Flywheels - How much damage is too much damage?

capguncowboy

Well-Known Member
#1
So, I've got a few different lighted flywheels and just about all of them have some level of damage. Some are just a few fins, and others are all of the fins. One of them is missing an entire fin.

How dangerous is it to run these engines with busted flyhweels? I've heard some people say they can come apart, and others say they'll just run out of balance. Does anyone have any statements that can support either claim?

Can they be fixed? I know the H50 lighted flywheels aren't too hard to find, but they are pricey. I'd like to avoid replacing them if I can. The HS40 flyhweels are harder to find, and even more expensive when you do find them.

This one is on a 1969 Lighted H50 Rupp Roadster engine. It's actually missing an entire fin, and all the rest have big chunks out of them









This one is on a 1970 Lighted H50 Gilson engine. It has a chunk out of every fin, biggest is probably 1/4" deep







And this one on a 1971 or 1972 Lighted HS40 Rupp engine (can't remember which). It's about he same as the H50 above.

 
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#2
No specific knowledge here but I suspect opinions is all you will get. :wink:

AFAIK the fins are just for cooling and the fan is likely oversized from the start. Missing weight from one location will add some small amount of vibration... but the weight of a fin compared to the weight of the flywheel is pretty small. If the vibration is unacceptable the blades could be removed and a plastic fan adapted.

My biggest concern would be what kind of impact did the thing take to bust a fin completely off - or bust chunks out of so many fins? I think many people, at least publicly will say that safety trumps cost and it's not worth the risk. :shrug: Without knowing HOW the thing got damaged its hard to make a recommendation. Who wants to get somebody else hurt?
 

capguncowboy

Well-Known Member
#3
Judging by the blower housing on the Gilson engine, I think someone laid it down while it was running. It dented the shroud and pushed the mounting stud into the flyhweel. The damage looks like it was achieved through a similar manner
 
#4
If they have taken a wollop, as they appear to have, the only way to know if there are more cracks in the fins is to have them tested (my brain just froze and I can't remember the test name). If the flywheel is spinning and one breaks off, it's like shrapnel. The shroud may or may not keep it away from your leg or worse. Balance would be a bigger issue with a cast iron flywheel and I would toss any cast iron flywheel with a broken fin--it's brittle to begin with. I have far less experience with aluminum flywheels, so others will need to weigh in.

Magnaflux was the term I was looking for.
 
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capguncowboy

Well-Known Member
#5
If they have taken a wollop, as they appear to have, the only way to know if there are more cracks in the fins is to have them tested (my brain just froze and I can't remember the test name).
Ultrasound? I remember watching an episode of Nova a few years back where Boeing was attempting to make a carbon fiber wing and used ultrasound to check it for hidden fissures and voids
 
#6
If they have taken a wollop, as they appear to have, the only way to know if there are more cracks in the fins is to have them tested (my brain just froze and I can't remember the test name). If the flywheel is spinning and one breaks off, it's like shrapnel. The shroud may or may not keep it away from your leg or worse. Balance would be a bigger issue with a cast iron flywheel and I would toss any cast iron flywheel with a broken fin--it's brittle to begin with. I have far less experience with aluminum flywheels, so others will need to weigh in.
Magnaflux? might be the test you were thinking of. I've never priced it out, might be more than the cost of a lighted flywheel.
 

bikebudy

Banned - Must pay $500
#12
I think I'd find a way to modify a plastic fan.

Take all the fins off the old one, drill, thread, and install the plastic fan.

Auction # 141896414944
 
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#13
Edited due to ongoing negativity and disinterest.

Bottom line, blend the fins and use them. Make it pretty and sell at a fraction of the cost, and warn would-be racers that their RPM is limited to oh, I dunno, 3600.
 
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#14
Not sure what to say. I replace all flywheels damaged like those photos to like new mint condition when I restore the engine. Which is probably pointless because I never actually run the engine again. :doah:
 
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