Colchester Student Mk1 Won’t Start

[larry phelan 1Participant @larryphelan1]

Not sure if this will help or not but when I moved to the sticks I borrowed a static converter to try it out. It would run my lathe and mill, each 1.5 hp but not my planer or spindle moulder, each 4hp, just make buzzing noises. Problem was solved by buying a Transwave 10 hp rotary converter. This is big enough to run anything in the shop. Perhaps your converter is simply too small? Static converters do not seem to have the same kick as rotarys and sometimes you need to adjust loads ect, this can be A-Pain-in-the arse.. With the rotary, just switch on and walk away.

[Swarf MakerParticipant @swarfmaker85383]

There seems to be some mis-reading of the circuit diagram going on here. The top set of switch contacts (6 off) in the upper part of the diagram all relate to the Santon switch.

Rotating the switch from 'OFF' to 'ON' just turns on the coolant pump and the contactor has no part in this.

Rotating the switch further additionally applies power to the terminals of the 'Motor Starter' (contactor). A contactor is used here to avoid the switch load on the Santon switch and to provide 'no-volt' release in the event of a power failure. It may also incorporate a means of disconnecting power to the motor if too much current is being taken.

I will leave things at that point rather than confuse the points made above.

[SillyOldDufferModerator @sillyoldduffer]

Posted by David Davies 8 on 27/11/2019 12:53:51:

SOD, I think you are mistaken.

''According to the circuit diagram the contactor has two pairs of 3 switches. One pair connects three phase to the pump and the other connects 3-phase to the main motor.''

The Colchester diagram shows the coolant pump being started directly from the rotary switch, by 3 of the poles, the other three poles are connected to the line contactor and thermal overload and thence to the spindle motor.

Hope this helps.

Dave

Dave and Swarf Maker are correct – I've misread the diagram. A1 to to C2 refer to the Santon Rotary Switch, not the contactor! Please ignore what I said! Sackcloth and ashes again!

Sorry,

Dave

[Phil WhitleyParticipant @philwhitley94135]

I am getting it wrong too! you lift the front lever to turn the lathe motor on, and push it down for off! I spotted this today when I used my lathe, you can't miss it really!. OK, time to drain the coolant sump unblock the pump, and see if it is actually running, or just buzzing. If it is actually running, we know that three phases are coming out of the converter.I think there is an exposed peice of pump shaft that you can see rotating, I will check tomorrow..

Here is the starting sequence, turn on the power, set the motor/coolant pump switch to motor, and lift the front lever with the red control knob, when you lift the lever, you should hear the contactor pull in, and the motor should run.

When you lift the lever, it operates the "limit" switch at the rear of the headstock which completes the circuit to the coil in the contactor, and the contactor pulls in, and the motor should start. if the fwd/rev switch is after the contactor (I suspect it is) then it may be that this switch is faulty. I assume you have tried switching between forward and reverse a few times, but if you haven't, do it with the power off, then try the lathe again. can you post up a pic of the contactor taken from square in front of it so we can see all the contacts and connections (several pics not objected to!), and also a general one of the headstock controls, and the motor panel, so we can see what we are dealing with. We will get to the bottom of this!

[Phil WhitleyParticipant @philwhitley94135]

just thought of something else, if the front start/stop lever is already up, and the lathe is operating as per handbook, the motor will not start. You must turn on the power with the start/stop lever in the down position, and then lift the lever to pull in the main contactor, and the main contactor makes a fairly loud clunk, as others have said! This is a safety feature of contactors/starters known as No volt release, if you are operating the lathe, and the power fails, the contactor drops out, and when power is restored, the lathe will not restart unattended. before you apply power, check that the start/stop lever is in the down position. switch power on, and then lift the start/stop lever. I will check this on my lathe tomorrow. CHECK THAT YOUR LATHE IS EARTHED!!!

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 27/11/2019 19:30:46:

I am getting it wrong too! you lift the front lever to turn the lathe motor on, and push it down for off! I spotted this today when I used my lathe, you can't miss it really!. OK, time to drain the coolant sump unblock the pump, and see if it is actually running, or just buzzing. If it is actually running, we know that three phases are coming out of the converter.I think there is an exposed peice of pump shaft that you can see rotating, I will check tomorrow..

