Unfamiliar capacitor

[SurreyNick]

I believe the component pictured below is a capacitor, but of a type I have not encountered before.

Assuming it's an original component, it dates from 1929. In my Marconiphone Model 55 it is being used to couple valves together and there are two fitted; one to couple valves 1 and 2, and another to couple valves 2 and 3.

Can anyone give me more information about this type of capacitor? (name, properties etc.). I'd like to know more about it.

Nick
   

[pwdrive]

Looks like the type that uses a coil for one of the plates .......possibly.....the coil in effect isn't inductive as such as all the turns were normally soldered together, I seem to remember that Philips used a type that was similar but physically smaller.

Lawrence.

[Ed_Dinning]

Hi Yes Philips used them as trimmers in some of their IFTs. They worked fine until you wound too much wire off !!

Ed

[SurreyNick]

Mm. I'd like to learn a bit more about them. Do they have a particular name so I can track down some literature/reference material?
N.

[Refugee]

From the photo it looks like the wire is wound on a piece of hollow wood with the inner plate made with the fixing screw.
It could be home made.

[SurreyNick]

Yes, I can see how you would think they might be home made, but I suspect not. I have the benefit of having the chassis in front of me and as you can perhaps see from this picture the capacitor is held between two tags which are riveted to the chassis and valve holder. This appears to be an original design feature and makes me think the capacitors were commercial items. They could have been a manufacturer-only item though i.e. made by Marconi, or for Marconi.
N.
   

[pwdrive]

Some of the early (ish) Marconi stuff was built with some oddball stuff, I reckon from various bits and pieces left over from other production jobs, the CR300 had a built in xtal detector (Board of Trade requirement for marine radios at that time) that could be used as a xtal set if the ships power or the electronics in the radio itself failed, if I remember rightly that seemed to be made with odds and sods.

Lawrence.

[SurreyNick]

I have never seen anything like them in any magazines from the period. It's for that reason i.e. intense curiosity that I'd like to track their provenance down and learn more
Lawrence/Ed you mention Philips made something similar. Do you know of any references I can look at?
Nick

[Crackle]

I have seen them in a 1929 KB 156 Suitcase portable.
   
This one is a brass cylinder with a paxolin end, wrapped with mica, then the wire is coiled over that and soldered.

Mike