Member postings for Simon Williams 3

Hi John, as a control panel builder in a previous life a "bundle of black wires all black and not numbered" sounds like the stuff of nightmares.

First check along the wires - are they laser marked within their length? Or is that too easy! Some industrial machinery - particularly if it was mass produced - had pre-formed and pre numbered wire looms assembled into it, worth checking carefully that there really isn't some ident system other than the usual coloured ferrules each termination.

Whether there is or no, you are really committed to un-bundling the wires and following individual cores. Messy, time consuming, confusing and difficult to put it all back together neatly. The search and find (battery and bulb) approach will tell you quite a lot, but it can be confusing to differentiate between a cross connection and a "real" connection.

Identifying the power into the circuit and the common return/neutral is a good start, after that think of the control circuit as rungs of a ladder - as they would be drawn in a plc diagram - there can only be a limited number of rungs, and mostly they will be interlocks or contacts in series. Easy to trace if time-consuming. Tag the ones you've sussed with sticky tape and numbers, just as you would expect to see idents if they'd been fitted.

And regular cups of tea. It's going to be a long job! Essentially you are reproducing the manufacturer's cct schematic, so having one of the same machine (even a similar machine) is a good start.

And when you've got all that done, now find the fault. Easier said than done, particularly if the innards of the machine are not familiar! But if it is just a switch that has failed, you can check them off one by one with your faithful battery and bulb, but you are going to have to disconnect the rest of the control circuitry to be absolutely sure exactly what you are testing step by step.

Good luck, Simon

Edited By Simon Williams 3 on 30/03/2016 20:53:27

Hi

I can see the logic that says "you took it to bits - so the warranty is now void" - (and anyway you can't put it back together if it's broken) - but you didn't break it, or if you did it's because of a manufacturing fault in the first place.

You only took it to bits to save the supplier the trouble of replacing it with one that wasn't full of c##p. That doesn't relieve the supplier of his duties under the sale of goods legislation.

I'd be inclined to have an open and honest conversation with the supplier at this point. You have the right to expect a serviceable item for your money, even if it does have some sharp edges you'd rather round off. I don't see you've invalidated the guarantee by trying to repair/improve a poorly made item, and discovering it's faulty in the process.

As the original "I can fix this if I could only work out how" delusionist I understand the incentive to make a silk purse out of a sow's ear, fix it yourself and not invoke the Sale of Goods Act, but now you've found a fault and it might not be easily surmountable, you still have the option (I believe) to ask for a replacement.

Good luck with it

Simon

David -

Where are you ion the planet? If anywhere near west Gloucestershire, (UK) I've got a small(ish) slotter in my shed for exactly this job.

Alternatively I've likely got a keyway broach to suit, and certainly a hydraulic press. It'll take longer to boil the kettle and make a cup of tea than do the job.

If you want to take this further, I think all you do is press the "message member" button, we can exchange locations and see how to proceed.

Best rgds Simon

There was a related (spin-off?) story by Desmond Bagley, called (IIRR) The Golden Keel. As I recall, the source of the wealth was even more dubious, but the engineering implications of a gismo which would melt small quantities of gold fascinated me. Though even at the tender age I was when I first read this, I just knew that the project management implications of using a small scale process to serve a big project (casting the keel of a boat) weren't going to end well.

And (without spoiling the story) they didn't!

But I think, to return to the original thread, there was more of the romance of engineering in Nevil Shute's various stories.

Rgds to all Simon

My apologies gents.if I came on a bit too strong, but the OP said he was a complete novice when it came to sparky stuff, and we are trying to deal with some quite clever measurements here, with nasty potential consequences like fire and death. Nothing to worry about.... I just don't like the thought of the case of the motor going live and the OP not being aware of the risks this presents.

I've got no problem with bypassing the trip, provided we also know that the motor is OK to ground and safe to energise. I know I said earlier that the trip won't catch an earth fault, but the user needs to be sure that this kit is safe to use for all the other tests it should have.had every 12 months for the last umpty-um years. Yes, we're talking PAT testing.

No the regs won't let an untrained tech do a PAT test, unless the tester is automated and the test procedure is set up by someone competent to do so. Quite right too.

Clean it and try it. Good luck.

Simon

The thing that none of us have put into words so far is that this is probably a shorted turn sort of a fault, rather than an earth fault. A shorted turn will give a pretty much instantaneous overheating which is consistent with the "it runs for a few seconds then the trip pops" of the OP. An earth fault wouldn't trip the trip, unless it was a gross fault in which case you might expect a fuse to blow somewhere sooner or later. The possibility of a gross earth fault is why I'm dead against (no pun intended!) running this without being absolutely sure the earth is 100% reliable.

Does anyone have a view on whether the trip is sensing over temperature or over current - or possibly both?

Having the starter winding left energised won't (I think) trip the trip as quickly as is described - the excess current is pretty marginal, and while there is a heating effect it is going to take a little while before the trip heats up enough to pop.

