The Clay Boss Wobble

[Ja.Sc.]

Hello to All!

I have been slowly converting the garage into a functioning studio.  It's been a number of years since I've used my clay boss, which had this perceived problem since before this unintentionally long break.  I have reviewed the other posts about wheel head wobbles, this one, and the one linked at the end about the dial indicator.  I plan to start deconstructing the wheel tomorrow to try and determine if something is not sitting right with the belt, or wheel head shaft/ and bearing.   The motion is definitely up and down not side to side,  enough that it will likely be a bother for me.  If there is any wisdom to impart before I begin dismantling, Please do!

[Mark C.]

How much up and down is the whole question

[Ja.Sc.]

https://imgur.com/gallery/0e0vsN1

 

https://imgur.com/gallery/pLtPdsX

 

 

[liambesaw]

Boy it's all over the place...  Bent shaft or shot bearings? This one will be difficult to suss out without taking it apart.

It has a left and right wobble as well as an up and down, if I had to guess right now I'd say bent shaft

[Mark C.]

One small item the video missed is how how much the top is out.You only show the bottom of wheel head . I see the bottom of the wheelhead is out but that can be a poor casting issue. Is the top going up and down as much as the bottom .If thats a yes then that head/shaft is bent. 

[Ja.Sc.]

I didn't have a great way to check the top.  I would need to put together a stationary arm of some sort first.  I went with the most efficient method first.  My hope is that the wheel head is just not sitting straight on the shaft.

As it happens a tree in my front yard fell last night and landed completely across my driveway and sidewalk, so that took priority over the days activities.  I don't think I'll have time again until next Friday to dismantle anything, but I might be able to rig up an arm to check the top side. 

 

[Hulk]

Likely you can hold something steady enough to get an idea how out the wheel head (top) is. If that bottom edge is machined, then likely it's even/parallel (whateever) with the top. My wheel head is machined over the top and the edge, but the bottom side is as cast.

There's more than one way to square a wheel to a shaft. I haven't seen many pottery wheels taken apart. So far, have seen the Skutt, where the shaft is tapered and pinned, which mates up with the machined taper and slot in the wheel head, and (pictures of) a Shimpo, which sits on a washer over  a circlip that sits in a machined groove in the shaft, the part of the wheel head that sits on said washer bein' machined parallel to the top of the wheel head. Point bein' some part of the casting likely is machined to match up with the shaft, and yeah, not likely the end of the bore with the top of the shaft, heh.

Any road, given the shaft runs true and steady - not bent/damaged, bearings good - the means by which the head squares up is compromised, and/or the casting is bent.

[Bill Kielb]

6 hours ago, Hulk said:

Any road, given the shaft runs true and steady - not bent/damaged, bearings good - the means by which the head squares up is compromised, and/or the casting is bent.

@Ja.Sc.

If the casting is bent very slightly I might be inclined to machine the top of the wheel flat by machine shop or home grown method  depending on what tools you have available or of course just get a new wheel head.

[liambesaw]

You can see a horizontal wobble too though if you watch the video

[Ja.Sc.]

I finally got the wheel dismantled!  But quickly realized I don't have the equipment or any way of determining if the bearings are bad, or the shaft being bent.   The only thing that I really had any influence over was the bearing retainer on the top and bottom of the wheel.   The wheel has been moved a fair amount since I got it so I wouldn't be surprised if the wheel head was bumped at some point slightly miss aligning the retainers.  After I put the wheel back together the wobble had diminished to an almost imperceptible amount.  I think it's safe to say that was causing the majority of the issue.  

I have noticed though, now that I have the extended feet back on that I can still see the whole wheel body slightly oscillating.  I am picking up some cinder blocks to replace the leg bottoms and hope that clears up this last bit enough that it won't bother me.  It really is a vast improvement from where it was, but I am going to be working towards production level use with this wheel; so I am really trying to get it dialed in before I start ramping up.  

There was a slight bend/impression in the belt that might be playing a part.  The motor and pulley is aligned from what I can tell.  Is there anything else to consider?  

[Bill Kielb]

2 hours ago, Ja.Sc. said:

I have the extended feet back on that I can still see the whole wheel body slightly oscillating.

Sounds like - more right rudder on takeoff …….. just kidding, if it oscillates or more likely vibrates that would  likely indicate  the main drive pulley is out of balance. Normally these run so slow that even  non vibrationally balanced arrangements are easily held steady. The vibration will go somewhere however so if the legs are not sturdy enough then it could show up and be perceptible.

Your block idea seems worth a try. Balancing the large pulley takes quite a bit of trial and error adding weight and some reasonably decent equipment when subtracting weight to get into balance is possible but not super simple. To measure vibration without any special tools you could tape a laser pointer on the wheel base (the fixed part, not wheel head)  and project it on an adjacent wall to get a relative sense of the magnitude of the imbalance (vibration)  while installing trial and error weights on the pulley. We actually have some cool instruments to do this with ($$$$$$$)  and there is a simple geometric method we would teach folks on the floor of a boiler room which required little math. Again for pottery wheels this seems a bit overkill. Stiffening the legs seems a most reasonable approach IMO.

I wouldn’t discount a flat spot in the belt though - same likely vibration issue.