I'm curious. Has anyone ever made their own flywheel? Maybe it was out of another flywheel where a flexplate ring was welded to it. Was it successful? Am I just crazy? Necessity is the key to innovation after all. Post some pictures if you have.
I have not made my own flywheel, although I have had several flywheels made for me. I did redrill a flywheel with larger, stepped bushings to move the holes from the OEM location to fit my '32 Plymouth crank. And when I had a SBC blowshield on a 392, the Weber 6 volt flywheel wouldn't fit in the can, so I turned it down to fit a Pontiac ring gear, I had and used a Pontiac starter. It's no big deal to have one made and modifying one is possible
And remember most standard trans flywheels are cast iron so welding is a no go. Considering the possible results of a failure be VERY careful. Turning down for lighting has been done forever but again you need to know what you are doing.
I didn't figure it to be an easy task, but I definitely knew that it would be worth a new Boy Scout patch. Maybe even worth a Metal of Honor. Well, maybe not that far.
in 1963,I was putting a built Corvair engine in my Porsche Speedster, using the Porsche trans/axle. I machined an aluminum flywheel that resembled the Porsche flywheel but fit the Corvair. I pressed the Porsche ring gear on the OD. and had the clutch surface Hard Anodized. The Hard anodize didn't hold up, so I had the clutch surface metal sprayed with bronze, and machined that, which worked very well.
Actually, the Flywheel to ring gear was a pretty good interference fit, so I froze the flywheel with dry ice, and heated the ring gear in the oven so it would slip on. never had any trouble with it except the Hard anodizing not working.
There is nothing magic about machining up a flywheel. But it obviously needs to be done right. After lathe work the friction side and flange should be blanchard ground flat and parallel. Ring gear press needs to be tight, but not so tight the ring gear is caused to yield, which will result in it ending up loose. That's especially an issue with aluminum flywheels. Rather than figuring this out, using the dimensions from an existing flywheel of the same diameter and material is easier. Even with the optimal press, it best to pin, screw, or otherwise help prevent the ring gear from spinning loose on aluminum flywheels. That's also the case on a steel flywheel when the ring gear is thinner than normal. An aluminum flywheel will need a friction surface insert. Friction coatings, like the old Schiefer flywheels had aren't very durable on a regularly driven street car. Steel has better friction properties than bronze. Bronze is less prone to distortion and warpage than steel. Both are used successfully. Again, copying a successful existing design saves a lot thought and uncertainty. Steel flywheels are made from low carbon "mild" steel. A hot rolled, fine grain, boiler grade material will have a more random grain structure than cold rolled material, so that's the best option. The smallest that comes is in 4' x 4' plates. It will likely take some searching to find someone willing to sell you a flywheel sized piece. Aluminum flywheels should be made from a high strength alloy like 6061-T6 or 7075-T-6. Cast plates of those alloys are available. Like the hot rolled steel, cast plates have a random grain structure, which is preferable. Steel is less tolerant of rubbing than iron, and it warps easier than iron. So while a steel flywheel is stronger than iron, it's more important to avoid excess slippage and excess heating with a steel flywheel. The more weight at the outer diameter of the flywheel, the more it is stressed by RPMs. The ideal high RPM flywheel shape is narrow and rounded at the outer edge, then progressively wider and thicker towards the center. Obviously that wouldn't work for what we are talking about, but the concept is worth keeping in mind when making or modifying a flywheel for a high RPM application..
I will add this... the ring gear can be welded on (with a very snug initial fit) to a mild steel billet. Same deal as many flex plates/converters. Just find a starter that fits your needs then source a replacement ring gear. .