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KBs PensNmore
15th Sep 2018, 03:23 AM
I'm in a position where I need to make a miniature welding rotator. Thinking of using a sewing machine motor to power it, but would need a variable switch to get the RPM right, would a fan control switch or light dimmer switch be sufficient to do it. The drive will be by toothed belt, so as not to interfere with the motor side of things
It'll be running a 4" 3jaw chuck and welding a bolt on the end of 15NB pipe, have several hundred of them to do, not all at once, thank God!!!!!
Kryn

BaronJ
15th Sep 2018, 05:49 AM
Hi Kryn,

Here you go !

375357

I know it says 230 VAC, it will happily work on 110 as well should you need it to.
C1, C2, R1 and L1 are interference suppression components. The circuit will work just as well without them.
If you get noise on your radio when running then include those components.

BobL
15th Sep 2018, 08:44 AM
What sort of motor is it motor and what RPM do you require?

Michael G
15th Sep 2018, 09:00 AM
My thoughts too. I would have thought for welding you would want something around 60rpm perhaps +60, -30rpm. A sewing machine motor is not going to do that straight out of the box. If the only thing you are doing are these bolts, perhaps a pin on a base plate and a socket on top of that would be enough to do the job (rotate by hand - use an old steering wheel, pulley or something similar)

Michael

BobL
15th Sep 2018, 09:37 AM
Sewing machine motors are typically in the 6 to 10k rpm range so to get 30rpm requires at least 200:1 reduction. Doing this electrically is a big ask so you will need some mechanical reduction before hand. Even if you can get a 10:1 mechanical reduction that still leaves a 20:1 reduction electrically which is 95% speed reduction where the motor may have little or no torque left to drive any load.

If you wanted to pursue this I'd be looking at a 12/24V DC motor with a full reduction gear box as they go for about $20 on ebay..

Karl Robbers
15th Sep 2018, 12:54 PM
Do you have access to a straight line oxy cutter? They make brilliant rotators as all the work has been done for you and you just need to mount a chuck or plate on the drive wheel.

russ57
15th Sep 2018, 01:12 PM
Hmmm

Are we talking domestic motor or industrial?
A domestic sewing machine foot controller lets you sew really slowly.. Down to a single stitch at a time. And the old ones are just a variable resistance.

Sewing machines don't have a massive reduction inside. A universal motor does have good torque at low speed.

But your weld positioner will probably have a lot more mass than a sewing machine, so you should aim for as much reduction as you can arrange.







Russ

KBs PensNmore
15th Sep 2018, 03:41 PM
Hi Kryn,

Here you go !

375357

I know it says 230 VAC, it will happily work on 110 as well should you need it to.
C1, C2, R1 and L1 are interference suppression components. The circuit will work just as well without them.
If you get noise on your radio when running then include those components.

Thanks for that John, only problem is that, to me it's just squiggly lines and black triangles.
Electronics ain't my field/interests.
The reason I mentioned using a sewing machine motor, is that I have several of them, didn't think that they ran that fast though.
Oh Well, back to the drawing board, might look at microwave motors, as they run about 3 rpm, which should be enough.
Thanks everyone for their comments.
Kryn

BaronJ
15th Sep 2018, 08:36 PM
Hi Kryn,

OK point taken :) I won't suggest a light bulb dimmer switch then, which would also work.

You could look at an oven rotisserie motor ! I don't think you will get anyway near enough torque from a microwave turntable motor.

RustyArc
15th Sep 2018, 08:37 PM
What about an old cordless drill with a 2 speed gearbox? In low gear and with the trigger only just depressed, they go pretty slow. You could also drop the supply voltage to go even slower.

KBs PensNmore
15th Sep 2018, 09:00 PM
Thanks for that Rusty, as I mentioned to John, electrics is not a field that I'm familiar with nowadays, so I'd like to stay away from voltage reducing equipment.
Was hoping to do a plug and play sort of thing.
10 years ago I wired up my shed, can't remember how to do a light switch now:doh:.
Kryn

Michael G
15th Sep 2018, 10:03 PM
If you had a lathe, you could chuck up a broomstick (insulator) and then support the free end in a bush. Cover the bed, attach the chuck to the end of the broomstick and put it on a slow speed and you might just be able to do it.

Failing that, I do have surplus spankers 20:1 gearbox here.

Michael

KBs PensNmore
15th Sep 2018, 11:19 PM
Thanks for the offer, Michael. How big is it, shaft sizes, etc.and how much do you want for it?
Kryn

Com_VC
17th Sep 2018, 08:02 PM
Do you have access to a straight line oxy cutter? They make brilliant rotators as all the work has been done for you and you just need to mount a chuck or plate on the drive wheel.

That is actually a really good idea Karl, never thought about that before.

KBs PensNmore
17th Sep 2018, 09:26 PM
Thanks for the idea Karl.:2tsup:
I don't have access to one but looked on gumtree and found one at a respectable price, no nozzle or track, not that I need them ATM.
Waiting on a reply from the seller. They're not a cheap item!!!!
Kryn

Karl Robbers
18th Sep 2018, 08:31 PM
Thanks for the idea Karl.:2tsup:
I don't have access to one but looked on gumtree and found one at a respectable price, no nozzle or track, not that I need them ATM.
Waiting on a reply from the seller. They're not a cheap item!!!!
Kryn
No, not cheap at all. At a previous workplace we had one that never saw an oxy torch fitted, yet ran miles of weld with a mig torch fitted and would probably have traveled around the world multiple times with the number of times it spun with stainless fittings being tigged up.
Sadly, so many have ended up in scrap bins over the years, but I haven't yet rescued one for myself!