The motor rating plate says it is only 1/6 HP, so it's a pretty small motor and is probably susceptible to having been overloaded for much of its life. (What sort of saw is this?). Chronic overheating, humidity and what we'll politely call "foreign matter" for a long time will take their toll on the insulation of the windings.

Detecting a shorted turn with a multimeter isn't something I can explain to the OP - and probably isn't do-able anyway. Hence I think the best advice we can give is to strip and clean it, try it for size, then throw it away if no success.

HTH Simon

Sorry John to disagree, but NEVER NEVER NEVER NEVER interrupt the earth connection. A clip on ammeter won't be sensitive enough to detect the leakage current and an inline ammeter has a fuse in it which could blow. It's against all the IEE regs and for someone like the OP who professes to little or no knowledge of sparky stuff, this is just a disaster waiting to happen.

I repeat DON'T PUT AN AMMETER IN THE EARTH.

The earth connection must be solid, and bolted to the frame of the machine, and connected to the supply incoming earth with continuous copper. And that's with a motor you DON'T think is faulty!!!!

Testing equipment that might become "chassis live" is a whole can of worms, and shouldn't be attempted at home.

Best rgds all, lecture over!

Simon (I do this stuff for a living!)

Couple of things you can do.

Dismantle the motor, clean out the dust, muck, whatever, check the centrifugal switch is freely operating. Be sure to take notes of which wire goes where on the terminal board when you disconnect. Now reassemble and power it up but be sure you've got an earth leakage trip upstream of the supply when you test it for your own safety.

If it still blows the motor trip it's most likely a winding fault. If it now blows the earth trip it's also a wiring or a winding fault. In either case discard it. If you want to know more take it to a motor rewind house and ask them to test it for you. There's not much you can do with a standard multimeter, you need some more specialist test equipment (at least an insulation tester) and the expert knowledge to use it.

It will be cheaper to buy a new motor than have this one rewound, unless you've got a.friend down the pub who can do it for a favour. As above, it could be the trip in the motor is faulty, but you then need some specialist expertise to replace it with an external one, as you'll never find a spare trip, this motor is old as the hills.

If it now runs OK put the machine drive back together and pat yourself on the back.

Best rgds and be careful of that nasty electric, it bites! Simon

Experience tells me that if I make a tubular structure.out of pipe it will be heavier than if I used tube.

If I pass sparks along it, it will be conduit. If it is used to carry water, then it's definitely pipe. Unless it's flexible, when it reverts to being tube again. If it carries oil or gas, then it's almost certainly made of tube, unless I've over-engineered it and made it out of pipe when it becomes a manifold. Or maybe it's a chimney, in which case it's made out of flue pipe.

Ambiguity? What ambiguity, we all understand each other.

Weight!

Sam's post raises another alarm bell. If the rack skates round the column as you move the table in the horizontal plane, then this creates a significant lateral bending moment on the rack. The friction of the lower end acts in one direction, and the force to move it is applied higher up, so the material from which therack is made has to resist the resultant bending force. I'd worry about an aluminium construction folding and dropping the table. The same is true but to a much lesser extent of extending the rack in steel.

Hopefully the rack is supported by the column, in which case the lateral bending moment isn't ann issue. But that presumably means that the table can't swivel on the column

Can we have some pic's of the OP machine please?

Rgds Simon

Edited By Simon Williams 3 on 27/02/2016 21:03:28

Hello All, Good evening.

Are the hole counts for the plates supplied with a 40 tooth worm wheel conventionally the same as those shown for plates A,B,C in Howard's PDF?

I've got a BS0 head but it has a 40T wheel. The numbers of holes in the three plates that came with it happen to coincide with the A B and C plates Howard uses - is this accident or design?

Thanks in anticipation

Best rgds Simon

Good evening Mick, I've been mulling over the way to solve exactly the same problem (and for the same application!) for some time now. It seems to me that the problem with cutting a rack in a milling machine - either horizontal or vertical - is running out of travel. If you mount the cutter on an arbour in a horizontal mill you've only got the travel of the y axis before you run out of space to index to the next tooth. So you really want to mount the work at right angles to the table, and also turn the axis of the cutter through 90 degrees. Keith Fenner has got a suitable gadget on his K&T mill, but I don't aspire to anything as fancy.

I could also cut the rack with the cutter in the vertical mill, but now the length of the rack I can cut is constrained by how much overhang of the cutter off the quill is bearable. Not much!

Fair play to Will, I hadn't thought of using the length of the lathe bed as the axis of the length of the rack. I don't have a DRO but if I could fettle up something with a long vernier caliper to measure the incremental position of the saddle under the cutter I'd be in business. Not sure I trust the leadscrew to do this measurement, but I guess that depends on the age of the lathe. Anyway. I happen to have a piece of precision ground 1" dia steel to use as an arbour. Just pop a key way in it and a couple of threads for locknuts and I'll give it a try.

Rgds

Simon

Presumably the lady called Susan was too lazy to take it with her when they moved camp?

Simon

Ian - that's interesting about the Tri-Leva with a two speed motor. I've met two speed three phase motors on cranes for example, but I didn't know you could do the same with a single phase motor. My mind is slightly boggled with how the starter winding gets in there somehow.

