Service Note #2           Author:  Tom Droege            Date: 011121

Replacing the chamois in the RA drive.

1) Remove the four screws from the cover.  It now slides off.

2) Remove the four screws holding the grooved block to the carriage.  It 
cannot be removed since there is not enough clearance between the block and 
the bearing bars.

     [ Note added by MWR: I was able to remove the block from  ]
     [ the RA rod at this point, without the additional step 3 ]
     [ described below.  I may have pushed things a little too ]
     [ much in order to gain the necessary clearance, but no   ]
     [ sign of trouble so far...                               ]

3) Remove two screws from one end of the carriage bar.  The bar can now be 
pushed back and the block removed.

4) Clean off the glue and the old chamois.  A good scrub with alcohol or 
whatever is your favorite to make epoxy stick.

5) Cut a strip of chamois and line the block.  I use a light coat of 5 
minute epoxy to hold it  in place.  A 1/4" screw will help hold it in place 
while drying.  Try to keep the glue from the working side of the 
groove.  Note the thickness of a chamois that you buy in the automotive 
section of your hardware store will vary.  Choose the thickness that seems 
right to you.  The chamois should pack the slot tight with a 1/4" screw in 
it.  But not so tight that it cannot turn.

6)  Cut two smaller strips of chamois that are slightly narrower than the 
groove in the block.  Stack them centered down the cover.  Glue to the 
cover and the second piece to the first piece.  Again try to keep the glue 
from the working side.

7) At this point I assemble the cover over the 1/4" screw and tighten the 
screws to see if There is a good fit.  One should be just able to turn the 
screw.  It will loosen up with exercise later.

8) When the epoxy dries, apply light machine oil or leather conditioner to 
the chamois.  I use something called Mink Oil I got in a sporting goods 
store.  I think this used to be called Neatsfoot oil, but they may not be 
the same thing.  Or use light machine oil.

9) Reverse the process above to reinstall.  Loosely tighten the cover screws.

10) Now start the exercise RA routine.  From the first menu, 2) Test, 
8)TstRA, 5)RAEx  Keep tightening the screws until the screw can just turn 
in the block.  As it runs, keep tightening the screws.  I can usually get 
the cover completely bolted down and still have enough power to move the 
carriage.

11)  I find that if I do this, the carriage can be moved by the RA drive 
and will stall the drive motor if it goes to a limit.  This is the ideal 
situation.  Once the drive screw starts slipping in the
drive nut it quickly reams out the chamois.

This is one operation where you will quickly appreciate the ss cap screws 
that I use in the Mark IV construction.  I was able to install the cover 
screws completely blind.  I just stood them on the end of an allen wrench 
and felt them into place.  This was written as I went through all the steps.