Arthur,
This was just on the caut list:
This is from Wessell, Nickel & Gross.
I understand the new cloth free bushing parts will be available very soon.
ES
WESSELL, NICKEL & GROSS
Procedure for cloth bushing replacement in WNG action parts.
A technician may desire to re pin a WNG cloth bushing to
achieve a friction which differs from that found. In the event that a
bushing is dislodged when repining the following procedure will
ensure that the integrity of our bushing design is maintained. Before
replacing any center pins however we strongly recommend checking the
calibration of your gram gauge. (See separate documentation for this
procedure.)
While extracting the center pin or while inserting a new
pin it is possible to inadvertently dislodge a cloth bushing from one
fork. Careful technique and an understanding of WNG bushings can
largely avert this. The cloth of WNG bushings is originally held in
place by mechanical action only. No adhesive is ever used. Instead
the holes in which the bushings are formed are threaded and during
the bushing formation process the cloth fibers move into the threads
thus locking the bushing in place. When a center pin is finally
inserted it is impossible for the bushing to move out of the hole.
This method of securing a bushing is superior to gluing as adhesive
will never be able to contaminate the cloth, uneven application of
adhesive is avoided, and re bushing is simplified.
The following is a relatively simple procedure which will
ensure features inherent in our bushings are maintained.
PIN REPLACEMENT
Remove center pin.
To avoid dislodging a bushing carefully position the
plunger directly on the center pin. Check that the plunger is not
pushing on the bushing cloth.
Insert new pin.
Push the pin through in several short successive strokes
rather than one push all the way through. This will allow the pin and
the parts to realign with the tool each time pressure is removed and
increase the likelihood that the pin will follow the path of the
formed bushing and avoid pushing out the second bushing.
BUSHING REPLACEMENT
Remove bushings.
Once a bushing is dislodged it will be necessary to remove both
bushings from the forks. Since the bushings are not glued in this it
done quite easily.
Pull cloth to form bushings.
Pull a piece of 7 mm wide and 1.3 mm thick bushing cloth through both
holes in the forks. Several flanges can be strung together in this
way for example. Pull the cloth in such a way that the "seam" formed
is not in line with the direction of thrust the pin will experience.
You can rotate the bushing at each fork by grasping the cloth with a
needle nosed pliers and rotating to the desired angle.
Trim cloth.
Trim the cloth so there is approximately 2 mm protruding from one
side of the part. The opposite side may be cut flush with the part if
desired. The area between the forks is not trimmed.
Insert sizing pin.
Insert a pin which is 1/2 to 1 pin size smaller than the final pin
size desired. Insert from the side with the 2 mm of cloth protruding.
Since a higher friction is desired in the balancier bushing use a
sizing pin 2 pin sizes smaller than the final pin size desired. While
inserting, the pin will tend to follow the path of least resistance
which will be the area where the bushing edges come together. Slight
pressure away from this "seam" while inserting will prevent an off
center pin in the second bushing. Check visually that the pin is
centered on both sides of the flange, re pinning when necessary.
Treat bushing with alcohol and water.
Create a solution containing 20% denatured alcohol in water. Soak the
bushing and center pin in this solution for several minutes to ensure
the cloth is fully saturated. The whole part may be submerged to
facilitate this.
Dry bushing cloth.
Dry in a low temperature oven at 90 to 110 degrees F for 4 hours. The
drying time is influenced by ambient humidity but the time and
temperature given will ensure the cloth is dry in any environmental
conditions.
Trim cloth flush.
Remove the sizing pin and trim the cloth flush with the part on all
sides of the forks using a new razor.
Fit final pin.
At this point you can test the fit of the desired final pin size in
the flange without assembling the parts yet. Insert the pin and hold
an open area of the pin with a needle nose pliers. Use a gram gauge
to measure the friction. Use incrementally larger broaches to enlarge
the hole until the desired friction is achieved. Use only smooth
broaches. Avoid broaches which have a knurled section which is
usually near the handle.
Note: Typical center pins can very in diameter enough within a given
size to affect the friction reading. Therefore it is recommended to
size a bushing for the actual final pin used. Manufacturers may also
inadvertently allow some pins to fall into the wrong batch. Pins may
be measured with a micrometer to verify diameter. Calipers usually
are not precise enough. Take measurements along the length of a pin
to check for consistency and at various axis to check for out of
roundness.
Assemble parts.
Assemble the parts using the final pin. Check final friction and re
pin if necessary following the above cautions.
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