Shopsmith Forums

My son-in-law has used his bandsaw quite a bit with his Power Pro, without any problem. When we first ran his PP with the 12" disk, there was vibration, however, a call to Wes quickly resolved this problem.

I have a power station that I run my bandsaw on. However I have used the PP in saw mode with the jointer coupled on the end without any vibration or noise.

These are great comments here. It may be that the tightness of the coupler, and the alignment with the SPT, may be critical factors with the Power Pro. This may be the reason why the factory cannot duplicate some of the porblems.

Charlese and others;
I had a rattling sound coming from my PP headstock for awhile and could not get it figured out and it was driving me nuts. (OK more nuts) It sounded like someone left a ring keys inside the headstock. I was making a bunch of toys for the Toys for Tots campaign so I ignored the rattle until I finished. THEN I decided to find the culprit.
I went over that thing with a mechanics stethoscope and found that the output shaft couplers were the culprits. The setscrews in the hubs had worked loose and the couplers could be rocked back and forth on the output shaft. The rattling was heard even with the machine running with no load.
I have come to the conclusion that the DVR motor is constantly making corrections to the RPM when it is running regardless of the load conditions. The motor speeds up and then slows down and speeds up again and this causes the coupler to rock back and forth on the shaft due the inertia of the couplers. The changing speed keeps accelerating and slowing the output shafts causing the rattle and the movement. The changing speed is not apparent to the eye but tightening the set screws cured the problem. I put a small dab of silicone caulk on the screw threads and they have stayed tight.
Bill V

8iowa wrote: These are great comments here. It may be that the tightness of the coupler, and the alignment with the SPT, may be critical factors with the Power Pro. This may be the reason why the factory cannot duplicate some of the problems.

wa2crk wrote: I have come to the conclusion that the DVR motor is constantly making corrections to the RPM when it is running regardless of the load conditions. The motor speeds up and then slows down and speeds up again and this causes the coupler to rock back and forth on the shaft due the inertia of the couplers. The changing speed keeps accelerating and slowing the output shafts causing the rattle and the movement. The changing speed is not apparent to the eye but tightening the set screws cured the problem. I put a small dab of silicone caulk on the screw threads and they have stayed tight.
Bill V

These two opinions are in my opinion - FACT!!
IMO this is exactly what was/is happening! I believe we have diagnosed the major problem. The PowerPro is a wonderful headstock that has a couple of brand new quirks the old headstock didn't have.

I would like to underline these machine requirements when using a bandsaw]alignment of hubs[/U], b)hub tightness and c)a snug fitting coupler.

The only step to yet be investigated is - can a computer fix be found that will not compromise other actions of the PowerPro.

Charlese;
Just read your last post and the thought occurred to me that the constant "twitching" of the motor speed may be causing a high frequency vibration which can not be felt or heard but may be responsible for the set screws working loose.

Charlese may be on to something here.

Vibration, what causes unexpected vibration and the damage that can be done by unwanted vibration are interesting phenomena. As a Qualification Test Engineer I got many, many surprises while doing vibration and shock tests. Adding temperature change to the formula made it even more exciting.

Maybe what Shopsmith should do is ship a new power coupler along with every new PowerPro. After reading this, I certainly would not operate a PowerPro with an old power coupler.

I'd also think seriously about using loctite on those set screws in the power line.

With an original Mark V the applied torque is constant. The torque with a PowerPro, as it adjusts for load variations is a "constant variable". That plastic power coupler is taking a beating to say nothing of the noises that it might be creating.

dusty wrote:Charlese may be on to something here....
After reading this, I certainly would not operate a PowerPro with an old power coupler...I'd also think seriously about using loctite on those set screws in the power line...That plastic power coupler is taking a beating to say nothing of the noises that it might be creating.

I've been reading this thread with great interest and since I have zero experience in this department, I've stayed out of it. But sometimes a fresh set of eyes is useful.

Maybe part of the appropriate solution is to redesign the coupler/hub concept:
- Possibly a coupler with integrated hubs that allows for tighter fit that isn't too difficult too mount. Something that is more substantial but still allows for failure at this union in the even of a hard stop.
- The hubs could utilize the set screw design that has a nylon button integrated into the threads for locking, like the new set screw SS sent me for leveling the way tube tie bar.
- Potentially, SS could make hubs with larger splines that fit into a coupler with deeper and longer grooves to facilitate alignment. Maybe more of a sprocket than a hub.
- Possibly a simple alignment jig could be devised to ensure proper alignment with the SPT.
- If the hubs are always required for SPT on the auxiliary spindle, and if only SPTs are driven from it, SS could incorporate positive integration of the hub into the spindle and also ship the redesigned shafts with the PP. Although that would liekly create problems with replacing the bearings on the drive sleeve assembly.
- Maybe redesign the shaft and hub to be fitted with a key.

I've never seen a coupler in person so maybe I'm WAY out in left field here (I don't own any SPTs).

The present day 'situation' with the hubs/couplers is I am sure an unexpected dilemma.

The original intent of the coupler was to provide a 'sloppy' method of coupling the headstock to the spt's so as to accommodate slight mis-alignment caused by differing spt's having slightly varying dimensions. It is also a 'sacrificial' part in the event of more severe 'issues'.

The ideas and 'solutions' present in this thread are I think on target to the current power pro idiosyncrasies, but greatly diminish the 'original' ability to accommodate varying spt's when they reside in a common shop with 1 or more Mark 5/V/7/VII.

Therefore IMHO the control loop needs to be be less responsive to small changes in load/rpm! Or, at least more sluggish in its response.

I agree quick response is appropriate for the lathe application, but all these wildly varying load conditions presented by various shopsmith spt's requires a more sedate, time averaging correction.

Methinks part of the 'problem' is that there is no 'coast' ability in the motor/control design. i.e. if it is running 'slow' it immediately attempts to speed it up. If it is running fast it immediately attempts(and succeeds all too well) to slow it down.

Add to all this the speed sensor is internal to the headstock and 'upstream' from all the load varying 'slop/play/....' and only detects it indirectly and 'after' over correction has occurred.

Like Dalton, a voice 'far removed' from the fray!:)

We (those of us who are attempting to engineer this by proxy) must acknowledge that Shopsmith has not made a technical statement. We don't know that Shopsmith agrees that there is a problem that can be resolved by eliminating the drive line slop. In fact, Shopsmith may know the cause and solution. They certainly have no obligation, except maybe to PowerPro owners, to even discuss this.

I would love to get into the analysis clear up to my elbows....but I don't have a PowerPro.

dusty wrote:We (those of us who are attempting to engineer this by proxy) must acknowledge that Shopsmith has not made a technical statement. We don't know that Shopsmith agrees that there is a problem that can be resolved by eliminating the drive line slop. In fact, Shopsmith may know the cause and solution. They certainly have no obligation, except maybe to PowerPro owners, to even discuss this.

I would love to get into the analysis clear up to my elbows....but I don't have a PowerPro.

Truth be told, Tis far easier to hypothesize when one does not have reality acting like hungry alligators swimming below you!;)

I remember an interesting fact now!

We've heard of 2 Beta Testers for the PowerPro. One was Ed Reible. And Ed stated on a few occasions over the years that he didn't have/use a Shopsmith bandsaw. He had a different stand-alone BS.