and 3 refer to Figure 4-27 unless otherwise specified.

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
1 P-1205-7 1 First inner tube section
2 P-1158-4 2 Spider (two halves)
3 P-1158-11 1 Spider bearing
4 P-1163-7 2 Stadimeter transmission shaft thrust collars
5 P-1179-24 8 First inner tube section lower end lockscrews
6 P-1179-24 4 First inner tube section upper end coupling lockscrews
7 P-1179-63 4 Spider flange lockscrews
8 P-1179-65 3 Diaphragm lockscrews
9 P-1179-179 1 Spider taper pin
10 P-1179-196 2 Stadimeter transmission shaft thrust collar taper pins
11 P-1205-6 1 First inner tube section upper end coupling
 
Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
12 P-1207-7 1 Diaphragm
13 P-1361-1 4 Tape guides 14 P-1361-2 4 Tape guide straps
15 P-1362-1 1 Air line coupling (round) (long)
16 P-1362-2 1 Short bend round air line
17 P-1362-3 1 Short round air line coupling
18 P-1362-4 1 Air line (flat and round)
19 P-1362-10 1 Air line strap
20 P-1362-11 1 Air line strap (soldered)
21 P-1362-13 1 Air line strap
22 P-1409-7 1 Stadimeter transmission shaft
23 P-1410-7 4 Stadimeter transmission shaft bracket
24 P-1422-1 4 Air line strap lockscrews

a. First inner tube section. The first inner tube section (1) is made of brass tubing and is approximately 57.125 inches in length. The inner and outer diameters are uniform throughout the entire length.

The inner circumference of this inner tube section upper part is provided with a threaded section, which screws on the threaded periphery of the lower part of the first inner tube section upper end coupling (11), while the turned alignment support section of this part of the coupling is a sliding fit in the inner circumference

 
137

of the inner tube. It is secured with four lockscrews (6) which are inserted in countersunk clearance holes in the inner tube section upper part and screwed into tapped holes in the lower alignment support section of the first inner tube section upper end coupling (11).

The internal surface of the inner tube section supports a diaphragm (12) which is located

  in the center part and secured with three lockscrews (8).

The lower part of this inner tube section is a push fit on the- upper alignment support section of the spider bearing (3) and is secured with eight lockscrews (5). These lockscrews are inserted into countersunk clearance holes in this inner tube section lower part and screwed

Figure 4-27. First inner tube section assembly.
Figure 4-27. First inner tube section assembly.
 
138

into tapped holes in the spider bearing upper alignment support section (3).

b. First inner tube section upper end coupling. The first inner tube section upper end coupling (11) is made of cast phosphor bronze and is 3.187 inches in length. It is a step design, stepped downward from the upper part. It forms a joint between the track sleeve (2, Figure 4-23) of the objective operating mechanism assembly and the upper part of the first inner tube section (1).

In the upper part it is provided with a threaded periphery and an alignment support section, to receive the internal threaded section and smooth counterbore in the track sleeve (2, Figure 4-23) and is secured with four lockscrews (23). These lockscrews are inserted into countersunk clearance holes in the track sleeve shoulder (2) and screwed into tapped holes in the first inner tube section upper end coupling alignment support section (11)

The center part is provided with a narrow shoulder 3/16 inch wide, and its diameter coincides with the diameter of the track sleeve shoulder (2, Figure 4-23).

The inner diameter is bored for light transmission and has anti-reflection threads. The upper part is counterbored a distance of 1 1/2 inches to lighten the coupling.

In the lower part it has a threaded periphery and straight turned section which serves as an alignment support section for the upper part of the first inner tube section (1). The threaded periphery screws into the internal, threaded section in the first inner tube section (1) and is secured with four lockscrews (6). These lockscrews are inserted in countersunk clearance holes in the upper part of the first inner tube section, and screwed into tapped holes in this coupling lower alignment support section.

c. Diaphragm. The diaphragm (12) is made of 1/32-inch spun brass of light weight and is 2 inches long. It is located in the central Part of the first inner tube section (1). The side wall of the diaphragm has an opening of ample size to permit the necessary light transmission. The diaphragm restricts the light rays from striking the inner wall of this inner tube section and confines it to the necessary clear aperture

  required. Three equally spaced brass strips are soldered on the inner wall of the diaphragm. It is a push fit in the first inner tube section and is secured with three lockscrews (8). These lockscrews are inserted into countersunk clearance holes in the first inner tube section and screwed into tapped holes in the soldered strips located in the diaphragm.

d. Air line sections. The air line section (29, Figure 4-21) extends downward from the second inner tube section (22) with a soldered air line coupling (28) on its lower end. It is secured to the upper part of the inner tube section with an air line strap (21) retained with two lockscrews (24).

The air line section (18) attaches to the air line coupling (28) of the air line section (29, Figure 4-21) in the upper part of the first inner tube section and extends downward through a soldered air line strap (20) soldered to the first inner tube section wall. The lower part of the air line section (18) has a soldered air line coupling (17) which couples with a bent air line (16). The bent air line (16) attaches to the soldered air line coupling (17) of the air line section (18). The bent air line (16) is secured to the lower part of the first inner tube section wall with a removable air line strap (19) secured with two lockscrews (24).

The bent air line (16) is bent in an S-shape and extends outward from the first inner tube section (1) to the air line hole in the spider (2), where it attaches to the long air line coupling (15)

e. Spider bearing. The spider bearing (3) is made of cast phosphor-bronze material and is 4.500 inches in lengths The upper part is smooth tuned a short distance to serve as an alignment support section, and push fit into the lower part of the first inner tube section (1) and is secured with eight lockscrews (5). These lockscrews are inserted in countersunk clearance holes in the first inner tube section lower part, and screwed into tapped holes in the spider bearing upper alignment support section.

Two narrow shoulders are provided, between which the spider halves (2) are attached and secured with four lockscrews (7) and an inserted taper pin (9).

 
139

The lower part of the spider bearing is stepped to a small shoulder. This small shoulder is provided with a threaded periphery and a straight turned section serving as an alignment support section. The alignment support section is a sliding fit in the counterbored and threaded counterbored section in the upper part of the eyepiece skeleton (42, Figure 4-28) and is secured with four lockscrews (37). These lockscrews are inserted into countersunk clearance holes in the eyepiece skeleton (42), and screwed into tapped holes in the spider bearing lower alignment support section.

The inner surface of the spider bearing is bored for light transmission and is provided with anti-reflection threads. The upper part is counterbored a distance of 3 1/16 inches, leaving a sufficient wall in the lower part of this counterbore.

f. Spider. The spider (2) is made in two halves of cast phosphor bronze and is 1 inch in width. It has three cast projections on the periphery set with their centerline 120 degrees apart in an extended Y-design. The periphery of these projections serves as a guide bearing in the lower counterbore of the outer tube (2, Figure 4-15). One projection is solid with a reamed hole serving as a bearing for the stadimeter transmission shaft (22, Figure 4-27). The other two projections are shaped like a plus sign with shoulders of nominal thickness extending outward from the wall periphery. An air line clearance hole is provided in the wall of one of these projections at assembly for the long air line coupling (15).

The wall periphery of each half is provided with projecting flanges of 1/16-inch thickness and are stepped. The set of flanges of one half is provided with two clearance holes each, while the set of flanges of the opposite half is provided with two tapped holes each for four lockscrews (7). The spider halves are assembled, and bored a snug fit for their assembly on the undercut section of the spider bearing between the two narrow shoulders. A taper pain (9), inserted in the wall periphery of the spider and the spider bearing, properly maintains its correct alignment.

g. Stadimeter transmission shaft thrust collars. The two stadimeter transmission shaft

  thrust collars (4) are made of brass and are cylindrical. They are of nominal thickness and are provided with a reamed hole in their center axis. These thrust collars are a sliding fit on the stadimeter transmission shaft (22), extending through the bearing hole projection in the spider (2), and are located on each side of the spider bearing hole projection. They are secured with two taper pins (10). These thrust collars retain the stadimeter transmission shaft (22) from axial displacement.

h. Tape guides. The four tape guides (13). are made of flat brass tubing and are 12 1/2 inches in length. These four tape guides are divided in two sets for assembly to the lower part of the first inner tube section on opposite sides and are secured with tape guide straps (14). Each set of tape guides (13) is secured with two tape guide straps (14) separated proportionally and soldered to the tape guides and the wall periphery of the first inner tube section (1). Each set of tape guides serves to guide the prism tilt and change of power shifting wire tapes (38, Figure 4-28) in their vertical position.

i. Stadimeter transmission shaft bracket. The stadimeter transmission shaft bracket (23) is made of 1/16-inch brass and has a developed length of 0.228 inch. The projecting part of the bracket is provided with a clearance hole for the stadimeter transmission shaft (22). It is soldered to the wall periphery of the first inner tube section located in the center part. This bracket serves to remove any whip of the long stadimeter transmission shaft (22).

j. Stadimeter transmission shaft. The stadimeter transmission shaft (22) is made of corrosion-resisting steel and is 75.125 inches in length. The tipper part of this shaft fits into the large readied hole in the stadimeter transmission shaft coupling lower part (14, Figure 4-23) of the objective operating mechanism assembly and is secured during final collimation with a taper pin (33).

The lower part of this shaft has a milled off section forming a male tang section. This section is a sliding fit into the upper part of the female tang coupling (68, Figure 4-24) attached to the integral transmission shaft pinion stub section (65) located in the stadimeter housing assembly.

 
140

The shaft extends downward from the stadimeter transmission shaft coupling (14, Figure 4-23) of the objective operating mechanism assembly through the soldered bracket (23), the upper thrust collar (10), spider (2), lower thrust collar (10), and the clearance hole in the eyepiece skeleton flange (42, Figure 4-28). The shaft extends downward the entire length of the eyepiece skeleton (42) and into the reamed hole and stuffing box section in the eyepiece box (11, Figure 4-29).

