Thread: electric motor/ single speed/ 600 -800 revs

First step is to get the prototype built out of whatever junk parts you can grab.
Would it be safe enough for a faster speed motor and a pulley/belt drive to reduce the table rpm?

Plan B: strap a cane toad to the table, turn it on and go away for the weekend.

Originally Posted by zongatron

I'm thinking a washing machine motor would be overkill, and use unnecessary power. Bit of overkill.

Thanks again

Ben

I';m about to play with a couple of washing machine motors so I will have more to say about these soon.

What does the machine currently use for a motor and controller?

I suspect something similar to a sewing machine motor and pedal judging from the mention of a control pedal. If it is something in that order, you could possibly use a 400W or higher lamp dimmer and an on/off footswitch with the current motor. Then the dimmer unit can be mounted in a box so the billylids cannot easily the speed knob, but you can still access it occasionally for setup/adjustment while they are out playing footy, taking nature walks etc and can't watch and learn how you get to the speed control.

If the motor is more powerful than the typical sewing machine unit, but is a variable speed capable universal (brushed) motor, you can get stand alone variable speed controls for power drills and other and tools as kits or possibly as completed units and do basically the same thing (controller and on/off pedal switch).

Edit.

Just found your earlier post, where you mention using a DC motor and speed controller, rather than an AC unit, and mention the possibility of switching between two or three fixed speeds. The same concept outlined above, using the existing control module and motor and an on/off pedal (or other style) switch. Multiple switched speeds could be achieved by adding a speed selection switch and using that and variable resistors to set the speed.

Awesome,

thanks guys. And I thought this was going to be simple - buy a motor, plug it in and spin away! Of course not.

I am going to ask a "motor rewinder" on Monday if he ccould come up with something - to try and get somewhere as I need to fast track the project as I already have a gig lined up.

I will print out these suggestions and take them with me.

Do you guys think that's who I should be seeing? Or should I just ring my friendly neighborhood electrician to see if he is interested in wiring a few of these up etc?


Ben

Originally Posted by zongatron

Awesome,
thanks guys. And I thought this was going to be simple - buy a motor, plug it in and spin away! Of course not.
I am going to ask a "motor rewinder" on Monday if he ccould come up with something - to try and get somewhere as I need to fast track the project as I already have a gig lined up.
I will print out these suggestions and take them with me.
Do you guys think that's who I should be seeing? Or should I just ring my friendly neighborhood electrician to see if he is interested in wiring a few of these up etc?

Most neighbourhood electricians won't (with some reason) work with second hand gear, won't know much about motors and will naturally recommend a solution that suits them.
A motor rewinder is likely to be more knowledgable but is also likely to recommend "new product" solutions.

I've just been messing with two washing machine motors and they seem like they would be ideal.
Both are 1440 rpm motors.
One is cap start and draws 0.6A free running while the other is a switched start motor that draws 1.5A

Somewhere I have a dimmer switch that I will try on the cap start motor and I'll see what happens.

Great Bob,

I await eagerly!

Although I must confess I know next to nothing about motors volts and amps. Cap starts etc. I have tried to make some sense of it here online but get confused very easily.

Thanks again

Ben

p.s. I did just learn a little about a cap start motor on wiki. That is interesting

I found the dimmer and hooked it up to the washing machine motor and it's a bit of a dud.

It works sort of between about 1440 to ~1250 RPM but below that the motor has increasingly limited power to the point when I can stop it running by hand at about 1150 rom and it stalls completely at about 1050 rpm.

I've noticed this before on fan motors but the RPM range seems to vary with the dimmer.

It can't be the motor being two powerful as it is only drawing about 125W

Hi Bob

Is there any reason why I would want a dc motor and not an ac motor?

Do AC motors need some type of cooling fan or something?

Do you think this would work? -

http://cgi.ebay.com.au/ws/eBayISAPI....tchlink:en

with this controller?

http://www.ebay.com.au/itm/1-5KW-2HP...f8581a8&_uhb=1


If I could get away with 900rpm, i wouldnt even need a vfd with this motor would I? Just an on and off switch?

I would be more than happy spending about three hundred on each motor.

The last person I spoke to said I wouldnt get anything speed controlled for less than $1500 each.

Thanks

Ben

p.s. Just lastly, I was reaidng a previous post and he had water issues.

The VFD is not a good look for what I am doing. Can I mount the VFD away in a box, and have separate on off switches to use on the actual unit?

