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shimpo wheel problems

updated mon 20 apr 98

 

Sue Hintz on thu 16 apr 98

I'm having problems with my approx. 20 year old, not used much until
recently, wheel. Can't seem to figure out the problem and have
taken it apart several times.

The wheel doesn't want to spin and once it starts going it stops
easily with pressure. It has gotten progressively worse. If I let
it spin for a while it seems to warm up and do better. By the end
of the day it does fine. If I put it on a fast speed quickly it
doesn't engage and won't go. Any ideas of what the problem could be
or how to adjust it?

Vince Pitelka on sun 19 apr 98

>I'm having problems with my approx. 20 year old, not used much until
>recently, wheel. Can't seem to figure out the problem and have
>taken it apart several times.

Sue -
Since your wheel is 20 years old, it is most likely an RK-2. There are
several possible reasons for the problem. If the rubber friction ring on
the jackshaft is old it may have shrunk and hardened a bit, in which case
you simply need to replace it. If the rubber ring is still resilient, then
you need to adjust the position of the motor so that the drive cone applies
more pressure against the friction ring. You only want to adjust it up very
slightly, as a small adjustment can make a big difference. If you adjust it
up too much, it will be difficult to engage the point of the drive cone with
the rubber ring.

The fact that your wheel can be stopped easily is an indication that one of
the two above explanations is accurate. And when it warms the motor shaft
expands, lengthening very slightly, which increases the pressure of the cone
against the ring. But I am surprised that there is so much resistance to
movement in the jackshaft and wheelhead. With the motor disengaged
completely, does the wheelhead spin very easily? If not, it is possible
that the drive belt(s) have stiffened from lack of use over the years. They
might loosen up after you increase the contact pressure between the drive
cone and the rubber ring. If not, replace them.

I love the good old mechanical-variable-speed shimpos, but I must admit that
the RK-2 is their worst design. That tilting motor assembly is nothing but
trouble, compared to the previous RK-1, with its horizontal sliding motor
assembly. It is far easier to adjust pressure of cone against ring on the
RK-1, and the pedal stays wherever you put it when you remove your foot.
Good luck -
- Vince

Vince Pitelka - vpitelka@DeKalb.net
Home 615/597-5376, work 615/597-6801, fax 615/597-6803
Appalachian Center for Crafts
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166