LUBRICATION.

TM 55-4920-201-14

qualified instrument repair shop or return to

5-21. Addition of Damping Oil to Balancing

manufacturer for overhaul.

Arbors. Should excessive oscillation of balance

indications develop due to inadvertent loss of arbor

5-18. Optical Alignment System (7HEL056 Kit).

dash-pot oil, or should change of dash-pot oil or oil

Local repair of this unit is not recommended. If

level become necessary, proceed as follows:

malfunction of the scope support assembly or the

scopes should occur, return the complete 7HEL056

a. Balancing arbor, part no. 2259 (7A050

kit to the manufacturer for overhaul.

kit). Remove the two filler hole screws located in

knurled section of arbor and, with arbor in upright

5.19. LUBRICATION.

position, fill arbor to filler hole level with OE/HDO-

5-20. General. Immediately prior to each ap-

50 oil, Military Specification MIL-L-2104. (See

plication of kit components, carefully wipe all

figure 5-1). Use only the specified oil and viscosity

external and internal mating surfaces of arbors and

in this arbor assembly. To insure that small air

adapter components with lint-free cloth or paper

spaces inside arbor are completely filled, repeat this

cleanring tissue to remove old oil and ac-

operation two or three timer at intervals of 10

cumulations of fine dust or other foreign matter.

minutes. To drain arbor dash-pot chamber, lay

Seizing of cones, bushings, adapterr, etc., on

arbor on its side and allow oil to drain through one

balance arbors is almost invariably caused by fine

of the open filler screw holes. Always reinstall filler

particles of dirt or other foreign matter. Thoroughly

hole screws following completion of draining or

cleaned mating surfaces will facilitate installation

refilling operation.

of close-fitting parts and will help insure

satisfactory balance.

Change 2 5-3