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+1! The three ways that, as an engineer, I've learned how to get through a brick wall are: (1) find a door, (2) explosives, (3) just beat your head against it until it gives up. That last one sometimes requires that you take a break.

That 55-degree "crown" looks like could be there to help scavenging, by guiding the puff of fuel/air from the transfer ports to the top of the cylinder. Flat-topping the piston, even after adjustments for proper timing, may not give good results.

It just makes me want to carve up some patterns and come visit.

I know we're pulling the thread off topic from the OP's original post -- but how do you get the plates into intimate contact with the knife? It seems like you'd clamp onto the blade's backbone -- where you want the hardening to happen least -- and not rapidly cool the edge -- which you do want...

So without a back-iron, the magnetic lines of force go through the coils and extend into the aluminum, where they are constantly changing because the dynamo magnets are turning. With the back-iron, the magnetic lines of force from a magnet pole goes through a coil or two, hits the back-iron...

Wait -- you expect us to read past the first line? One of the suggestions is to block the holes with screws and then heat treat -- that seemed pretty direct.

Plain old 64, according to it. It's not going to get me down to tenths, but I feel pretty confident that if it says I'm centered to half a thou or so then I'm really there. (I'm not that close on this one -- it's a hair less than a thou, and I'm calling it good).

I'm definitely committed to using only the most up-to-date precision-made tools. One day I'm going to get myself an indicator with an actual dial. And maybe buy tools instead of making them out of bits of wire lying around the shop.

There's a whole thread out there that I started on how to thread a long rod without bending it, and I can't find it! The upshot for using a die to thread a rod: Make sure the rod is the correct size. Check Machinery's Handbook for the size thread you'll be cutting (or spelunk on the web --...

On top of everything else -- if you can't fix a part, don't be afraid to chuck it and start over.

Man, I'm much too much of a cheapskate. My next thought was "old tin cans?"

I've been thinking of making little boxes to hold tool bits, that I can pack with charcoal then put into an oven or forge. Is that a good idea or stupid?

Youch! I just priced that! $30 for 10 square feet of the cheap stuff! Granted, that much would last me until I die, but still. Can you re-use pieces, or is it wise to use once & toss?

Since I'm feeling comfortable with the cutter, onward and upward to the second try at the crank bearing block. I've cut out a piece a bit over 1" long, marked it out for center and used my scribe to make a shallow punch mark in that center. According to Gimp, the center is about 0.002" off...

If I got onto stunthanger.com and told the folks there that I was going to do that I'd get yelled at. Quietly by a couple of guys who own businesses making, reworking, and selling competition model airplane engines, and loudly by at least one guy who spends a lot of his spare time evaluating...

I think that one could use enameled mild steel wire (probably by starting with mild steel picture-hanging wire, then enameling it with shellac or some modern equivalent). Just wind it around a form into a toroid, in much the way the coils were wound, and use it to back up the magnets. As long...

I got curious and looked. I didn't find any either -- you could maybe take a 1" diameter, thicker cutter and grind it thinner, but the shank might get in the way, and you'd need a toolpost grinder or a really dab hand at a bench grinder. Or, there seems to be a good selection of 1" diameter...

So, is a claw hammer an approved machinist's tool?

That one Scott just posted looks like my starting point when I was a kid. I think I built half a dozen of them, starting by following the directions, then experimenting from there. (Oddly enough, I'm now an electronics engineer, and while I don't build motors, I've got some expertise in...

I have a couple of 3D drawings. Unfortunately, they're in my head. Nails, or pieces of welding rod, tin cans, masking tape to build up the commutator form, and if you want to get fancy, brass sheet for the brushes and commutator. Dunno if I could sketch something up, though. Do you want any...