Any US WW2 screened ignition systems?

[fv1609]

Were any WW2 US vehicles fitted with a screened ignition system? If so were they 12v or 24v? If there were any, did they use a ballast resistor?

 

I did find one GMC that once had a screened ignition system, but the owner thinks it was a later modification by the Dutch Army & it has long since been removed.

[Gordon_M]

Yes, sort of - Dodge radio trucks.

 

Right back into 1940, the VC 1 Command had ordinary electrics, but the VC 2 Radio had similar components encased in big, clunky radio shielded housings. I've never actually owned one though.

 

Some images here;

 

http://forum.ww2dodge.com/viewtopic.php?f=5&t=9936&p=58384&hilit=shielded#p58384

Edited August 19, 2012 by Gordon_M

[Adrian Barrell]

White Scout Cars and Half tracks, 12V, anything with a radial engine, 12 and 24V. No ballast resistors as far as I know.

[fv1609]

Thank you Gordon, in that link it was nice to see some original screened fittings. So often even in relatively modern vehicles the screened system is ripped out & dumped. I suppose I can see the temptation to rip it out, but few people consider keeping it so a future owner could make use of it.

 

Adrian thank you, the few WW2 British vehicles I have looked at with a screened system don't seem to have had a ballast resistor either.

 

I suspect at that time (1941) that it was only the Germans who realised how to overcome the capacitive effect of the screened HT cables by reducing the time constant by loading the LT with resistance to reduce the effect of the inductance of the coil.

[Richard Farrant]

Clive,

The Windsor Carrier, built by Ford Canada in late war, was a 12v system with 6v coil and ballast resistance. The system was screened, the distributor was contaned in a metal box with screened conduits attached, so a simple modified system with no special distributor required. The manual does not state if 12v is applied to the coil when starting, you would assume so, but there is no wiring diagram in my manual nor illustrations of the ballast resistor. By the way, the engine was a Ford V8 in case you were wondering!

[fv1609]

Richard that's interesting then. I wonder when the Canadians twigged the advantages of a shunt? This 1941 Berlin document seems to be instructions for a retro-conversion.

 

Hmm now where can I take a picture of such an example?

[deadline]

Not sure what you mean by 'screened'. DO you mean a metal covering (yes, there were) or suppression of RF (almost all were).

 

Off the top of my head:

 

DUKWs

G506

Halftracks

 

Here is the early Chevy G506 shielding:

 

 

 

 

And the early DUKW shield (partial)

 

 

Later DUKWs, G506 and G508s had various filters, and lateer they were grounded and screened.

Edited August 23, 2012 by deadline

[fv1609]

Not sure what you mean by 'screened'. DO you mean a metal covering (yes, there were) or suppression of RF (almost all were).

 

Thank you for the pictures. I hadn't considered that the whole ignition system might be screened off. That looks easy to manufacture & avoids the problem I'm about to describe.

 

What is I was looking for was whether any systems had screened cables, ie coaxial HT cable. Because with that comes capacitance that has to be 'charged up' by the HT & energy lost. To off set this the HT can be 'boosted' by reducing the time constant of the circuit by loading it with resistance & using a lower voltage coil.

 

I've studied a Dingo & although it is comprehensively screened & filtered there is no ballast resistor.

 

Richard has pointed out that in the late part of the war the Canadians had started to use a ballast resistor in a screened ignition on a carrier. So I'm just wondering whether this 1941 Berlin document marks the first use of a screened & ballasted system before anyone else?

[Gordon_M]

Tad different on the DUKW reasoning though, as that was primarily to keep water splash off the ignition ( makes more sense when you consider the bonnet air scoop on the early DUKW )

 

Any DUKW part that was considered sufficiently waterproof, like the regulator box, was left unshielded.

[fv1609]

Gordon, good point I hadn't thought of that reason.

[deadline]

My understanding was that the metal shields were a major pain. They were thin tin sheets and broke/bent easily. While they do look kinda cool, there most likely is some truth to the previous statements... precious few have survived.

[deadline]

Tad different on the DUKW reasoning though, as that was primarily to keep water splash off the ignition ( makes more sense when you consider the bonnet air scoop on the early DUKW )

 

Any DUKW part that was considered sufficiently waterproof, like the regulator box, was left unshielded.

 

I don't know much about the DUKW, but looking at the photo, the coil is connected to the shield via a condenser. Is this just a convenient ground or was the shield more RF shield than waterproof container?

 

Just wondering.