motor

Hello everybody, I have found your forum and am hoping that someone may be able to help. Apologies if this is the wrong site on which to post this query, but I am at a loss. I have a motorised turntable that spins so fast I fear that anything i put on it will be flung to the other side of the room. While this would be rather funny to watch, it doesn't help me much. I want to add a speed controller to the motor but herein lies the problem. I need to know what type of motor I have, whether it would be possible to fit a speed controller to it and how I would do it if it were possible (not much then!). I have added some photos to help. Any advice would be very gratefully received. Cheers, Terri

t looks like a single phase induction motor of some kind. Post a picture of the information plate on the motor. It is unlikely that will be able to reduce the speed of this type of motor. What is the speed of the motor and how many RPM do yo want the turntable to rotate ? It would be better to reduce the speed of the turntable with a gearbox or a suitable pulley system.

Les.

You appear to have a single phase induction motor which is not really practical to change the speed. It looks possible to change the pulleys fairly easily or you could fit a 3 phase motor and use a single to 3phase variable frequency drive (VFD).

Mike

Terri, as Les said it looks very like a capacitor start or start/run induction motor. If so you cannot control its speed, it runs at about 80% of mains synchronous speed - ~1480 rpm if 4 pole or 2800 rpm if 2 pole. Reducing the speed would need a bigger pulley ratio and perhaps another pulley stage depending on what speed you want. You could control the speed if you replaced the motor, either with a commutator motor and speed controller or a 3-phase induction motor with a variable frequency drive but that would be expensive. Depending on what speed you want even then you might need more mechanical speed reduction.

Think here tumble dryers - the belt is likely a poly-V, the drive pulley about 2 cm driving around the drum which may be close to 60cm diameter, say 55cm (most domestic appliances are 60cm wide, these days).

That gives nearly 30:1 reduction ratio. So a motor at 1425 (4 pole) would provide about 50rpm - not much good if you are throwing and centring clay.

The typical tumble dryer would have an idler to wrap the drive belt around the motor pulley. As above, the ideal would be a three phase motor with variable frequency drive and that sort of belt reduction system, I would think. The drum pulley from a washing machine would probably suffice.

Another alternative would be a three phase geared unit from one of the suppliers (look up gearedmotorsuk.com as one example) along with a small powered VFD.

Edited By not done it yet on 03/09/2018 16:29:20

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60/2 =

Please Sir, is it 30?

Mike

Damn. I mixed up my units - I originally wrote 600mm and 2cm; corrected the mismatched units but forgot to correct the calc. Mind you, I did get the right answer - 50rpm, not 5rpm. Post corrected now.

As an addition, a variable speed drill or a 3 phase geared unit (gearedmotorsuk.com, as an example) with a suitable VFD (Variable Frquency Drive) might be alternatives. If for a variable speed application, a foot operated controller may be needed.

.

As I suspected

... It's easily done

MichaelG.

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P.S. I agree that Poly Vee would be a good solution

... with a 20mm pulley on the motor, a plain flat pulley might suffice for the driven one.

... maybe 2 or 3 driven ones [and a tensioner] for different ratios ?

Edited By Michael Gilligan on 03/09/2018 16:47:29

Wow, thank you all so much for your help. You people certainly know what you are talking about. I was hoping to use this as a flat lap machine for my rocks and gems but as I can't control the speed it'll have to go. I'm not too upset, it means I can spend some money on a newer flat lap (something hubby was hoping to avoid). Anyway, thank you again for your help and advice, much appreciated. Terri.

Terri

Some of the suggestions were to slow the turntable down by way of different pulleys, which would not necessarily be expensive, is in principle easy to do, and would save the cost of replacing the turntable.