Re-motoring Unimat SL

[Richard Jones]

Hi,

 

The  original motor on my Unimat SL recently gave up the ghost, and via the Unimat Yahoo group, it was suggested that a 24v electric scooter motor was an economic replacment.

 

Here is said motor (£12.99 of ebay) + another £13.20 for the switch mode power supply and £2.79 for the Pulse width speed controller fitted and working on my Unimat (and a lot quieter that the original motor)

 

Many thanks to Keith of the Unimat Yahoo group for the original idea, and Peter Boorman for making me the new (8mm bore) pulley on one of his other lathes...

[Horsetan]

I wonder if power consumption is reduced?

[JeffP]

My Emco Compact 5 suffered motor failure.

 

I had the motor serviced by a local motor rewinds place, £20, it's now like new.

[Richard Jones]

My Emco Compact 5 suffered motor failure.

 

I had the motor serviced by a local motor rewinds place, £20, it's now like new.

Hi Jeff

I think the insulation on the field windings of my original motor have deteriorated - it would have been nice to find someone to repair it, but I suspect a set of field windings would have been a lot more than £20.... if I could have found someone to do it!

cheers

Richard

[JeffP]

I was lucky with mine, it was a relatively easy repair.

 

It's recently been refusing to start, which was a sure sign the motor capacitor had gone. A new EMCO one was £20+.

 

I did a bit of research and bought one from an electronics supplier for under £4 delivered, had to modify one connector.

 

Speaking of capacitors: TIP: if removing a motor, DO NOT touch the capacitor...they don't have give you a belt!

[Guest Nevadablue]

Nice job on the motor! It looks like my expensive variable speed eBay purchase. I bet it is the same one.

[nigelb]

mmmmmmm  this has solved a ll problem of mine   have an old lathe  wiith no motor

chhers

[Roy@C-K]

Hello Richard,

 

I like your approach, with help, on the Unimat motor problem (I must try and get one of these lathes - mine is a Myford ML7 - a bit big and has to stay in the garage!). I've been looking for a compact low voltage motor to power a small "sensitive" drilling machine, which is usually powered off of a lathe mounted pulley with belts. When I was given this little rig it was powered by a 3/4 HP motor, it worked but was just ridiculously dangerous - so much power. Never thought of a scooter motor - perfect. So I've found where to obtain a motor, but from where did you obtain the other components? Are you able to confirm website details please.

 

Best regards,

 

Roy

[Richard Jones]

Hello Richard,

 

I like your approach, with help, on the Unimat motor problem (I must try and get one of these lathes - mine is a Myford ML7 - a bit big and has to stay in the garage!). I've been looking for a compact low voltage motor to power a small "sensitive" drilling machine, which is usually powered off of a lathe mounted pulley with belts. When I was given this little rig it was powered by a 3/4 HP motor, it worked but was just ridiculously dangerous - so much power. Never thought of a scooter motor - perfect. So I've found where to obtain a motor, but from where did you obtain the other components? Are you able to confirm website details please.

 

Best regards,

 

Roy

Hi Roy,

 

All of them came from ebay traders:

 

motor - http://www.ebay.co.uk/itm/Electric-E-Scooter-MOTOR-24v-120w-Belt-Sprocket-24-Volt-120-Watt-Stand-On-Ride-/171551206555?pt=UK_Sporting_Goods_Scooters_LE&hash=item27f13fac9b

 

speed controller - http://www.ebay.co.uk/itm/400603057253?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

 

switched mode power supply - http://www.ebay.co.uk/itm/151123354933?_trksid=p2060778.m2749.l2649&var=450206468321&ssPageName=STRK%3AMEBIDX%3AIT

 

I have no connection with any of the above retailers except as a satisfied customer. The first power supply went "pop" when turned on, but they supplied a replacement foc and that works fine - I've been turning up split axles this morning.

 

I think my next purchase will be a set of collets..... (unless Father Christmas delivers some!)

 

Hope that helps

 

best wishes

 

Richard

[Roy@C-K]

Hi Richard,

 

Thank you for the information and links, that takes the guess work out of component selection. I went on one site looking for the speed controller - and there were so many!!!!! to choose from, I would almost certainly have selected the wrong one. Thank you for your trouble.

 

Best regards,

 

Roy

[barleybill]

Hello Richard

                      Very interesting that you decided on the scooter motor. I had researched motors and the 120W 24V scooter motor was already favourite. Your comments finalised the selection and I have one temporary fitted to my unimat. I say temporary because it is hanging on one screw from the old motor that just about fitted. Did you fit a second screw and if so, how did you achieve drilling and tapping. I am loath to undo the long screws that appear to go right through the motor in case everything falls out in a pile of bits never to work again. Drilling into the fully assembled motor would fill it with swarf and leaving it hanging on one screw is asking for the casting to get broken.

