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MMD > Archives > December 1998 > 1998.12.29 > 08Prev  Next

Replacing Wind Motor Bushings
By Bruce Clark

Matthew Caulfield seems to have problems with his wind motor, and it
may be time for a tune-up.

Matthew says:  "The motor now lopes badly, and I think that the problem
is mostly due to slop in the crankshaft and the five connecting rods
driving it.  The motor seems pretty tight: it is pretty impossible to
turn it in the reverse direction".

The bushings on the crankshaft may not be the problem, but most likely
should be re-bushed.  If you are not sure you can do the job, better
take it to an expert or someone experienced.  Or you may attempt the
following if you have confidence.

Have you checked the motor timing?  Do all the slide valves uncover
their ports using equal distance in their travel?  Find the exact
center of the valve travel.  Be certain that the valve moves exactly
the same distance up, as it does from down from the center position.
If not, adjust them either by slight bending of *valve rods* that move
the valves.  (Some have a adjustable leather nuts on threaded wire.)

Check the motor pneumatics for "hinge bind": that is, perhaps someone
recovered the motor and covered the hinge end with the pneumatic in an
open position.  To check this, remove the flanges on the back of the
air motor, and see that the pneumatics are not binding at the hinge
end, or that someone did not make one pneumatic a slightly different
size.  Each should open and close fully without binding.

While the motor is apart, check for leakage.  Put masking tape over
*all* the holes that are covered by the valve sliders.  Test for
leakage...both on the nipple and each individual pneumatic.  If there
is leakage on the supply nipple, one can pour in about a cup of shellac
down into the supply nipple (be sure to keep masking tape tightly over
the valve ports), rotate the motor to distribute liquid shellac within
it, and pour it back out and allow to drain back into the can of

This sounds crazy, but it can be done and seals up any porous or
leaking places within the internal parts of the air motor.  Allow a
couple of days to dry.  Wash the valve surfaces with alcohol, and
resurface both mating surfaces, and rub in very fine graphite.

To re-bush:  First check to see if there is any sloppy lost motion
of the bushings.  If that is the case, the old bushed pieces on the
crankshaft *can* be removed.  It is a matter of carefully removing
the flanges on the back of the air motor pneumatics, and slide valves,
and maneuvering them over their twists and turns.  I caution you to
keep them in order (number them) and not get them mixed up.  Once they
are removed, polish the crankshaft with "never-dull" until it has a
brilliant shine, and is very smooth.  (This will facilitate putting the
newly re-bushed parts back in place.)  Mark one end of the crankshaft
with an identifying mark so you will not get it placed backwards.
By all means do not bend the crankshaft!

Next, soak the wooden pieces in lacquer thinner for two days, to remove
any oil or grease.  Remove the old bushings, and using *bushing cloth*
(not ordinary felt) cut a tapered piece of paper (thin pie shape) and
feed the point into the cleaned out bushing hole to obtain a correct
measurement.  (Mark the paper with a pencil line where the taper meets.)

*Tear* the bushing cloth to size -- it is necessary to have a torn edge
that meets itself.  Cut a similar tapered pointed piece of bushing felt
and feed the pointed end into the cleaned out area, until the torn
edges meet within the hole to be bushed.  Back up, place a small amount
of hot glue on the backed up piece, and feed it back into the bushing
hole, leaving a slight overhang on both sides.

Hold the bushing in place ( I use the handle of a small tapered paint
brush)  until glue is dry.  Next, work quite a bit of powdered graph-
ite into the felt surface that will be touching the crankshaft.  Feed
the bushed pieces back on the crankshaft, in proper order, but at a
high point where the bushed piece will not finally rest, take an X-acto
knife, and place on the overhang of the bushing felt, and rotate the
wooden piece until the excess felt bushing is sliced off.  Move the
piece forward to it's correct position.

Bruce Clark

(Message sent Tue 29 Dec 1998, 13:20:54 GMT, from time zone GMT-0500.)

Key Words in Subject:  Bushings, Motor, Replacing, Wind

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