ID on Relay

[manta22]

I have a large relay that looks like the type that was used as an engine starter contactor on WW II aircraft. It is marked "Type A3 BUL 6041H43C" and it looks like the ones made by Cutler-Hammer or Eaton. The puzzle it that it is 12 volts, not 24 volts. What might it have been used on?
It appears to be NOS, never used. I'm using it as the main power relay on a race car that I built.

Thanks, Neil Tucson, AZ

 

[Brent]

don't believe it is warbird as most of them are 24 volt, as you say. But the average Piper/Cessna and my homebuilt are commonly 12 volt that would seem to be the original usage. If it is rated for continuous duty it should work fine on your hot rod. Relays like this but not marked continuous duty would be used as a starter relay and will overheat if used on the main power supply

 

[manta22]

don't believe it is warbird as most of them are 24 volt, as you say. But the average Piper/Cessna and my homebuilt are commonly 12 volt that would seem to be the original usage. If it is rated for continuous duty it should work fine on your hot rod. Relays like this but not marked continuous duty would be used as a starter relay and will overheat if used on the main power supply

Thank you, Brent. What is your homebuilt?

 

[Brent]

Bearhawk scratchbuilt 4 place with an IO-360 200 HP

 

[Wurger]

 

[MiTasol]

I have a large relay that looks like the type that was used as an engine starter contactor on WW II aircraft. It is marked "Type A3 BUL 6041H43C" and it looks like the ones made by Cutler-Hammer or Eaton. The puzzle it that it is 12 volts, not 24 volts. What might it have been used on?
It appears to be NOS, never used. I'm using it as the main power relay on a race car that I built.

Thanks, Neil Tucson, AZ

Hi Neil
It looks like the start relay from any of the trainers like the AT-6 and BT-13.
The majority of US WW2 military aircraft under about 6-700hp used 12 volt systems.
I will check my references when I get home and see what I can find
A major supplier of starters, generators and relays was Eclipse so it may also be one of theirs.

 

[MiTasol]

6041H43C means it was made by Cutler-Hammer

 

[MiTasol]

Here is a 1930s selection of Eclipse Starters it could have been used with. JAHCO (Jack and Heintz) made a similar range. Other companies made a smaller range. You will note that 12 volt starters are just as common as 24 volt and that 12v direct cranking starters were used for to 900hp engines.

Direct cranking means that the starter turned whenever the start button was pushed/pulled. Your car engine uses a direct cranking starter.

On inertia starters the electric motor is used to accelerate a heavy flywheel and once the flywheel has sufficient inertia the starter is engaged using an cable or solenoid. The flywheel has enough inertia to turn the engine over up to three revolutions.

If you prime it right and have the throttle set right that is more than enough to start the engine even is sub-zero weather where batteries are next to useless at the best of times. Pure inertia starters are also lighter. Inertia starters often had a hand cranking option which meant that you could start an aircraft which has a dead battery. Inertia starters with both electric and hand cranking are heavier but require (lighter) smaller diameter wiring, smaller relays and a smaller battery so were popular on fighter aircraft as the overall weight was less. Some inertia starters had no electric motor.

Aircraft ignition systems use magnetos which do not need batteries.

 

[manta22]

Bearhawk scratchbuilt 4 place with an IO-360 200 HP

VERY nice, Brent! Great looking airplane. Here is my project. Regards, Neil Tucson, AZ

 

[manta22]

6041H43C means it was made by Cutler-Hammer
View attachment 550676

Thank you ; this forum is a wealth of information. Since the Cutler-Hammer relay users are listed as "Army" or "British", your suggestion of a AT-6 sounds likely.

Regards, Neil Tucson, AZ