You could also bore out a bit of EN8 but the tube looks an easier option.

J

I thought cast iron was the material of choice for cylinder liners as it is a self lubricating material ?

Steel liner and a CI piston without rings is quite common on small glow and diesel engines of that sort of bore.

J

Peter, I'd go with JasonB, there is not too much difference friction wise, and the steel might be easier to work with. You will have a bit of work finishing the bore, and the outside needs to be reasonably finished too. I don't know the engine you intend to build, but my idea of a cylinder is a steel cylinder, with fins, and the head of aluminium shrunk, and screwed on, or held in place by long cylinder studs from the head to the crankcase. At least with AC spec chrome molly steel(4130), it is seamless. When you get it it is in the normalized condition, it can be heat treated to give it higher strength. Its a good steel for welding. Ian S C

Isn't 4130 steel what is used in these fancy bicycle frames ? A trip to the local bike shop could have got you some perhaps ?

Thats quite a bit of work for a first aero engine, I presume you are using the plans from MEB. Here's a PIP for those that don't know it

Edited By JasonB on 20/02/2014 13:16:29

I'm not too sure, but the 4130 tube used on bike frames is welded, not the seamless stuff used in aviation, The seam in pipe is a right old pain when making cylinders.

A good source of seamless tube, is the tube inside an automotive shock absorber, its a bit of a raffle getting the right size, but if you pull enough of them apart, you get a number of sizes, 25 mm to 35 mm is a good average. With my hot air engines being my own design, I can design around the tube that I have, rather than finding tube to fit someone else's design. The shocks also provide a good bit of chrome plated steel rod, and the outer case comes in handy at times too, my last use for that was a muffler for a 3hp Kawasaki motor. Ian S C

Ian only the cheaper CrMo tubesets are welded, a decent quality frame will have seamless and butted tubes. The Butting is where the wall thickness varies along the tube to put more metal at the joints and less in the middle to save weight.

J