So I Have A Crazy Idea I Don't Know If It Will Work.

So I have a 1946 Chevrolet truck with a foot pedal starter. I love how simple it is and it's something that is not seen anymore. I know the early CJ's had the foot pedal starter but I didn't know the M38A1's had them but they are 24volt. Would it be possible to run a 24 volt starter on 12 volts? I have a source on a M38A1 starter for under $80 all I would need is the floor pan and the starter pedal.

 

Sorry 24V won't run on 12.

 

I imagine the windings are thinner in a 24v starter so be aware of things getting warmer than usual...

You could wire the starter in 24v with two batteries and get a few misc parts to run everything else 12v. Series parallel switch might be one of the parts you need.

 

Get an early-type civilian set up, and a six volt starter will work on 12volts.

 

Running at 24v starter on 12v will probably not work very well because it will only draw half the amps at 12v, or so says Ohm's law:

E = I * R (volts = amps * resistance)

To make the math simple, suppose the starter draws 24 amps on the 24v battery:

24 = 24 * R
R = 1 ohm = the resistance of the starter

The resistance of the starter is fixed and doesn't change with the input voltage. Therefore, with a 12v battery:
12 = I * 1
I = 12 amps

The starter will only get half the power at 12 v. A 12v starter with the same torque as the 24v starter would draw 48 amps.

 

Similar to early willys (Jeep) pickups, however.

 

I run my cj2a with a foot starter and 12v battery no problem. Does turn the engine over much faster than when it was 6v

 

True, but going from 6 volts to 12 you are cutting your current in half. Back to ohms law. The original post was 24 volts down to 12. The current will double.

 

I wonder if a rebuild shop could convert it to 12volts?

 

The field strength is proportional to current, not voltage. So correct, lower current means a weaker field and a slower starter. Realize that Ohm's law is correct but only in this simple form for DC, sp. no time dependence. This gives you a very limited view of the motor's action.

No easy way to change the voltage dependence other than rewinding the motor. Expensive, I would imagine. More reasonable to go with the 6V starter and let it spin faster. Experience shows that the Willys 6V starters do ok on 12v, and if the 6V motor fails, you can easily find a replacement.

 

I've done this with several old 6V Farmalls. Over several decades, I've never had a starter failure. That said, I limit the cranking time.

 

Another idea - If the Willys floor starter is just a big switch in the floor, why not run the 12V starter with the floor switch? If you can't eliminate the solenoid from the 12V starter, you can still activate the solenoid with the floor switch.

 

This seems like the path of least resistance....no pun intended!

 

Thats seems easier fo deconnect the contact starter form the key system and to trnffer it to an independant switch.
I did it to ha the start swith on the dash. I turn the key to have electricity then I push the switch to action the starter.
Eawy to do the same with a foot witch but avoid to put the foot on it when engine runs... or add a device to cut isolate in this case but more complicated so more risks of problem...

 

Had a foot started on my ‘51 3A, ‘52 M38 and currently on my 6v ‘56 CJ5... wouldn’t have it any other way. Cool factor is 100% and the defy the anti-theft quotient is incalculable.

get your starter and electronics rebuilt or in line with the voltage system you’re running 6v, 12v or 24v and you’ll be A-OK.

 

Many 6V Jeeps have been converted to 12V over the years and retained the 6V starter which works fine. I don't know of anyone installing a 12V starter into a 24V system, but I understand the question, just don't know what would happen. If it did work it would probably spin pretty fast for a while anyway.

 

It will work it spins faster and will wear out prematurely but will do its job just don’t crank on it for long periods limit to 15 or 20 seconds let cool for a minute and try again