Magneto Drive?

R

RDVAARK

Member
At the first day of the two day Hollandia Car Show/Fall Festival at Hollandia Nurseries, a large crew of experts and advisers was able to start a Gordon Smith Model A Compressor for the first time in many years. It runs on two cylinders and compresses on two.
Can the governor drive off the timing and cam be used to drive a magneto? I think the small gear on the crank is the same as the one in the nice housing and shaft on the outer side of the timing gear that runs the governor. This would give a power take off at crank speed. I've got several magnetos (Bosch DU series and Farmall Wicos), one of which may have a reduction drive on it, also, some DU's have advance/retard devices.
I haven't yet really studied this. Have any of you? I'll see it again today, and may get expert advice on this. It,s amazing how fast this thing pumps air before even warming up the engine without a radiator. Also the oil sump probably needs cleaning.
 
RDVAARK said:
At the first day of the two day Hollandia Car Show/Fall Festival at Hollandia Nurseries, a large crew of experts and advisers was able to start a Gordon Smith Model A Compressor for the first time in many years. It runs on two cylinders and compresses on two.
Can the governor drive off the timing and cam be used to drive a magneto? I think the small gear on the crank is the same as the one in the nice housing and shaft on the outer side of the timing gear that runs the governor. This would give a power take off at crank speed. I've got several magnetos (Bosch DU series and Farmall Wicos), one of which may have a reduction drive on it, also, some DU's have advance/retard devices.
I haven't yet really studied this. Have any of you? I'll see it again today, and may get expert advice on this. It,s amazing how fast this thing pumps air before even warming up the engine without a radiator. Also the oil sump probably needs cleaning.
Click to expand...

Some can, -and some can't. The key to this is making sure the drive of the governor turns at the same speed as the crankshaft due to ensuring the spark timing correlates with the piston at or near TDC of each piston.
 
Most aircraft drive their magnetos off the cam with 1:1 idler gears to get alignment. They mostly all run two magnetos for back up and a way to test one against the other before flight. The cam turns once for every two revolutions on a four stroke engine or 1/2 the crankshaft speed.

A governor is just a way to maintain a specific rpm. It adds throttle to maintain the same rpm no matter the load. They can work off the cam or crankshaft but they need to be set to engine rpm through gearing if run on the camshaft for the sake of sensitivity.
 
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The governor doesn't matter in this case, take it off. What is important is the shaft driving it at 1:1 crank speed- if the little crank gear turns the big engine timing cam gear at 1:4, the cam gear will drive a small gear equal to the crank gear at 4:1, which gives a shaft speed equal to crank speed. Lots of work, but the result is a set of gears all ready set for mesh and alignment,bearings and lube, a solid casting and a shaft protruding through a cast, solid, ready-machined flange with a bolt pattern. When my DU-4 magneto is mounted on my White truck engine, that's what it needs (it sets on a base). If an adapter between mag and flange (a coupling, or a plate like an engine conversion adapter, only small) is made, then I guess the question is mag rpms versus crankshaft rpms. The only variable left is whether a mag with a reduction of 2:1 can be found or rigged.
On the White truck,the mag is driven at 1 magneto revolution per two crankshaft revolutions, firing every fourth stroke of the piston. Intake stroke of the piston down (1),compression stroke up (2), ignition at say,TDC, power stroke down (3), exhaust stroke up (4). Some Wisconsin engines, using a rotary Wico mag at 1:1 crank speed, fire at(2), and again at (4). The second firing is apparently useless and possibly harmless, but eliminates a gear reduction.
I'd like to hear more. Please bear with me. After a day of watching the Gordon-Smith air compressor, with an Aeormore whistle for amusement, I would like a simple, plain, patient explanation.
Again, instead of driving a governing device, can a Magneto (of what sort?) be driven by the same shaft? Thanks.
Russ
 
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Brent, I think you mean that the magneto should turn at the same speed as the camshaft, like the distributor. As far as I know, the only magnetos that turn at the same speed as the crankshaft are one cylinder engines that have a waste spark during the end of the exhaust stroke.

There is one of those compressors at the Old Cranks Museum in Galax, Virginia, see http://www.oldcranks.net/.
 
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I'm using one of these governors to operate a Mallory Distributor. It turns the same speed
as the crankshaft so its a wasted spark ignition. Nothing wrong with that. Just means
it fires on the compression stroke and the exhaust stroke.
I made an adapter plate to mount the distributor and used a love-joy coupler to connect
the two. I didn't want the distributor up top on a Riley head.
 
Thank you Dodge,
You have answered my question absolutely perfectly. You even named parts so I could recognize them! I knew someone on F.B. must have done this.
Of all the mags I have, the Bosch DU-4 is the one I will mount. I still will count gear teeth on the internal reduction gear just to be able to imagine/understand what I'm doing and to verify rotation and timing.
The DU-4 is (to me) a good looking mag. It has big steel horse-shoe magnets. an easily mounted base, usually made of brass,a large fan-shaped reduction gear to determine number of cylinders, an available manual advance setup, and parts are actually available if I look. And these mags are widely used and can be readily found. I have a copy of the 1937 Bosch Manual #525, which lists all their mags, and lots of other auto- electric products, and would try to answer questions about it.
I've seen custom built mounts on the side of Ford A engine, but you have confirmed the use of a ready-made drive, parallel to the crank and same rotation. I've even seen pictures of them above the A engine, both vertically and with a right angle drive, not my favorites.
Next question is: does the waste spark on a double spark like yours have to grounded to protect the mag's insulation? I was taught never to make a spark without grounding it, or it had to be lost inside someplace. I could tear apart a Wico rotary mag and look, but I'd rather have an experienced opinion,thanks. I've seen this double spark setup used on an in-line air-cooled Wisconsin, but didn't look for this detail then.
Russ
 
Bruce,
I wonder what I was thinking, of course Secrets of Speed Society's magazine would have the answer! Which issue had mag drives? I 'shared' my back issues temporarily, and in my newest, Vol 33,No.1, there is an excellent article on the familiar Mallory dist. and determining advance curves, but not what I remember as a mag-drive article. Their indexes don't always include information found in letters, ads, and larger articles with other subject titles (at least that I can always find).
Thanks for the good answer, and I hope you can point me at that article on mag-drives.
Russ
 
2 Oct,2023. Now I see the light-a new issue of SOSS is out With many of my questions answered. Thanks, guys. To quote someone, "I know the voices in my aren't real, but sometimes they have some good ideas." So now, I will read to the voices, and we will talk amongst ourselves.
Russ
 
Self contained magnetos seldom have spark control. The are generally set for full advance all the time. Exceptions are mags that have an impulse coupling for starting the engine. They are fine for all out running but don't work well for street use. It just depends on how the engine is to be operated.
 
rdvaark, in the wasted spark system it fires the plug twice so the spark plug is the ground
for the magneto no problem.

Its funny my SOSS just arrived today also, it should give you lots of ideas for you project.
 
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