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Dipping a toe into VFD stuff

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Robin Graham06/03/2021 00:41:12
807 forum posts
209 photos

I'm having a bit of a clearout and want to get rid of a potter's wheel which my wife bought some years ago. It has a 10 inch wheel head (potters' jargon for the the bit they bung the clay on) driven by a 250W motor though a cone / tyre drive to give variable speed:

potterywheelmotor.jpg

potterywheelspindledrive.jpg

I understand that this is a true and trusted design but my problem is that it has been so badly implemented (bits held together with rusty bolts and cable ties!) that I can't in conscience sell it on as as is.

I'm wondering about replacing the mechanically complicated cone/tyre arrangement with with a 3-phase motor and VFD, but I don't know enough about the low speed torque performance of these things. I had a look around and found a pottery wheel supplier who says:

"The Bailey wheel is powered by a super smooth, super quiet 0.5hp motor controlled by a computer-enhanced VF drive. This unique design delivers a peak equivalent of 1hp under heavy loads to give constant, smooth power throughout the speed range."

In the specs the the speed range is given as 0-280 rpm. I'm confused! What does 'peak equivalent' mean? What does 'computer-enhanced' mean? Can VFD/motor combinations actually deliver the rated motor power at, say,10 rpm?

If anyone can explain or point me to educational material I'd be grateful.

Robin.

John Olsen06/03/2021 02:18:34
1156 forum posts
92 photos
1 articles

First, you won't get your money back if you put in a three phase motor and VFD. It's like an old car, you might put in a new engine but you will still only get an old car price. Sales people don't normally have consciences, they find them an unnecessary burden!

Second, marketing BS is not necessarily rationally explicable. Peak power is pretty meaningless. Power is the rate of doing work, if you store energy in a flywheel and then dump it into a load, you get a very high peak power but the average is still low. The advantage of the vfd is that the torque of the three phase motor will be smoother and higher than that of a single phase, if your wife wanted to keep it and use it the VFD would be a good idea.

John

ChrisH06/03/2021 10:10:14
956 forum posts
30 photos

+1 for that

Oldiron06/03/2021 11:01:01
763 forum posts
23 photos

IMHO. Just clean it up and replace any dodgey bolts etc. Replace the cable ties for nice shiny new ones and sell it on. Anybody looking for a second hand wheel will want it cheap so will not be willing to pay the price for a shiny new VFD & motor.

regards

V8Eng06/03/2021 11:17:35
1560 forum posts
31 photos

If it were me I would put it on eBay or somewhere like that and specify selling for for spares or repair only.

Any other way will probably cost you lots of time and money without a guaranteed outcome financially or operationally.

Emgee06/03/2021 11:41:23
1988 forum posts
250 photos
Posted by Robin Graham on 06/03/2021 00:41:12:

I'm wondering about replacing the mechanically complicated cone/tyre arrangement with with a 3-phase motor and VFD, but I don't know enough about the low speed torque performance of these things. I had a look around and found a pottery wheel supplier who says:

"The Bailey wheel is powered by a super smooth, super quiet 0.5hp motor controlled by a computer-enhanced VF drive. This unique design delivers a peak equivalent of 1hp under heavy loads to give constant, smooth power throughout the speed range."

In the specs the the speed range is given as 0-280 rpm. I'm confused! What does 'peak equivalent' mean? What does 'computer-enhanced' mean? Can VFD/motor combinations actually deliver the rated motor power at, say,10 rpm?

If anyone can explain or point me to educational material I'd be grateful.

Robin.

Robin

The Bailey wheel is likely to be powered through a gearbox with the motor controlled by the VFD.

Emgee

Robin Graham07/03/2021 02:40:57
807 forum posts
209 photos

Thanks. I have a gearbox ( from a Clarke bench grinder) which takes 2-pole motor speed down to 135rpm and I had it in the back of my mind that I could somehow deploy that with a new motor / vfd to get the right torque /speed characteristics for this application. But reading your replies in the sober light of day, well, you're right. It would be quite a lot of work to make the mountings for the new motor and gearbox, apart from the cost of the parts. And all I'd have for it would be a glow of satisfaction which would soon fade. I'll just bung it back together with proper fasteners etc. Might bring back some of the 300 quid it cost (second hand) that way. And then I could put the money towards a VFD for my lathe, which would give a longer-lasting glow I suspect.

Robin.

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