John Rodgers on tue 15 apr 03
I have a wheel type project and wondered if anyone has ideas/info on how
to build a variable speed friction drive that works without the need for
a variable speed electric motor. I would like to be able to get
components from hardware stores, etc. if possible. Places like Grainger,
Home Depot, MSC, etc. I have a capacitor-start 1-HP electric motor that
turns at 3350 rpm. I want to gear that motor down through the fricion
drive so the final drive shaft speed is "0" rpm (disengaged and in
neutral) variable to 200 rpm max. when engaged.
Any input will be most appreciated.
Thanks,
John Rodgers
pdp1@EARTHLINK.NET on tue 15 apr 03
Hi John,
You could use your 1 Horse Motor to run a Hydraulic
pump...use the pump's output to run a Hydraulic
'Motor'...that'll give you the 0-whatever rpm...and use less
parts, and less complexity of them.
Phil
lv
----- Original Message -----
From: "John Rodgers"
To:
Sent: Tuesday, April 15, 2003 7:18 AM
Subject: Wheel Drive Systems
> I have a wheel type project and wondered if anyone has
ideas/info on how
> to build a variable speed friction drive that works
without the need for
> a variable speed electric motor. I would like to be able
to get
> components from hardware stores, etc. if possible. Places
like Grainger,
> Home Depot, MSC, etc. I have a capacitor-start 1-HP
electric motor that
> turns at 3350 rpm. I want to gear that motor down through
the fricion
> drive so the final drive shaft speed is "0" rpm
(disengaged and in
> neutral) variable to 200 rpm max. when engaged.
>
> Any input will be most appreciated.
>
> Thanks,
>
> John Rodgers
>
>
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Vince Pitelka on tue 15 apr 03
> I have a wheel type project and wondered if anyone has ideas/info on how
> to build a variable speed friction drive that works without the need for
> a variable speed electric motor. I would like to be able to get
> components from hardware stores, etc. if possible. Places like Grainger,
> Home Depot, MSC, etc. I have a capacitor-start 1-HP electric motor that
> turns at 3350 rpm. I want to gear that motor down through the fricion
> drive so the final drive shaft speed is "0" rpm (disengaged and in
> neutral) variable to 200 rpm max. when engaged.
John -
This has been discussed quite a bit in the past on Clayart. The problem
with most mechanical variable speed devices is that they do not deliver
constant torque through the speed range. For example, early powered
railroad speeders (small inspection cars and Snapper lawn mowers both use a
horzontal disk geared from the engine output, with a dip in the center of
the disk. On the driven member, a rubber-lined friction wheel sits over the
dip in the center, and there is no contact. A fork linkage can move the
friction wheel in either direction - one direction is for forwards, the
other is reverse. As the wheel moves from the dip in the center of the
driving disk, it contacts the disk surface, and turns slowly. As it is
moved further towards the rim, the speed increases. The problem is that at
the higher speeds there is very little torque. Thus this system does not
work for a pottery wheel.
Another common variable-speed drive system used in washers and dryers and
some yard equipment involves variable-width shivs, or pulleys. The spacing
between the pulley "walls" is controlled by a precision linkage, and as one
pulley widens, the other is narrowed. Thus the belt rides closer to the
axle on the wider pulley, and closer to the rim on the narrower pulley. As
the adjustment is changed, and the pulley widths change in opposite
proportion, the output speed changes accordingly. Unfortunately, the speed
range is inadequate for a pottery wheel. And in order for this system to
deliver the kind of torque required for a pottery wheel, it would have to be
extremely sturdy and high-precision, and thus would be prohibitively
expensive.
Another common variable speed device in industry is the hydraulic
hydrostatic transmission, a self-contained hydraulic pump and motor in one
unit, with a variable speed system built-in. I have heard of people
adapting small hydrostatic transmissions from lawn tractors to run pottery
wheels. The problem is that most of those devices are very noisy, and the
quieter ones are prohibitively expensive.
It would be possible to build a very efficient variable-speed power system
for a pottery wheel with a hydraulic motor, and a very small motor would
have plenty of power, and could be set up for whatever speed range you wish.
