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brian Rupnow
06-05-2013, 08:43 AM
A question was asked on one of the other forums I inhabit, about what was the best materials to use when building model engines. I put together the following list, based on my own experience. I have built 14 working engines, and the following list covers the materials that worked best for me.
Anything subject to a lot of rolling friction such as shafts, should be made from steel. Hot rolled or cold rolled mild steel is the preferred steel to use. Cold rolled is a very nice steel to use for shafting, as it has no mill scale on the outer diameter and requires no external machining, and the outer diameter is very accurately sized. Hot rolled steel has a nasty black scale on the outside that must be machined away, and it generally is supplied slightly oversized to allow for this. The best material for cylinders is grey cast iron, as the high carbon content in it allows a certain amount of self lubrication. Likewise, pistons can be made from grey cast iron for the same reasons, although with a fast revving engine the mass of a cast iron piston can cause oscillation problems, so it is acceptable to use aluminum for pistons. Anything which a shaft revolves in, another very high friction area is best built of bronze----however, many of us substitute brass, and while it isn't quite as good a bearing material as bronze, it is much better than "steel on steel". Grey cast iron can also be used for bearing blocks, again because of its high carbon content which helps with the lubrication. The main body of an engine which everything else bolts to can safely be built from aluminum with no problems. There is one caveat to remember though---Most home shops are not set up to weld aluminum, so if anything absolutely must be welded to it, then use mild steel. Connecting rods can safely be machined form 6061 aluminum, although it is preferred that they have a bronze or brass bushing in the ends. Crankshafts, whether they are built up or machined from solid should always be made of steel. Valves can be made from cold rolled steel or from drill rod. Flywheels should be as heavy as possible for a really smooth running engine, and consequently be made from mild steel or brass. Baseplates for engines can be made from aluminum. Camshafts should be made from steel. Cylinder heads which bolt on can safely be made from aluminum. Carburetor parts can generally be made quite safely from either brass or aluminum, except for any shafts such as throttle shafts which rotate should be made from steel.--Valve seats can be made from steel or brass. Any connecting linkages are generally made from steel, although in highly rust prone engines such as steam engines, brass is preferred. Cylinder rings for internal combustion engines should be machined from grey cast iron.-Brian.

ammcoman2
06-05-2013, 06:22 PM
I would add 1144 stress-proof to the list for crankshafts. Nicer to machine than CRS and it can be hardened up to Rc 45 by heating to red heat and dunking in oil. "leadloy" (c12l14) is also very nice to machine.

Geoff

CCWKen
06-05-2013, 06:46 PM
12L14 may be nice to machine but it's crap for show models unless it's plated. It will rust if you look at it more than once.

brian Rupnow
06-05-2013, 07:14 PM
How straight does a crankshaft machined form 1124 stay after being "heated to red hot, then dunked in oil"???

sasquatch
06-05-2013, 08:18 PM
I was wondering that also???

ammcoman2
06-06-2013, 09:06 AM
How straight does a crankshaft machined form 1124 stay after being "heated to red hot, then dunked in oil"???

I understand from the "master" in our Club that it works very well as long as the shaft is dunked vertically into the oil. He is very particular and would not advocate this if it didn't work. I haven't actually tried it myself though.

Regarding CCWKen's comment, I have to agree about the rust problem with 12L14. But, there is an easy solution that has worked for me. Either do the final polish with an oil soaked emory cloth/paper (400/600 grit) or spray it with Bostik "Topcote". The latter dries to a whitish film but you just give the part a rub with a cloth and it looks and stays perfect. I made the vise for my recent model shaper from 12L14 and used the spray coating.

Geoff

CCWKen
06-06-2013, 08:02 PM
Good tip Geoff. It's now called "GlideCote". I should get some of that for my table saw, band saw and a few other tables.

caveBob
06-06-2013, 09:04 PM
Anyone ever heard of or try Ballistol. Someone on another forum mentioned how well it works on their hand planes, curious...

Paul Alciatore
06-07-2013, 04:06 AM
Good tip Geoff. It's now called "GlideCote". I should get some of that for my table saw, band saw and a few other tables.

You have me curious. Living near the Gulf, things rust at the drop of a hat here. Tell me more about it and Ballistol too. Just what are they? A clinging oil or grease? Some kind of paint or coating? A chemical process?

And where do you get them?

ammcoman2
06-07-2013, 07:48 AM
Re the Glidecote, I get it from Lee valley http://www.leevalley.com/en/wood/page.aspx?p=40952&cat=1,43415,43440

I believe it is a type of wax. Once wiped with a cloth you can't tell that it is on the surface. For years I used floor wax on my table saw and it did the trick. This is easier to use on intricate parts.

Geoff

caveBob
06-08-2013, 12:42 PM
You have me curious. Living near the Gulf, things rust at the drop of a hat here. Tell me more about it and Ballistol too. Just what are they? A clinging oil or grease? Some kind of paint or coating? A chemical process?

And where do you get them?

Paul, I haven't used it yet, but ordered some via Amazon (free Prime shipping). Ought to be here next week. I trust the guy who mentioned it (he is a metal handplane maker) who said he has used it for years. Just adds a few drops to replenish a soaked (stored in a plastic bag) tee shirt.

Had a nice little 3" toolmakers vise show up in the mailbox yesterday, cleaned off the packing/shipping oil this morning & plan on using the Ballistol on it when it comes in...