Bandsaw and the PowerPro

wurlitzerwilly · Post by **wurlitzerwilly** » Sat Oct 15, 2011 5:12 pm

dusty wrote:There are some other coupler solutions, that I have never tried or even laid hands on, but I had purchased two new couplers from Shopsmith that are now in-service. For use with the PowerPro, I have no experience there so I have no ideas of value to offer.

Sorry, I misunderstood. I thought you lost the couplers due to PowerPro.

I've never lost a coupler or had a hub come loose with the standard motor.

Anyone else have an idea on a Power Pro solution, I'd be pleased to hear it.

wurlitzerwilly · Post by **wurlitzerwilly** » Sat Oct 15, 2011 5:19 pm

michaeltoc wrote:Many of us have had issues with the band saw making banging noises with the PowerPro. After talking with Wes and adjusting the settings it got better, but not good enough. suspecting that backlash is causing the PowerPro to jump around, I did an experiment.

I tried resawing a piece of 2x6, and confirmed the noise. In place of the SPT coupler I used a clamp-style rigid shaft coupling. This has the added benefit in that I could get the bandsaw and the headstock perfectly aligned. I slipped on the coupler, locked down the headstock, then loosened the SPT lock and the setscrews that lock the bandsaw tubes. I tightened the shaft coupler while "wiggling" the bandsaw so that it would align perfectly.

I tested the setup and I could resaw without any banging noise! Suspecting that misalignment may be the cause, I reinstalled the SS power coupler, and the banging came back. I put the rigid coupler back on, and the banging stopped.

I also tried a Ruland curved jaw-type coupling with a hytrel spider (for high torque). I did not use a standard Lovejoy, as they have some degree of backlash, and the Ruland claims that it is "zero-backlash". It worked like a charm!

I would happily buy a Ruland coupling, but can't immediately see which one would be suitable. Do you have a part number or catalog page, please?

billmayo · Post by **billmayo** » Sat Oct 15, 2011 6:53 pm

The DVR motor is only a recent concept converted into a much improved motor. I believe the sensitivity of the constrolling circuits to maintain a specific speed under varing load conditions (PowerPro) causes most of the current stress/hammering effects. This is an area where improvements are still on-going. Teknatool along with Shopsmith will solve these problems as more uses for the DVR motor are incorporated into existing and new products.

The original Nova DVR lathe used a direct drive motor with no belts involved. Therefore, really tight belts are needed on the PowerPro to help stablize the feedback/compensation circuits. The complexity of these electronics is many times greater than for a 3-ph electric motor.

For me, I have found the following web site to have many hours of reading on various related topics: http://www.ece.umn.edu/users/riaz/index.htm

Also, for anyone interested, there is many references available on this recent product. Google on Switched Reluctance Motor.

JPG40504 wrote:The DVR motor creates extreme torque pulses and as such will indeed put the entire drive train under a stress 'test'.

If all is tightly joined, I do not think a catastrophe will eventually occur.

That sloppy plastic forgiving shopsmith coupler on the other hand does not meet that new criteria.

I think an 'improved' quick on/off coupler design is indicated!!!!!!!

Although a 'new' unused current design coupler may 'work', it will degenerate eventually IMHO.

michaeltoc · Post by **michaeltoc** » Sat Oct 15, 2011 7:45 pm

wurlitzerwilly wrote: Michael, what coupler did you find that eventually worked well?

Ruland JC26 with a 5/8" bore. Grainger #3HPX3 (you need 2 of these), and a hytrel spider, Grainger #3HRF1.

It's a tight fit, so it does not slide on and off as easily as the SS power coupler, and the 3 jaws are exposed on the headstock, which could pose a safety hazard. I'm thinking of making some type of cover or shield.

michaeltoc · Post by **michaeltoc** » Sat Oct 15, 2011 7:51 pm

dusty wrote: The force that you were willing to put on the couplers by using clamps was probably not enough to affect a change in gripping force applied to the hubs. That small circle of nylon just did not collapse much under the pressure of that clamp.

I thought that there would have been enough gripping force, as I could not slide the headstock away with the clamps applied.

Although the TriStateAuto coupler is cheaper than the Ruland coupler that I used, it is still plastic or nylon and not "zero-backlash", so I would be reluctant to try it.

michaeltoc · Post by **michaeltoc** » Sat Oct 15, 2011 7:57 pm

billmayo wrote:Therefore, really tight belts are needed on the PowerPro to help stablize the feedback/compensation circuits.

Thanks, Bill. There have been a number of recents posts referencing that you need tight belts. I would suspect mine are not tight enough, so I'll need to do another test with the SS coupler after tightening the belt.

wurlitzerwilly · Post by **wurlitzerwilly** » Sat Oct 15, 2011 8:05 pm

michaeltoc wrote:Ruland JC26 with a 5/8" bore. Grainger #3HPX3 (you need 2 of these), and a hytrel spider, Grainger #3HRF1.

It's a tight fit, so it does not slide on and off as easily as the SS power coupler, and the 3 jaws are exposed on the headstock, which could pose a safety hazard. I'm thinking of making some type of cover or shield.

Thanks for that, I may well buy a set.

One reason for less backlash may be the length of the overall coupling. Adding their figures, it looks like the entire coupling is under 2". I didn't look, but I presume the headstock will sit right under the bandsaw table with clearance. I would probably have to remove the existing plastic shield over the headstock hub.

michaeltoc · Post by **michaeltoc** » Sat Oct 15, 2011 8:36 pm

wurlitzerwilly wrote: One reason for less backlash may be the length of the overall coupling. Adding their figures, it looks like the entire coupling is under 2". I didn't look, but I presume the headstock will sit right under the bandsaw table with clearance. I would probably have to remove the existing plastic shield over the headstock hub.

The length does not necessarily affect the backlash - it is the coupling design.

Yes, the assembly is 2" and the headstock sits just under the table. I do not have a plastic shield - perhaps that was a later addition?

wurlitzerwilly · Post by **wurlitzerwilly** » Sat Oct 15, 2011 8:45 pm

michaeltoc wrote:The length does not necessarily affect the backlash - it is the coupling design.

Yes, the assembly is 2" and the headstock sits just under the table. I do not have a plastic shield - perhaps that was a later addition?

It was only a guess about the length affecting it.

The plastic shield was offered a few years back and I retro-fitted mine, as the original headstock was made in 1993.

JPG · Post by **JPG** » Sat Oct 15, 2011 8:50 pm

wurlitzerwilly wrote:It was only a guess about the length affecting it.

The plastic shield was offered a few years back and I retro-fitted mine, as the original headstock was made in 1993.

Anybody ever get injured by an exposed upper shaft with or without a hub?

I think that shield is a solution searching for a reason to exist! Once you put the coupler on it is 'exposed' again!