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This topic has 39 replies, 15 voices, and was last updated 16 August 2020 at 08:16 by Tom Walker 1.

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12 August 2020 at 06:23 #490210
Tom Walker 1
Participant
@tomwalker1
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.
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12 August 2020 at 06:23 #40883
Tom Walker 1
Participant
@tomwalker1
Intro
12 August 2020 at 08:18 #490224
Brian H
Participant
@brianh50089
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
12 August 2020 at 09:01 #490231
Howard Lewis
Participant
@howardlewis46836
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
12 August 2020 at 09:33 #490239
Chris Evans 6
Participant
@chrisevans6
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)
12 August 2020 at 12:18 #490266
Thomas Cooksley
Participant
@thomascooksley79020
Hi Tom, Welcome to the forum. from another Tom.
12 August 2020 at 15:58 #490293
Howard Lewis
Participant
@howardlewis46836
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
12 August 2020 at 18:03 #490323
Tom Walker 1
Participant
@tomwalker1
Posted by Chris Evans 6 on 12/08/2020 09:33:09:

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)

Thanks for all the welcomes.

Chris, I have taken off the VFD inverter and re-arranged the cables to supply the motor with my 3 phase.

I dont actually know if its a 2 speed motor or not, I need to look at the plate. But the switch would be a give-away surely?

The lathe would be a better machine with a 2 speed motor, and seeing as most people with 2 speed Bantams want to convert to single phase, which means ditching the 2 speed motor, I was hoping someone would have one under their bench.

As you can see, I am an optimist!
12 August 2020 at 19:34 #490341
Steviegtr
Participant
@steviegtr
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.
12 August 2020 at 19:43 #490344
Jon Lawes
Participant
@jonlawes51698
Posted by Steviegtr on 12/08/2020 19:34:35:

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.
12 August 2020 at 22:59 #490368
Steviegtr
Participant
@steviegtr
Posted by Jon Lawes on 12/08/2020 19:43:24:

Posted by Steviegtr on 12/08/2020 19:34:35:

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.
13 August 2020 at 09:53 #490394
Anonymous
Posted by Steviegtr on 12/08/2020 19:34:35:

Not sure why you would take off the inverter, when that would have given you any speed you wanted.

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
13 August 2020 at 10:06 #490395
Emgee
Participant
@emgee
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
13 August 2020 at 10:20 #490398
Simon Williams 3
Participant
@simonwilliams3
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
13 August 2020 at 14:00 #490435
Tom Walker 1
Participant
@tomwalker1
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
13 August 2020 at 14:13 #490437
Tom Walker 1
Participant
@tomwalker1
The inverter I took off is an IMO CUB5A-1. Outputs 0.75kW/1HP. 5.0A
13 August 2020 at 14:28 #490439
Howard Lewis
Participant
@howardlewis46836
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..
13 August 2020 at 14:38 #490440
Tom Walker 1
Participant
@tomwalker1
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
13 August 2020 at 14:52 #490445
Tom Walker 1
Participant
@tomwalker1
Probably not because that is only a 21% increase.
13 August 2020 at 15:46 #490453
Anonymous
They're the speeds for 50Hz and 60Hz. And the two currents are for 230V delta and 400V star respectively.

Andrew
13 August 2020 at 18:00 #490467
Tim Stevens
Participant
@timstevens64731
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)
13 August 2020 at 18:05 #490468
Simon Williams 3
Participant
@simonwilliams3
Ah ha!

We seem to have established this is a single speed drive, so the top speed is likely to be 800 rpm. It would be useful to know (by measurement in real life) what the top achievable speed is, also what does the gearbox plate say it is?

I have a 1.1 Kw motor on a Bantam 2000, my experience is that the top gear/high speed is beyond the capabilities of this motor. Otherwise it's brilliant, run off a Telemecanique/Schneider ATV inverter converting single phase to three on a simple 13amp plug.

On that basis I'd expect a 1 HP motor to drive the (low?) top speed perfectly well. BUT it's got to be configured in delta for a 230 volt line to line out of a simple inverter. The soft start function (if it's available) is an advantage.

As for the motor being weedy, give it some work and see if it struggles. More power isn't necessarily "a good thing" , it depends on whether you can turn (pun intended) it into useful work.

HTH Simon
13 August 2020 at 19:33 #490492
Tom Walker 1
Participant
@tomwalker1
Well Tim, Im not an engineer, so "weedy" was my definition of choice!

I am now thinking that it is the soft start that gives that impression. Im used to my machinery starting rapidly.

This advice has all been very useful, I am thinking of going back to the inverter.

Simon, what is your fastest speed, and are you happy with it?

Thanks, Tom.
14 August 2020 at 08:54 #490557
Harry Wilkes
Participant
@harrywilkes58467
Hi Tom

If you do re-install the VFD you could set the frequency to 60Hz to get a little more speed, it may be possible to up the frequency even more I think 25% is the recommended max.

H
14 August 2020 at 15:13 #490597
Tom Walker 1
Participant
@tomwalker1
That is very useful information Harry. I am not good on the finer points of "electric" as they say round here.

The inverter which was fitted to the Bantam when I bought it, came with a manual about an inch thick. I will have another go at reading it, and now you have pointed that out, it should make more sense. Much obliged.

On another note, the Bantam is installed beside my farm lathe which has been there for 30 years. It is a Colchester Mastiff, with an 8 ft bed, so they look fantastic side by side!! I would put up a photo if I could work out how…
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