4K2. Disassembly of the first inner tube section assembly. The first inner tube section assembly is disassembled in the following manner:

1. All air line sections, air line straps, thrust collars, and the stadimeter transmission shaft (22) pertaining to this assembly were removed previously for the separation of the various telescope systems and their individual assemblies.

2. Remove the four lockscrews (6) from the upper part of the first inner tube section (1). These lockscrews are unscrewed from tapped holes in the lower alignment support section of the first inner tube section upper end coupling (11).

3. Unscrew the lower part of the first inner tube section upper end coupling (11) from the upper part of the first inner tube section (1).

4. Remove the eight lockscrews (9) from the lower part of the first inner tube section (1) These lockscrews are unscrewed from tapped holes in the upper alignment support section of the spider bearing (3).

5. Tap the spider bearing (3) from the lower part of the first inner tube section (1).

6. Remove the four lockscrews (7), unscrewing two from opposite side flanges of the spider halves (2). Remove the taper pin (9) from the spider half, and remove both spider halves from the spider bearing (3).

7. Remove the three lockscrews (8) from the central part of the first inner tube section (1). These lockscrews are unscrewed from tapped holes in each soldered strip in the inner wall of the diaphragm.

8. Tap the diaphragm (12) out through the lower part of the first inner tube section (1).

  4K3. Reassembly of the first inner tube section assembly. The first inner tube section assembly is reassembled in the following manner:

1. Check all reference marks for the reassembly of any part to prevent incorrect assembly.

2. Using an air hose, blow out the internal surfaces of the first inner tube section. If a circular brush is available, it should be used first. This procedure should be carried out also with the couplings.

3. Place the diaphragm (12) in the central part of the first inner tube section from the lower part. The diaphragm side wall faces up ward toward the first inner tube section upper end coupling (11). Tap the diaphragm in until the tapped holes in the inner tube section and the diaphragm coincide.

4. Insert and secure the three lockscrews (8) in the tapped holes in the diaphragm soldered inner wall strips.

5. Screw the first inner tube section upper end coupling (11) lower threaded periphery section into the upper part of the first inner tube section (1).

6. Insert and secure the four lockscrews (6) into countersunk clearance holes in the upper part of the first inner tube section (1) and tapped holes in the first inner tube section upper end coupling lower alignment support section (11).

7. Place the upper alignment support section of the spider bearing (3) in the lower part of the first inner tube section (1). Using a rawhide mallet and a block of wood, tap the spider bearing in until its narrow shoulder comes in contact with the lower end of the first inner tube section.

8. Insert and secure the eight lockscrews (5) into countersunk clearance holes in the first inner tube section and screw them into tapped holes in the upper alignment support section of the spider bearing (3).

9. Place both halves of the spider (2) on the spider bearing (3) between its two narrow shoulders.

10. Insert and secure each spider flange half (2) with two lockscrews (7) inserting them into clearance holes in one flange half and screwing

 
141

them into tapped holes in the other flange half of both sets of opposite flanges.

11. Insert the taper pin (9) in the spider half (2) and the spider bearing (3).

  12. The air line sections, air line straps, thrust collars, and the stadimeter transmission shaft (22) are assembled later, upon the connection of individual assemblies of this lower telescope system.
 
L. EYEPIECE SKELETON ASSEMBLY
 
4L1. Description of the eyepiece skeleton assembly. The eyepiece skeleton assembly is apart of the lower telescope system. Figure 4-28 shows the eyepiece skeleton assembly. All bubble numbers in Sections 4L1, 2, and 3 refer to Figure 4-28 unless otherwise specified.

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
1 P-1133-9 4 Shifting wire spindles
2 P-1133-10 4 Shifting wire clamps
3 P-1133-11 4 Shifting wire clamp nuts
4 P-1133-12 8 Shifting wire spindle adjusting nuts
5 P-1160-1 2 Ball bearings for rayfilter drive gear
2 Ball bearings for eyepiece prism shift gear and eyepiece drive
4 Ball bearings for training handle rack gears (right and left)
6 P-1160-1A 4 Dowel pins for rayfilter and eyepiece drive housings
7 P-1160-2 2 Ball bearing housings for training handle rack gears (left and right)
2 1 Ball bearing housing for rayfilter drive mechanism
8 P-1160-4 2 Retaining collar for training handle rack gears
9 P-1160-9 1 Ball bearing housing for eyepiece prism shift gear
10 P-1160-10 1 Eyepiece prism shift gear
11 P-1160-11 1 Eyepiece prism shift bevel gear
12 P-1161-3 1 Rayfilter drive gear
13 P-1161-5 2 Eyepiece prism actuating gears
14 P-1161-6 2 Eyepiece prism actuating gear shafts
15 P-1163-11 1 Eyepiece prism shift bevel gear key
16 P-1173-3 1 Eyepiece lens clamp ring
17 P-1173-4 1 Eyepiece prism upper clamp ring
 
Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
18 P-1173-5 1 Eyepiece prism upper retaining plate
19 P-1173-6 1 Eyepiece lens mount
20 P-1173-7 1 Eyepiece prism mount
21 P-1173-7 A&B 2 Eyepiece prism mount stem gear racks
22 P-1173-7C 5 Eyepiece prism stem gear rack lockscrews
23 P-1173-7A1 4 Eyepiece prism stem gear rack dowel pin
24 P-1173-8 1 Eyepiece prism front retaining plate
25 P-1177-6 1 Counterweight
26 P-1177-7 2 Counterweight strap retaining plates
27 P-1177-9 2 Counterweight straps
28 P-1179-46 16 Ball bearing housing lockscrews
29 P-1179-57 28 Counterweight strap and shifting rack retaining plate lockscrews
30 P-1179-58 2 Eyepiece prism shift actuating gear shaft lockscrews
31 P-1179-59 8 Eyepiece skeleton flange and eyepiece box lockscrews
32 P-1179-60 1 Eyepiece prism shift bevel gear lockscrew
33 P-1179-62 8 Counterweight strap lockscrews
34 P-1179-67 8 Eyepiece prism retaining plate upper and front lockscrews
35 P-1179-190 2 Retaining collar taper pins
36 P-1179-192 2 Eyepiece box alignment dowel pins
37 P-1310-17 4 Spider bearing and eyepiece skeleton lockscrews
38 P-1314-3 4 Shifting wire tapes
39 P-1318-1 2 Training handle rack gears and integral shafts
40 P-1318-8 1 Rayfilter drive male coupling half section
41 P-1389-4 2 Eyepiece lens clamp ring and eyepiece prism clamp ring upper lockscrews
42 P-1402-1 1 Eyepiece skeleton
 
142

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
43 P-1403-1 1 Prism shifting rack (left)
44 P-1403-2 1 Prism shifting rack (right)
45 P-1403-3 1 Power shifting rack (right)
46 P-1403-4 1 Power shifting rack (left)
47 P-1409-1 2 Retaining plates for shifting racks
48 P-1417-2 1 Upper eccentric eyepiece prism centering ring
49 P-1417-3 1 Front eccentric eyepiece prism centering ring
50 P-1417-4 1 Eyepiece prism front clamp ring
51 P-1418-13 1 Eyepiece prism
52 P-1418-14 1 Eyepiece lens
53 P-1422-177 1 Rayfilter drive coupling half section taper pin
  a. Eyepiece skeleton frame. The eyepiece skeleton frame (42) is made of cast phosphor bronze with an over-all length of 18.062 inches. It is cast with various cored projections and recesses to accommodate the eyepiece drive, ray filter drive, change of power, and prism tilt mechanisms.

The upper part is provided with a large shoulder flange having a narrow shoulder as part of its lower face. The diameter of the large shoulder flange coincides with the diameter of the straight, turned alignment support section of the eyepiece box (11, Figure 4-29), while the narrow shoulder serves as an alignment support section, a sliding fit in the shallow counterbored section in the eyepiece box. The large shoulder flange is provided with eight

Figure 4-28. Eyepiece skeleton assembly.
Figure 4-28. Eyepiece skeleton assembly.
 
143

equally spaced clearance holes for lockscrews (31) to secure the eyepiece box on the narrow shoulder against the large shoulder flange. These lockscrews are inserted into clearance holes in the large shoulder flange of the eyepiece skeleton and screwed into tapped holes in the upper face and alignment support section of the eyepiece box.

Two opposite reamed dowel pin holes are provided in the same hole circle as the eight clearance holes, and are located 22 degrees 30 minutes from the vertical centerline. These reamed holes receive dowel pins (36) of a drive fit, and provide the necessary radial alignment of the eyepiece box (11, Figure 4-29) for assembly.

A clearance hole for the stadimeter transmission shaft (22, Figure 4-27) is provided in the large shoulder flange, and is located at an appropriate center distance from both the vertical and horizontal centerlines. An air line tapped hole is provided at assembly in the large shoulder flange for the long air line coupling (15) of the first inner tube section assembly.

Two elongated openings are provided in the large shoulder flange for the counterweight straps (27) located on opposite sides of the vertical centerline. These elongated openings are of appropriate size to allow clearance for the vertical travel of the counterweight (25) carrying the attached counterweight straps (27).

The straight turned section above the large shoulder flange has sufficient bearing surface length to carry the counterweight (25) vertically for all positions of focusing minus and plus.

The upper part is bored for light transmission to a depth of the large shoulder flange lower face and is provided with two counterbore, sections. The small counterbored section serves as an alignment support section to receive the lower alignment support section of the spider bearing (3) while the large threaded counterbored section receives the threaded periphery of the spider bearing (3), secured with four lockscrews (37). These lockscrews (37) are inserted in countersunk clearance holes in the eyepiece skeleton bearing section wall and screwed into tapped holes in the spider bearing lower alignment support section (3).

