Member postings for Andrew Tinsley

Clive is dead on the money, my Alpine responded to the treatment that Clive suggests. When I first got it, the performance was rubbish and it stayed in a corner for maybe 25 years. I needed the space so it was either make it work or dump it time. It is now surprisingly good and I am very pleased with it.

Andrew.

Hello again,

I replaced the rear bearing with an oilite bush. Result no noise in reverse.

The only thing noted on the rear part of the shaft was a deep score. with no corresponding damage to the bearing. I suspect this means that the rear bearing had been replaced. The rear shaft was turned down from 17 mm to 16 mm to fit the new bush, hence the score was removed.

The play of the shaft in the new bush was about 3 thou, the same as before. So the noise has gone and nothing much else has changed! I really am at a loss to explain the phenomena.

Still I have a good result which is what was required, but why?

Regards,

Andrew.

Robert, you have some very strange ideas on gravity. Turning an oscillator on its side does not change gravity from 0 G to 1 G

I have specialised in the study of relativity and gravity for the last 50 years and you are just plain wrong.

Andrew.

Just shows that you need to specify reasons when you ask a general question.. If you did, then you would get a reasoned response.

Andrew.

If the selected atom outputs light at a given frequency then the higher the frequency then there are more subdivisions of time available and hence greater potential accuracy..

Ignore Roberts quip re difference in gravity and hence frequency if his oscillator is upright or on its side. However time does alter depending on gravity. A satellite born atomic clock will give a different time to one on the ground . This has to be taken into account for GPS location otherwise the system will give an incorrect result.

Andrew.

The motor is a standard Crompton Parkinson made in the now defunct Doncaster factory. I would reckon in the late 70s or early 80s. No external fan, simply the paddles which blow the air out of a ring of holes in the casing, thus drawing air through each end plate ventilation holes.

The surface of the rotor is cast aluminium at each end and blued steel in between, anything catching on either surface would show up like a sore thumb, just as good as engineering blue and not so messy!

Changing end plates from front to rear is a problem, because there is nowhere to mount the inner terminal plate for the electrical connections

The motor is powered from an inverter, so no chance of getting a phase backward. I am going to put in an oilite bearing in the rear bearing position tomorrow. at least that will eliminate that bearing. The oilite bearing is a simple drop in replacement for the Vandervell white metal bearing, except that it is 16 mm ID rather than the 17 mm ID of the white metal bearing. So just a skim off the rear of the main shaft to make everything fit.

I will report back tomorrow evening, after I have done the modification.Thanks again for all the ideas and interest.

Andrew.

Hello all.

It is a 3 phase motor, so no centrifugal switches. The rotor is firm on the shaft. As far as the "fan" is concerned this is just some ears on one end of the stator. They don't appear to have any pitch (angle) to them. I suppose they deflect air to the holes cut in the casing. So there is no axial force on the stator due to the "fan" blades

I have used a stethoscope on the motor and for what its worth, the noise seems to be coming from the rear bearing area. The sleeve bearing at both front and rear are well lubricated The knocking sound is at motor frequency by the sound of it. If I hadn't stripped the motor down a couple of times to check. I would say the stator was just touching something. But it isn't and why the sound only in the reverse direction?

I may well install an oilite bush in the rear bearing set up, or simply replace it with a ball bearing. The only clue I have is that it seems to be coming from the rear of the motor. Either retrofit is a quick job, so I may well do it out of curiosity.

Andrew.

Edited By Andrew Tinsley on 05/04/2021 15:33:43

Hello Old Mart,

I will disassemble it again and this time I will cut open the sealed block and see what there is inside. As the Altivar 11 is quite an old design, it may be that the full wave rectifier is a simple diode set up. I believe more modern designs use SCRs and are used to tame the surge current on switch on rather than a surge resistor and shorting relay.

Assuming they are diodes, then I just may be able to do a repair.

Andrew.

I have a an old Graham Engineering 6 x 4 It was awful and was dumped in a corner for years. I then decided to fix it. Now cuts superbly and I am very pleased with it.

Just looked up the price of a Warco 712. I don't usually comment, but I am afraid "more money than sense" leaps to mind.

Andrew.

Hello Old Mart,

I really don't know, There is no mention of country of manufacture on the unit!

I cannot see any of the 3 output devices anywhere on the PCB and hence assume they are in the block with the Bus diodes. The block has quite a few holes in it and very long pins on the underside of the pcb which fit through said holes; Thee of the 15 or so pins have ferrite beads on them, so I assume they are from the 3 output devices.

Very annoying having to scrap the VFD for want of a bridge rectifier, I can't even squeeze one in on the heatsink, even if I worked out the pin out!

Thanks for your interest,

Andrew.

OK, I have stripped the motor down again and checked with a magnifying glass to see if there is contact between rotor and stator. There is no sign of any rubbing whatsoever.

Checked the sleeve bearings and shaft and they are fine, with 3 thou clearance both ends The shaft and bearings were much better than they looked. There is one score mark on the rear end of the shaft, there were no rough patches on either bearing surface. Minimal end float and the two PTFE washers were fine.

