33 replies to this topic

[helix]

I also use small inverter to run my mill. I found a geared down 3 phase induction motor on ebay for about £20 and use it to directly drive a jar. I just ramp up the inverter until the mill makes the most noise and run it at that, it seems to work fine.

James

Just out of interest does anyone else use a 3 phase motor and an inverter to drive their mills or rollers.
A 3 phase motor can be picked up on ebay, often new, often for less than a tenner. Likewise an inverter for 30 - 40 quid.
This combination allows you to infinitely variably control the speed of rotation by easily varying the frequency from 0 - 200 % of 50 Hertz, with I believe, minimal loss of power.
I know that when mine is set to 18 Hz, the rpm is 95, which according to the passfire calculator is optimum for my jars.

I've recently bought a ridiculously large hobart dough mixing bowl to build a star roller, but I'm having a seriousl re think since seeing the great little one at the agm.

As Digger says, a pleasant half day tinkering about building your own which will be 100 times stronger than a gem polisher, is time well spent

Martyn.

[dr thrust]

looks like you don't need a motor at-all, eco ball mill

[leosedf]

This is my large mill. Can hold several small and large jars at once. It was an almond cleaning machine and we modified it.
Hope this gives you an idea too.

[dr thrust]

just needs a set of back wheels and a steering wheel, you could go to work on it

[leosedf]

Haha!
It's powerfull enough.

[dr thrust]

talking about three phase motors, ive procured a piece machinery that has a 1/2hp 3 phase on it but its inverter unfriendly, so im plannig a single phase, capacitor assisted motor..
so would i have to incease the hp? say get a 1hp motor? to make up for any shortfall?

Edited by chris m, 15 June 2010 - 10:12 PM.

[dr thrust]

anybody! arrggghhh

[Mumbles]

You give only very vague information. It's hard to give recommendations based on "a piece of machinery".

I always thought power was power, no matter the phase. The capacitor start would help to make up for the lesser low end torque of a 3 phase. It may not be as efficient, but it should still be able to do the same work. I think you'd be fine with the same 1/2HP in 1 phase. Take this with a grain of salt though, I know very little about electronics.

[dr thrust]

ahh, great stuff its for an old donkey saw, i didnt want to splash the cash on a motor with no guts

[phildunford]

If I remember, you can usually persuade a 3 phase delta wound motor to run, by just adding a capacitor - they are a bit slow to start and don't run at max power, but motors are usually bigger than required & it might be worth trying before you splash out on a new motor...

[dr thrust]

interesting, mines got the star configuration, just three pins showing when i take off the plate on the back, and the digital inverters Ive seen recommend the motor wired delta, anyways, got plenty to be going on with, degreasing, sanding, painting, bits everwhere.
my drive looks like fred dibnahs yard lol

[PyroCreationZ]

Heya,
I'd like to know if I can get some speed adjustment for my single phase motor (with capacitor)?

I have two motors from old washing machines and would actually like to use them for all kinds of tools but a starroller doesn't need such fast RPM so it would be nice if I could control them.

I know frequency regulators exist but I thought those were very expensive?

So, is it possible to regulate the speed with a cheap solution?

Not knowing too much about mechanics it's always a wild guess what size pulleys I need...

[cooperman435]

You wont be able to slow it down enough (or even close) to use it as a star roller without pulleys sorry.

Working out pulleys is easy!

Motor speed (EG 1400rpm)
desired speed of final drive in this case the roller drum (EG 100rpp)

ratio needed is 1400:100=14:1

motor pulley (EG 45mm) diameter (from the base of the pulley grove) x Pi (3.142) = 141.39mm circumference

141.39x14=1979.46

1979.46mm is the desired circumferance of the drums pulley so 1979.46/Pi= 630mm is the diameter of it

Job done!

[dr thrust]

Working out pulleys is easy


Job done!

easy for you!, im a bit thicker so i use this conversion table thingy