Here is the starting sequence, turn on the power, set the motor/coolant pump switch to motor, and lift the front lever with the red control knob, when you lift the lever, you should hear the contactor pull in, and the motor should run.

When you lift the lever, it operates the "limit" switch at the rear of the headstock which completes the circuit to the coil in the contactor, and the contactor pulls in, and the motor should start. if the fwd/rev switch is after the contactor (I suspect it is) then it may be that this switch is faulty. I assume you have tried switching between forward and reverse a few times, but if you haven't, do it with the power off, then try the lathe again. can you post up a pic of the contactor taken from square in front of it so we can see all the contacts and connections (several pics not objected to!), and also a general one of the headstock controls, and the motor panel, so we can see what we are dealing with. We will get to the bottom of this!

In that case i definitely do not hear the contactor, the only noise i hear is the slight click of the red or in my case black knobbed handle clicking into place.

Can't get any more pictures of the lathe till the 13th, but i think i may have a few other pictures somewhere

Thats the isolator box i had to wire a plug to when I first received the lathe, not too relevant I don't think, but just covering all bases, as there could be issues anywhere

And that's how i wired it, I think it was 2.5mm 4 core. So as you said that should be earthed?

Looking closer at the motor plate it says its from 1955, so quite old. It also says if i read it properly that the motor is 1.5hp. perhaps the earlier models had smaller motors. I will double check this when i'm home as the picture isn't the best. However, if it is 1.5hp then perhaps a 3.5hp static converter will be enough to power it for now (especially if Mal said his powered it for a few years)

This is where the wires leave the control board and lead through the casing to the coolant pump, just the 3 white wires

Another random picture, doubt it's of any use, but the more the better

Was this the sort of straight on picture you wanted?

That's the lathe itself, still has a lot of cleaning to be done, but need it working first. As you can see, my forward reverse switch is not original like on your lathe Phil.

I'll be able to get more pictures and even videos when i'm back

Edited By Richard Kirkman 1 on 27/11/2019 20:07:49

[Swarf MakerParticipant @swarfmaker85383]

Well, I see the nice new cable with its plug going into the big switch box. What I don't see are any wires coming from the output contact set of that switch and into the lathe itself. Are they routed through the backplate of that switch? There is a hole for the wires to come out but nothing visible.

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Swarf Maker on 27/11/2019 20:32:39:

Well, I see the nice new cable with its plug going into the big switch box. What I don't see are any wires coming from the output contact set of that switch and into the lathe itself. Are they routed through the backplate of that switch? There is a hole for the wires to come out but nothing visible.

Yeah they go out the back into the casing, don't have any pictures of where they go. Not too sure if I even know where they go, but it shall be investigated

[Phil WhitleyParticipant @philwhitley94135]

Right Richard, that is the same as mine, save for the fact that yours is earlier, and has the flat cast iron gear handles, mine has all rod type handles. The pic of the contactor panel is exactly what I wanted, I will look it over and get back to you, meantime I have messaged you, if you look at the top bar of the page, you will see a little envelope flashing! Your lathe has a hole near to the top right hand corner of the electrical panel, this is where the dual speed motor switch was fitted, I wonder if the motor has been changed? I thought this hole was only drilled when needed, which would indicate that yours was once a dual speed motor. Yours is gap bed, mine is straignt bed, Mine has the two speed motor, and needs new main spindle bearings, which luckily, I have! very original looking machine. We will have it running, one way or another!

[Phil WhitleyParticipant @philwhitley94135]

Right, there are several areas of the contactor I am not happy with, mainly, as everyone else has noted, the middle of the three contacts appears to be missing, but I can't be sure of that, it may have been modified so that it still works. When I first saw these pics at the top of the post, I thought they were examples of a different lathe, not your actual machine, I see from the ones you have just posted that they are yours. I will pull my control panel tomorrow, and have a look, but I think mine has the later contactor (Crabtree?) fitted. Below the plug in pins on the board, you see three coils, these are the overload tripping coils. the long straight bit of paxolin that goes across the top of all three appears to be a manual reset, you could try pushing it up from the bottom end, where the long arm sticks down, and see if it clicks and closes the overload contacts, may have tripped out if the phase convertor cannot produce enough power for starting. There are various areas on the whole panel that look to be overheating, or have been in the past, and TBH, rather than try to repair it, it would be easier and quicker to take the old contactor off the panel, and replace it with a modern one, keeping all the outside controls as original, but putting new guts inside! having said all this, if two phases are getting to the motor, it should growl and try to turn, and if the contactor is not pulling in, the overloads are irrelevant, as they come after the contactor in the circuit, and the way you have described it, the main contactor is not pulling in anyway. they are LOUD!!

