Shopsmith Forums

Hi all,

Update:

Squeezed out some time today to work on this. The video was immensely helpful. Thanks Chad. That reverse table setup in Drill Press mode is ingenious. I had to take the lift assist off to allow the headstock and table to be a comfortable working height.

ok -

1) Got the main pulley and belt off. The key and key slot look good, nice and smooth. I don't think the slot is deformed at all. Took some juice to get the pulley off after removing the compression ring. However, there are a few nicks on the outside of the pulley (pix attached.). Are these bad enough to cause replacing the pulley? (Not sure the pix are showing in the actual post. They aren't in the preview.)(that didn't work, so here are links to two pix.) (Ok- I see the pix were too big to post. - another try here. That didn't work. I give up - here's the links.)

https://drive.google.com/file/d/1jETJ2f ... sp=sharing

https://drive.google.com/file/d/1QC653o ... sp=sharing

2) While I had this apart, I manually turned the upper shaft while the upper belt was still on. There was a scraping sound, not metal on metal, but perhaps rubber against metal. Had my wife turn it while I recorded this 28 second video. I can't see anything rubbing? What do you think? https://youtu.be/n4wsHGHK02A

thanks for all the help. I'm more hopeful than ever that I can fix this problem.

hal

If it was me, I'd probably use the pulley unless/until I found it caused excessive belt wear. I'd work it to smooth any burrs with a small file. I'm assuming that this may be a pricey part. I would also heed the loc-tite, or similar thread locking compound, advice for the setscrew.

It's difficult for the observer to know how loud that sound is on the video. If it was mine I'd probably try to determine the source before connecting up the motor. One thing you can do to make it easier for your wife to turn is put a sanding disc on that upper aux. spindle. I'd probably start by taking out the quill because typically it is overdue for waxing anyway. If noise is still present I'd first loosen the upper belt a little to see if that changed the noise, then loosen it enough that I could spin the upper and lower shafts independently. By this time you ought to know the source with reasonable certainty. I'm not sure that I would repair it, depends how loud it is and whether it is getting worse. It does not strike me as a typical bearing noise. I'm thinking belt noise, wondering what the forum thinks of using automotive belt dressing or perhaps something else (silicone spray?) on the belt. The upper PP belt is, I believe, identical to poly-V in conventional headstocks except probably harder to replace. As long as dressing is only applied to the outside, I'm thinking it should be okay. In fact I think I've used it before but on my gilmer belt.

- David

For the benefit of future forum users when those Google links no long work. The 3 key picture size parameters are maximum 2050 pixels wide x maximum 1180 pixels high x maximum 2 MB file size.

If you can I would pull that pulley and ask Shopsmith if they would replace it. The nicks on the grooves and splines will only add to premature failure and wear of the belts..
Bill V

JPG mentioned the rapid acceleration and deceleration of the motor by the speed control circuit as being the culprit for the loosening set screws. I noticed this almost 10 years ago when I got my Power Pro headstock. After a short period of use the hubs on the auxiliary shafts came loose and the machine sounded like someone was jingling a set of keys in their pocket. They came loose a second time and that's when I put them back with some blue Loctite and the problem was resolved.
Getting back to the rapid acceleration/deceleration I was wondering if some hysteresis could be programmed into the speed control electronics to soften the response and prevent the "slapping" effect that causes the screws to loosen.
hysteresis (A fancy word to indicate a slow response to an input signal) What say the engineers on the site.
Bill V

Maybe I missed the post somewhere, but is your Power Pro still under warranty by chance?

I ask that because the motor pulley looks to be made of cast steel (not cast iron which is softer). Cast steel is a hard material (and not as ductile; which means it won't just bend, but also and more likely break or crack). From my experience (I'm a machinist by trade) that pulley looks like it was dropped or something was dropped on it prior to installation at Shopsmith. Those "skips" in the peaks of the V's are not from just normal belt wear. It took something hard to chip off those peaks. The V's are machined in or ground in after the pulley is cast.

The only other explanation for those chipped V's is a bad casting with porosity (voids or pockets of air in the internal casting itself) which show up during machining or grinding (trust me, I know this all too well, unfortunately). If this is the case, I would have to believe the pulley would have been rejected by the manufacturer before it was ever shipped to Shopsmith, and if it had been shipped, then certainly Shopsmith would have rejected it prior to assembly.

