When preparing an engine for a rebuild, (for my speedster) I was surprised to find that all the gear from the magneto, the plate, magnets, bolts, screws etc; weighed in at around 32KGs or 70 lbs.
I always new it was a heavy lump of a thing, but not that heavy.
Magnets don't weigh that much. Is your decimal point in the wrong place or you talking about the whole flywheel?
No Ken I wasn't including the flywheel....but I have just re-weighed it and you are correct. I'd got it wrong. Its about half of what I posted. My apologies.
Coil plate, magnets, bolts, screws, spools and clamps etc = 15kgs or 33lbs approx
That's still a lot of weight. Would there be any benefits to leaving the magneto out? My buddy and I often discuss the idea of building a speedster, and this is one of our theoretical physics problems. Is the better performance of a magneto ignition worth carrying all that extra rotational weight? Anybody got any ideas on the subject?
Lot's of people do, though I never would. Less mass on the flywheel would give better throttle response and although it is not spinning, not having the coil ring would lighten the car by a few pounds making the car accelerate easier (Although I bet you'd have to have some sensitive measuring equipment to ever notice). It's all in what you want....what's important to you.
I have removed the magnets and coil ring and run a distributor on my cars. But I have been driving a couple of cars of friends lately that still are on coils and mag and still have cast iron pistons. It appears to me that as long as the original equipment is working properly and is in great working order, they run very well. This is for touring purposes and not speedster runs or hill climbs, just good ole fun model T driving as they were designed to do. I guess it makes the rebuild easier to do, not having to worry about clearances on the mag to the flywheel, etc., for running on mag. The extra weight of the cast iron pistons on the crank is probably hard on Babbitt and the crank, but if I am driving a 100 year old car set up as original, and it runs well, I guess I should leave well enough alone.
We were discussing a speedster application. My opinion in regards to removing weight would be to eliminate the starter. Once the car is running it's just dead weight you have to carry. If you had some sort of quick disconnect that would make a crank easily removable, you could start the car and take it off. This would eliminate the drag a crank could create, even how small it would be, while still allowing the weight of the electric starter to be removed.
It would be interesting to run performance runs on similar engines, with and without the magneto. If I had to guess, and engine with cast iron pistons would need the additional mass of the magneto ring to better equalize the rotational mass. However, if you had aluminum pistons, there would be less rotational mass to create force on the crankshaft to displace. Maybe someone else would have a more educated opinion to give on the subject.
Running in my Fronty with Chevy rods and crank:
It's 20 lbs, IIRC.