Phil

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 27/11/2019 20:47:28:

Right Richard, that is the same as mine, save for the fact that yours is earlier, and has the flat cast iron gear handles, mine has all rod type handles. The pic of the contactor panel is exactly what I wanted, I will look it over and get back to you, meantime I have messaged you, if you look at the top bar of the page, you will see a little envelope flashing! Your lathe has a hole near to the top right hand corner of the electrical panel, this is where the dual speed motor switch was fitted, I wonder if the motor has been changed? I thought this hole was only drilled when needed, which would indicate that yours was once a dual speed motor. Yours is gap bed, mine is straignt bed, Mine has the two speed motor, and needs new main spindle bearings, which luckily, I have! very original looking machine. We will have it running, one way or another!

The picture of the lathe appears to show a hole, but its just a small sticker that has a 1 on it

So I'm pretty certain that it has never ever been dual speed. The motor is definitely original too, so I don't think its a possibility.

And yes, I watched a video of someone dismantling a similar lathe and repairing it, but the circuitry was different as it was a later model similar to yours.

**LINK**

At about 9:10 you can see the inside of his lathe

and there is a better video of a crabtree here

**LINK**

But, i couldn't really see how it worked compared to my model

[Phil WhitleyParticipant @philwhitley94135]

well richard here is the internals of mine, for what its worth !(not a lot as it is different), the start stop lever does work as I said earlier, if you put power on to the lathe with the start lever in the up position, the pump will run, but the main motor will not, until you press the handle down then lift it up again.

Looking at the pics of your contactor,The three black wires connected to the terminals to the right of the three pin plug, on the overload coils, go to the motor, the three blue wires connected to the other side of the overload coils are the feed from the contactor. You should, with a multimeter, be able to test three seperate phase wires from the isolator switch (check the action of the switch to make sure all three blades are going in to the contacts properly) on the back, through to the three pin socket in the back of the control box, then test from the pinsof the "plug" part to the rotaty switch , out of the switch to the contactor, from the other side of the contactor to the overloads, and then on to the motor, via the reversing switch. The missing contact on the contactor is irrelevant for now, as the contactor is not even pulling in, and it should do this even if it only ends up sending two phases to the motor because of the missing contact. When you have established that three phases are getting to the input side of the contactor, check that you have continuity through the contactors operating coil, and then you will see that one side of the coil is connected directly to a phase and the other end of the coil goes off to the safety switches on the gearbox end cover, and then to the "limit" switch on the back of the headstock, which completes the circuit to pull in the main contactor. Looking at the oily state of the limit switch that could be full of muck and oil, and not making contact, take the lid off and check it, I am going to try to post up the wiring diagram from my lathe, although the contactors are different, they are electrically identical, and this diagram is somewhat easier to read and understand.

Phil

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 28/11/2019 21:14:38:

well richard here is the internals of mine, for what its worth !(not a lot as it is different), the start stop lever does work as I said earlier, if you put power on to the lathe with the start lever in the up position, the pump will run, but the main motor will not, until you press the handle down then lift it up again.

Looking at the pics of your contactor,The three black wires connected to the terminals to the right of the three pin plug, on the overload coils, go to the motor, the three blue wires connected to the other side of the overload coils are the feed from the contactor. You should, with a multimeter, be able to test three seperate phase wires from the isolator switch (check the action of the switch to make sure all three blades are going in to the contacts properly) on the back, through to the three pin socket in the back of the control box, then test from the pinsof the "plug" part to the rotaty switch , out of the switch to the contactor, from the other side of the contactor to the overloads, and then on to the motor, via the reversing switch. The missing contact on the contactor is irrelevant for now, as the contactor is not even pulling in, and it should do this even if it only ends up sending two phases to the motor because of the missing contact. When you have established that three phases are getting to the input side of the contactor, check that you have continuity through the contactors operating coil, and then you will see that one side of the coil is connected directly to a phase and the other end of the coil goes off to the safety switches on the gearbox end cover, and then to the "limit" switch on the back of the headstock, which completes the circuit to pull in the main contactor. Looking at the oily state of the limit switch that could be full of muck and oil, and not making contact, take the lid off and check it, I am going to try to post up the wiring diagram from my lathe, although the contactors are different, they are electrically identical, and this diagram is somewhat easier to read and understand.