  A reamed hole is provided in the base of the eyepiece skeleton frame in the center of a shallow counterbored recess to receive the eyepiece skeleton centerscrew (12, Figure 4-29) which extends upward from the eyepiece box. The centering screw stabilizes the lower part of the eyepiece skeleton in the eyepiece box (11).

b. The eyepiece drive mechanism is composed of numerous mechanical internal parts to operate the eyepiece prism vertically to any diopter setting desired by an observer for his individual eye setting by means of suitable connecting attachments.

1. Eyepiece prism mount. The eyepiece prism mount (20) is made of cast duralumin. It provides the necessary body to retain the eyepiece prism (51) and the eyepiece lens (52) in a fixed vertical moving position in the optical axis. The mount has two side walls, which protect the eyepiece prism from sideward thrust. Each sidewall is provided with four tapped holes in the upper and front faces to retain the eyepiece prism upper retaining plate (18), and the eyepiece prism front retaining plate (24) with four lockscrews each (34).

Each side wall is provided with two rail bearings, and each is a sliding fit into the rail bearings located in each inner flat wall of the eyepiece skeleton frame (42). The mount is provided with a stem which projects downward from the center part of the rear body of the mount. On each side of the mount, the stem Fear racks (21) are assembled to the stem projection with four alignment dowel pins (23) and five lockscrews (22). The stem gear racks (21) engage two eyepiece prism actuating gears (13) assembled on the eyepiece prism actuating gear shafts (14). The shafts extend into the front of the center wall, through the bearing hole in the eyepiece prism actuating gear, and the center section, and further into the rear wall. Each shaft is secured with a lockscrew (30).

2. Eyepiece prism upper retaining plate. The eyepiece prism upper retaining plate (18) is made of aluminum. It is a rectangular plate with a cylindrical projecting shoulder. The bore is threaded to receive an eyepiece prism upper clamp ring (17) which is secured with a lockscrew (41). The side facing toward the front

 
144

is beveled at right angles to form a 90 degrees miter joint with the beveled upper side of the eyepiece prism front retaining plate (24).

3. Eyepiece prism front retaining plate. The eyepiece prism front retaining plate (24) is made of aluminum. It is a rectangular plate with a cylindrical projecting shoulder. The bore is threaded to receive the threaded periphery of the eyepiece prism front clamp ring (50) and the eyepiece lens mount (19).

4. Eyepiece prism. The eyepiece prism (51) is a crown element, with a curvature ground on the entrance and exit faces called a dioptric prism or a double-convex right angle prism, with the 45 degrees reflecting face silvered, copper plated, and lacquered. It serves to deviate the optical axis from a vertical to a horizontal direction. Refer to Section 4U8 (e). The eyepiece prism is retained snugly in the eyepiece prism mount (20) in the fixed central position, with eccentric centering and clamp rings.

In the upper part of the mount, the eyepiece prism is secured by the application of an upper eccentric eyepiece prism centering ring (48) backed up with a threaded eyepiece prism upper clamp ring (17), of nominal thickness, secured with a lockscrew (41). The eccentric centering ring has a chamfer on its lower face, to offer the curved surface of the upper part of the eyepiece prism an equal bearing surface. This provides a means of distributing the pressure equally over at least 1/4 of the area of the reflecting surface by tightening the clamp ring. The front eccentric eyepiece prism centering ring (49) serves at the front curved surface of the eyepiece prism in similar manner to the upper. It is backed up with a threaded eyepiece prism front clamp ring (50) of nominal wall thickness.

5. Eyepiece lens mount. The eyepiece lens mount (19) is made of aluminum. It is cylindrical and provides the outer wall to retain the eyepiece lens (52) in a concentric position in the eyepiece prism front retaining plate (24). The lower part is undercut and threaded to engage in the internal threads of the eyepiece prism front retaining plate (24). The threaded shoulder has sufficient length, that the when large shoulder of the mount is a metal to metal contact with the projecting cylindrical shoulder of the eyepiece prism front retaining plate, it

  serves internally to lock the eyepiece prism front clamp ring (50). The mount is bored with a counterbored beveled section, with a shallow shoulder remaining as the front wall. The counterbored beveled section conforms to the conical wall of the eyepiece lens, with the outer surface following the same pattern, to provide a uniform wall thickness. The lower part of the internal surface of the mount is provided with two additional counterbores, one for the periphery of the eyepiece lens. The other is threaded to receive an eyepiece lens clamp ring (16). The clamp ring engages into the internal threads in the mount to retain the eyepiece lens snugly in the mount, and is secured with a lockscrew (41).

6. Eyepiece lens. The eyepiece lens (52) is made of two optical elements, consisting of a double-convex crown element cemented to a double concave flint element, forming a positive doublet. It is mounted in the eyepiece lens mount (19) and is secured in the mount with a clamp ring (16). The clamp ring is provided with a lockscrew (41) to prevent it from unscrewing from the mount.

7. Counterweight. The counterweight (25) is made of cast composition brass, and is cylindrical. The periphery is 1/16 inch smaller in diameter than the large, shoulder flange of the eyepiece skeleton to allow the counterweight vertical clearance for its focusing travel. It is provided with cored sections on opposite sides of the vertical centerline for the insertion of lead. The amount of lead added should conform to the weight of the assembled eyepiece prism mount. The counterweight serves to counterbalance the assembled eyepiece prism mount, and stabilizes the mount in any position of the allowed diopter setting the observer desires.

Two rectangular slots are provided on opposite sides of the horizontal centerline 180 degrees apart for two counterweight straps (27) and secured with four lockscrews (33) each. The inner walls of the cored sections provide a sufficient wall thickness in each half from the rectangular slots and the bore of the counterweight. An air line clearance hole is provided to the rear of the rectangular slot a nominal distance on the right side at assembly for the long air line coupling (15). A solid part of the cored section corner

 
145

on the left side to the rectangular slot rear wall has a clearance hole for the stadimeter transmission shaft (22, Figure 4-27). The counterweight is bored a sliding fit on the bearing section of the upper part of the eyepiece skeleton (42). The counterweight slides vertically on this eyepiece skeleton bearing section.

8. Counterweight straps. The counterweight straps (27) are made of cast phosphor bronze and have an over-all length of 12.840 inches. The upper part of each counterweight strap is attached to a rectangular slotted face on opposite sides of the counterweight (25). The lower part is provided with a raised gear rack of 12 teeth of 32 diametral pitch 1 3/4 inches long. Each gear rack meshes with an eyepiece prism actuating gear (13) projecting through slots in each side of the eyepiece skeleton frame (42). Each strap has a pronounced inward bend, from near the upper part to a short distance from the gear teeth of the gear rack. The bent section is supported with a narrow cast rib directly in the center. The counterweight straps form linkage arms between the counterweight (25) and the eyepiece prism actuating gears (13). When the eyepiece prism mount (20) is moved upward, the counterweight is moved downward and vice versa, by means of the actuating gears. The lower part of each counterweight strap is retained in the vertical recess groove in each side of the eyepiece skeleton frame with the counterweight strap retaining plates (26) secured with six lockscrews (29) each. These lockscrews are inserted in countersunk clearance holes in the retaining plates (26). and screwed into tapped holes in the vertical recess groove raised shoulders of the eyepiece skeleton frame (42).

9. Eyepiece prism actuating gears. The eyepiece prism actuating gears (13) are made of phosphor bronze and are 1 7/16 inches in diameter with a nominal width. Each gear is provided with 44 teeth of 32 diametral pitch which mesh with integral gear racks of the counterweight straps (27). Both gears have a reamed hole axis serving as bearing hole on eyepiece prism actuating gear shafts (14) and are provided with two narrow hub sections. The gears fit between two semicircular raised sections in opposite sides of the eyepiece skeleton center framework inner walls.

  Both gears extend from slotted openings to engage the counterweight straps (27) mounted in vertical recess grooves on the opposite outer side walls of the eyepiece skeleton framework (42). Each gear is engaged with the mounted stem gear racks (21) of the eyepiece prism mount (20). The right eyepiece prism actuating gear (13) is also engaged with the eyepiece prism shift gear (10), and the rayfilter drive gear (12), located on opposite sides, in its upper and lower part.

10. Eyepiece prism actuating gear shafts. The two eyepiece prism actuating gear shafts (14) are made of corrosion-resisting steel material and are 1 9/16 inches in length with a diameter of 5/16 inch. Each shaft serves to retain the two eyepiece prism actuating gears (13), and fits into reamed holes in the center and rear walls of the eyepiece skeleton, retaining the actuating gears between the two semicircular raised sections. Each shaft is secured with a lockscrew (30) which is inserted into a countersunk clearance hole and screwed into a tapped hole in opposite sides of the side wall and rear semicircular raised section of the eyepiece skeleton extending into a spotted recess in each shaft.

11. Eyepiece prism shift gear. The eyepiece prism shift gear (10) is made of phosphor bronze and is 1.281 inches in length. It has 16 teeth of 32 diametral pitch cut integral with the shaft in the shoulder part, while the main body part is mounted in two ball bearings (5) which in turn are mounted a press fit into a ball bearing housing (9). The stub section of the integral shaft is provided with a key way for the insertion of the key (15). This stub section receives the eyepiece prism shift bevel gear (11) with a keyseat and is secured with a lockscrew (32). This eyepiece prism shift gear, when mounted in the eyepiece skeleton center cored section, engages with the 44 teeth of the right eyepiece prism actuating gear (13) on its upper part.

12. Ball bearing housing. The ball bearing housing (9) is made of phosphor bronze and is 0.582 inch in length. It is cylindrical with a large shoulder flange, having a nominal wall thickness. Two undercut shoulders are provided, the larger is a sliding fit in the reamed hole and counterbored recess in the right side rear wall of the eyepiece skeleton, while the small shoulder

 
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section is undercut for clearance in the reamed hole, and provides sufficient wall area and length for the inner ball bearing (5).