I shall be turning a new pulley wheel in the next couple of days and wondered how you did that. Did you simply make a 8mm diameter bore and ignore the flat side of the motor spindle? It looks to me as though a couple of grub screws onto the flat would hold it in position. Did you keep the pulley ratio of the two larger grooves of the old motor pulley? I can see that with the slower motor speed (from 4000 rpm of the old motor to 2500 rpm of the new one) the largest pulley diameter would be required to achieve maximum speed and that the motor input voltage can be reduced in order to get lower speeds.

 

Regards

 

William

[Richard Jones]

Hi William,

 

Yes, I fitted a second screw. I would strongly advise against drilling the hole with the motor assembled!!! - Mine only required two long bolts to allow removal of the end plate, which can then be drilled safely without any fear of damage or swarf ending up in the motor.

 

As I mentioned, my friend Peter, who was also doing the same conversion on his Unimat but has the luxury of several other lathes to use, turned up both the "top hat" bush and the new pulley. I've attached 4 photos:

 

DSCF4916 -  the inside of the motor end plate, as purchased

 

DSCF5259 - inside of motor plate with "top hat" bush fitted inside

 

DSCF5158 - outside of re-assembled motor showing the "new"  mounting hole from the outside

 

SAM_0294 (2) - new pulley, as turned up by Peter - plain 8mm bore, with grub screws locating onto the flat of the motor shaft

 

By the way RDG Tools supply spare Unimat Pulleys....

 

hope that helps

 

Richard

Edited March 11, 2015 by Richard Jones

[barleybill]

Thanks Richard that is most helpful. I am half way through making a pulley wheel and after your reading your new information will also make a top hat bush. My discipline is RF Electronics, so all of this lathe work is new to me but I must admit it is enjoyable. I am running the motor on the lath to make the new pulley wheel; bit of a lash up but I only have the one lathe. it has been interesting to observe the current being drawn by the motor when turning and it rarely exceeds 1.5 Amps, so at 24 Volts that is only 36 Watts and well within the rated 120 Watts of the motor.

 

Regards

 

William

[gasman2015]

I would really like to change the motor on my Unimat SL and this looks perfect. I have bought the scooter motor but am struggling to remove the drive gear from the shaft. There is a retaining flange on the end of the shaft but even after removing this and with a gear puller, i am unable to pull the gear from the end. Any hints? Time to get the Dremell out? Many thanks for any advice, John

[2mm Dabbler]

I've read of a few similar conversions in the Unimat Yahoo group. As well as the circlip fitted to the end and the flat on shaft the gear or belt sprocket is also fitted with a very strong retaining compound/adhesive. Most have had to heat the fitting with a small gas torch to degrade the grip of the adhesive.  One fellow however, pointed out that the sprocket was sintered and quite brittle - he rested it on an anvil and used a cold chisel.

 

I have a similar conversion intended for my Unimat 3. which will at least overcome the intermittent duty cycle.

[gasman2015]

Thank you - that was very helpful advice. I can confirm that the belt sprocket comes off easily after removing the circlip, grinding off the peaned end and gently heating until lightly smoking and then gently tapping with a drift punch. The sprocket didn't seem very brittle - I gave it a good bash on the anvil after removal without much effect other than squashing it slightly.

 

On to stage 2...

[Simon Mills]

My unimat 4 motor has stopped working and i read your post with interest and it looks to be the way forward. I have some questions that i hope you can answer.

The power supply that you bought was it 24V and what power or amperage is it?

You incorporated a speed controller is this so you don't need to change the drive belt as rpm is controlled through this? If i decided to still use the pulleys then would the speed controller be necessary?

Any other advice would be helpful.

Thanks Simon

[bertiedog]

In any DC motor change it is possible just to use the power controller, but it still pays to use the belts with the motor running at high pace to transfer as much power as possible to the work.

With the higher ratio belt setting plus the low speed control you gain the ability to cut iron or other harder materials as well, Most DC motors will also run faster than the single speed AC so top speed is increased as well,

Make sure the controller is rated as much as practical above the wattage on the motor.

One tip, do not set the belts too tight, it soaks up power, the belts can be slacker than you expect as the pull drives the round belt into the groove under tension, while working

Always use the heat joining green belting, far more durable than rubber, adjustable, and cheap.

I have used the Unimat of mine for the last 45 years, still going strong, mainly set up as a milling machine these days.

[bertiedog]

On reading the details supplied about the controller, can I recommend that the 20A versions of the controller are used, they cost only a couple of quid more on ebay, but the rating is higher, and gives a better margin on the ratings. The same can be said of the power supply, get as high a rating in amps as possible. It should be added that these switched mode supplies are really for lighting etc., and not motors, Motors can draw a surge current as they start, so get the rating high to cope.

Another consideration is where to put the on/off switch, in the mains feed or switch the DC on and off.. Best to switch the mains really, as these power supplies like a small load on them to function right, like a DC bulb across the feed, before the DC off switch, if used.

 

Thanks for the scooter motor references, I am working on a Lorch mini lathe that needs a new motor and the 24v volt type looks fine, especially at the price!

