b. Inspection and Repair.
(1) Cylinder Compression Test.
(a) Place the cylinder upside down on a
bench and seal off the air port into the cylinder.
(b) Remove the rings from the piston,
then drop the piston into the cylinder. The piston
should move slowly into the cylinder. If the
piston falls into the cylinder it is defective and
must be replaced.
(2) Piston, Ring Gap.
(a) Place one ring at a time in cylinder,
making sure it is not tilted.
(b) Use a feeler gage and measure the ring
cap. If the gap exceeds .015 in. it is defective and
must be replaced.
(c) Each new ring must also pass the
above test. If the ring will not turn over in the
cylinder, file the gap slightly so the ring will turn
over.
NOTE
A close cap clearance in air motors
presents no problem in air motors since
there is no expansion of parts due to heat.
(3) Connecting Rod Bushing. Inspect the
connecting rod retaining rings for cracks or
breaks. Replace rings if cracked.
(4) Rotary Valve Drive Pins.
(a) Check, the th ree drive pins on the
crankshaft end of the rotary valve for a snug fit
into the holes of the crankshaft.
TM 5-3820-241-34
(b) If the holes in the crankshaft are
enlarged, the crankshaft must be replaced. The
tramming motor cannot develop its rated horse-
power if the porting in the rotary valve does not
match the timing of the piston strokes.
(5) Oil Seals and Bearings.
(a) Inspect the bearings for excessive
wear. Replace defective bearings.
(b) Discard and replace all oil seals.
(6) Rotary Value. Check the clearance
between the rotary valve and the valve bushing.
When wear exceeds .010 inch, replace the housing
and bushing.
6-4. Tramming
Motor Reassembly and In-
stallation
a. Reassembly.
(1) Coat all parts with a light film of oil
before reassembly.
(2) Reassemble the tramming motor in the
reverse of numerical sequence as illustrated in
figure 6-1.
(3) Install the connecting rod retaining rings
(26) and (30) with the chamfered side next to the
connecting rod (27).
b. Installation.
(1) Install the tramming motor (para 2-14).
(2) Refer to LO 5-3820-241-12 and lubricate
the rock drill.
Section II.
TRAMMING TRANSMISSION,
B R A K E A N D C R A W L E R D R I V E
6-5. General
The tramming motor brake assembly is mounted
between the tramming motor and the trans-
mission gear case. The brake is a deadman type
and when the tramming motor is off. The trans-
mission is a planetary type with a 35:1 gear
reduction.
6-6. Tramming Transmission, Brake and
Crawler Drive Removal and Disassembly
a. Removal.
(1) Remove the tramming motor (para 2-13).
(2) Remove the tramming transmission and
brake housing (para 2-17).
b. Disassembly.
(1) Tramming Brake.
(a) Disassemble the tramming trans-
mission brake in a numerical sequence as il-
lustrated in figure 6-2.
6 - 3
