[Milsurplus] 400 cycle 3 phase and WW2

[Taigh Ramey]

My impression of the early use of 115v 400cy (pre war/early war) was for
selsyn transmitters used for instrumentation. Instead of direct reading
instrumentation where you would have to run tubing from the engines to the
cockpit they elected to use selsyn transmitters and instruments. 

Many of the fighters and bombers had selsyn instrumentation for things like
fuel flow, oil pressure, fuel pressure etc. This would also limit the amount
of flammable liquids in the cockpit.

There was also a problem of the fluids in the long runs to the cockpit
congealing in cold environments (especially engine lubricating oil) thus
causing instrumentation errors both on the ground and in flight.
Mechanical/hydraulic transmitters were tried on several aircraft where the
fuel or oil would flow through a short run of 1/4 inch line to the
transmitter. This transmitter has a diaphragm that has the engine oil/fuel
on one side and then a special fluid (compass fluid) on the other side of
the diaphragm which would then be run to the cockpit. This instrumentation
fluid would not congeal in the extreme temperatures and was not as flammable
as the fuel being piped to the instruments.

The flux gate compass system and some gyros for autopilots used 115/400cy in
WWII aircraft as well as some radio and most radar gear. The Sperry S-1
bombsight and A-5 autopilot also used 115/400cy for its main power. The
Norden sight used 28vdc but the C-1 autopilot had its own 115v inverter
instead of relying on the ships inverter or inverters/dynamotors.

The remote compass system common in smaller aircraft where the flux gate was
too big also used AC but it was 26 volts at 400 cycles. These systems used a
small rotary inverter just for the compass which was smaller than the
dynamotor on an ARC-5/274N receiver.


Taigh

Taigh Ramey
Proprietor, Vintage Aircraft
7432 C.E. Dixon Street
Stockton, California 95206
(209) 982-0273 Shop
(209) 982 4832 Fax
www.twinbeech.com
'KEEP 'EM FLYING...FOR HISTORY'


-----Original Message-----
From: milsurplus-bounces at mailman.qth.net
[mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Jack Antonio
Sent: Wednesday, January 12, 2011 11:09 AM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] 400 cycle 3 phase and WW2

I  remember reading that the Douglas XB-19 which was
used as a test bed for large aircraft systems, used AC power,
but no technical details were provided.

Jack Antonio WA7DIA/4



On 1/12/2011 1:46 PM, Ray Fantini wrote:
> Thought all the old WW2 stuff ran from 28 volts DC and the B-36 was the
first aircraft to exclusively use 115 volt 400 cycles 3 phase AC
distribution? Being that AC distribution reduced design weight by several
thousand pounds on a large aircraft. Recall reading something along this
line in "Magnesium Overcast" by Dennis Jenkins. Maybe there was some
application of 400 cycle AC prior to the B-36 but don't know what it would
be. Did the old GO and GP transmitter have engine driven generators or motor
generators  to develop their voltages from the ships DC distribution?
> Ray Fantini KA3EKH
>
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