The Ford Barn

harvest · 03-21-2024, 10:45 PM

what is this? found this in the box of some model A parts i picked up.

Dan McEachern · 03-22-2024, 01:41 AM

yes it is, but that mounting plate for the mag is way too thin!

rotorwrench · 03-22-2024, 07:39 PM

The gearing should be 1:1 for a mag or distributor and that gear looks smaller. It might be better suited for a governor of sorts or driving something else.

johnneilson · 03-22-2024, 10:05 PM

It is an attempt at a side drive magneto
The gear is properly sized for a mag with 2:1 gear reduction or a governor

Most aircraft mags are 2:1 or crank speed.

J

rotorwrench · 03-23-2024, 11:42 AM

All the Lycomings and Continentals I've ever worked on had cam driven mags. They use an idler on one to keep direction of rotation the same. Drive off the cam is 1:1 and the cam runs at half of crank speed. Radial engines have their own way of magneto & distributor function but all of them have to work for 4-stroke operation.

Dan McEachern · 03-23-2024, 01:07 PM

Sponsored Links (Register now to hide all advertisements)

All vintage 4 cyl automotive magnetos- Bosch, Eiseman, Dixie, Splitdorff,Bendix, etc, with the exception of Wycos, run at crankshaft speed. These magnetos have a 2:1 reduction gear set built into the magneto in order to run the rotor at half crank speed. With that said, a side drive magneto on a Ford four banger uses a 25 tooth (crankshaft size ) gear on the magneto shaft. The cam gear in this instance is simply an idler for mag drive purposes. There are some distributor setups (Pierce Arrow/ Delco) that mount on the mag drive platform, but these have a 2:1 gear reduction in them to, again, run the rotor at half crank speed.

03-21-2024, 10:45 PM	#1
harvest Senior Member Join Date: Feb 2014 Location: Lehigh Valley PA Posts: 843	what is this? what is this? found this in the box of some model A parts i picked up. Last edited by harvest; 03-27-2024 at 05:04 AM.

03-22-2024, 01:41 AM	#2
Dan McEachern Senior Member Join Date: Aug 2010 Location: SF Bay Area Posts: 194	Re: what is this? mag drive? yes it is, but that mounting plate for the mag is way too thin!

03-22-2024, 07:39 PM	#3
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: what is this? mag drive? The gearing should be 1:1 for a mag or distributor and that gear looks smaller. It might be better suited for a governor of sorts or driving something else.

03-22-2024, 10:05 PM	#4
johnneilson Senior Member Join Date: Jun 2010 Location: 34.22 N 118.36 W Posts: 1,057	Re: what is this? mag drive? It is an attempt at a side drive magneto The gear is properly sized for a mag with 2:1 gear reduction or a governor Most aircraft mags are 2:1 or crank speed. J __________________ As Carroll Smith wrote; All Failures are Human in Origin.

03-23-2024, 11:42 AM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,440	Re: what is this? mag drive? All the Lycomings and Continentals I've ever worked on had cam driven mags. They use an idler on one to keep direction of rotation the same. Drive off the cam is 1:1 and the cam runs at half of crank speed. Radial engines have their own way of magneto & distributor function but all of them have to work for 4-stroke operation.

03-23-2024, 01:07 PM	#6
Dan McEachern Senior Member Join Date: Aug 2010 Location: SF Bay Area Posts: 194	Re: what is this? mag drive? Sponsored Links (Register now to hide all advertisements) All vintage 4 cyl automotive magnetos- Bosch, Eiseman, Dixie, Splitdorff,Bendix, etc, with the exception of Wycos, run at crankshaft speed. These magnetos have a 2:1 reduction gear set built into the magneto in order to run the rotor at half crank speed. With that said, a side drive magneto on a Ford four banger uses a 25 tooth (crankshaft size ) gear on the magneto shaft. The cam gear in this instance is simply an idler for mag drive purposes. There are some distributor setups (Pierce Arrow/ Delco) that mount on the mag drive platform, but these have a 2:1 gear reduction in them to, again, run the rotor at half crank speed.