Rgds

Simon

Michael - Thank you for the magic link button.

Colin - I think you're wasting your money until you've had someone check the motor.

If you are going to change the motor there are a couple of things you need to know. Although my machine is a lot older, and isn't the same make, (but I bet its very similar) I found that the motor was a non standard one when I came to swap it for a three phase unit. The motor shaft was a non standard size (22 mm, standard motor is 19 mm shaft) and also was longer than standard. The motor shaft carries a 4 groove cone pulley, and the pulley sits over the end of the shaft with two grubscrews (yuck!) holding it in place. At least it had a keyway!. The smallest pulley for the slowest speeds is smaller than the shaft diameter, so the pulley cone overhangs the end of the shaft. I made a new pulley to suit an IEC standard 19 mm dia motor shaft for a 80 frame 3 phase 4 pole motor. Oh, and the frame size of the original motor was an oddity as well (from memory 85 mm).

I bought a standard cast iron taper lock pulley with a single groove on it corresponding to the biggest diameter pulley closest to the motor, and turned a register in the upper face of the cast iron. I then turned a piece of aluminium up to replicate the other diameters. The aluminium is stacked on top of the face of the taper lock pulley, with a radial face key to transmit the drive. The two parts are clamped together with a central M6 allen cap head screw though the centre, threaded into the end of the motor shaft. The M6 screw doesn't carry the drive torque, it just holds the two parts of the composite cone pulley together.

The stuff about two pole (which I really don't believe it can be) or 4 pole doesn't really matter. Just buy a motor with approximately the same speed figure on the rating plate as the original. I'll bet you pretty much anything that it says something like 1420 rpm full load speed on a 50 Hz supply (could be anywhere between 1400 and 1470) - this is a four pole motor. It can't be a two pole motor (full load speed somewhere in the 2800 - 2900 range) because you'd need an enormous reduction ratio to get down to your 125 rpm bottom speed. Big reduction ratio means big pulleys driven by really small pulleys. Also if you had a two pole motor your top speed would be a lot higher (3500 rpm - maybe more) just from the geometry of how the belts and pulleys have to be configured.

There's much to be said I reckon for buying a slower motor than the original (6 pole motor running at approx. 1000 rpm) and running the whole thing more slowly, but this isn't an option on single phase.

HTH Rgds Simon

Edited By Simon Williams 3 on 19/02/2016 19:59:14

Hi Colin, that's a very handy bit of kit, especially if the price was right. I've got one myself, albeit with a different badge on the front.

You might like to look at another thread which relates to that same family of machines, being

"RF-25 Belt-sizes and Table Stop Info Please"

Sorry but I haven't worked out how to copy the URL for the link to this thread, but if you look in Latest Posts you'll find it.

Rgds Simon

I agree with Duncan - once you find yourself replacing the motor it's VSD and three phase motor every time. Not for the variable speed so much, but for a smooth speed ramp up and a controllable stop. Most VSD's will provide DC braking which is now mandatory in industry, and a Very Good Idea for us chaps (and chapesses) in sheds. And the controllable speed is a bonus.

BUT>>>

Not all three phase motors are VSD compatible. Quite apart from the issues over choosing a motor which can be connected in delta and is suitable for use at 230 volts supply, there is much complication in the internals of the motor to permit successful torque generation at frequencies other than 50 Hz. Some cheap (and some not so cheap!) motors are effectively useless as you depart from their nominal design frequency. All three phase motors are not created equal, so it's worth buying a motor and VSD combination from a reputable supplier. I've seen threads here recommending such.

You can buy VSD's which will generate three phase 415 volts, but that's a whole lot more expensive than doing it the simple way with a 230 volts compatible motor.

And just for my naked nosiness, what model is the mill?

Rgds Simon

Hi Darren you can get a paper copy via Tony Griffiths at lathes.co.uk, his stock code MC300A. Follow the link from the home page to instruction manuals, then Colchester and scroll down till you hit the Bantam Mk2, then follow the instructions to order.

Don't know if he can do a PDF -but you might like to try this

nQAAOxyj4hTGtJ1">http://www.ebay.co.uk/itm/Colchester-BANTAM-lathe-manual-on-CD-in-PDF-format-/361476671620?hash=item5429b04884:gnQAAOxyj4hTGtJ1

The picture shown is of a Mk1 Bantam, but maybe the vendor has a MK2 manual in the same format. Worth messaging him and find out?

Rgds

Simon

Good morning Colin

Two capacitors probably indicates a start capacitor and a run capacitor, so they do different things. Not sure about the apparent anomaly with their rated voltage without knowing some more about the internal windings, but if it's never been apart it's probably right. So I think you need a motor rewind house to check over the motor for you. Once you know the answer to whether the motor is actually serviceable you can plan from there. Notwithstanding the new warm and heated environment you now have (you lucky devil) damp or debris in the windings of some kind is always your first suspicion. Unfortunately , whatever anyone else says about "cook it and it'll be OK" once the internal wiring has flashed down to the case it'll never be right. Good luck with it, keep us posted. Rgds Simon