The inside surface is bored for the integral shaft of the eyepiece prism shift gear (10) and has two counterbored sections. The upper and lower parts are counterbored for the insertion of two ball bearings (5), a press fit into each counterbore. The large shoulder flange is secured to the counterbored recess in the right side rear wall of the eyepiece skeleton with four lockscrews (28). These lockscrews are inserted into countersunk clearance holes in the large shoulder flange of the housing and screwed into tapped holes in the rear wall of the eyepiece skeleton. Two dowel pins (6) inserted in opposite sides of the large shoulder flange, permit a rapid alignment reference for reassembly of the housing in the reamed holes in the counterbored recess face in the eyepiece skeleton.

13. Ball bearings. The two ball bearings (5) are of antithrust type, and are mounted a press fit in the inner and outer counterbored sections of the ball bearing housing (9). The integral shaft of the eyepiece prism shift gear (10) is a push fit into these ball bearings. The ball bearings provide a smooth actuation of the eyepiece prism shift gear and its integral shaft (10).

14. Eyepiece prism shift bevel gear. The eyepiece prism shift level gear (11) is made of phosphor bronze, with a reamed hole in its center axis, and is provided with a keyseat. The large periphery is provided with 28 bevel teeth of 32 diametral pitch, and has a pitch cone angle of 60 degrees. It meshes with an identical gear called the eyepiece drive mechanism shift bevel gear (1, Figure 4-35) of the eyepiece drive packing gland assembly. The bevel gear is a push fit over the inserted key (15) and the stub section of the eyepiece prism shift gear and integral shaft (10) and is secured with a lockscrew (32). This lockscrew is screwed into the tapped hole in the hub section and extends into the spotted recess in the integral shaft stub section.

c. The rayfilter drive mechanism is composed of numerous mechanical parts forming an internal assembly to synchronize the movement of the rayfilter attachment with the eyepiece drive mechanism.

  1. Rayfilter drive gear. The rayfilter drive gear (12) is made of phosphor bronze and is 1.469 inches in length. It has 16 teeth of 32 diametral pitch cut integral with the shaft in the shoulder part, while the main body part is mounted in two ball bearings (5), which in turn are mounted a press fit into a ball bearing housing (7). This rayfilter drive gear when mounted in the eyepiece skeleton center cored section (42) engages with the 44 teeth of the right eyepiece prism actuating gear (13) in its lower part. The outer part of the integral shaft receives the rayfilter drive male coupling half section (40) which is secured with a taper pin (53).

2. Ball bearing housing. The ball bearing housing (7) is made of phosphor bronze and is 0.635 inch in length. This housing is similar in design to the ball bearing housing (9) except for the thickness of the large shoulder flange and the overall length, which allows a thicker shoulder in the internal part. It is provided with two counterbored sections in the inner and outer part for the ball bearings (5), a press fit in each counterbored section. Two undercut shoulders are provided; the larger is a sliding fit in the reamed hole in the front right center wall of the eyepiece skeleton (42), while the small shoulder section is undercut for clearance in the reamed hole and provides sufficient wall area for the inner ball bearing (5). The housing is bored for the integral rayfilter drive gear integral shaft (12).

The large flange is provided with four equally spaced countersunk clearance holes to accommodate lockscrews (28) and is also provided on opposite sides with two dowel pins (6). The dowel pins permit a rapid alignment reference for reassembly of tree assembled housing (7) to the raised shoulder section of the front right center wall of the eyepiece skeleton (42) and to which the assembly is secured with four lockscrews (28).

3. Ball bearings. The two ball bearings (5) are of antithrust type, and are mounted a press fit in the inner and outer counterbored sections of the ball bearing housing (7). The integral shaft of the rayfilter drive gear (12) is a push fit into these ball bearings. The ball bearings provide a smooth actuation of the rayfilter drive gear (12) and its integral shaft.

 
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4. Rayfilter drive male coupling half section. The rayfilter drive male coupling half section (40) is made of phosphor bronze of short length. It is cylindrical with a reamed hole in its center axis. Two projecting lugs of nominal thickness, width, and depth are provided on opposite sides. These lugs engage in opposite slots in the female coupling section (2, Figure 4-32) for interconnection with the rayfilter drive packing gland assembly. The male coupling half section is a push fit on the outer part of the integral shaft section of the rayfilter drive gear (12) and is secured with a taper pin (53).

d. The change of power mechanism is composed of numerous mechanical parts forming the internal assemblies for connection with an external attachment for change of power.

1. Right training handle rack gear and shaft. The right training handle rack gear and shaft (39) is made of phosphor bronze and is 1.156 inches in length. It has 32 teeth of 32 diametral-pitch cut integral with the shaft in the shoulder part, and meshes with teeth of the right and left power shifting racks (45 and 46) for change of power. It is mounted in two ball bearings (5) which in turn are mounted in a ball bearing housing (7).

The stub section of the integral shaft is provided with a retaining collar (8) secured to the stub section with a taper pin (35). The retaining collar serves as a thrust collar, to establish only sufficient clearance for its operation with the ball bearings.

The gear shoulder is provided with a recess in the outer part to form an inside male coupling section, with opposite lugs projecting toward its axis. This recess provides clearance for the female coupling section (3, Figure 4-36). The male coupling section provides the interconnection for the right training handle packing gland assembly. The ball bearing housing (7) and ball bearings (5) are identical to the housing (7) used for the rayfilter drive gear (12). It has no dowel pins inserted in the large shoulder flange. The assembled housing is secured in the reamed hole and to the counterbored face in the lower right side of the eyepiece skeleton (42).

2. Power shifting racks right and left. The power shifting racks right and left (45 and

  46) are made of cast phosphor bronze, having an over-all length of 7.375 inches. Both racks are provided with offset arms and hubs to establish the center axis of each hub with proper clearance on each side of the mechanical centerline, and to provide clearance for the shifting wire spindle assemblies.

The left power shifting rack (46) is provided with gear teeth in the lower straight section in the right side face which mesh with the training handle rack gear and shaft teeth (39). The right power shifting rack (45) is provided with gear teeth in the lower straight section in the left side face, to mesh with the training handle rack gear and shaft teeth (39) on the opposite side.

The arm of the right shifting rack (45) is offset to the right of the lower straight section, and slightly outward. The hub section is offset to the left and slightly outward, with a reamed hole in the center of the hub, to carry the shifting wire spindle assembly. The arm of the left shifting rack (46) is offset to the right and outward. The hub section is offset to the right and slightly outward, with a reamed hole in the center of the hub to carry the shifting wire spindle assembly. Both racks are carried in the vertical recess slotted sections in the right side of the eyepiece skeleton frame (42), to operate vertically for change of power. They are retained in the vertical recess slotted sections with a rectangular retaining plate (47), which is secured with eight lockscrews (29). The retaining plate is provided with a clearance hole in the central part for the female coupling section (3, Figure 4-36) of the right training handle packing gland assembly.

3. Shifting Wire spindles. The two shifting wire spindles (1) are made of phosphor-bronze rod and are 2 inches in length. The periphery is threaded to carry two shifting wire spindle adjusting nuts (4) on each spindle in the lower part on opposite sides of the hub section of the power shifting racks (45 and 46).

The upper part has a 16 degrees countersunk section in the center axis to receive a 14 degrees tapered shifting wire clamp (2). The center axis of the spindle has a clearance hole for the phosphor bronze wire of the shifting wire tape (38). Each shifting wire spindle is a sliding fit in the reamed hole

 
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axis of each power shifting rack hub section, and has an adjusting nut on opposite sides. The adjusting nuts provide a variation in supplying tension or slack in the shifting wire tapes as desired.

4. Shifting wire clamps. The two shifting wire clamps (2) are made of corrosion-resisting steel material. A clearance hole is provided in their center axis, with a sawed slot, the depth of which corresponds to the length of the tapered part. The upper part is undercut and forms an alignment support section in the clamp nut (3). The slotted tapered section, when assembled in the upper countersunk section in the spindle, closes as the clamp nut (3) is tightened, and in this manner secures the phosphor-bronze wire of the shifting wire tape (38).

5. Shifting wire clamp nuts. The shifting wire clamp nuts (3) are made of hexagon phosphor bronze. The center axis has a clearance hole for the phosphor-bronze wire tape (38). A small counterbore in the upper part serves as an alignment support section of the shifting wire clamps (2), while the large counterbore is threaded to engage on threads of the spindle periphery.

6. Shifting wire tape. The four lengths of shifting wire tape (38) are made of monel metal and their length is determined at assembly. The upper part of each tape has two clearance holes for attachment to the head prism shifting racks (40 and 42, Figure 4-17) and is secured with two clamp blocks (16) and lockscrews (12). The lower part of each tape has a clearance hole located 1 1/4 inches from the end for the bronze wire. The section below the clearance hole has a 90 degrees groove bend 0.050 inch deep in the centerline. A suitable length of bronze wire 0.040 inch in diameter is inserted through the clearance hole with its upper end bent at 90 degrees. The monel metal tape is heated and bent to overlap the phosphor bronze wire, with its 90 degrees bent part a metal to metal contact with the monel metal overlapping end which is soldered together.

e. Prism tilt mechanism. The prism tilt mechanism is composed of numerous internal parts to operate the head prism for all degrees of elevation and depression. This is accomplished with internal connecting linkage and a suitable external attachment.

  1. Left training handle rack gear and shaft. The left training handle rack gear and shaft (39) is identical to the right training handle rack gear and shaft (39) with the exception that it is used in the left side of the eyepiece skeleton (42). This gear, cut integral with the shaft, engages with teeth of the left and right prism shifting racks (43 and 44) located on opposite sides. The integral shaft is mounted in two ball bearings (5) which in turn are mounted a press fit in the ball bearing housing (7). The ball bearings (5), ball bearing housing (7), and retaining collar (8) secured with a taper pin (35) are identical to their respective parts for the power shift side.

