Glens Machine Shop: The new design.

Building a 4 stroke model engine

The design of a four stroke, gasoline powered, air cooled, model engine.

Ok, this is the start of a new engine design. The previous engine was the first engine that I have ever made. The engine does run, but it is so bad out of balance that a redesign has to be made. The crankshaft has to have much more counter-balance added to it. There is not enough room in the crankcase for it. So I am going to re-design the engine to correct this problem and some others that are not quite so obvious.

When I was building the previous engine, I really had no idea of what I was doing. But now, with a little experiance (just a LITTLE) I feel that now I can design and build a much better engine.

Here are some of the goals and features that I want in this new engine.

first: I want the crankshaft to have a double throw. This means that both pistons move away from the crankshaft at the same time. This will eliminate the need for balancing the engine. Just make sure that all pistons and rods weigh the same and the major part of the balanceing is done. That should not be too difficult.

secound: I want the engine to have an oil pump. I plan to design this engine much like an automobile engine with the same type of crank and rod bearings. This will require forced lubrication. I noticed in the previous engine that there was a lot of wear on the crankpin, wrist pins and cylinder and rings. I think this can be eliminated with lubrication, better materials and a better design.

Third: I want to be able to put this engine on an R/C plane and fly it. This means that it will have to be much lighter than the previous engine. I plan to make the castings with a reasonable wall thickness. This will require a designed core; a core will have to be designed for the inside of the casting just as a pattern is designed for the outside of the casting. This is something new for me, but I don't think this will be a problem.

fourth: I want this engine to run on just plain gasoline with a spark ignition. I don't want the high cost of glow fuel, or the worry of having to drive 30 miles to get some. And I hope that a spark plug won't be too much trouble.

How can I obtain these objectives? I have my past experiance with designing and building an engine and I have seen some of the problems associated with it. I have also studied the plans for some small engines that have a good running history. I also have discovered the proper way to construct some of the parts that have given problems before. Such as cylinders, and rings. I have added to my foundry some Petro-Bond moulding sand, which should give a much better casting. I have added some tools and accessories to my machine shop. Together with new construction techniques, I think that I can build an acceptable engine.

If you are interested in constructing an engine, send me some e-mail or just let me know that you have seen this page. Here is a link to the Model Engine club., a nice bunch of guys that are a lot of help.

Kurt Bjorn has a web page about constructing a 9 cylinder radial engine. He has lots of tips, problems and pictures. He has a page of links to all kinds of related stuff.

8-3-00 contact Glen Bond