I only bring this up because those deformed V's will, not might, but will cause premature belt wear no matter how well you deburr the sharp points and edges. The raw surface of the exposed casting material is very abrasive, just like sandpaper, and over time will eat at that belt like it's a hot supper.

Thank you BR549 - appreciate you getting these pix online. After loading them up several times, I thought I discovered the size limitations, reduced the images to meet the criteria and reloaded. I don't know how you made this work, but thank you.

br549 wrote:For the benefit of future forum users when those Google links no long work. The 3 key picture size parameters are maximum 2050 pixels wide x maximum 1180 pixels high x maximum 2 MB file size.

hal

wow Chad - always nice to have an expert explain what they see - thanks. Sadly I'm sure the headstock isn't under warranty (bought 2011), but CONFESSION here that probably caused the nicks on the pulley.

CONFESSION - embarrassing and probably cause of nicks. When I first opened up the headstock and got access to the motor pulley, while the belt was still on, I probed the setscrew hole with a small allen wrench. I got drawn away and came back later. I turned on the motor to see if I could better isolate the noise and didn't see the wrench still there. YIKES. At that time, the only thing I saw was the belt was part way off the pulley and the wrench was still in the hole. I got the wrench out and pried the belt back into place. It wasn't until reading your words about the pulley material that I remembered the wrench event.

Bill V and others who explained the damaged pulley would probably cause damage to the belt, thank you. That sure makes sense. For sure now, I'll replace the pulley. AND also use the blue Loctite on all the setscrews. Although the belt looks ok, I think I'll replace that too.

And David - I chuckled as you notice how hard it was for my wife to turn the spindle. Now that I feel more confident about taking apart some of the Power Pro headstock, I'll definitely take out the quill and wax it up.

Question on video belt tensioning @ 1 hr 36 minutes - he "loosens the top screw" and "tightens" the bottom set screw to "keep the adjusting bar aligned parallel. Seems to me you'd need to tighten or loosen both screws to keep it parallel. How does this work?

Calling SS to order the parts. Much thanks all. more to come as this progresses.

hal

Chad and Bill both make a good point that I didn't consider when I said I would run it and see how the belt did. Even though the OP said this was long since out of warranty, I believe there is a lifetime warranty on defects in materials and workmanship. (Original owner only, IIRC) Setscrews coming loose and the pulley issues are both potentially defects IMO. I'm not sure SS would agree though. If the belt is wearing badly that would tend to support the argument. (Apologies, my post got out of order to Hal's, but I want to add this to the discussion for posterity.)

Bill V - I was a Systems Engineer plus I know nothing about the specific motor technology, and I don't consider myself qualified for the hard engineering part of this answer. But when I put my DIY kit together one of the things I looked for and did not find was a programming port (the other was a reset). So in my field we would call the product in question "firmware." The primary difference to us users is the difficulty and cost of reprogramming. But fundamentally, yes, the response to any digital control loop can be softened at a cost of response time. The design engineer(s) would have almost certainly studied this trade-off during development.
Notes - Things I've read lead me to think there are at least two versions of firmware for the PP. Others lead me conclude that there are some tune-able parameters that are not controlled as part of the version, but are retained in firmware. But there is very little information on any of this that is available to the users. We don't even have a comprehensive list of error codes.

- David

Bill makes a very valid point on the PowerPro and this is a possible explanation for why setscrews are coming lose on the PowerPro. From a system control theory standpoint this would make a lot of sense. I did offer a possible alternative explanation in the thread below and it could be inter-related to Bill's theory. The PowerPro motor is a switched reluctance design and these kinds of motors are well known to have natural frequencies and vibration modes associated with them (see link below). Either a Striatech engineer and/or a Shopsmith engineer should have performed a modal analysis to determine where these are located and change the design to shift them, if possible, to avoid nasty things like screws coming lose. My guess is either this didn't occur or they were unable to alter the design enough to minimize them.

https://www.shopsmith.com/ss_forum/view ... on#p265716

P.S. The NOVA drill press and lathe, as well as some Rikon bandsaws use the same DVR motor from Striatech that Shopsmith uses. It would be interesting to know if any of those other products experience a similar problem of screws coming lose. Also, those products, as I understand it, have a port where you can re-program and update the firmware on those products.