2. Prism shifting racks left and right. The prism shifting racks left and right (43 and 44) are made of cast phosphor bronze, having an overall length of 7.375 inches. Both racks are provided with offset arms and hubs to establish the center axis of each hub with proper clearance on each side of the mechanical centerline. They also provide clearance for the shifting wire spindles (1).

The left prism shifting rack (43) is provided with gear teeth in the lower straight section in the right side face to mesh with the training handle rack gear and shaft teeth (39). The right prism shifting (44) is provided with gear teeth in the lower straight section in the left side face to mesh with the training handle rack gear and shaft teeth (39) on the opposite side.

The arm of the left shifting rack (43) is offset to the left of the lower straight section and slightly outward. The hub section is offset to the right and slightly upward, with a reamed hole in the center of the hub to carry the shifting wire spindle assembly. The arm of the right shifting rack (44) is offset to the left and outward. The hub section is offset to the left and slightly outward, with, a reamed hole in the center of the hub to carry the shifting wire spindle assembly. Both racks are carried in the vertical recess slotted sections in the left side of the eyepiece skeleton frame (42) to operate vertically for the elevation and depression of the head prism. They are retained in the vertical recess slots with a rectangular retaining plate (47), secured with eight lockscrews (29). The retaining plate is provided with a clearance hole

 
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in the central part for the female coupling section (3, Figure 4-34) of the left training handle packing gland assembly.

3. Shifting wire spindles. The shifting wire spindles (1), shifting wire clamps (2), shifting wire clamp nuts (3), shifting wire spindle adjusting nuts (4), and the shifting wire tape (38) are identical to those used for the change of power mechanism.

4L2. Disassembly of the eyepiece skeleton. The eyepiece skeleton is disassembled in the following manner:

1. Remove the eyepiece prism mount (20) by vertically pulling it clear of the rail bearings in the inner side walls of the eyepiece skeleton (42). In some cases it may be necessary to free the lower part of the counterweight straps (27) to accomplish this removal.

2. Remove the lockscrew (41) from the eyepiece prism upper retaining plate (18). The lockscrew is unscrewed from a tapped hole in the upper retaining plate and the eyepiece prism upper clamp ring (17).

3. Remove the four lockscrews (34) from the eyepiece prism upper retaining plate (18). The lockscrews are unscrewed from the tapped holes in the upper side walls of the eyepiece prism mount (20). Remove the eyepiece prism upper retaining plate (18) carrying with it the eyepiece prism upper clamp ring (17). Unscrew the clamp ring (17) from the upper retaining plate (18). Also remove the upper eccentric eyepiece prism centering ring (48).

4. Remove the eyepiece lens mount (19) carrying with it the eyepiece lens (52), eyepiece lens clamp ring (16), and its lockscrew (41) by unscrewing the eyepiece lens mount from the eyepiece prism front retaining plate (24).

5. Remove the lockscrew (41) from the eyepiece lens mount (19) and the eyepiece lens clamp ring (16). The lockscrew is unscrewed from the tapped hole in the clamp ring.

6. Remove the eyepiece lens clamp ring (16), unscrewing it from the eyepiece lens mount (19).

7. Remove the eyepiece lens (52) from the eyepiece lens mount (19) and wrap it in clean

  lens tissue. Place it to one side to prevent scratches and breakage.

8. Using lens tissue, slide the eyepiece prism (51) out of the eyepiece prism mount (20) from the upper part. Wrap the eyepiece prism with lens tissue and place it to one side to prevent scratches and breakage.

9. Remove the four lockscrews (34) from the eyepiece prism front retaining plate (24). These lockscrews are unscrewed from the tapped holes in the front side walls of the eyepiece prism mount (20). Unscrew the eyepiece prism front clamp ring (50) from the front retaining plate (24) and remove the front eccentric eyepiece prism centering ring (49).

10. Remove the three lockscrews (22) from the left eyepiece prism mount stem gear rack (21) removing the rack. These lockscrews are unscrewed from the tapped holes in the eyepiece prism mount stem (20).

11. Remove the two lockscrews (22) from the left side of the eyepiece prism mount stem (20), removing the rack. These lockscrews are unscrewed from the tapped holes in the right eyepiece prism mount stem gear sack (21).

12. Remove the two shifting wire spindle assemblies from the right and left power shifting racks (45 and 46). The lower two shifting wire spindle adjusting nuts (4) were removed previously. Remove the two upper shifting spindle wire adjusting nuts (4). Unscrew them from the lower part of the shifting wire spindles (1).

13. Remove the two shifting wire clamp nuts (3), unscrewing them from the upper part of the shifting wire spindles (1). Remove the two shifting wire clamps (2).

14. Remove the eight lockscrews (29) from the power shifting rack's retaining plate (47). These lockscrews are unscrewed from tapped holes in the center raised section above the reamed hole and counterbored recess in the lower right side of the eyepiece skeleton (42). Remove the retaining plate (47), and the right and left power shifting racks (45 and 46).

15. Remove the four lockscrews (28) from the right training handle rack gear and shaft ball bearing housing (7). These lockscrews are unscrewed from tapped holes in the counterbored

 
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recess face in the lower right side of the eyepiece skeleton (42). Remove the ball bearing housing (7), carrying with it the right training handle rack gear and shaft (39), two ball bearings (5), retaining collar (8), and its taper pin (35).

16. Follow the procedure outlined in Steps 12 and 13 for the removal of the shifting wire spindle assemblies of the prism shifting racks (43 and 44).

17. In case the assembly described in Step 15, is damaged or corroded, it requires removal. Remove the taper pin (35) from the right training handle rack gear and shaft (39) and the retaining collar (8).

18. Remove the right training handle rack gear retaining collar (8) from the stub section of the integral right training handle rack gear and shaft (39).

19. Remove the right training handle rack gear and shaft (39) from the center races of the two ball bearings (5). Push the integral shaft out from the small end of the ball bearing housing, carrying it out from the large shoulder flange end of the ball bearing housing (7).

20. Remove the two ball bearings (5) from the ball bearing housing (7), one from each side.

21. Remove the eight lockscrews (29) from the prism shifting rack retaining plate (47). These lockscrews are unscrewed from tapped holes in the center raised section above the reamed hole and counterbored recess in the lower left side of the eyepiece skeleton (42). Remove the retaining plate (47) and the left and right prism shifting racks (43 and 44).

22. Remove the four lockscrews (28) from the left training handle rack gear and shaft ball bearing housing (7). These lockscrews are unscrewed from tapped holes in the counterbored recess face in the lower left side of the eyepiece skeleton (42). Remove the ball bearing housing (7), carrying with it the left training handle rack gear and shaft (39), two ball bearings (5), retaining collar (8), and its taper pin (35).

23. In case the above assembly is damaged or corroded, it requires removal. Follow the procedure of disassembly in the same manner as

  described for the right side under Steps 16, 17, 18, and 19.

24. Remove the six lockscrews (29) from each counterweight strap retaining plate (26). These lockscrews are unscrewed from tapped holes in the two raised shoulders on each side of the eyepiece skeleton (42). Remove the two retaining plates (26).

25. Remove the four lockscrews (33) from the upper part of each counterweight strap (27). The lockscrews are unscrewed from tapped holes in the rectangular slotted faces in opposite sides of the counterweight (25). Remove each counterweight strap (27).

26. Remove the counterweight (25) by sliding it off the cylindrical bearing section of the upper part of the eyepiece skeleton (42).

27. Remove the four lockscrews (28) from the eyepiece prism shift gear ball bearing housing (9). These lockscrews are unscrewed from tapped holes in the counterbored face in the eyepiece skeleton rear wall. Remove the ball bearing housing (9) carrying with it the two ball bearings (5), eyepiece prism shift gear (10), eyepiece prism shift bevel gear key (15), and eyepiece prism shift bevel gear (11), its lockscrew (32), and two dowel pins (6).

28. In case the above assembly is damaged or corroded, it requires removal. Remove the lockscrew (32) from the eyepiece prism shift bevel gear (11). The lockscrew is unscrewed from the tapped hole in the hub of the eyepiece prism shift bevel gear (11) and its contact in the spotted recess in the integral shaft stub section of the eyepiece prism shift gear (10).

29. Remove the eyepiece prism shift bevel gear (11) from the integral shaft stub section of the eyepiece prism shift gear (10), and remove the inserted key (15) from the stub section.

30. Remove the integral shaft of the eyepiece prism shift gear (10) from the center of the two ball bearings (5), pushing it out from the large shoulder flange end of the ball bearing housing (9), and carrying it out from the small end of the ball bearing housing.

31. Remove the two ball bearings (5) from both ends of the ball bearing housing (9).

 
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32. Remove the four lockscrews from the rayfilter drive gear ball bearing housing (7). These lockscrews are unscrewed from tapped holes in the raised shoulder of the eyepiece skeleton front center wall. Remove the ball bearing housing (7) carrying with it the two ball bearings (5), rayfilter drive gear (12), male coupling half section (40), its taper pin (53), and two dowel pins (6).

33. In case the assembly is damaged or corroded, it requires removal. Remove the taper pin (53) from the rayfilter drive male coupling half section (40) and the integral shaft of the rayfilter drive gear (12).

34. Remove the rayfilter drive male coupling half section (40) from the integral shaft section of the rayfilter drive gear (12).

35. Remove the integral shaft of the rayfilter drive gear (12) from the center of the two ball bearings (5), pushing the rayfilter drive gear out from the large shoulder flange end of the ball bearing housing (7), and carrying it out from the small end of the ball bearing housing.

36. Remove the two ball bearings (5) from both ends of the ball bearing housing (7).

37. Remove the two lockscrews (30) from the spotted recess in each eyepiece prism actuating gear shaft (14). These lockscrews are unscrewed from the tapped holes in the rear raised shoulder on each side of the eyepiece skeleton (42).

