Re: A bit OT - Rotary converter??

Well spotted Nick, yes, it's Air Ministry. Only a mains motor as far as I can see, there is no provision for a current take off.
I've got another similar thing somewhere - I'll dig it out, but I'm certain the other device really is a rotary converter as it will light a mains bulb from a 12 Volt battery ;o))
I've also got a 300 AMP dynamo from a Canberra and a phase converter from a Shackleton. The latter is fan cooled and sound just like a gas turbine spooling up!
Regards,
Kim Siddorn

Looks like a step-up ratary converter for radios in aircraft.
Radio valve HT voltage is 250V DC or so, the aircraft only has 24V DC so they used these for jumping up the supply volts. Some also had a 6V feed for the valve heaters as well, and a few had AC output so you could run a mains tranny off them.
Kind regards,
Peter
Peter Forbes Prepair Ltd Luton, UK email: snipped-for-privacy@easynet.co.uk home: snipped-for-privacy@easynet.co.uk

But it says "1/8th horsepower, 4000 RPM, WARNING the frame of this motor should be efficiently earthed." The operative words here being, of course, "motor" and "horsepower" ;o))
On my rotary converter it says "12 volts input, 240 volts output". Other ones I've seen have a comm. at one end and slip rings at the other. None of them have "motor" on the label.
Good-o, an interesting problem! I think I'll go and play with it through a RCD. If there is a power cut in the SW tonight, you know who to blame.
Regards,
Kim Siddorn

Kim, As peter said its a rotary converter, I had one similar for a while mine you could put in 24v and get 240v out.
Martin P

In message , Campingstoveman writes I have something very similar with just two commutators languishing at my mum's house. I had it as a schoolboy (30 years ago) and it did run on 240V - I can't remember the output.
Regards
Pete

Right then. My curiosity piqued, I delved amongst my bench corner where I keep Interesting Electrical Devices Wot I Will One Day Use and found the following.
Three AC motors, a 1920's 50V dynamo and the ex-Canberra dynamo.
The ex Shackleton inverter (24/28v to 115 v. 770 watt, 400 CPS)
An Electro Dynamic Construction Company Converter (12V DC to 230V AC at .521 amps)
A "Transformer rotary, HT 20 watt, No. 2. Volts, 11/480. Amps, 3.4 to .04"
The latter certainly seems to fit the radio slot that Peter came up with.
And of course, this weekend's purchase. Having sat down with it, I am more than ever convinced that it is some kind of electric motor. It says so and - unlike all the rotary converters - has a pulley and drive shaft sticking out of the end. Having cleaned all three comms. I feel that it has never had much use, all the segments are sharp edged and the insulation deep cut on both end comms. The two end brush holders accept the same kind of (unworn) brushes, but the inside brush holders are smaller and the comm. is much finer.
The Air Ministry terminal box is a red herring (well spotted!) and my feeling now is that it is an electric motor from some kind of fairly sophisticated device - perhaps a business machine of some kind - from the 1940's. Off now to my Science museum contact and my mate Tim who is as nuts about old electrical stuff as we are about old engines!
Updated pics at
Regards,
Kim Siddorn
I'd rather have a free bottle in front of me than a free frontal lobotomy!

Kim, Could not the pulley also be a red Herring ? Just a thought.
Martin P p.s. did you receive picture.

Hi all I've been lurking for a while and couldn't resist this one as I have probably burnt my fingers on most of the rotary devices in pictures posted by Kim :
1/ Bought one of these (similar) from an ad. in Wireless World back in the late 60's 'Mains Power Anywhere'? - thought I would supply the whole house from a car battery! I was only about 11 years old at the time!
2/ Fairly standard HT rotary transformer - used one to power a 'portable' valved transmitter in the 70's. Funny how your brain lulls you into a false sense of security with 12v derived equipment - 200V DC really does hurt !
3/ I think that this may be a motor generator i.e. shaft power for driving say a gramaphone turntable and HT/LT from the commutators for a valve amplifier. The number of segments on the comms give a clue to the voltage.
4/ The dreaded Rotax 108A rotary - normally mounted on a chassis along with associated control gear and stuffed in some hard to get at corner of a military aircraft. VERY heavy and a real pig to set-up on a cold windy airfield with a noisy smelly Houchin GPU beside you supplying the 28V DC. The 108A was (still is ?) used to supply 115V 400cs (Hz) for TACAN etc (Hunter,Canberra)
Thats my input - any errors are down to middle-aged brain fade.
Arthur

No ideas, but the production records for Electro Dynamic Construction Ltd are archived at Unversity of Glasgow. What exactly the records will provide requires means some DYOR.
See a starter.

"Arthur" wrote Motor-Generator? That begins to make sense - but why not just use an ordinary transformer?
I don't suppose you'd remember which connections provided the output?
Regards,
Kim Siddorn

As Mr Dingley states in his reply - transformers are not a lot of good for DC. Motor generators were very popular before and during the war for both battery and mains powered equipment requiring various voltages.
108A inverter : It's the sort of thing that one tries to forget really - never had a bench test rig so testing was 'live' on the aircraft. From your photographs, you only seem to have the inverter. A control panel is also required to control the voltage and frequency (Type 26 ?) This was pre solid-state and used carbon piles to control the stator windings along with a separate resistive "soft-start". If you have the control unit, I can probably find the connection info. I think that the box on top only contained the filters.
HTH
Arthur

It is probably not aircraft unless 28V DC running voltage, but there were plenty of other applications for these things.
Regarding carbon piles, Newton-Derby were still making these to go with big DC dynamos in the 1970's, and the Cub gennies all have carbon pile regulators, a move on from the Isenthal rotating contact ones that were used previously.
Kind regards,
Peter
Peter Forbes Prepair Ltd Luton, UK email: snipped-for-privacy@easynet.co.uk home: snipped-for-privacy@easynet.co.uk

We are talking about the same piece of kit ?
As in Arthur

Sorry, no. I was still thinking of that other motor.
Yes, the Rotax set is clearly aircraft kit. If I had more bookshelves, I could find the magic Book For Training Erks on aircraft electrics of this period.
(actually Kim, you're welcome to a loan or a photocopy)

[snip]> You can't put a transformer onto DC!
Dave