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COLCHESTER BANTAM PROBLEM

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TIM RALPH02/12/2020 22:32:29
3 forum posts
3 photos

Hi. I have a Colchester Bantam Mk2 800. It's a 3-phase machine running off a Transwave converter. Recently it won't start and I've now discovered why. The foward / reverse electrical switch mustb have developed and fault and has been arcing and burnt away part of the switch. No wonder the overloads kept tripping. Does anyone have a spare switch, know where I might obtain one or got any other suggestions? I realise I could fit a straight forward FORWARD/OFF/REVERSE switch and may have to go that route if I can't obtain one but it will be so much better and safer to use the standard operating lever as I have been for the past 20 years. Thanks. Tim

Baz03/12/2020 11:42:57
524 forum posts
2 photos

Have you tried Colchester Lathe Spares?

Simon Williams 303/12/2020 12:24:24
561 forum posts
80 photos

My copy of the parts list shows a part number of the F/O/R switch but doesn't show a picture. It's a long time since I had the switchgear in pieces, and I can't readily get to it, so could you post a picture of the offending item? Does it have a manufacturer and a part number on it? The operating mechanism is a bit special, but the body of the switch if I remember right is a standard item.

From the cct diagram it's drawn as a six pole cam switch with four changeover poles (i.e. two as on/off/off and two as off/off/on) , the third (correction - fifth)  pole is on-off-on, and the fourth (correction - sixth) pole is off/on/off so it's nothing special. If you take the original to your local electrical wholesaler - City Electrical or Newey and Eyre or similar - they should be able to identify something functionally equivalent.

HTH Simon

Edit - corrected the pole numbers, I originally mis-counted the number of poles as four not six.

Edited By Simon Williams 3 on 03/12/2020 12:45:56

TIM RALPH03/12/2020 12:25:52
3 forum posts
3 photos

Yes thanks I emailed them last night but they replied this morning that they don't hold any electrical items. The original manufacturer of the switch Klockner-Moeller still exists in USA so I've emailed them about it.

TIM RALPH03/12/2020 12:58:28
3 forum posts
3 photos
Posted by Simon Williams 3 on 03/12/2020 12:24:24:

My copy of the parts list shows a part number of the F/O/R switch but doesn't show a picture. It's a long time since I had the switchgear in pieces, and I can't readily get to it, so could you post a picture of the offending item? Does it have a manufacturer and a part number on it? The operating mechanism is a bit special, but the body of the switch if I remember right is a standard item.

From the cct diagram it's drawn as a six pole cam switch with four changeover poles (i.e. two as on/off/off and two as off/off/on) , the third pole is on-off-on, and the fourth pole is off/on/off so it's nothing special. If you take the original to your local electrical wholesaler - City Electrical or Newey and Eyre or similar - they should be able to identify something functionally equivalent.

HTH Simon

Thanks Simon.. If I don't get any joy I will try somewhere. The switch is awkward to get to and took ages for me to get it off. As you say the funcitonality of it is fairly standard. The problem I envisage is that for a direct swap it must mate up with the operating mechanism and needs to turn by the same amount (about 30 deg in each direction).

Here are a couple of photos of it

F/R SWITCH 1

F/R SWITCH 3

If I don't get any joy I may be able to strip, clean and rebuild the switch so that it only uses the 1st undamaged segment. and only for feeding a contactor to bring in anothe FORWARD/REVERSE switch. That way the lathe will still be started and stopped in the same way and the rebuilt switch will only be operating on 110v and with minimal current to operate the contactor.

Tim

DC31k03/12/2020 13:28:08
340 forum posts
1 photos

If you put t2b-3-20 into Google, you obtain many results. Try this one as a starting place:

https://www.klocknermoeller.com/moeller.electric/2008/rotary-switches.pdf

It looks like the part numbers have changed, but I think the one you have is almost the exact centre of page 10.

As you say, it is an absolutely standard rotary drum switch. Every proper manufacturer will make one with the equivalent functionality.

If you cannot find one with an identical arc of operation, that is an engineering challenge that might easily be overcome with some thought.

Simon Williams 303/12/2020 15:16:59
561 forum posts
80 photos

I had a look in the Kraus and Naimer catalogue, they certainly do similar things. You might need to get your local K & N rep to take an interest!

Copy of the Kraus and Naimer C and CA switch catalogue here

There seem to be options for the operating angle, including 30 deg. I didn't find the precise electrical functionality, but it's only a combination of stuff they do in other switches. I've even (in desperation) mixed and matched the internals 'cos I was a long way from home and it was my ticket to paradise, but it's a pig of a job.

Let us know how it goes.

Rgds Simon

Tim Stevens03/12/2020 15:56:40
avatar
1306 forum posts

Hello Tim

I have just taken the electrics out of a Student (much the same as a Bantam, it seems) and so I have several electrical bits including a reversing switch. Contact me directly if you still need one. I also have the original 2 speed motor, and an earlier (1980?) big box to turn household single-phase mains to run the original motor, and the 'spare' 5 hp motor needed to sort out the 3-phase. Please form an orderly queue at 2m intervals.

But in the process of fitting a Transwave kit, I reduced the need for lots of complex 3-phase switchgear etc. Why not use the reverse facility - a simple switch - if the original is a problem?

Regards - Tim - bobweight@btconnect.com - 01547 529946 - half way along the Welsh border.

Simon Williams 303/12/2020 16:26:44
561 forum posts
80 photos

Sounds like that's a plan!

I've got a Bantam 2000, which is the same thing as an 800 but originally with a two speed motor and slightly different gearing (drive pulleys?).

One of the functions of the original switch is to stop you energising the controls after power on if the apron switch is not in the "stopped" position. So the motor can't do an involuntary start if the mains fails and returns (no volt release function).

I use this as part of the E stop function via the foot switch, so that once you have pressed the foot switch you have to move the apron switch to OFF before the controls will re-energise. It means that the foot brake is an emergency stop, which is not ideal if threading up to a shoulder for example, but I thought it was a price worth paying.

I re-built mine to use a VFD whilst keeping the original switches so it looks and functions as closely as possible to the original. The reversing function uses the switch contacts of this F/O/R switch connected directly into the VFD , no longer taking the motor current.

Rgds to all

Simon

The two speed function is now achieved by feeding a single speed motor with 50 or 100 Hz. Actually this won't get me the top 2000 rpm speed as the motor runs out of puff, but otherwise it's been very successful.

old mart03/12/2020 18:44:56
2464 forum posts
169 photos

There should not be any switch between the motor and a VFD.

Simon Williams 303/12/2020 19:32:45
561 forum posts
80 photos

If that's aimed at me, there isn't.

But thank you for your concern.

Simon

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