[chola]

Not sure if this is in the right place but.....

I have a micro lathe (C1), yes I know...very small, etc etc, however is perfect for what I use it for, have even CNC'd it!

Anyway, the only real thing it lacks is power, the motor is only 150watts (I have still managed to turn down 60mm alloy bar but did take a while). I have read a lot about replacing lathe motors with those from treadmills, but here in Australia they are a little hard to come by, but have found quite a lot of Electric Scooter motors (you know, the ones that the elderly people use to run you down with in shopping centres!).

They seem to have the right rpm (usually up to around 2750), 20 to 35 or so amps, would obviously have a lot of torque (usually around 1.5 to 2 hp) and vary on the voltage.

If this was coupled with a suitable speed controller, could anyone see a potential problem with using this type of motor?

Thanks.

COlin

[Al_The_Man]

Check to see if it is permanent magnet field, its probabally 12~24vdc? (low voltage-high current).
So you may have to put together a simple controller for it.
Al.

[chola]

HI Al,

Here is the link for just one of the motors I've found.

http://cgi.ebay.com.au/NEW-Electric-...QQcmdZViewItem


Like all good things it's on ebay!

The controller you mean is just a speed / direction controller I assume?

Thanks.

Colin

[Al_The_Man]

Looks like some of your buddies down under are persuing the same idea.
http://cnczone.com/forums/showthread.php?t=29029
Al.

[chola]

Hmmm, interesting.

I would only be wanting to use it as a straight replacement for my existing spindle motor (no need for encoding / turning into a servo motor).

Seems like this should be fine with the appropriate speed control circuit, any idea where these can be bought off the shelf, or a suitable kit?

Thanks.

Colin

[higgrobot]

Chola, you keep your eyes off my servo motors

[higgrobot]

Btw, did you have a look at the other things he's selling, speed controllers and other motors, a 24V system would workout a lot cheaper than the 36v one.

[Al_The_Man]

Seems like this should be fine with the appropriate speed control circuit, any idea where these can be bought off the shelf, or a suitable kit?

I think these can be upgraded to higher current, they are available in Oz.
oops http://kitsrus.com/pdf/k166.pdf
Al.

[chola]

hi higgrobot,

all's fair in love and ebay

What suburb / town are you in? I'm on the Gold Coast (Arundel).

Have you used / connected these up before? If so how were they, what speed control circuitry / power supply did you use?

Thanks.

Colin

[chola]

Wow, you're not wrong, 24v it is then!!

Not being overly technically minded, how hard do you reckon it would be to add a variable speed / direction function to the speed controller's he has?

Colin

[higgrobot]

I have no idea if his speed controllers can reverse? But,all you'd have to do is switch the output, jaycar sells a speed controller kit and HD switch. At 10A the switch is a little underated but will probably outlive the motor

edit: I'm in Perth, much closer to him than you are, hehe.

[chola]

HI Higgrobot,

Doh...OK, I'm in check-mate! Oh wait...I get to go to bed 2 hours before you do! I was in Perth about 12 months ago for a holiday, loved it! Can't wait to go back, hopefully later this year.

Would be simple to add the reversing switch to the Jaycar kits, just a little dubious about pushing that much power through it, I think the Jaycar ones are rated to 15amp????

Al The Man, I've found a local supplier here for the kits you mention, www.oceancontrols.com.au

These definately look like the go, seem like they will also run a 24 volt system straight up, just maybe needing a bit of extra cooling (small fan / heatsinks) for higher amp units.

So the setup will consist of the above mentioned motor controller, suitable motor and a power supply that will handle the current required.

The big question is, of course, will the wiring in my house handle that amount of current continuously?

Thanks for all the help so far, you guys are awesome.

