Electroplating Engine Bore

How big of an engine? What's it for? Will you find joy when it finishes first in a 1000 mile race, or when it manages to run once on a test stand?

I wouldn't think too hard about plating up a worn bore to save making myself a piston, unless perhaps it's a miniature engine with a lapped piston. You're probably better off making at least one part (cylinder liner or piston) new and fitting everything up.

Consider that if the cylinder is so badly worn, the piston probably is, too, which means that at the least you'd have to either plate the piston up to size, too, or you'd have to turn it undersized which would require that you plate all the more material onto your bore.

Does anyone still hard anodize cylinder bores? I know there was a brief rage for it around 2000 or so with model airplane engines, but it seems that everyone doing it went back to hard chrome or nickel.

Keep in mind that anodizing is not a plating process. The surface does grow, because given the same amount of aluminum, aluminum oxide is bigger than just aluminum -- but the anodizing penetrates into the parent material as much as it grows out of it. The anodizing is way hard (it's basically sapphire), but if it were such a hot-s**t way of doing it, why isn't it still done by model airplane engine manufacturers?

Hard chrome is -- hard, and low friction.

Nickel is low friction, but I don't know if nickel-phosphorus is; I'd be interested in how well it stands up (OS engines uses nickel plate on some of its engines, but I'm not sure if it's nickel phosphorus, and I'm not sure if it wears super well).

Maybe heat transfer is not so good? Insulators are not usually good heat conductors. Some exceptions..diamond comes to mind.

It could be. Or maybe it doesn't stand up so well when you abuse the engine. Or maybe it's because it was pioneered by a Russian company that ended up having typical Russian QA problems (Norvel, now NV engines -- they got a reputation as being really good engines as long as you stripped your brand new engine down to the component parts, washed off all the chips left in the engine, and reassembled).

OS Engines, who is The Name in reliable mid-priced model airplane engines these days, toyed with it but rapidly went back to nickel plated brass or aluminum cylinder liners.

(The state of the art seems to be hard-chromed brass or aluminum liner, and a high-silicon piston. Sometimes the brass or aluminum liner is nickel plated. A normal engine, when cold, has a slightly too-tight fit at TDC. As the engine heats, the cylinder liner expands ever so slightly more than the piston, and the fit becomes perfect. If you adjust the thing too lean and get a too-hot run, you get low power, excessive blow- by, and when things cool down an undamaged engine. Most other piston/ liner combinations that have good wear qualities will let the piston expand more than the cylinder, so at the end of that same really lean run you'll have a galled piston or liner, or a loose piston/cylinder fit, neither of which is a Good Thing).

I know one popular type for motorcycles is nikasil- 1000 cc engines running 12K rpm. No idea if it's home-brew-able.

If you're doing a one-off, it'd be better to let somebody do the plating for you. Plating aluminum and getting a good bond is tricky. Not saying it couldn't be done at home, just that you'd probably end up with an engine full of nickle flakes a few times before you got the hang of the process. On any of the plating processes, the first item, after polishing, is removal of the oxide film and keeping it removed until the plating occurs. Poor prep=3Dpeeling plate.

Anodizing would be about the last thing I'd use for a surface I needed low-friction sliding on. It's basically a glass-hard, very fine abrasive surface.

Now if you're really going to get rolling in production, a removable liner of some other metal would probably be the way to go. Wear out the liner, put in a new one.

Stan