Colchester Student Mk1 Won’t Start

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Phil Whitley on 25/05/2020 10:53:57:

Hi both, that is the same capacitance meter that I use Richard, dont forget to short out the capacitors before you test them, any residual charge will blow the meter! Now I have seen the bearings on the feet, I am even more jealous!! Herman has the feet, Richard has the holes where the feet should be, but I don't think I even have the holes, I will check today, photograph, and report back!

Phil

Best is to take a 60W 230V incandescence bulb and screw this into a bulb holder with two wires connected. At the end of the wires put two insulated prongs. Now touch the terminals of the caps with the prongs and the bulb will briefly flash. No bang, no sparks and no need to be scared.

@Phil, I can measure the locations of the feed if you want to install your own.

[Herman van der MerweParticipant @hermanvandermerwe76509]

BTW I uploaded a very interesting manual on dismantling Colchester lathes on groups.io.

[Richard Kirkman 1Participant @richardkirkman1]

I don't have an incandescence bulb lying around, so I'll just scare myself.

That isn't a loose wire at T1. I checked all the wires were tight when it arrived. It seems like I'm going to have to strip everything out and clean everything. It looks like I'm going to have to learn how this works. I am interested in the exact working and how easy it would be to reproduce.

I found someone on eBay selling a LO faceplate. Turns out he's also selling a converter the same as mine, but with some actual info. It's made by Danebury. Mines the 3.7Kw or 5hp

[Phil WhitleyParticipant @philwhitley94135]

Evening all!, well I was right, I haven't got the holes, or the threads, I have two bolting down holes without threads at the headstock end, and one,central, at the tailstock end

 

The hole that you guys have in the cupboard at the front of the lower shelf is not there on mine! Don't bother with the measuring Herman, it is sitting firmly on a level floor, and it is staying where it is until after I have replaced the spindle bearings and then do the alignment!

Phil

Edited By Phil Whitley on 25/05/2020 20:48:57

[Richard Kirkman 1Participant @richardkirkman1]

Capacitance meter arrived, It seems fine

I've taken the capacitors out and measured them all, but they're all within tolerance?

The stuff at the bottom honestly looks like bird poo to me.

Small one is 60 micro farrads and the big ones are both 80.

The wire you said was loose isn't loose, it's just not pushed in far enough. It will be sorted

Any thoughts on anything?

What is the red box for and what does it do.

Found the capacitors online, or similar replacements. not sure if they're the identical ones I need. But a full set of 3 would put me back around £75. 

60

80

Edited By Richard Kirkman 1 on 27/05/2020 18:08:55

[Phil WhitleyParticipant @philwhitley94135]

If the capacitors are measuring within tolerance, I would leave them for now, I must admit I did think you would have seen at least one out of limits. There is another test you can do, but it requires another tester, although it would be a lot cheaper than new capacitors, look up "equvalent series resistance tester or ESR. I would definitely replace the blackened spade connector, that has overheated and is not carrying the current it should be, that could even be all that is wrong with the convertor. I think the red box is a timer relay that switches the motor from start to run in the time set by the control on top. give the relay contacts a clean, replace the spade tag, and try it again.

Phil

[Richard Kirkman 1Participant @richardkirkman1]

I will measure the capacitors again tomorrow to double-check

I'm not sure how the relay can be cleaned, seems like a lot of pins to me

I sorted the wiring that was poking out too far

Where do I find replacement spade tags? Just eBay?

I checked the contactors for continuity and they were all very clear good connections

[Phil WhitleyParticipant @philwhitley94135]

I meant the black contactors, but if they are good electrical connections, they should be ok, do you have compressed air, blow out all that dust, and wear a mask! When contactors get dust in them, it burns/melts onto the contacts, and they arc, but there may not be any way you can get into them to clean them, remember I am old school from the days when everything could be stripped, cleaned and rebuilt! when it is clean, check the operation with the lid off to check for arcing.

Phil

[Herman van der MerweParticipant @hermanvandermerwe76509]

Hi, sorry watching SpaceX launching the two astronauts. Amazing!

That most definitely is not bird poo. That is a chemical spill from a leaking capacitor that failed due to age and then overloaded the circuit, hence the burned spade connector.

Someone obviously replaced the cap that was there with the silver one. Only issue is the value is incorrect. The white ones are 80uF whilst the silver one is 60uF. AFAIK the three needs to be the same value to ensure the phase formation is a smooth sine curve.

The age of the white caps are more than 10 years. The white caps reads 05/07/99. This is beyond design lifespan. They might measure to the correct value with your meter, but under load operational parameters must be determined as I said with a stop watch and a low voltage supply such as a 9V battery.

Me, I would never use caps more than three years old. Remember that the value of caps deteriorate in a logarithmic curve of capacitance vs time.

Question – Can you try and get hold of the circuit diagram of the unit?