[higgrobot]

The house can handle 10-15Amps @ 240VAC, when converted down to 24VDC the house can handle over 100Amps. To get 24Vdc you have to first get a transformer thats rated at the current you want, for a 250W motor the 300VA 18V toroid (Jaycar MT2132), when the output windings are in parallel it will supply 16.6Amp @18VAC. You then get a Bridge rectifier (Jaycar-ZR1324) to convert it to DC and you end up with ~24VDC but rather noisy. You have to then smooth this with smoothing caps before connecting it to your speed controller else it may just do some strange things. Off the top of my head it's (0.007 X 16.6Amps / 0.1 x 24V) x 1000000 = the caps required for 10% ripple current = 48417uf.or higher, That's basically 10 x 4700uf caps in parallel. Just make sure the caps are rated over 24v. ie 35V or 50V, 25V won't do..

You may be able to lessen the ripple requirements but you will have to ask the electronics gurus or ocean if they would know, i'm just a machinist

There are probably better cheaper ways to get 24Vdc @ 10+amps, surplus 24V battery chargers, haxing computer power supplies together (tricky), 2 x 12V Batteries (easy and you dont have to buy rectifiers or caps).

You may even have more luck finding a 240V motor and running it with a big light dimmer (tricky and won't reverse)

[Al_The_Man]

Al The Man, I've found a local supplier here for the kits you mention,
These definately look like the go, seem like they will also run a 24 volt system straight up, just maybe needing a bit of extra cooling (small fan / heatsinks) for higher amp units.

I think you could also beef up the H bridge FET's to allow for higher current, but on a miniature lathe, you may never require the max torque they can deliver so you may get away with a lower rated drive/supply.
Al.

[chola]

HI Guys,

I think I will will try to buy a power supply as I'm not confident enough to try to make one (I'm still young and do want to get to old age!!).

Would there be a problem running a motor rated at say 30amps, with a supply rated at 15, or 20? Obviously not the preferred way of doing things, but would this make a major difference to the performance of the setup?

Al THe Man, you are right, I more than likely won't see full amps on my lathe, I pretty much only machine alloy, but I would certainly like the extra power when neede. At the moment I am somewhat limited to the cut size I can make because of the motor (150w).

Thanks again for all the help.

COlin

[balsaman]

Look on ebay for a DC drive. No power supply needed (they plug in to household power and most have speed control and reverse built in.

E

[Al_The_Man]

Look on ebay for a DC drive. No power supply needed (they plug in to household power and most have speed control and reverse built in.

E

I believe they are for 90v or 180v motors though, they may not work down-under as I think the supply is 230vac so they would only work with a 180vdc motor.
Al.

[chola]

Thanks balsaman. Al is right, we run on 230~240 volts. Doesn't mean to say we don't have somthing similar around here though.

All you guys have given me some great ideas. I was consiering buying another lathe purely for the gain of a more powerful motor, but by the looks of it I should be able to do this to my existing one for less than $200 AUD, and more than likely end up with a more powerful motor than the bigger lathe would have given me.

Thanks again.

COlin

[higgrobot]

It would be nice to just click buy on an American webpage and get yourself a power supply http://www.trcelectronics.com/Meanwell/s-250-24.shtml problem is, when it arrives here in Australia some 6 weeks later the postage would exceed the price of the item.

Keep an eye on ebay for things like this:
http://cgi.ebay.com.au/Battery-charg...QQcmdZViewItem
however, something like that would have also cost a lot to send interstate, it looks heavy.

You may have to find someone to make you one around where you live, though it's probably best to get the motor first.

[higgrobot]

You can join the 12V outputs of two computer power supplies together to get 24V. Providing the supplies are identical and the shassis of these two supplies don't touch. Both need to be turned on first, this is done by connecting the green wire to ground (black) on each supply. Then the yellow wire(s) from one supply is connected to the black wire(s) of the other supply. The 24V will show up between the unjoined yellow and unjoined black wire(s), umm let me draw a picture.

The pic is for a 20 pin plug, the newer supplies have 24pin.
20pin: http://pinouts.ru/Power/atxpower_pinout.shtml
24pin: http://pinouts.ru/Power/atx_v2_pinout.shtml

Just make sure the supplies you end up with have a current rating for +12V suited to your needs, most of the time it's written on the top of the supply.
Also, as the current is pretty high it's a good idea to parallel the wires together, ie join two more yellow wires to the other supply and use more than one black wire.