Treadwall
®
Service Bulletin # 26 Replacing Pump Woodruff
Key
The Treadwall is controlled by a hydraulic braking mechanism that is located on the upper
right side of the machine.
To remove the sheet metal cover, slide off to the right. The cover fits under lugs welded to the
top of the frame, and the fit might be quite tight. Use a mallet or block of wood and hammer to
get it started if necessary.
Examine the hydraulic mechanism. From the top, looking down, you can see the chain-type
coupling that connects the pump to the large main shaft. If the Woodruff key is broken, the
Treadwall runs free without resistance. The coupling will turn, but the shaft of the pump will not
be turning when the wall is in motion. To replace the key it is necessary to remove the pump
unit.
There are two valves in the hydraulic assembly. Remove the arms from these two valves by
taking off the 3/8" nuts on the valve shafts and pulling the arms off. Be very careful not to drop
the nut from the front valve down the front leg of the frame. The large arm on the rear valve can
just be left hanging from it cords.
Loosen all the setscrews on the coupling (four in all) and with a 9-16" open end wrench,
remove the four bolts that mount the pump onto its angle-bracket. The lower rear bolt is the
hardest one to get out, but with an open end wrench it is not too bad.
Take off the pump unit and the chain-coupling.
Remove the remnants of the old Woodruff key from the pump shaft. Woodruff keys are
semi-circular. It may take a bit of effort to get the old key out - use a small screwdriver and
hammer if necessary.
When installing the new key, make sure that it is seated fully down into the slot in the shaft.
Use a soft mallet or a block of wood and hammer, but do not strike it directly with a hammer.
Slide the coupling back onto the pump shaft. If the key is not seated straight, The coupling may
be a very tight fit. Use your mallet to drive it on and alternately hit the side of the coupling right
over the keyway to straighten out the key. If it is too tight, it is ok to file a little off the top of the
key (not the sides) to make a better fit. If you must pry the coupling off the pump shaft, use two
large screwdrivers or wrenches on either side at once.
The coupling must be far enough onto the pump shaft so that only 1/8" of the Woodruff key is
showing outside of the coupling. If it is not put on this far, the new key may break again.
Once the coupling is on the pump, put it back on the machine. Line up the key on the large
shaft and slide on the coupling. Bolt on the pump, tightening the mounting bolts alternately so
that it will be in alignment. When the pump is properly aligned, the chain on the coupling will be
slightly loose all around. Re-align if necessary.
When replacing the valve levers, be very careful not to cross-thread the nuts onto the valve
shafts. The shafts have flat sides, and it takes a little patience to get the nuts on straight.
When the machine is operating properly, replace the pump cover, making sure it slides under
the mounting lugs.
Summary of Contents for Treadwall AM
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