Optical Trammeling

TM 55-4920-201-14

rotor blade and snapping spring-loaded roller

support assembly setscrew (4) with 1/8-inch hex

across trailing edge of rotor blade. (See views B and

wrench (8, figure 1-13).

D). Gage pins should align with inboard edge of

NOTE

blade tip cap, with body of target assembly parallel

Zero position of scope support index plate

to inboard edge of blade tip cap.

(10, figure 4-38) lies directly above scope

k. Remove scope (7) from scope wheel (8).

support assembly setscrew (4). If scope

Install scope (7), part no. 2421 (7HEL056 kit).

support index pin (5) is not in this position,

and adjust eyepiece to bring cross-hairs into

lift index pin and rotate scope support

sharpest focus. Tilt scope wheel (8) in vertical

assembly on index plate until index pin can

plane to align cross-hairs on body of target

be engaged in index plate directly over

assembly (17) at rotor bade tip. Shift blade tip

scope support assembly setscrew. (See view

chordwise by gentle hand tapping as required to

A).

bring alignment target (18) into visual field of

e. Apply light grease or heavy oil to surface of

scope. Slide scope (7) in scope wheel (8) to bring

rotor hub upper cone seat, and install balancing

alignment target (18) into sharpest focus, and lock

arbor (11) downward through rotor hub and

scope in this position with scope lock screw (9).

fixture assembly (15) pilot hole, seating lower end

Bring blade into final precise alignment by hand

of scope support assembly (3) firmly into rotor hub

tapping of blade tip and/or tilt scope wheel

top cone. Install bushing (12), knurled hub up-

slightly to bring point of intersection of scope cross-

ward, over lower end of arbor, seating bushing

hairs (19) within innermost circle of alignment

against bottom surface of fixture assembly (15). Do

target (18).

not lock bushing setscrew.

NOTE

f. Install spacers (13) over lower end of arbor,

To prevent faulty indications, do not

and install hand wheel (14) in bottom end of arbor.

disturb position of this blade during

Do not fully tighten hand wheel at this time.

remainder of trammeling and balance

g. Install scope (7), part no. 2420 (7HEL056

checking operation.

kit), through scope wheel (8). Adjust scope eye-

l. Adjust damper assembly between the two

piece (6) to bring scope cross-hairs into sharpest

trammeled blades so that, in neutral position, its

focus. Tilt scope wheel (8) and rotate scope

attaching bolt hole aligns precisely with attaching

support ant! arbor assembly to align intersection of

bracket hole of the trammeled blade. Install

scope cross-hairs on exact center of crossed-line

damper bolt, with original washers, being careful

intersection on top surface of any one of the four

not to disturb position of either trammeled blade.

rotor lag hinge caps. (See view A). Slide scope (7)

m. Repeat steps h, i, j, k, and l to align

in scope wheel (8) to bring this target into sharpest

remaining two rotor blades, and install damper

focus, and lock scope in this position with scope

bolts.

lock screw (9). Recheck alignment of scope cross-

hair intersection on intersection of hinge cap

n. Repeat steps h, i, j, and k, recheck align-

crossed lines, and adjust as required.

ment of all rotor blades to make certain no shift has

occurred during trammeling operations or in-

h. Tighten hand wheel (14) in bottom end of

stallation of damper bolts.

arbor to clamp spacers (13), fixture assembly (15)

hub, rotor hub, and scope support assembly (3)

NOTE

firmly together.

Blades must remain in their trammeled

NOTE

positions throughout subsequent balancing

To prevent misalignement of scope with

operation. If position of blades is inad-

rotor huh, it is essential that no rotation

vertently disturbed, repeat entire tram-

between these parts be permitted during

meling operation before proceeding with

the remainder of the blade alignment

balance check.

operation.

o. Remove scope (7) from scope wheel 13).

i. Recheck alignment of cross-hairs on target.

Remove hand wheel (14), spacers (13), and

If necessary, loosen hand wheel (14) to adjust

bushing (12). Remove balancing arbor (11) and

cross-hair alignment; always be sure hand wheel is

scope support assembly (3) from fixture assembly

firmly tightened before proceeding.

(15) and rotor hub. Remove scope support

i. Install target assembly (17) on tip of rotor

assembly (3) from balancing arbor (11). Remove

blade in line with scope by holding two target

target assembly (17) from rotor blade.

assembly gage pins (16) across leading edge of

4-61