Originally Posted by zongatron

Hi Bob
Is there any reason why I would want a dc motor and not an ac motor?
Do AC motors need some type of cooling fan or something?

DC motors generally have a much wider speed range with the same power across the speed range than AC motors.
But this sounds like it's irrelevant to your needs.

Do you think this would work? -
http://cgi.ebay.com.au/ws/eBayISAPI....tchlink:en
with this controller?
http://www.ebay.com.au/itm/1-5KW-2HP...f8581a8&_uhb=1

Yep - the motor is 240V 3Phase Delta capable so that would work - the prices are good but I have no idea what a sparky would charge to wire it up.

If I could get away with 900rpm, i wouldnt even need a vfd with this motor would I? Just an on and off switch?

Nope - you will need the VFD because it is s 3phase motor and unless you have 3 phase sockets where you are operating you will need the VFD to convert 240V single to 240V 3 Phase.

I would be more than happy spending about three hundred on each motor.
The last person I spoke to said I wouldnt get anything speed controlled for less than $1500 each.

Maybe he was a sparky?

Hi Bob,

Would this VFD work with this motor?

http://www.ebay.com.au/itm/2200W-3Hp...e64bf80&_uhb=1



http://www.ebay.com.au/itm/111323102...84.m1438.l2649

Thanks mate.

Ben

Originally Posted by zongatron

Hi Bob,

Would this VFD work with this motor?

http://www.ebay.com.au/itm/2200W-3Hp...e64bf80&_uhb=1

http://www.ebay.com.au/itm/111323102...84.m1438.l2649

Thanks mate.

Ben

Yes it would but it is overkill to use such a high power VFD on such a small motor. You are better off getting a smaller one.

BTW I tried out an old school (500W) versus near new (400W) Light dimmer on a washing machine motor this arvo - same problem.

This would like a better deal so far: http://www.ebay.com.au/itm/291127571936
but you can also scale down and save a bit with this VDF: http://www.ebay.com.au/itm/221229448192 which is still overkill...

If I may make a suggestion: det a heater fan motor from the local wreckers and a wire-wound rheostat (potentiometer) of similar (or higher) power to the motor you find and connect them to a 12V powersource of some kind (of adequate power). I think that would do your job easily!
You could try it out without the rheostat first and see if it's fast enough and measure how many amps it actually uses under your load, then get the rheostat and powersupply to uit (maybe a cheap transformer battery charger, for example). To just try it, use your car battery. The whole exercise would cost heaps less and be much easier to install.... and no concern for water ingress etc. 12V wont hurt you if it all goes pearshape at some point (like you drop your paint bucket in it )...

If you dislike using secondhand gear, have a look here: http://secure.oatleyelectronics.com/...oducts_id=1060
A new suitable power supply for this combo would be $25.47 from here: http://www.ebay.com.au/itm/350865972144

I'd feel much happier about you using the 12V options as suggested by Joe. Much safer and simpler and a lot cheaper by the looks.

I thank you all again.

I think i am finally coming to grips with my options.

It is very overwhelming trying to work out electric motors with little to no knowledge about them or electricity, and it seems I was misled by my first phone enquiry, whom told me i would not get anything speed controlled for under $1500.00.
Since then I have been trying to problem solve a problem that is not really there.

You guys have helped me get close enough to be confident when talking to my electrician.

1) This is going to be used at schools and fetes etc, it will have an awful lot of use so im thinking something a little more industrial would be better.

2) I need to mount a pulley onto the shaft (onto which I can mate some chequerplate on which to mount a canvas) and cant seem to find a pulley under 12mm, So shaft size is important.

Where Im at now -

If i simply buy a .18kw 3 phase 4 pole engine (for around $90) then buy the appropriate VFD ( for around $100-150) I will have a speed controlled electric engine with decent sized shaft diameter that should easily turn the load of about 400grams.
I have found an electrical engineer who has said he will wire it all up for me no problem.
He is even trying to source the motor and VFD for me.

The only uncertainty is if it will run slow enough for me at around 300rpm,
One person told me it should give you a complete range of speed from 0 to upwards of 1440. While another said it might not go slower than 500rpm as the motor still needs to kick...)


So I am very happy with the outcome so far as I can afford that combination.

And if a 4 pole motor wont run at less than 500 rpm, I can always trial a 6 pole I guess.

I trialled a single phase at 1440 and it was way too fast.

I need about 300 up to 1440 rpm

I will let you know how it goes.

Thanks again everyone, and you Bob.

Ben