I reassembled the motor and carefully rotated the shaft by hand in both directions no sign of anything rubbing or catching.

So I give up! I shall only be using the motor in the forward direction, so it will be quiet. If I have missed anything then it may show up with more run time.

Thanks everyone.

Andrew.

Hello again,

I have found the fault, there is no bus voltage, so hardly surprising it doesn't run! The diode block is sealed and probably contains the output devices as well. Probably zero chance of a spare block, unless anyone else knows different?

The usual suspect for zero bus volts is the precharging resistor. It reads 46 ohms and is labelled up at 47 ohms, so it looks like a one way trip to the tip.

Andrew.

P.S. Even if the parameters are pass word protected you can do a factory reset. I have done it once from a site on the net. You should find it with a bit of googling.

Hi Rod, you seem to have a lot of faith in our privatised utility companies. I don't think many here share that view.

Andrew.

I have only tried the motor off load, that is without the belt fitted. I will check the motor again for any signs of contact between rotor and field windings. It does sound as if the rotor is clouting something, but I could see no marking on the rotor I will measure up the bearings and shaft while I am at it to see what the wear is.

After a close inspection tomorrow morning I will reassemble the motor and see if I can detect any contact as the shaft is rotated.

It is quite safe to oven any motor at 70 centigrade. Remember this is without the motor coils energised! Rule of thumb is that all motors can run to a temperature of 100 degrees Centigrade under load. more modern motors can be run at 120 Centigrade and very recent motors designed for high temperature running are good for 150 Centigrade.

The bearings are of Vandervell white metal construction. Standard Doncaster build for around the 1970s. A bit of a problem, as there have been no replacement parts available for many years. If it is a bearing problem, it sounds as if it is coming from the rear bearing, which is most odd If that is so, then a ball race can be fitted (have done this on another motor). Usually it is the front bearing which wears first due to over tightening of the drive belt.

I still can't figure out why the noise is only heard in reverse. As the motor is to be used only in a forward direction, I am almost tempted to leave well alone. However that really isn't the way to go, something is wrong and should be corrected.

I will update my findings after tomorrows session.

Thanks everyone for your input.

Andrew.

Hello Dave,

I did think that the rotor could be making the noise as you suggest. However the play of the shaft in the bearings is minimal. I stripped the motor down and there are no marks on either the stator or field coils, so I don't think that is the answer.

As an afterthought let us assume your answer to be correct, surely one would get the knocking sound in both forward and reverse rotation? Or am I missing something?

Andrew.

This Crompton Parkinson motor came from a Myford ML7 and was stored in poor damp conditions. I have taken it apart and cleaned everything up, reassembled it after converting windings to Delta.

The motor was then left for a week in an electric oven at 70 centigrade, to make sure the windings were dry. Lubrication was dealt with and it rotated smoothly.On turning it on, I was rewarded with a very quiet motor. I then reversed it and there was a high speed knocking. which disappeared when .forward was selected.

The bearings are simple sleeve bearings and although not immaculate they should be good. I have seen and used sleeve bearing motors whose sleeves were more worn than this specimen and they were pretty silent. The rotor shafts were in reasonable condition, some light scoring but otherwise good.

What can cause such a difference between forward and reverse rotation? I am at a loss for an explanation. The motor would have been used exclusively in the forward direction if this is significant.

I have never changed sleeve bearings in these old motors. I assume that it would not be difficult to change them. The major problem might be in getting them! Maybe a make it yourself job.

Andrew.

Edited By Andrew Tinsley on 01/04/2021 19:08:37

Hello Anthony, the inverter is ramping up to 50 Hz over 5 seconds (or should be!) no poteniometer control, just another thing to give trouble!

Andrew.

Thanks for that, I have the manual for the Altivar 11 and that isn't helping for this problem! I suppose I can't complain as I purchased it second hand for very little money. It has been first class in sorting out various problems with old motors which come through my shop, so it doesn't owe me anything.

I still have a sneaking suspicion that it is something simple that I am missing, so it won't get binned yet.

Thanks again,

Andrew.

Hello Old Mart,

I did say in the original post that the switches were checked and found to be working correctly.

Andrew.

I use this VFD to check out 3 phase motors after converting from star to delta. Last time I used it, it was fine. This afternoon I connected up a motor and switched on, the usual rDy (ready signal) was displayed. Flicked the forward run switch and nothing except the display showing zero Hertz, same with reverse switch. Checked out the motor on a second Altivar and it ran perfectly. So it seems the little old Altivar 11 has a problem.

I checked out every parameter in the program (against my list of value) nothing had changed. Checked that the common output voltage for digital inputs were present. Yes +15 Volts was present and the mechanical switches worked as they should.

Now these all singing and dancing VFDs are usually fast enough to tell you what the fault condition is (usually motor fault) but often VFD problems as well. But not this time!

Not sure where to check next, but it seems that the switch digital inputs pull the +15 Volt common supply to zero if it is connected to an analogue input. Now this can't be correct?

Andrew.