Froment Engine

Hi Colin, I have a drawing of one at

First time I've heard of Froment! Some handy looking pictures here:

Soft iron sounds more authentic (and workable (and less fragile!)). Can you actually buy something called 'Soft Iron' these days?

I can't help with the coils, but the above pictures give you a good idea what's needed, I think. You'll be striking a balance between supply voltage & current, solenoid size, wire diameter, number of turns, temperature rise in solenoid, proportion of time solenoid is powered, and speed of motor. I would make the solenoids a sensible size and then fill them with various wire diameters to see what happens! The supply may need to be quite high current. Start with lots of turns of thinner wire to keep the amps sensible. You may have to suppress large sparks as the current to the coils switches off (back EMF). A reversed diode does the trick on relays and would work with this. See the bit about 'Quenching Diodes' halfway down this page:

Perhaps they tried Leyden jars back in Froments days! They didn't have to worry about interfering with al the local radios and TV's though! You could do with a current limited variable voltage supply while you work this stuff out, but it may need to be protected from these back EMF spikes - also yourself - they can be quite painful!

Hope this is of some use, given that you're a Tesla coil builder already!

Scrim

Soft iron sounds more authentic (and workable (and less fragile!)).

what's needed, I think. You'll be striking a balance

turns, temperature rise in solenoid, proportion of time

size and then fill them with various wire diameters

lots of turns of thinner wire to keep the amps

switches off (back EMF). A reversed diode does the

worry about interfering with al the local radios and

this stuff out, but it may need to be protected from

Looking at the pictures it seems like a nice project. The ones I like I have put a couple of pictures on

"next" for the second) Can anyone understand how the distributer contacts work on either of these? The two versions seem similar but different.

Some examples of Froment motors in collections in the USA...

Enjoy.

Regards, Marv

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Hi Chaps,

Thanks for the helpful links! Dave I couldn't get the picture but wil try later. Scrim thats been a help thanks. I will wind a couple o coils the weekend and try it with some steel through the middle to se what power I get. I look forward to posting some pictures of this soon. I have some nice phenolic spools to give it that authentic look for th coils I will varnish them the weekend and wind. Cheers Coli

-- colinheat

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