Paul,

You have a rotary convertor, around WW2 vintage. It was used to generate the voltages needed for valved electronic equipment in a car, lorry or tank.  From the voltages  would suggest a transmitter or radar equipment. It is a 12V motor with extra windings and commutators-but no drive shaft.  As the motor spins the secondary windings see a changing magnetic field that induces the higher voltage in the secondary coils. Millions of these things were made in WW2. With the advent of  transistors rotary convertors became obsolete.

regards,

Alan

Motor-generator set, shortened to M-G set?

 

Regards,

 

Andrew

 

Edit: Ah well, beaten to it!

Hi, I do believe they were from WW2 era. My farther had one very similar and I think he said it was somthing used for old radio’s before the National Grid, as local ES was DC then. Never did know how is was wired though.

Had a look at the photos in the album ,no.1 could be used as a generator, its proberbly got a good output watt wise.

Back in the 60s when I started in agricultural aviation we were just getting rid of the American military(ww2) ARC-5 radios (they weighed tons), an they had genimotors in them, ours were changed from 28V to 12V. We changed from some thing that was about a 2ft cube+ the remote control unit, to a bit bigger than a normal car radio, a locally made transistor transciever. These radios were in Cessna 180/185 aircraft.

12-15 landings an hour in a 12 hour working day on rough farm airstrips was rather hard on valve radios, plus the radio took over 100lb of the pay load. Ian S C

Had one similar years ago. In our ignorance just wired one end to a car battery, other end would run Wolf drill or similar, (no mains then). Also converted one to a grinder, can’t remember how, but worked ok.

Hi Paul,

 

Don’t use any sort of abrasive on the com copper filings will get in the segments and cause shorts. Just use meths to clean the dirt off. What you have is a rotary transformer. It allows mains powered AC to be used mobile, usually RT sets. 2 windings, or more on the armature and only one field winding.  Not a lot of use for anything else due to DC output.

 

Rotary converters were much more useful, same idea but with slip rings instead of a commutator giving AC instead. As an apprentice the firm I worked for  had several of these used to run PA systems where no mains supply was available. A variety of DC inputs, usually 12 or 24 volts and according to the state of the batteries from around 200 to 230 volts output. The ones I used were rated at 250 watts, so a bit heavy and chunky but very reliable and quiet.

 

Chris.

Well, as somebody else already said, abrasives, particualrly emery, are not really the done thing on commutators.

 

The use of a broken hacksaw blade to clear back the Mica from between the segments seems to be the standard approach, at least everything I have seen on the subject has had a little diagram of how to grind one end of the blade to make a suitable cutter.

 

I am not sure that I agree with the “100% reliable” bit, we would not be talking about how to clean up commutators if they never gave trouble. The modern transistor one, at least if from a reputable supplier, probably has a much longer mean time between failures. However, when it does give trouble, you need access to the right spares, while you could generally recondition a dynamotor with a pretty ordinary workshop.

 

When I was about so high, my Dad took me along on a visit to the power station for the trolley buses that they had at that time here in Auckland. This had previously been the power station for the tram cars. They did not generate their own power, at least not as far as I can recall, but they had three generations of equipment for turning AC mains into DC for the  overhead wires. First was rotary convertors, giant versions of what we see above, although built more in the old style, eg a very large diameter relative to the length. Next was mercury arc rectifiers, one of which is actually still operational now at our transport museum at Western Springs, driving the trams there. Finally they had some of the then newfangled and high tech silicon rectifiers. All of these were still in use at the same time. I am not sure now if the silicon rectifiers were just straight diodes, or if they were SCRs. (Thyristors to some)

 

regards

John