Webster Flywheel Question

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Nov 27, 2017
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Woodinville, WA
I'm getting ready to start on a Webster and I hope to tap into the experience of others who have built one and have much more experience that I do.

I don't have any 3.75" steel or cast iron laying around for the flywheel but I do have a beautiful bronze ring 4.75"OD, 3"ID, .866 thick. It's a bit bigger than the design calls for. It would be easy enough to raise everything by the .5" increase in radius. Will the increased mass of the flywheel or increasing the height of the engine be an issue?

This would have to be a two-piece flywheel. I was thinking about cutting a step in the center an press fit a disk with the hub into the ring. Any suggestions on where to look for two-piece flywheel construction ideas?
It will be fine using upsized dia. flywheels. Webster will run slower at the same throttle or mixture feed. Shouldn't need plans to press fit your bronze tire around a 3 inch hub wheel.
Heavier is better for slow running. Lifting the engine. 5 or so will not affect the running. Simply add .5 to the nessary dimensions.

Alternatively you could cut a slot in the base plate.


Andrew in Melbourne
Sailplane, FWIW, when I made my "Steel Webster" version, I (probably naïvely) was unconcerned about the exact size and weight of the flywheel. The first criterion I used was suiting the materials I had on hand, and the second was for it to be "reasonably heavy," under the assumption that too heavy would be better than too light. In spite of my completely uninformed approach (and the fact that this was my first IC engine), what I came up with has worked just fine.

Now, whether sharing that bit of experience helps at all, I don't know ... :)
I did some calcs on the bronze ring vs. the design flywheel. The moment of inertia of the bronze ring will be about 4 times that of the original design. That sounds a bit on the high side. I think I'll dig around some more and see if I can scrounge up something else. Maybe a trip to WalMart and buy some cast free weights.
Steel outer rim. Aluminum center and hub. 1/8" bronze or steel pins dipped in Loctite to get everything together, then turn o.d. smooth after 24 hours dry time.---Brian
Sailplane Driver,

I've got a piece of 12L14 steel that's 3.4 dia and 0.9 inches thick that you are welcome to if that would help.

You could always Loctite a steel ring to the smaller diameter.

PM me if interested.