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COLCHESTER BANTAM PROBLEM

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TIM RALPH02/12/2020 22:32:29
6 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
714 forum posts
2 photos

Have you tried Colchester Lathe Spares?

Simon Williams 303/12/2020 12:24:24
652 forum posts
82 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
6 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
6 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
662 forum posts
2 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
652 forum posts
82 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
1588 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
652 forum posts
82 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
3728 forum posts
233 photos

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

Simon Williams 303/12/2020 19:32:45
652 forum posts
82 photos

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

But thank you for your concern.

Simon

needleworks04/01/2022 09:03:24
14 forum posts

I know this is an old thread but did this problem ever get resolved ??

I am now having the exact same problems.

TIM RALPH04/01/2022 20:38:05
6 forum posts
3 photos

It took a few months but I finally got there. I couldn't find a suitable switch anywhere. I did eventually manage to get another switch on ebay from a Colchester Student that looked similar but internally it was quite different and the connections were completely wrong. I did however manage to salvage enough from mine to build one out of the two, modifying some parts as necessary. I thought I had some photographs but can't find them and my memory's very hazy about what I actually did. It works absolutely fine now.

I found the problem had been caused by oil getting into the switch causing the arcing.

If I had to fix it again I would search for klockner moeller t2b on ebay. A switch with 3 or more segments would do. I would then hope I could make one out of the 2. When I was searching I did find a few on ebay that were from abroad but the only one that wasn't stupidly expensive kept refunding my money when I tried to but it. I wasn't prepared to pay a great deal of money for something that might instantly have proved to be totally unsuitable when it arrived.

Good luck.

needleworks05/01/2022 09:20:43
14 forum posts

Thanks for the info Tim, much appreciated

Brian Wood05/01/2022 10:08:10
2549 forum posts
39 photos

Needleworks,

I think you might find Radio Spares stock these drum switches, if you can find your way through the on-line catalogue!

Regards Brian

needleworks10/01/2022 06:46:42
14 forum posts

Thanks Brian, had a shot at fixing it this weekend and here's where I'm at now. I got one of my friends round who is actually a plant electrician, which means he works with 3ph motors all day long. I purchased another rotary cam switch which he said "yeah, that should do" He wired it up according to the numbering which was already on the old switch, and nothing ! He checked again, moved a couple of wires around, this time the contactor clicked in, but as soon as he tried to put it in either forward or reverse, it just tripped the breaker. We tried for over 4 hours with a combination of moving wires to where he thought they should be, but all we can come up with is either nothing or a tripped circuit. Does anyone know if we are missing something here as I am starting to pull my hair out ! Surely it's only a simple switch !

TIM RALPH10/01/2022 09:49:15
6 forum posts
3 photos

Do you have a manual with a wiring diagram in it? Sure it is a simple switch but with specific connections on each setting (ie FORWARD - OFF - REVERSE). You definitely need to have the connections correct straight away not trying different combinations! I don't know if your switch will be the same as on my Mk2 800. The problem I had when trying to source a replacement switch was that there are plenty of forward/reverse switches out there which simply make the connection for the 3 separate phases in FORWARD and swap over 2 of the phase connections in REVERSE but in the OFF position there is no connection at all. However on my lathe Colchester also used the same switch to pull in the contactor when in the OFF position. This means that the switch has a separate pair of contacts that are only made in the OFF position and are open in the Fwd/Reverse positions. I could not find that on any of the replacement switches that I looked at. Assuming the wiring is the same as for my lathe, unless your new switch has the 4th set of contacts to be made in the OFF position you will never be able to get it to work without modifying the lathe wiring. I did not want to do that as the safety feature it provides works brilliantly with the standard fwd/reverse lever.

john fletcher 110/01/2022 10:04:48
785 forum posts

In former time when I rebuilt multi terminal rotary switches I used to do it in a large clear plastic bag then any wayward screws, clips etc would be captured. Also for Tim friend needs to write up a truth table for the switch, which will clearly shows which pair of contacts are open and which are closed 0 and 1. I don't know how to send a table on here, but if Tim sends me a PM with his email address I'll send him one, for single and three phase motors. klockner moeller switches are readily available from many electrical wholesalers. John

needleworks10/01/2022 10:45:11
14 forum posts

Unfortunately I don't have a wiring diagram Tim, it sounds to me like your lathe is just the same as mine though. My mate already discovered that the contactor needed to be pulled in when in the off position, so we tried a 4 pole switch which turned out to be unsuccessful. Like you, I would much prefer the lathe to run as was intended, eg using the apron lever without any modifications.

needleworks10/01/2022 10:50:11
14 forum posts

I wish I could find some kind of table/diagram John, it would help me out a lot. Also I am finding it really hard to locate a Klockner Moeller switch in the UK that is similar to the one I am trying to replace.

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