Good morning

Hallo I have just joined, as I now have more time being semi retired. So now I want to get stuck in to more fettling. (So does my missus!).

I am a vintage car/bike enthusiast, living in Leicestershire UK. I have set up a small machine shop in my workshop, and have been a keen reader of the ME website for many years.

I have just bought a nice Colchester Bantam lathe (square head, not sure which MK) which came with an inverter. I have 3 phase, so re-connected the motor, and it works very nicely.

But I would like to get it running with the 2 speed motor. So I need to find someone who has one, and hopefully the necessary switch gear to make the change.

Also any advice gratefully received.

Thanks, Tom.

Hello Tom and welcome. Can't help with the lathe I'm afraid but I'm sure someone who can will be along shortly

Brian

Welcome!

When things approach normal, if ever, do join a local Model Engineering Club, to socialise and get face to face help when it is needed.

Lots of experience on here, so lots of advice, should you need it, waiting in the wings.

Howard

Welcome along Tom. Does your lathe still have the original two speed motor ? Some Bantams I have seen are fitted with a single speed motor and VFD inverter.

Chris. ( another vintage bike guy)

Hi Tom, Welcome to the forum. from another Tom.

Welcome!

A lathe is a most useful tool.

Now can you will able to do all sorts of jobs.

Beware the neighbour "Got a little job for you, shouldn't take long. Can you just..... )!

At least you stand a good chance of repairing something that breaks at 7:00 o'clock on a Saturday night, and is in constant use or need.

Go for it!

Howard

Not sure why you would take off the inverter, when that would have given you any speed you wanted. Oh & welcome to the Forum.

Steve.

You assume it was a variable inverter.

Yes. I know there are some transverters that are not. But most inverters that i have come across are variable. Wait for op to respond maybe.

Steve.

Probably because the OP has 3-phase available and if he wants to run his industrial machine to capacity he'll be better off using the motor as designed rarther than an inverter. Power is more important than infinitely variable speed.

Oh, and welcome to the forum Tom.

If the lathe has a 2-speed motor I assume there must be an electrical switch somewhere on the controls for low and high ranges? Both of my machines that have 2-speed motors have these switches, two in the case of the horizontal mill.

Andrew

As Andrew says the Bantam 2 speed motor is controlled by a 2 speed switch/contactor arrangement, 800rpm spindle speed in low range with max 1600 in high range. Full wiring details in the manual.
From memory there are 6 selectable speeds by lever in each of the ranges, lowest being 32rpm in the 800rpm range.

Tom

If you want copy of the manual send me a PM (click on Message Member at bottom of message) with your email address and I can send you a copy.

Emgee

Edited By Emgee on 13/08/2020 10:11:53

Good morning Tom, welcome to the madhouse. From the sounds of it you have yourself a very pretty Mk2 Bantam, comes in various guises, the two speed ones are either 1600 RPM version or a 2000 rpm version.

The original motor is wound as a 4 pole or a 2 pole machine, and the connections to it go via a multipole four position switch (high/off/low/off) located under the front of the chip tray, The original motor will have been taken off because the windings need 400 volts and the conversion to run in delta on 230 volts is too complicated.

Unfortunately the 2 speed motor I took off mine got scrapped in the last factory move, but I'd stick with the inverter for sure. High and low speeds - particularly the ability to go below the marked bottom speed on a large diameter item - soft start, dynamic braking and all the other advantages of a VFD. Assuming, as above, that the inverter has these functions. If not I would spend the money on fitting one that does, not resurrecting the original controls.

Power limit with a geared head machine is unlikely to be a deciding factor in a hobby shop, and if it is I suggest a Bantam isn't the right tool for the job.

If you do want to return the electrics to original all the details are in the user manual, copies often on ebay or from Tony at lathes.co.uk. There are circuit diagrams for all the variants.

HTH Simon

OK, I can see there are a few things to consider.

My Bantam seems to have a single speed motor, because the switch is only On and OFF. I will see if the plate states otherwise,( though I dont really know what Im looking for).     It came with a variable speed inverter, so initially I ran it off my single phase supply.

I did make some (probably bad) assumptions. ..............

1. It felt a bit "weedy" (probably the soft start).

2. If you have 3 phase, everything should be on it.... you will have more horsepower, which HAS to be a good thing.

3. I didnt think that the fastest speed was fast enough, in either inverted form or with the single speed 3phase motor. When tuning small jobs, I thought I could do with more revs. (I didnt put a rev counter on it in either form though.)

So the easy thing to do was to take off the inverter, and re-jig the connections to give me 3 phase. Then I read about the 2 speed motor, so that has become the Holy Grail. Just how my mind works!

Thanks for the advice so far, please let me know what you think.

Tom.

Edited By Tom Walker 1 on 13/08/2020 14:02:48

Edited By Tom Walker 1 on 13/08/2020 14:24:29

The inverter I took off is an IMO CUB5A-1. Outputs 0.75kW/1HP. 5.0A

My lathe (12 " swing 24" centres ) is not really in the Colchester class, but as part bf the deal, to buy new, the 2 hp single phase motor was replaced by replaced by a 1.5 hp 3 phase with VFD.

So may be yours appears a bit "weedy" because it is underpowered?

What power was the original , presumably three phase, motor?

Having said that, have never found anything too much for the 1.5 motor on mine. maybe i don't work it hard enough!

Howard..

OK, so the motor plate says all this. It is an AEI motor.

Type:    BK.2410 CG B56

Volts:    220/250-380/440

Phase:   3      C/S: 50/60

HP : 1       A: 2.82/1.63

RPM:    1425/1725

BS 170: CONT (not very legible, may be wrong)

So, does the dual figure for RPM mean it IS a 2 speed motor?

Edited By Tom Walker 1 on 13/08/2020 14:38:55

Edited By Tom Walker 1 on 13/08/2020 14:40:24

Probably not because that is only a 21% increase.

They're the speeds for 50Hz and 60Hz. And the two currents are for 230V delta and 400V star respectively.

Andrew

Hello Tom Walker

It is not general in engineering (or the rest of stuff) to evaluate the power of a component by feel. Especially if there is no information about how the feel was detected or measured. And even if there was, weedyness is not a unit (metric or imperial) to be found in any of the various text books, etc. But stick with it Tom and welcome to the Forum. I changed my (smaller) lathe from a single speed motor to a variable inverter system and I would not go back - there are so many advantages.

Regards, Tim (mid wales borders)