38. Remove the eyepiece prism actuating gear shafts (14) and the two eyepiece prism actuating gears (13). The shafts and gears slide out easily.

4L3. Reassembly of the eyepiece skeleton. The eyepiece skeleton is reassembled in the following manner:

1. Apply lubriplate No. 110 lightly to all rotating parts as the assembly procedure is followed.

2. Particular attention show d be directed to the reference marks and numerals on various parts for their proper coincidence for reassembly.

3. Place both eyepiece prism actuating gears (13) in the center cored section in the eyepiece skeleton. Reference marks on both

  gears and shafts corresponding to reference marks on the framework should be noted for correct assembly.

4. Place both eyepiece prism actuating gear shafts (14) in the reamed hole in each front center and rear wall; the shafts extend into the front wall, then through the center bearing hole of each eyepiece prism actuating gear (13) into the rear wall. Insert lockscrews (30) into a countersunk clearance and tapped hole in the rear raised shoulder of each side wall and raised semi-circular section into a spotted recess in each shaft (14) for securing the shafts axially.

5. Place the counterweight (25) on the upper turned bearing section of the eyepiece skeleton. Slide the counterweight down to the large shoulder flange, with the cored opening face upward.

6. Place each counterweight strap (29) through the cored opening of the large shoulder flange of the eyepiece skeleton (42). The counter weight straps fit on the slotted face of opposite rectangular slots in the counterweight. Secure each counterweight strap to the rectangular slotted faces on each side of the counterweight with four lockscrews (33) each. These lockscrews are inserted into countersunk clearance holes in each counterweight strap and screwed into tapped holes in the opposite slotted faces in the counterweight (25).

7. Engage the lower part of each counterweight strap rack gear (27) in mesh with each eyepiece prism actuating gear (13). Place the retaining plates (26) over each counterweight strap (27) on the two raised shoulders of each outer side wall, securing each retaining plate with six lockscrews (29). These lockscrews are inserted into countersunk clearance holes in each retaining plate (26) and screwed into tapped holes, the two raised shoulders on each outer side of the eyepiece skeleton (42).

8. Place the two eyepiece prism shift gear ball bearings (5) in the eyepiece prism ball bearing housing (9) from both ends, pressing them snugly against the internal shoulder seats.

9. Place the eyepiece prism shift gear integral shaft (10) in the center of the two ball bearings (5), pushing it in from the small end of the ball

 
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bearing housing (9). The shoulder of the eyepiece prism shift gear is a metal to metal fit with the center race of the ball bearing.

10. Place the eyepiece prism shift gear key (15) in the keyway in the integral shaft stub section eyepiece prism shift gear (10).

11. Place the hub section of the eyepiece prism shift bevel gear (11) over the inserted key (15) located in the stub section integral shaft eyepiece prism shift gear (10). Secure the bevel gear to the stub section with a lockscrew (32). The lockscrew is inserted into the tapped hole in the bevel gear hub section and screwed into the spotted recess of the stub section integral shaft.

12. The mounted eyepiece prism shift gear (10) and the eyepiece prism shift bevel gear (11) are assembled to the eyepiece skeleton by placing the ball bearing housing (9) in the reamed hole and counterbored recess in the right side rear wall of the eyepiece skeleton (42). The eyepiece prism shift gear (10) engages with the right eyepiece prism actuating gear (13) in its upper part, with coinciding reference marks. The ball bearing housing, after proper engagement of its dowel pins (6) in reamed holes, is secured with four lockscrews (28). These lockscrews are inserted into countersunk clearance holes in the housing and screwed into tapped holes in the counterbored recess face.

13. Place the two rayfilter drive gear ball bearings (5) in the rayfilter drive gear ball bearing housing (7) from both ends, pressing them snugly against the internal shoulder, seats.

14. Place the rayfilter drive gear integral shaft (12) in the center of the two ball bearings (5), pressing it in from the small end of the ball bearing housing (7). The shoulder of the rayfilter drive gear (12) is a metal-to-metal fit with the center race of the ball bearing.

15. Place the rayfilter drive gear male coupling half section (40) on the integral shaft rayfilter drive gear stub section (12) and secure it with a taper pin.(53).

16. The mounted rayfilter drive gear (12) is assembled to the front center wall of the eyepiece skeleton by placing the ball bearing housing (7) in the reamed hole and raised section on the

  right side of the front center section of the eyepiece skeleton. The rayfilter drive gear (12) engages with the right eyepiece prism actuating gear (13) in its lower part, with coinciding reference marks. The ball bearing housing, after proper engagement of its dowel pins (6) in reamed holes, is secured with four lockscrews (28). These lockscrews are inserted in countersunk clearance holes in the housing and screwed into tapped holes in the raised section on the right side of the eyepiece skeleton front center wall.

17. Place the two training handle rack gear ball bearings (5) in the ball bearing housing (7) from both ends, pressing them snugly against the internal shoulder seats.

18. Place the training handle rack gear and integral shaft (39) in the center of the two ball bearings (5), carrying it in from the large shoulder flange end of the ball bearing housing (7). The shoulder of the training handle rack gear (39) is a metal to metal contact fit with the center race of the ball bearing.

19. Place the thrust collar (8) over the inner stub section of the training handle rack gear and integral shaft (39) and secure it with a taper pin (35).

20. The mounted training handle rack gear and integral shaft (39) is assembled to the right side of the eyepiece skeleton by placing the ball bearing housing (7) in the reamed hole and counterbored recess of the lower right side of the eyepiece skeleton (42). The ball bearing housing (7) is secured with four lockscrews (28). These lockscrews are inserted into countersunk clearance holes in the housing and screwed into tapped holes in the counterbored recess face.

21. Reassemble the left training handle rack gear and integral shaft (39) in similar manner to that described in Steps 17, 18, 19, and 20 for the right training handle rack gear and integral shaft (39).

22. Place the power shifting racks right and left (45 and 46) in the vertical recess slotted sections in the right side of the eyepiece skeleton (42). The racks are placed with their lower ends even with the base of the eyepiece skeleton frame (42). The reference mark on the training

 
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handle rack gear (39) must coincide with reference marks of the power shifting racks.

23. Place the retaining plate (47) over the power shifting racks right and left (45 and 46) on the raised shoulders. Secure the retaining plate with eight lockscrews (29). These lockscrews are inserted into countersunk clearance holes in the retaining plate and screwed into tapped holes in the raised center shoulder sections above and below the counterbored recess in the right side of the eyepiece skeleton.

24. Place the prism shifting racks left and right (43 and 44) in the vertical recess slotted sections in the left side of the eyepiece skeleton (42). The racks are placed with their lower ends even with the base of the eyepiece skeleton frame. The reference mark on the training handle rack gear (39) must coincide with reference marks of the prism shifting racks.

25. The retaining plate (47) is placed over the prism shifting racks left and right (43 and 44) and secured to the lower left side of the eyepiece skeleton (42) in similar manner to the procedure described for the opposite side retaining plate (47).

26. Place the four shifting wire clamps (2) in each of the four shifting wire spindles (1) and place the four shifting wire clamp nuts (3) on the upper part of each spindle over each shifting wire clamp (2) Place four shifting wire spindle adjusting nuts (4) on the lower part of each spindle, and place each assembled spindle in the hub section reamed hole in each head prism shifting racks (43 and 44) and power shifting racks (45 and 46) carrying them in from the upper part. Place the second set of four shifting wire spindle adjusting nuts (4) on the lower part of each spindle, below each hub section.

27. Place the right eyepiece prism mount stem gear rack (21) with its dowel pins (23) on the right side of the eyepiece prism mount stem (20). Secure the rack with two lockscrews (22), inserting them from the opposite side of the eyepiece prism mount stem. The lockscrews are inserted in countersunk clearance holes in the stem section and screwed into tapped holes in the rack.

28. Place the left eyepiece prism mount stem gear rack (21) with its dowel pins (23) on the

  left side of the eyepiece prism mount stem (20), and secure it with three lockscrews (22). These lockscrews are inserted in countersunk clearance holes, in the left rack and screwed into tapped holes in the stem section.

29. Place the eyepiece prism front retaining plate (24) on the front face of the eyepiece prism mount (20). Secure the front retaining plate (24) with four lockscrews (34). These lockscrews are inserted in countersunk clearance holes in the front retaining plate and screwed into tapped holes in the eyepiece prism mount (20).

30. Clean the eyepiece prism (51), using clean lens tissue; also clean off any surface dust. Then place the eyepiece prism in the eyepiece prism mount (20) from the upper part, with the shortest radius facing the eyepiece lens side.

31. Place the eyepiece prism upper retaining plate (18) on the upper face of the eyepiece prism mount (20). Secure the upper retaining plate with four lockscrews (34). These lockscrews are inserted in countersunk clearance holes in the upper retaining plate and screwed into tapped holes in the eyepiece prism mount (20).

32. Place the upper eccentric eyepiece prism centering ring (48) and the eyepiece prism upper clamp ring (17) in the upper retaining plate (18). The beveled side of the centering ring should bear to the curvature of the eyepiece prism (51). The upper clamp ring (17) is screwed down on the upper eccentric centering ring (48) until the lockscrew holes coincide. Insert the lockscrew (41) into the countersunk clearance hole in the upper retaining plate and screw it into the tapped hole in the upper clamp ring (17).

33. Place the, front eccentric eyepiece prism centering ring (49) to bear on the eyepiece prism (51) in similar manner to the upper eccentric centering ring, and place the eyepiece prism front clamp ring (50) in the front retaining plate (24). The front clamp ring (50) is screwed down on the front eccentric centering ring (49).

