Looking for flywheel suggestion

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Z.hb71

Z.hb71

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Mkaaaaaaaaayyyyyyyyyyyyyy i need suggestions. SO a little back story, on my custom engine, its custom (obviously) and with that nothing is preset or has a specific requirement, basically, everything is up to the builder. and that includes ignition timing. soooo I don't know where my timing is supposed to be at so i will be making a custom adjustable ignition system. hers how i explain it https://www.largescaleforums.com/threads/custom-70cc-engine-build.22765/page-20 so my problem is my flywheel is too thick and doesn't allow enough back spacing for my gears, soooooooooooooooooooo i want to remove 5mm off the back/bottom of the flywheel so i will have enough clearence, will this upset the balance? it will be with a lathe so it will be even all around. IF it will screw up the balance, what should I do for a flywheel?? I was thinking of removing my flywheel and replacing it with a clutch plate (yes a clutch plate), put a small magnet on it, and use that as a flywheel. But I want other suggestions. Oh and also, my engine doesn't use a cooling type flywheel, it just doesn't need one. SOOOOOOOOOOOOO i want suggestions for a flywheel substitute. i don't wanna make one.
 
Whoduh said:
I don't think I'm totally getting what you are asking...

You want to remove 5mm off of the BACK of the flywheel or remove 5mm from the BOTTOM of the flywheel? Thats the part i'm not getting...the bottom?

Will one of these work? Looks like the fins have been shortened to half the original size.

http://www.davesmotors.com/T2070-71110-Zenoah-RC-Flywheel-lightened-version.html

http://www.davesmotors.com/DarkSoul-CNC-Lightened-Flywheel-for-RC-CY-Engines-.html
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no becuase those flywheels have a way big diameter. heres what i wanna remove
flywheel mod.webp
flywheel mod2.webp
the second pic is the same side and same every thing. i wanna remove 5 mm down with a lathe.
also btw this flywheel is 36mm diameter. one more thing this isnt to lighten it even though it might a tiny bit, its to get back spacing
EDIT: would this work??? https://www.horizonhobby.com/flywheel--42mm:-31-dyne0520
its for that dynamite 31cc gas engine for the lst2xxl, it already has a magnet and its 42 mm which is slighly bigger but will work, id have to dril the center out but that would be a problem. oh and knock those dowel pins out
 
Last edited:
I thought you were using the marine / airplane version on the Zen flywheel I had seen you had posted. If so look at the response I gave in your other topic area about the dangers.
 
Top Dead Center said:
Machining 5mm off the back should not upset rotational balance. Are you doing the machining or taking to a machine shop?
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Machine shop. I don't think I'll be able to to remove 5mm actually, because @TODD made me aware of center wieghts, which my center wieghts are pretty much 1mm or 2mm at best below the surface. And at that point 2mm won't help. Soooooooooooo ? what do you think of this idea?
https://www.largescaleforums.com/threads/custom-70cc-engine-build.22765/page-22 post #433
 
Inform the machine shop of the center weights and they can adjust the speed and feed rate for steel instead of aluminum. They should be able to cut it without any problems. As far as the other flywheel, it will need to be machined with the same taper as your crank and have a keyway cut in. Even though the flywheel is lightweight, when you are doing a full throttle take off, the crank will spin faster than the flywheel. When you go balls to the wall, and go down a full stop or just releasing the throttle to idle, the flywheel will spin faster than the crank. These occurrences are in milliseconds but these forces are happening with every throttle input. Without a keyway, you may get 1 run or 100, at some point you will spin the fly wheel and lose timing.
 
Top Dead Center said:
Inform the machine shop of the center weights and they can adjust the speed and feed rate for steel instead of aluminum. They should be able to cut it without any problems. As far as the other flywheel, it will need to be machined with the same taper as your crank and have a keyway cut in. Even though the flywheel is lightweight, when you are doing a full throttle take off, the crank will spin faster than the flywheel. When you go balls to the wall, and go down a full stop or just releasing the throttle to idle, the flywheel will spin faster than the crank. These occurrences are in milliseconds but these forces are happening with every throttle input. Without a keyway, you may get 1 run or 100, at some point you will spin the fly wheel and lose timing.
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Okkkkkkk. So what would you do? The first option is cheaper but might be more of a hassle and has way less back spacing intern will need the ignition gear machined or cut the center with a lathe vs the other needs a keyway and a taperd hole drilled in it.
Oh also, thank for the valuable information!!!!!
 
Top Dead Center said:
Will 10mm give you the room you need? IMO you can cut back as much as you need as long the hub of the flywheel completely covers the woodruff key
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10mm will do. If I take off 10mm off the flywheel, id end up cutting the magnets. Wouldn't that be a issues? Cuz if I cut the magnet, there's nothing covering or attaching the bottom of the magnet to the actual flywheel so im affraid thAt will fly apart and screw everything up
 
That's a no go for me if you are getting in to the magnet. I would still probably take 5mm off the back and have the gear cut as well. If money is not an issue the other flywheel can be done and look like it is spec. The machinist will need to make a tapered broach bushing to match the flywheel taper and cut the keyway. So, we are talking more expense for time and material. I'm a cheapskate so I go for cheap and functional.
 
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