 

Stephen

[Richard Jones]

I would really like to change the motor on my Unimat SL and this looks perfect. I have bought the scooter motor but am struggling to remove the drive gear from the shaft. There is a retaining flange on the end of the shaft but even after removing this and with a gear puller, i am unable to pull the gear from the end. Any hints? Time to get the Dremell out? Many thanks for any advice, John

Hi

hopefully you are sorted by now - unfortunately at the time of your posting we were in the Southern Hemisphere for November, December and January

I couldn't shift the gear on the motor and ended up using a nut splitter to remove(destroy!) the gear whilst leaving the shaft intact

Cheers

Richard

[monkeysarefun]

 I know this is an oldish  thread but I bought an SL second hand in 1978 for $180 ,( which included almost every accessory). I was 15 and fully haired back then and that was a lot of pocket money...

 

Anyway, the motor burned out 2 months ago and I've been getting more and more dejected at the price of refurbished ones, so to find this topic here andt to find that I can resurrect my lathe is brilliant news.

I've had it for 39 years, and  apart from my body parts, I've owned nothing longer than I've owned my unimat. So thank you very much for posting this.

 

Just one question, Ive found a supplier of the same motor with the same specs here, but your link to the power supply doesn't work any more so I'm not sure on what  power supply I should get as regards to the Amp output. I last did anything  to do with amps and volts and stuff in science class  back in 1979, so I'm sure they've all changed since then, what with computers and the internet and so on.

 

Anyway, basically here's a list, which one should I get, they are all 24V?

 

10A 240W

20A 480W

30A 720W

5A 120W

15A 360W

17A 400W

 

 I've had this lathe for ages, and I just would love to get it working again...

 

Anyway, thanks again for posting this.

Edited May 27, 2017 by monkeysarefun

[bertiedog]

Just get the highest rated one available on Ebay, as long as it does not leap up in a price lurch. Check the Voltage it is meant to use, and provide a DC power supply, again via Ebay to suit the motors max rating. You cannot go far wrong by picking the highest ratings, it is just turned down in normal use.

 

A transformer and bridge rectifier can be used to power it, or a modern switched power supply, or two car batteries and a charger! Most of the motors are 24volts, but do check carefully in the listings. AND take with a pinch of salt the claims for Kilowatts of power or very high revs, the salesmanship of the Chinese knows no bounds with truth!

 

Go for a listing that quotes the ampage and voltage, ( you can get the real wattage by calculation), multiply them together.

If the power rating of the controller is Ok and the price is low, then by a spare at the same time, just in case of failure.

If the controller does not have a reversing switch , simply add a very heavy duty one from Ebay, centre off and forward and reverse, very simple to wire up.

 

Also generally use heavy duty cable to connect everything, the lighter meter spur cable is sound for the currents involved. Mains cable may over heat at full current. Also make sure all connections are soldered or screwed up really tight, no bad joints, they will burn if bad.

 

Again as always, if in doubt get an electrician to look over the whole thing to make sure it is safe to use, especially if you use a transformer at these currents. The power is not that high, but high currents do strange things to bad contacts, despite the lower voltage.

 

Stephen

[monkeysarefun]

Hi Stephen, thanks for the prompt reply. I've since found a website with more info on the motor I bought.

 

 

https://www.motiondynamics.com.au/united-my6812-24vdc-150w-2750-rpm-electric-motor-chain.html

 

Given this, I've found a site that sells power supplies, these are the options I have on a 24V one. I'm trying to take the easy way out by getting someone else to choose the right one from this list, given the above specs:

 

10A 240W

20A 480W

30A 720W

5A 120W

15A 360W

17A 400W

 

Thanks sincerely for the help so far.

Edited May 27, 2017 by monkeysarefun

[leopardml2341]

Hi Stephen, thanks for the prompt reply. I've since found a website with more info on the motor I bought.

 

 

 

https://www.motiondynamics.com.au/united-my6812-24vdc-150w-2750-rpm-electric-motor-chain.html

 

Given this, I've found a site that sells power supplies, these are the options I have on a 24V one. I'm trying to take the easy way out by getting someone else to choose the right one from this list, given the above specs:

 

10A 240W

20A 480W

30A 720W

5A 120W

15A 360W

17A 400W

 

Thanks sincerely for the help so far.

Looking at the spec sheet for the motor, for max torque (ie just at stall point) the motor delivers 267W of output power for which it needs 387W of input power.

 

Based on your figures I would choose the 17A 400W supply. But if there is a massive price difference between that and the 15A 360W I'd probably buy that one, knowing that I wouldn't be using it flat out all the time.

 

That's purely based on the info you have given for power ratings; you may want to research compatibility between the motor and type of power supply.

[monkeysarefun]

Hi Andy,

Thanks for the info. The site that has the motor recommends that power supply type (plus a DC speed controller) to power its motors, I just wasn't sure which rating to go for for that particular one. Thanks again