34. With the counterweight (25) at the extreme lower position, the assembled eyepiece prism mount (20) is placed in the rail bearings of the eyepiece skeleton, and moved downward. Move the counterweight upward to engage the eyepiece prism actuating gears (13) with

 
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the eyepiece prism stem gear racks (21). The upward movement of the counterweight now causes the engagement of both the eyepiece prism actuating gears (13) with the eyepiece prism stem gear racks (21).

35. Clean the eyepiece lens (52) in similar manner to that noted under Step 28.

36. Place the eyepiece lens (52) in the eyepiece lens mount (19) with the shortest radius facing toward the eyepiece prism (51).

37. Place the eyepiece lens clamp ring (16) in the internal threaded part of the eyepiece lens mount (19). Screw the clamp ring into the mount until the lockscrew holes coincide, and secure the clamp ring with a lockscrew (41). This lockscrew is inserted in the countersunk clearance

  hole in the eyepiece lens mount (19) and screwed into the tapped hole in the clamp ring (16).

38. Place the assembled eyepiece lens mount (19) in the internal threads of the eyepiece prism front retaining plate (24). Screw the mount in until the shoulder of the mount is a metal to metal contact with the shoulder of the front retaining plate.

39. To determine the accuracy of the eyepiece skeleton assembly, a few simple observations can be made. If instructions have been correctly followed, the essential travel of the counterweight (25) and the eyepiece prism mount (20) should be 25 mm; the essential travel of the prism shifting racks should be 35 mm; and the essential travel of the power shifting racks should be 30 mm.

 
M. EYEPIECE BOX AND MISCELLANEOUS ASSEMBLIES
 
4M1. Description of the eyepiece box and miscellaneous assemblies. The eyepiece box and its miscellaneous assemblies are described as follows. Figure 4-29 shows the eyepiece box and miscellaneous assemblies. All bubble numbers for Section 4M1 refer to Figure 4-29 unless otherwise specified.

Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
1 P-1163-3 1 Outer tube and eyepiece box angular alignment key
2 P-1163-8 1 Main coupling
3 P-1179-51 2 Name plate lockscrews
4 P-1179-65 2 Outer tube and eyepiece box angular alignment key lockscrews
5 P-1310-35 20 Side plate and pressure gage assembly lockscrews
6 P-1310-38 1 Star wheel lock plunger screw head
7 P-1314-12 2 Main coupling lockscrews
8 P-1314-13 1 Outer tube and eyepiece box soft rubber gasket
9 P-1353-5 1 Side plate
10 P-1353-6 2 Side plate and pressure gage soft rubber gaskets
11 P-1401-1 1 Eyepiece box
12 P-1409-4 1 Eyepiece skeleton centering screw
13 P-1409-5 1 Eyepiece skeleton centering screw lead washer
14 P-1410-1 2 Air inlet and outlet plugs
 
Ill.
No.
Drawing
Number
Num-
ber Re-
quired
Nomenclature
15 P-1410-2 2 Air valve bodies
16 P-1410-3 2 Air valve screws
17 P-1410-4 2 Air valve screw 3/16 inch steel balls
18 P-1410-5 2 Air valve body lead washers
19 P-1412-8 4 Anchor screw pins
20 P-1430-7 1 Name plate
21 P-1454 1 Pressure gage assembly
22 Assembly 1 Spring type stadimeter transmission shaft packing gland
23 Assembly 1 Hycar type stadimeter transmission shaft packing gland modification
24 Assembly 1 Rayfilter drive packing gland assembly
25 Assembly 1 Eyepiece drive packing gland assembly
26 Assembly 2 Left and right training handle packing gland assemblies
27 Assembly 1 Eyepiece window assembly

a. Eyepiece box. The eyepiece box (11) is made of cast phosphor-bronze material and is 16.500 inches in length. It forms the outer shell covering the eyepiece frame (42, Figure 4-28). Various projections and recesses accommodate numerous inward projecting assemblies, also interconnecting with the external assemblies.

 
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The upper face has eight tapped holes, two reamed dowel pin holes, and one air line clearance hole, to match with holes of the eyepiece skeleton large shoulder flange (42, Figure 4-28).

The inner circumference of the external upper alignment support section is bored to allow it to slide on the narrow alignment support shoulder of the eyepiece skeleton large shoulder flange, while the upper face contacts this large

  shoulder flange and is secured to it with eight lockscrews (31, Figure 4-28). The two dowel pin reamed holes of this upper face, when assembled over the protruding dowel pins (36, Figure 4-28) re-establish the correct angular alignment of the eyepiece box to the eyepiece skeleton (42, Figure 4-28).

The upper part of the eyepiece box is provided with an undercut section serving as an alignment

Figure 4-29. Eyepiece box and miscellaneous assemblies.
Figure 4-29. Eyepiece box and miscellaneous assemblies.
 
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support section, a sliding fit in the lower counterbore in the outer tube (2, Figure 4-15). A keyway is provided in the front centerline in this section for the insertion of an angular alignment key (1) secured with two lockscrews (4). The key maintains the angular alignment of the emerging light rays within prescribed tolerance limits.

The threaded periphery section has 12 left-hand threads per inch to receive the lower internal threaded part of the main coupling (2). The joint shoulder face of the threaded periphery is provided with a triangular annular groove, to receive the soft rubber gasket (8) which is compressed by the tightening of the main coupling (2). This brings the triangular annular ridge detail of the lower joint shoulder of the outer tube (2, Figure 4-15) in contact with the soft rubber gasket (8) and upon further tightening of the main coupling, compresses the gasket into the above mentioned triangular annular groove of the eyepiece box forming an hermetically sealed joint.

The base of the eyepiece box is rectangular in shape with the corners rounded to conform to the remaining cored periphery of the eyepiece box. Four tapped holes are provided in the four corners to receive the four stadimeter housing bolts (30) which secure the stadimeter housing (67, Figure 4-24) to the base of the eyepiece box (11). Two dowel pin holes of shallow depth are provided diagonally on opposite sides to receive the protruding dowel pins (22, Figure 4-24) of the stadimeter housing (67, Figure/4-24).

The center axis of the rectangular base is provided with an opening which consists of a reamed hole and partially tapped section. It also has two counterbored sections near the outer face for the eyepiece skeleton centering screw (12) and a lead washer (13).

A countersunk tapped drain hole is provided at an appropriate place in the base. This hole is countersunk sufficiently to receive a lead washer and to allow the drain screw to be slightly recessed upward from the lower surface of the eyepiece box base. This drain hole is provided to drain out water which may accumulate during flooding of the instrument.

A shallow tapped hole of 1/4-28 is provided in the base at an appropriate distance from both

  the horizontal and vertical centerlines to accommodate a short screw (6). The head of this short screw projects below the eyepiece box base sufficiently to contact the star wheel lock plunger (62, Figure 4-24) in order to compress the star wheel key (60, Figure 4-24) and holder (61, Figure 4-24) when the stadimeter housing is assembled to the base of the eyepiece box. This releases the automatic stop of the stadimeter housing assembly for operation of the stadimeter.

A semi-circular projecting solid section is provided in the inner cored wall of the eyepiece box and forms part of the inner base wall. This section allows sufficient wall space after the machining of a stadimeter transmission shaft stuffing box. This stuffing box consists of a reamed hole for the stadimeter transmission shaft (22, Figure 4-27) and a larger reamed hole and threaded counterbored section.

The large reamed hole is chamfered in its inner shoulder at 30 degrees for flax packing, while the remainder of its length accommodates the various parts of the packing gland. The threaded counterbored section receives the spring retainer (3, Figure 4-30) of the spring type stadimeter transmission shaft packing gland assembly, or the packing retainer (2, Figure 4-31) of the modified hycar stadimeter transmission shaft packing gland. The 30 degrees chamfered seat receives the flax packing of the first type mentioned, or receives the gland filler piece (3, Figure 4-31) of the modified type.

This stadimeter transmission shaft packing gland assembly of either type provides the hermetically sealed joint for the protrusion of the stadimeter transmission shaft (22, Figure 4-27) for its interconnection with the stadimeter housing assembly (Figure 4-24).

All the various openings and recesses are described under each individual assembly as follows:

b. Main coupling. The main coupling (2) is made of cast phosphor-bronze material and is 2.531 inches in length. The outer diameter is within 0.010 inch of the outer tube diameter (Figure 4-15). In the center of the upper and lower internal threaded section, a threaded relief is provided to separate the left and righthand threads when machining and serving as an

 
157

area for the expansion of the rubber sealing gasket (8). The upper internal threaded section has 12 right-hand threads per inch, to engage on the right-hand threaded periphery of the lower part of the outer tube (2, Figure 4-15). The lower internal threaded section has 12 lefthand threads per inch, to engage the lefthand threaded periphery of the upper part of the eyepiece box (11).

The main coupling connects the lower part of the outer tube (2, Figure 4-15) to the eyepiece box (11). A soft rubber gasket (8) fits between the triangular annular ridge detail of the outer tube, and the corresponding triangular annular groove of the shoulder joint of the eyepiece box (11).

The compression of the soft rubber gasket (8) by means of the coupling's being tightened, causes the gasket to follow the triangular annular ridge and its corresponding groove to provide a hermetically sealed joint. Two lockscrews (7), located usually in opposite sides of the main coupling, screw into tapped holes in the coupling and extend in spotted recesses of the outer tube, to prevent the coupling from unscrewing and thus maintain the hermetical seal of the joint.

The main coupling has four sets of twin holes of shallow depth equally spaced. These holes accommodate a special spanner, wrench provided with twin prongs for the breaking or making up of the joint.

c. Air valve bodies. The two valve bodies (15) are made of phosphor-bronze material and blued. Both air valve bodies are of duplicate design, one is used as the AIR INLET and the other for the AIR OUTLET. Engraved markings for each valve are stamped in the eyepiece box above the individual valve body.