The red box is a monitoring overload relay. It checks if the incoming voltage is more than the set value. If so, it will disconnect the circuit. Yours will disconnect at 300VAC as the selector is set to that.

Do have access to compressed air? Simply blow the contactor set clean.

[Herman van der MerweParticipant @hermanvandermerwe76509]

@Richard, I found an O-ring in the tumbler bearing bush. It is part # 6842. This O-ring was as hard as anything and could never seal. It is inside the bush on the gearbox side of the tumbler arm.

[Richard Kirkman 1Participant @richardkirkman1]

So, they all need replacing, and they should all be the same size?

I cannot get a circuit diagram, the only information I have is the ones from 3 posts ago.

I do not have access to compressed air either

what should the disconnect be set at? Or is 300vac where it should be?

Interesting oil seal, no doubt mine could do with being replaced too!

I have just emailed danebury electronics asking for a wiring diagram or other information about it. I am doubtful that I will get a response, but hopefully I will.

The one I saw on eBay has sold, so I cannot ask the person to look inside for me. On another note, the seller is now selling a collet chuck with l0 taper and 2 sets of collets. it's going to go for a fortune. Especially since they've listed the collets and the chuck separately. Everyone's going to outbid each other to try and get both. I'll watch it, but I don't plan on placing a bid. Just interesting to see the price.

Edited By Richard Kirkman 1 on 27/05/2020 23:16:21

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Richard Kirkman 1 on 27/05/2020 22:43:10:

So, they all need replacing, and they should all be the same size?

what should the disconnect be set at? Or is 300vac where it should be?

If it was me? Yes I would replace the three caps and all to the same value (not size). Buy a good brand. They are not cheap though.

300V is fine. Leave it be.

Two things you cannot live without in a workshop is compressed air and a Dremel tool. Buy those as first priority.

[Herman van der MerweParticipant @hermanvandermerwe76509]

I see you gave a link to caps. The 80uF link is for PP caps used in audio applications. You are after power factor correction running caps.

IMHO you can buy an electronic VFD drive brand new for the cost of the three caps… sorry for the bad news.

[Richard Kirkman 1Participant @richardkirkman1]

Inverter drives are about £150-200 so yes it does seem like bad news. But it's fine since I don't want to use a VFD

Are these appropriate caps

Caps

Since they're 83 instead?

It shouldn't be an issue as I bought the converter from a company so hopefully, they will pay towards the capacitors since they're not functioning properly

I've managed for 3 years without compressed air, I don't particularly have the space for a compressor or see the use apart from blowing things. I do have a Dremel however

[Richard Kirkman 1Participant @richardkirkman1]

I received an email back from the converter company! He wanted the serial number, so I have given it to him. It's looking like I might get a circuit diagram.

Another update, I went to smith and Allen in Darlington and I picked up a litre of their dove grey b694 tractol paint. I also got some Ransomes green for the mower. So I will finally be able to paint the traveling steady the correct colour.

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Richard Kirkman 1 on 28/05/2020 11:10:41:

Inverter drives are about £150-200 so yes it does seem like bad news. But it's fine since I don't want to use a VFD

Are these appropriate caps

Caps

Since they're 83 instead?

It shouldn't be an issue as I bought the converter from a company so hopefully, they will pay towards the capacitors since they're not functioning properly

No, those are three phase caps. You need single phase caps.

Out of interest, can you not send the unit back for a refund? I do not know what the CPA in the UK says, but over here, if it is sold as working and it ain't then you can return for a full refund.

Why do you not want to use a VFD? It gives all you want + braking + reverse + full speed control.

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Richard Kirkman 1 on 28/05/2020 11:10:41:

I've managed for 3 years without compressed air, I don't particularly have the space for a compressor or see the use apart from blowing things.

Air tools are just so much easier to use. Look at a vertical compressor and a separate long cylindrical air storage tank. These fit in two corners or even a corner and just below the ceiling. It is one of those items that once you have it you want to kick yourself for not installing it earlier.

[Richard Kirkman 1Participant @richardkirkman1]

Okay single phase caps then.

This appears to be the identical model that is in my cabinet.

LINK

I do not want to return it because it was a good deal, and I still need one. I would not find one like this again. If I can get the replacement parts and have them pay for it, that would be preferable. Since if they take it back they'll have to fix it anyway and resell it. Also, it weighs a lot and I don't want to post it back to them, especially since I just broke up the pallet they sent it on.

I have used a VFD in the past for my belt grinder. I want to keep all the wiring inside the lathe and keep it original. A VFD needs to be connected directly to the motor and would bypass all the work that I've put in wiring the lathe back to original (ish) workings. I don't want to use a VFD, it's not for me.

There might actually be one place I could possibly store a compressor. Maybe one day…

Edited By Richard Kirkman 1 on 28/05/2020 18:54:21

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Richard Kirkman 1 on 28/05/2020 18:52:26:

Okay single phase caps then.