Phil

Thanks Phil, I think I'm starting to understand a bit the stuff you're saying.

I've responded to your message, so there should be something in your inbox.

Thanks

[Phil WhitleyParticipant @philwhitley94135]

Moderators! can you move these pics 90 deg to the right please!

some pics of the inside of the "limit" switch which is used as the start/stop switch on the student.

First in the OFF position

And in the ON position

Off connects the red to the blue, and on connects the yellow to the blue, both contacts on the blue side of the switch are linked. the problem we have here is trying to reproduce the wiring diagram, as ALL the manuals I have looked at so far have small diagrams that will not enlarge without loss of print quality, and also some badly printed with wires that fade out to nothing! Making it work is easy for a sparky, but I want to reproduce a wiring diagram that shows the factory wiring, as this is what Richard has to deal with, I will soldier on, but if anyone has a copy of the wiring diagram without printing flaws, and of a reasonable readable size, post it up!! The basic contactor/switching arrangement is all there, but the safety/NVR circuit has bits missing on all the diagrams I can find

[Phil WhitleyParticipant @philwhitley94135]

Hold the bus!! I have just looked at the PDF of a Colchester Clausing manual, which states that the limit switch has THREE positions, and having now tested mine, find this is correct! there is an intermediate position where the red and blue remain connected together till the handle moves past the mid position, and the overcentre spring mechanism jumps from the bottom pair of contacts to the top pair (see pics above, which need rotating 90 deg) The clausing manual has a better wiring diagram, but I need to check out some of the none SI symbols to confirm it is the same.

Phil

[Richard Kirkman 1Participant @richardkirkman1]

Posted by Phil Whitley on 05/12/2019 14:40:50:

Hold the bus!! I have just looked at the PDF of a Colchester Clausing manual, which states that the limit switch has THREE positions, and having now tested mine, find this is correct! there is an intermediate position where the red and blue remain connected together till the handle moves past the mid position, and the overcentre spring mechanism jumps from the bottom pair of contacts to the top pair (see pics above, which need rotating 90 deg) The clausing manual has a better wiring diagram, but I need to check out some of the none SI symbols to confirm it is the same.

Phil

So what does each position do to the circuit. It's the part from the no volt release sort of bit, the ring with the key and cover and stuff, so is the intermediate position where we lifted the handle and it only beeped for a second and stopped after the handle was raised further?

Also, I've sent my flatmate back to Driffield with something I've made for you. Nothing too special, but you can always heat your workshop with it if not.

Thanks

[Phil WhitleyParticipant @philwhitley94135]

Right richard, here we go, the clearest and best wiring diagram is in the free download manual from the Colchester site, even though it is for a Mk1.5 with a different make of contactor, they are electically identical.

Refering to the drawing you will see what we call the limit switch (because that is what it says on the case) is referred to as the Craig and Derricot release switch.

Starting at the contactor coil, you will see that one side of the coil is connected to L1 which is an incoming phase. Remeber that the coil works between two phases, there is no neutral in this set up!

The other side of the coil connects to terminal 2 on the contactor, and then to the red wire which goes to the C&D switch terminal 3.

The other phase used is L3 which goes via a link wire through terminals 10 and 9 on the contactor, which are the overload cut out switches, and then on through the yellow wire from terminal 9, through the end cover and lock switches to terminal 1 on the C&D switch. Note a mistake on the drawing, in that the yellow and red wires which cross adjacent to terminal 3 on the C&D switch are NOT connected but the semicircle has been ommitted from the drawing!

When the end cover is fitted, and the key switch is on, terminal one, yellow wire on the C&D switch is "live".

When the switch is lifted from the off position to the intermediate position, (we will call the unmarked terminal on the C&D switch 4) 1 and 4 are connected together, and 2 and 3 remain connected. the live goes from1 to 4, down the link to terminal 2 across the switch to 3 and back to the coil on the red wire, and the contactor pulls in/motor starts.

on the contactor, the holding in contacts close the circuit between 1 and 2, and as the start handle is moved fully in to the on position, the C&D switch opens 2 and 3, and 1 and 4 remain closed. Machine is now running, and terminals 1 and 4 on the C&D switch have become part of the holding in circuit and the machine will continue to run till the contact is broken by pushing the lever to stop, or if the power fails, the end cover is removed, or the key switch is turned off.

