Military Desynn Test Set

[David Simpson]

Folks, does anyone know anything about this item, please? A military item for testing "Tank Units", going by the instruction card in the lid. Stores Ref. 6C/437.
There is no mention of a particular Army Tank, or any reference to the traverse of the Turret. Just Desynn Transmitters & Receivers. The wooden case is 10" square & 3 3/4" high. There is no date on it, but I'm guessing 1940's.

Regards, David

PS. Just started googling - seemingly ex RAF, made by Smiths. Before my time, certainly. So not Army. There had been one on eBay. DS.

[ms660]

There's a similar looking one here:

http://www.meea.co.nz/images/Newslet...eral-copy-.pdf

Lawrence.

[woodchips]

Isn't a Desynn transmitter or receiver just another type of synchro? Torque variety rather than signals. I also dimly remember it uses one phase back to front from synchros, or is it DC like the step by step transmitters used in the gyro compasses?

Not much help really!

[Ed_Dinning]

Hi David, yes a test set for synchros. Could make a useful bit of kit to demonstrate these units with.
There were many different types available as well as different voltages and frequencies.
You could make a simple computer with them

Ed

[Radio Wrangler]

It's a DC sort of syncro with a multi-wiper continuous pot as the transmitter and a permanent magnet suspended within a 3-phase stator energised by the pot.

It doesn't need an AC supply or a regulated supply. But unlike the synchro, it isn't brushless.

Good item as a talking point at an ex-airfield?

David

[ms660]

Mods permitting for ID purposes only (completed listing):

https://www.ebay.co.uk/itm/VINTAGE-T...p2047675.l2557

Lawrence.

[Dave757]

Hi,

I seem to remember that Desynn Indicators were associated with prop pitch motors on
aircraft. But to be fair I don't trust my memory that much!

The 6C/ reference is certainly RAF.

Kind regards
Dave

[AC/HL]

You can just make out the word "Flap" on the instructions, which would confirm avionics use.

[M0FYA Andy]

Section 6C is for 'Instrument Test Equipment'.
The reference to Tank Units is nothing to do with army tanks, but to fuel tank sender units, some types used a float operating a Desynn transmitter.

Andy

[David Simpson]

Many thanks guys for replies. 'Specially Lawrence for the NZ info, and the eBay link. I'd only uncovered an earlier eBay post when one was flogged for about £60. This later eBay one went for £14 + £7 postage. Mine, today, - cost me a tenner at a local sale.
It would seem that these were used by all three services. RAF - wise, back in the 60's, I was tasked to build a test bench for the new Elliot-Marconi ILS/VOR system we'd started to use, which used selsyns, desynns or whatever ?('Twas 50 years ago, but cant remember). I wasn't given anything like one of these testers, so had to adapt spare aircraft transmitters & receivers & make up interconnecting cabling using an AVO8 & a "suck it & see" method to get them to synchronise. As an AP hadn't been produced yet, & E - M wouldn't release a Manual!

Regards, David

[jamesinnewcastl]

Hi

It happens that I made a quick video of the operation of a Desynn 'pair'. The URL given in the video leads to an interesting article on this and similar devices.

https://www.youtube.com/watch?v=UkQq0BSnYwY

I think that your test set might interest the historic aviation enthusiasts.

Cheers
James

[M0FYA Andy]

This video on the restoration of Avro Lancaster NX611 shows a tank sender being tested on this type of test set.

https://www.youtube.com/watch?v=BjQYW3x6olI

Andy

[David Simpson]

Thanks James & Andy for the Youtube links, very interesting. There are 3 aviation museums up this way - Montrose, Morayvia at Kinloss, and Inverness. I'll probably drop it off at Kinloss if they want it, as they're nearest.

Regards, David

[Ed_Dinning]

Hi Gents, I have seen the tank units, with a recalibrated gauge head used as a direction indicator on a sonar system for fish tracking. Fitted to the loch in Stirling university.
They were being re-purposed in the early 70's

Ed

[David Simpson]

That's interesting Ed, an old RAF chum from Cosford back in the 60's, Pete Wallace, ended up doing a marine biology degree at Stirling in the early 70's. He also spent a fair bit of time at the research station near Oban. Converting a desynn tester would've been up his street, as we'd worked together in the same test equipment section, and he was always experimenting with old stuff. Although that was mainly scopes, sig gens & AVO's.

Regards, David

[Ed_Dinning]

Hi David, I was the experimental officer working on the fish tracking project at the university and we had 3 acoustic receivers mounted on underwater dishes, so we could triangulate onto our chosen fish. These were driven by stepper motors and we bought this kit from Lisle street as it was advertised as being suitable for rotatable beam antenna's.
From memory it was pretty cheap and did the business.

Ed

[The Philpott]

David, what you have there is a ticket for a free guided tour of (whichever) museum you choose to honour. Don't settle for an 'ooh, that's lovely, thankyou!'

The way East Kirkby are attending to little details in the video it looks like they are shooting for the sky. PTF, COA, chocks away! (Funds permitting)

Dave

[David Simpson]

Right oh, Guys, me thinks I've finished. What took up the most time - the wooden case ! The bottom half needed completely diss-assembling & re-gluing & clamping. Bladed & sanded off all the manky darkish varnish & revealed a lovely oak construction. Just used a clear lacquer to re-varnish.
The master transmitter's top & bottom wipers needed a good clean.
They call the Sender/Transmitter a "Tank Unit" which is a bit confusing. However, Martin(GM8AGM) has leant me an old exWD Sender(6A/1641), and a wee Smiths Compass Repeater. Under the internal "Test" procedure, it was found that the tank unit's cursor's was slightly out of alignment, but once that was re-adjusted, testing Martin's old Sender & Repeater was fine. It would seem that old desynn senders & meters kept the same numbered terminals. Makes the testing procedure simple enough.

Regards, David

[David Simpson]

More pictures. DS. Oh I, just remembered - The carrying handle was missing(you can see the shadow & screw holes on the front), so I'll be on the look-out for a replacement. Roughly 4" between the screw holes.

[M0FYA Andy]

David, there's nothing at all confusing about calling the Transmitter a 'Tank Unit'!

As I mentioned in post #9 and then #12, this test set was primarily intended for testing the Desynn Transmitters used in aircraft fuel tanks to measure the fuel level therein, in much the same way that a motor-car fuel tank level sensor might use a potentiometer. A float on a lever rotates the Transmitter shaft, and the electrical output is connected to the fuel gauge in the cockpit.

Andy