But once again, if such a system were set up to run just one pottery wheel,
the price would be prohibitively expensive in comparison to even the very
best commercially-made variable speed wheels available. On the other hand,
for a large production installation with multiple wheel stations, it would
be possible to install a single hydraulic power unit with a regulated flow
divider, and with individual controls on each wheel. Then it would become
economically feasible, and the noisy power unit could be in a remote
location.
But regarding the mechanical variable speed systems that are really
practical for pottery wheels, no one knows better than Shimpo. They are a
gigantic corporation, and their specialty is power transmission. They make
huge marine drive units, gear reducers, and all sorts of variable speed
transmissions. They are among the world's foremost experts in this field.
Except for the RK-2 with the curved drive cone, which sucks, their wheel
drive systems are brilliant. The original RK-1, with the flat cone, is a
wonderful system. If you posess a high level of knowledge and skill in
machine hardware, welding and fabrication, you can buy the drive cone and
rubber friction rings from Shimpo and build the rest yourself. That is the
ONLY homemade friction-drive variable speed wheel I have ever seen that
really works well. I know, because I built one around 1976, and it has been
working perfectly ever since.
Best wishes -
- Vince
Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University
1560 Craft Center Drive, Smithville TN 37166
Home - vpitelka@dtccom.net
615/597-5376
Office - wpitelka@tntech.edu
615/597-6801 x111, FAX 615/597-6803
http://iweb.tntech.edu/wpitelka/
Steve Mills on wed 16 apr 03
Dear John,
Many years ago I came across two or three wheels which had been built
using the differential gear from an automobile, these used the entire
back axle, with the nose piece (where the prop-shaft attaches) set
vertically and the throwing surface bolted to it. Drive was applied to
one side using a vee-belt from the motor to a road wheel (the brakes
were removed from that side). On the other side the handbrake mechanism
was retained, and operated by a foot pedal. As the principle of a
differential gear is the transfer of power along the path of least
resistance, speed was increased by pressure on the foot pedal operating
the brake. The reverse was achieved by a simple lever brake under the
wheel head. The disadvantage of this design was size, as it meant the
whole wheel was the width of a car! The advantage was cheapness as
virtually all the components required could be obtained for little money
from a scrap yard.
As there are now a number of vehicles available with independent rear
suspension, their differentials are much more compact and often have
disk brake assemblies attached to them. This would make a much smaller
unit, and it would not be difficult to replace one disk brake with a
pulley, and make a hydraulic pedal, the front of which operated the disk
brake, and the rear a pressure pad on the underside of the wheel head.
Just a thought!
Steve
Bath
UK
Date: Tue, 15 Apr 2003 08:18:18 -0600
From: John Rodgers
Subject: Wheel Drive Systems
I have a wheel type project and wondered if anyone has ideas/info on how
to build a variable speed friction drive that works without the need for
a variable speed electric motor.
--
Steve Mills
Bath
UK
Clay Art Information on thu 17 apr 03
John,
Good afternoon sir! The RK-10 and RK-2's don't have a controller. The
motor is AC, and we have a RX link, similar to a clutch that disengages
and engages. The Cone Drive system is patented by Shimpo, which is used
also in our drives division as transmission for golf carts.
Best regards,
Arthur Morales
Shimpo Ceramics
www.shimpoceramics.com
www.shimpoamerica.com
John Rodgers wrote:
> I have a wheel type project and wondered if anyone has ideas/info on how
> to build a variable speed friction drive that works without the need for
> a variable speed electric motor. I would like to be able to get
> components from hardware stores, etc. if possible. Places like Grainger,
> Home Depot, MSC, etc. I have a capacitor-start 1-HP electric motor that
> turns at 3350 rpm. I want to gear that motor down through the fricion
> drive so the final drive shaft speed is "0" rpm (disengaged and in
> neutral) variable to 200 rpm max. when engaged.
>
> Any input will be most appreciated.
>
> Thanks,
>
> John Rodgers
>
> ______________________________________________________________________________
>
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
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