Refer to the wiring diagram whilst reading this, as I did when writing it, or it will make no sense! My money is on the key switch being in the off position. Good luck with it, and I will still be here for any further questions you have, and any further assistance you may need,

I'll make a sparky of you yet!

Phil

Edited By Phil Whitley on 07/12/2019 18:10:45

[Phil WhitleyParticipant @philwhitley94135]

Link to manual.

https://colchesterlathe.groups.io/g/main/files/Colchester%20Student/Colchester%20Student%20-%20Mk1%20%28Round%20head%29/Colchester%20Student%20Mk1%20-%20Instruction%20and%20spare%20parts%20manual.pdf

[Richard Kirkman 1Participant @richardkirkman1]

Been back to have a play today, had a look inside the "limit switch" and it doesn't look the same as Phils.

Thoughts?(apart from it being filthy)

[Phil WhitleyParticipant @philwhitley94135]

Hi Richard, all the wiring diagrams using this type of switch use three wires to the switch, the yellow is missing, and it is the yellow wire that takes the "live" through the end cover switch and the key switch to the C&D switch! the red is connected to the terminal where the yellow should be, see if you can trace the red back to the starter and see where it goes. even if it has been wired in some way to make it start, the NVR cannot work unless tyhere are three wires at the C&D switch.

Phil

[Phil WhitleyParticipant @philwhitley94135]

Take the red tape off the yellow wire in the starter area, leave the end cover on, remove the panel round the key switch and see if you can test from the yellow wire in the starter to the key switch to see if you can find out where the yellow wire goes to. It should start at C1 on the contactor, go through the end cover switch, through the key switch, and to terminal one on the C&D switch.

Phil

[Phil WhitleyParticipant @philwhitley94135]

Richard, the switch mechanism seems to be working correctly, but I would guess it is lacking the correct live feed, I am going to reproduce the wiring diagram out of your original manual in a more readable format, with the errors taken out, but I am working tomorrow, so will do it at the weekend. in the meantime, see if you can find any other disconnected wire ends, especially yellow ones!

Phil

[Richard Kirkman 1Participant @richardkirkman1]

The lathe is alive. I spent quite a while using a multimeter testing for continuity in the circuitry, however I couldn't find anything wrong except from the way someone has changed the wiring. They have changed it so it no longer has the safety features, so the key switch, switch in the left of the headstock for the gear cupboard and others don't affect it. No longer has a no volt release either.

So I had a play with the wires in the isolator, swapped two of the phases round and it worked. Someone suggested this a while ago.

However, even though the lathe is now spinning a bit, it's still not happy about it.

Phil, I mentioned that your lathe spun a lot more easily than mine did, I think there's too much resistance as the static converter is struggling to power the lathe.

The converter has different power settings, from 0.5 to 3.5hp. but it works best on 2hp for the 1.5hp motor. I'll get some footage of the lathe on different speeds and the effect it has on the converter and post it later. I took the brake apart and it's not causing any resistance (apart from when pushed).

Any thoughts? Videos to follow

[Richard Kirkman 1Participant @richardkirkman1]

On second attempt, trying every speed, it seems to be able to get into most but the higher speeds. Also running the phase converter at full 3.5hp instead of the 2hp stated before

52 speed video

86 speed video

118 speed video

192 speed video

272 speed video

445 speed video

It doesn't seem to want to get up to speed when the 445 speed is set

I'm not sure what condition the motor is in, Its the original from 1955 so it could be knackered?

But, also the phase converter may be old already since I bought it from the back reduced section of machine mart

[Stuart BridgerParticipant @stuartbridger82290]

My money would be on the converter not having enough oompf. The "phantom" 3rd phase approach of thesedevices is not ideal.

Also if it as not been run for a while, ltet it warm up for a while before trying the top speeds. It may need the oil needs warming up. When I first got my Chipmaster it wouldn't go a full pelt (3000 rpm).
There is not much that can go wrong in an induction motor, so I expect the motor is OK

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