This appears to be the identical model that is in my cabinet.

LINK

Excellent price as well! Yes, buy those and then ask the guy you want three matched caps with the test printout to verify the three are a matched set. Me, I would request each cap to be within 5% value of each other. You can even offer him a few bob to do this matching.

[Richard Kirkman 1Participant @richardkirkman1]

I'm not going to order them just yet or message.

I will wait till I have the wiring diagram or some more contact from the producer of the converter. Because they all might be wrong, it could have had anything done to it.

Those capacitors are just normal motor start capacitors, what were you on about power factor corrector capacitors for?

Honestly Herman, now I'm thinking about looking for an air compressor. Don't put any more tool ideas in my head!

[Phil WhitleyParticipant @philwhitley94135]

Hi Richard, Just recieved my parcel!! Thank you so much!! I shall put all this stuff to good use, and I am thinking of something like a DTI, or maybe even a couple of DTI's to go in the beautiful wooden box. I have a couple of Verdict dti's which are approaching the quality of the box, so I may use it to house them! As we used to say in west Yorkshire

Am reet med up lad!

Thank you!

Phil

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Richard Kirkman 1 on 28/05/2020 20:36:52:

I will wait till I have the wiring diagram or some more contact from the producer of the converter. Because they all might be wrong, it could have had anything done to it.

Those capacitors are just normal motor start capacitors, what were you on about power factor corrector capacitors for?

Honestly Herman, now I'm thinking about looking for an air compressor. Don't put any more tool ideas in my head!

Yes, wait for the correct diagram and check the values as per the diagram. You might find that the design called for two running caps and a third starting cap. Who knows? So best get the diagram for us.

Nope, do not make the mistake of thinking starting caps can be used as running caps. A vast difference! Power factor correcting caps or running caps are constantly in use and must be constructed to offer the correct capacitance value under load and operating temperature to ensure the phase angles remain in place.

I actually enjoyed the design of phase correction caps in my first year of engineering studies. Many, many moons ago …

Well if you have the money buy a vane compressor … evil grin … that is on my wishlist …

[Richard Kirkman 1Participant @richardkirkman1]

My pleasure Phil. It's nice to give back for once, just to show my appreciation. I wouldn't have got to where I am without you. I figured you'd probably be more likely to use the contactors than me. The sides of the box are some form of mahogany and the top and bottom panel are some really hard stuff that seems like Bubinga, not too sure, but it polishes up nicely. There should be plenty of gasket material there to redo all the gaskets in the lathe or whatever you want to use it for.. I didn't know what drill sizes you had already, but I'm sure they can be used for something. I had some duplicates after buying 2 job lots. I have any size I could possibly need up to 7/8ths pretty much. And still, the mt4 drill that I need to turn the taper down on. I still aspire to make better quality boxes, but that box was a good step in the right direction. I'm sure you'll put everything to good use!

Herman, so are power correcting caps the same as running caps, and how are starting caps different from running caps.

I think I'd have to start off with a small compressor and see how that went. Meanwhile, I think its time to design and make a new and improved 50x1500mm belt grinder. The first iteration just isn't as good as I would have liked it to be.

[Herman van der MerweParticipant @hermanvandermerwe76509]

Posted by Richard Kirkman 1 on 28/05/2020 22:23:06:

Herman, so are power correcting caps the same as running caps, and how are starting caps different from running caps.

I think I'd have to start off with a small compressor and see how that went. Meanwhile, I think its time to design and make a new and improved 50x1500mm belt grinder. The first iteration just isn't as good as I would have liked it to be.

Yes, they are the same IMHO. Here is a very good practical article for your information.

No, do not try to go a small compressor route. You will waste your money as you will want to upgrade in the first week of use. A small compressor is good for blowing dust and maybe pump tires. What you need is one that can give lots of volume, and I mean lots of volume and do this at a minimum pressure of 5 bar. This means you can do all your die grinding, sanding, cutting, drilling, nibbling with it.

Heck, the best belt grinders/sanders I know of are air driven. On my wishlist you will find one.

If you buy old quality pneumatic tools (Chicago, Ingersoll Rand), you can replace the vanes by making your own to fit and also replace the bearings and you have a brand new tool for next to nothing. I once bought a BIG crate full of scrapped air tools for GBP10 and only one of the tools in there I could not fix.

Just one tip. Never ever blow your lathe's ways clean with air. You will force the chips into places where they will cause grave damage.

Edited By Herman van der Merwe on 29/05/2020 07:44:12

[Herman van der MerweParticipant @hermanvandermerwe76509]

@Richard and @Phil, would you please post photos of what the back splash plate looks like where it bolts to the headstock. Mine is all smashed in at this corner and I do not want to bend it to far back as I have no idea as to what it should look like.

Top view, side views is what I am after please.

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