The inlet valve body has an external threaded section, with a short straight shoulder to carry a lead washer (18) next to its large shoulder. It engages into a tapped hole above the focusing knob assembly (Figure 4-39) in the eyepiece box (11). The lead washer rests on the counterbored recess seat to form an hermetical seal of this joint. Two tapped holes are provided in the valve body, one is large for the insertion of an air valve screw (16) with an assembled ball bearing (17). The ball bearing when tightened

  rests in a 90 degrees ground recess seat and seals off the nitrogen clearance hole. The second tapped hole opposite the large tapped hole is shallow, and is provided for the insertion of a nitrogen charging connection. The seat of this tapped hole is provided with a clearance hole, connecting the air valve hole at a 45 degrees angle. This tapped hole carries an air inlet plug (14) when the periscope is charged. Two opposite shallow holes are provided in the face of the air valve bodies for the insertion of a special wrench.

The air valve body section in the eyepiece box (11) is a solid cylindrically cored projection section in its inner cored wall. It has sufficient wall area to accommodate the air valve body (15). An air line section of 4 3/4 inches in length connects this cylindrical wall seat section with a drilled hole, and is soldered to the clearance hole in the narrow flange section as well as to the inner wall of the eyepiece box.

The outlet valve body is located below the focusing knob assembly (Figure 4-39) with direct clearance from the threaded section to the internal part of the eyepiece box.

The inlet valve is connected by the soldered air line, to the various air lines and couplings to the air line adapter (11) which is attached to the fourth reduced tube section (9, Figure 4-19) to carry the charging nitrogen to the skeleton head, and for its circulation downward through the reduced tube sections and inner tube sections. It passes through the various channel provisions of each lens mount for as thorough circulation as is possible.

d. Pressure gage assembly. The pressure gage assembly (21) is a commercial product, manufactured by the Certified Gage and Instrument Co., of Long Island City, N.Y. This gage is graduated from 0 to 10 pounds, and can withstand a maximum pressure of 300 pounds. The gage is tested within 30 inches of vacuum with a corresponding mercury gage for leaks, and at 300 psi under water for 30 minutes, and then calibrated. This gage is assembled on the right side of the periscope in a rectangular recess and opening. A soft rubber gasket (10) is placed in the recess seat under the rectangular flange of the pressure gage assembly, and is secured with 10 lockscrews (5). The pressure

 
158

gage provides a constant indication of the internal gas pressure of the periscope.

The rectangular opening on this right side in the eyepiece box serves to allow the repairman access to the shifting wire spindle assemblies of the change of power mechanism, thus the repairman can make adjustments for removing or increasing the tension of the shifting wire tapes for the change of power mechanism without the removal of the eyepiece box. In the case of this instrument, it is necessary to remove the shifting wire spindle assemblies for disassembly of the skeleton head assembly from the outer taper section (1, Figure 4-15).

e. Side plate. The side plate (9) is made of phosphor bronze and is of rectangular shape, having a nominal wall thickness. It is provided with two shoulders of rectangular design, of which the larger forms the flange and fits over a rectangularly shaped soft rubber gasket (10) placed in the rectangular recess and opening in the eyepiece box (11). The rectangular opening in the left side serves the same purpose for the prism tilt mechanism on this side as that used for the pressure gage assembly on the right side for the change of power mechanism. The rectangular flange of the side plate (9) has 10 countersunk clearance holes for the insertion of lockscrews (5) which extend into the shallow tapped holes in the rectangular recess face in the eyepiece box. The side plate and pressure gage rubber gaskets (10) are made of crude rubber 0.030 inch in thickness of rectangular shape, having a width of 0.374 inch. The gasket is fitted in the rectangular recess seat below their respective rectangular flanges of the pressure gage assembly and the side plate to maintain the hermetical seal of these two joints, when drawn evenly by 10 lockscrews (5) of the side plate and pressure gage assembly.

f. Eyepiece window assembly. The eyepiece window assembly (27) is assembled to the front large bored hole and, counterbored recess seat in the eyepiece box (11). The eyepiece window frame rubber gasket (8) is placed between the frame flange and the counterbored recess seat. The frame flange is secured to the gasket and recess seat with four short and eight long lockscrews (2 and 3, Figure 4-38). This rubber gasket maintains the hermetical seal

  of this assembly, with two more rubber gaskets located in the front and rear face of the eyepiece window (9).

g. Rayfilter drive packing gland assembly. The rayfilter drive packing gland assembly (24) is assembled to the front bored hole and square recess seat in the front of the eyepiece box (11). This packing gland provides an internal coupling connection at the inner part with the eyepiece skeleton, and an external connection with the rayfilter assembly. The rayfilter drive stuffing box body rubber gasket (9) is placed between the stuffing box body flange and the square recess seat. The stuffing box body flange is secured to the gasket and recess seat with four lockscrews (13, Figure 4-32). This rubber gasket maintains the hermetical seal of this assembly along with the flax packing under spring pressure.

h. Eyepiece drive packing gland assembly. The eyepiece drive packing gland assembly (25) is assembled to the center right rear wall of the eyepiece box (11) in a bored hole and counterbored recess seat, between both air valve body assemblies. This packing gland assembly provides an internal connection with the eyepiece prism shift bevel gear (11, Figure 4-28) of the eyepiece skeleton assembly at the inner part, and an external coupling connection with the focusing knob assembly (Figure 4-39). The eyepiece drive stuffing box body rubber gasket (11) is placed between the stuffing box body flange and the counterbored recess seat. The stuffing box body flange is secured to the gasket and recess seat with six lockscrews (3, Figure 4-35). The rubber gasket maintains the hermetical seal of this assembly with the flax packing under spring pressure.

i. Left training handle packing gland assembly. The left training handle packing gland assembly (26) is assembled to the lower part of the left side of the eyepiece box (11) in a bored hole and counterbored recess seat. This packing gland assembly provides an internal coupling connection at the inner part with the eyepiece skeleton assembly (Figure 4-28), and an external connection with the left training handle assembly (Figure 4-43). The training handle stuffing box body gasket (10) is placed between the stuffing box body flange and the

 
159

counterbored recess seat. The stuffing box body flange is secured to the gasket and recess seat with six lockscrews (1, Figure 4-36). The rubber gasket maintains the hermetical seal of this assembly along with the flax packing under spring pressure.

j. Right training handle packing gland assembly. The right training handle packing gland assembly (26) is assembled to the right side of the eyepiece box, in a bored hole and counterbored recess seat. Refer to the left training handle packing gland assembly, as it is identical, and is secured in similar manner.

k. Angular alignment key. The angular alignment key (1) is made of monel metal. It has a nominal length, thickness, and width, with the upper and lower corners rounded off. It is secured in the machined recess keyway in the front centerline of the upper alignment support section of the eyepiece box (11) with two lockscrews (4). This key is a sliding fit in the inside keyway of the lower part of the outer tube (2, Figure 4-15). It provides the angular maintenance of the emerging light rays within the prescribed tolerance of five minutes of arc with the entering light rays.

l. Angular alignment determination of the eyepiece box and eyepiece skeleton. The correct location of the two inserted dowel pins (36, Figure 4-28) of the eyepiece skeleton (42, Figure, 4-28) large shoulder flange and their proper engagement in reamed dowel pin holes of the eyepiece box are determined as follows: This alignment is first determined by placing a false plate in the rail bearing slots in the inner side walls of the eyepiece skeleton, while the eyepiece box is being held to the large shoulder flange of the eyepiece skeleton. A depth micrometer is used to measure the distance from the counterbored recess seat of the eyepiece window assembly opening. The depth micrometer provides an accurate measuring device to determine the necessary rotation of the eyepiece box for obtaining equal distance to the false plate on opposite sides of the centerline. The reamed dowel pin holes are spotted in the eyepiece box, from the previously drilled holes of the large shoulder flange in the eyepiece skeleton. Thus permanent angular alignment is maintained for future disassembly and

  reassembly of the eyepiece box to the eyepiece skeleton.

m. Eyepiece skeleton centering screw. The eyepiece skeleton centering screw (12) is made of phosphor bronze and is 1.750 inches in length. It is provided with a smooth stem section, which is a sliding fit into a reamed hole in the base of the eyepiece skeleton. It stabilizes the lower part of the eyepiece skeleton (42, Figure 4-28) in the eyepiece box (11). The threaded periphery section of the centering screw engages into a tapped section in the eyepiece box, in the upper part of the inner wall of the base. The short shoulder carries the lead washer (13) against the large shoulder of the centering screw, and fits in the small counterbored recess, while the large shoulder carries the lead washer against the large counterbored recess seat in the base, of the eyepiece box. The lead washer maintains the hermetical seal of this opening. The head of the centering screw is slotted for the insertion of a screwdriver.

n. Name plate. The name plate (20) is made of nominal thickness and is of rectangular shape. It is secured to a cast recess of similar contour to the eyepiece box (11). The name plate is located in the cast recess in the rear wall of the eyepiece box above the horizontal optical centerline. It is secured with four lockscrews (3) which are inserted into clearance holes in the name plate and screwed into shallow tapped holes in the wall of the cast recess. Refer to Chapter 1, Section 1A6 for data inscribed on the name plate.

o. Anchor screw pins. The four anchor screw pins (19) are made of corrosion resisting steel and are 0.641 inch in length. Two anchor screw pins are provided in the two raised bosses of the front flat cast section below the eyepiece window assembly of the eyepiece box (11), while the other two are provided in the rear flat cast section in similar manner. Shallow tapped holes are provided in each raised boss with an appropriate center distance between bosses to receive the threaded periphery section of the two anchor screw pins. The upper part of each pin has an undercut section to allow the spring tension of the finger grip levers (1 and 2, Figure 4-41) of the variable density polaroid assembly to snap into the locked

 
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position. The outer shoulder of the undercut section retains the finger grip levers, a metal to metal fit on the bosses. The large shoulder   section has two opposite sawed slots 180 degrees apart, for the attachment of a special wrench for disassembly or reassembly.
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