Member postings for Andrew Tinsley

If it is only for occasional use then go vernier NOT digital. Digital ones fail, because of electronic faults. mechanical ones will last as long as you do!

I purchased a top of the range digital Mitutoyo, for peanuts, because it didn't work. I took a chance on repairing it and managed to effect a good repair. I thought that this was a warning, so sold it on as a worker that had been repaired.

If I had spent that kind of money on a new one, I would have been mortified! If you buy a cheap one, don't expect it to last.

Andrew.

Might just be a bit quicker to make one or modify one from a mini lathe. At least you could get on and use it, rather than waiting a long time for unobtanium to turn up. Not a difficult project.

Andrew.

My problem has always been trying to stop the damn stuff falling off, you must have had a top notch company powder coating company do your frame!

Andrew.

I purchased some round blanks laser cut from sheet. The edges were incredibly hard and a file would barely touch them. So beware, you may get a shock when you try tidying up the cut. . In my limited experience, you don't get this problem with water jet cutting.

Jason B seems to be happy with his laser cutting, so hardness of the cut seems to vary.

Andrew.

You may have trouble trying to cut native mica into circles. I made a botch when I tried it, although it is done commercially. I suspect that a sharp circular punch might do the job.

Andrew.

If it comes to scrapping the boiler, maybe think of using gas firing rather than coal? Just a thought. In the longer term I think there are major advantages in using propane in any case. I am seriously looking at doing so on the two locos that I am building.

Andrew.

Thanks Chris, now I understand!

Andrew.

I think that the usual configuration for these motors are capacitor start capacitor run, rather than a simple capacitor start system. I don't have a clue as to the capacitance values required for a 3HP motor. Anyone any idea of rough values?

Andrew.

When I purchased my Centec 2b, it was fitted with what looked like a large single phase motor. I fitted a 3 phase motor and VFD and put the single phase motor to one side.

I have been sorting and testing all my electric motors over the past month and this particular motor puzzled me, it has two separate windings and nothing else, no centifugal switch or any capacitors although it has a large (empty) box on top of the motor. One coil was connected to the mains feed when it was taken out of the mill.

Subsequent research reveals that it is a 3HP single phase motor designed for air compressor use. There is no manufacturers plate and the clue was given by some lettering on the aluminium casting.

Seems a waste of a motor and goodness knows how the last owner thought it would run in the mill! I am not bothered about the starters used in air compressors. I was thinking of wiring it up as a capacitor start motor, with a suitable starting capacitor. Not sure which of the windings would be the start winding, but should be able to figure this out. There is room for a centrifugal switch with some modification.

My concern is that these air compressor motors may have some unusual feature that might prevent such a simple minded approach from working. Not being familiar with them, makes me a little cagey. Googling for some while left me non the wiser.

Andrew.

Edited By Andrew Tinsley on 03/01/2021 19:23:58

Thank you Andrew.

When a sine wave filter was mentioned (and also referred to as a transformer), I certainly got confused! I can well understand an LC filter on each leg of the supply looking like a 3 phase transformer. Very easy to get the wrong end of the stick, which I most certainly did!

Andrew.

Hello Tim,

Just looked up Lea Francis on Wicki. As I thought the modern company was founded by Barry Price, in the 1980s to provide spares for the old Lea Francis cars. Somewhat similar to the company supplying Bentley spares for the pre RR Bentleys.

Hardly the same as a company in continuous production, supplying spares for a product which ceased manufacture 75 years ago..

Andrew.

Hello Steve. and Chris,

The little AEI motor is in fact wound for dual voltage operation all six wires come to the terminal board and there is the modern link system to convert from 240 to 415 volts. I have had it for at least 45 years, but I think it is probably quite a bit older than that. So the layout was probably the precursor to modern motors.

Hello Chris,

Now that is interesting. I had no idea that you could use a transformer between VFD and motor. I have visions of all sorts of nasties happening to the transformer!!!! But obviously not. I am not a great fan of static 3 phase converters. I just rigged up a V type "3 phase" to see if the motor would run (and it did). I suppose that 3 phase transformers are not uncommon (I had some powering continental kit on 3 phase (our voltage was a tad too high for the kit!). However, I have never seen a small 3 phase transformer. I presume you could use 3 single phase ones instead?

I was going to use the AEI motor on a period Delapena honing machine which has some fascinating history. The original 3 phase motor was burnt out, hence the interest in getting the little AEI motor going. I have at least three 240 volt isolation transformers knocking about, so I will give it a try unless someone knows better.

Thanks all,

Andrew.

Hello Tim,

That is quite interesting! Is the company the original Lea Francis, or some company set up to make spares? A friend of mine has a 1926 Bentley and there is a company that makes spares for that vintage, new engines, gearboxes etc. I think the big difference is that there is a demand for spares, for cars like this and there are people prepared to pay extremely high prices for them, hence it is an economic proposition.

Spares for ML1-4 lathes would not have a very large market and owners of such lathes would not be prepared to pay the necessary prices to make such an operation an economic one. The exception being people like Brian Wood, who can make a batch, effectively a very welcome cottage industry! A commercial firm could not possibly survive catering for such a market

Andrew.

Edited By Andrew Tinsley on 03/01/2021 14:59:22

I suspect that it may be phase to phase leakage from the first few centimetres of the windings. John Cox mentions this somewhere in one of his books on electric motors in the workshop practice series. At least I think he does, but can't find it at the moment.

Andrew.

I have just tried running my antique AEI 1/4 horse motor on an open V, 240 Volt 3 phase supply. Surprise, surprise, it runs without a murmer of a complaint.

Just for the record, I supplied the "phantom" phase via a 10 microfarad run capacitor. I didn't bother with a higher value start capacitance as the motor was running under no load conditions.

Out of interest, I did check the VFD output via my storage scope and could see no difference between the antique motor and a modern ones that run correctly. Storage scope necessary because the VFD shuts down PDQ on the antique motor! I do have the correct gear to do this check, please don't try to do it with a normal scope.

Andrew.

Hello Old Mart,

It wasn't me that talked about a 50 year old letter. Just letting people know that the new Myford's don't stock parts for the ML 1-4 range.

I don't know of any company that would have spares for a product discontinued maybe 75 years ago, do you?

Andrew.

If it is a single phase motor, it sounds as though you may have a dodgy start capacitor (one that has gone low in value.).

Andrew.

The company does NOT stock spares for the old ML 1-4. Think you must be still on a high from New Year!

Andrew.

Thank you guys,

As I suspected, the motor is probably fine, so is the VFD. Seems as though 50 year plus motors just do not like VFDs.

I shall keep the motor because it is a museum piece and I like the silver AEI logo on the black background. It really looks smart!

Andrew.

I have been checking out my stock of 3 phase motors using an Altivar VFD.

All ran fine, except one dinky little AEI 3 phase motor. It must be at least 50 years old and has never been out of its original box.

The Altivar would barely get it moving before switching off with an earth leakage message. Tried it a couple of times and the second time it tripped the supply RCD for the VFD.

OK a leaky winding to earth, not too surprising. The motor is wired in delta, Before binning it, I tried meggering the windings to earth. At 500 volts DC, the earth resistance was 100 megohms, at 1000 volts DC it was 50 megohms.

Now those figures suggest that the motor is actually good! All I can think of is that the spikey VFD output is causing the insulation breakdown. Maybe on a true 3 phase supply it would be OK?

Any Thoughts?

Andrew.