This website is for people interested in rolling thier own giant scale two-stroke model airplane engines. I decided on a twin cylinder horizontally opposed (boxer) engine with the propellor directly connected to the crankshaft. I hope some will start the hobby of building simple engines with minimal tooling and expense other than a fairly large time investment. For me the hobby is an experiment to see if a larger engine can be made with smaller model airplane engine construction techniques which I'm familar with. I decided on a twin cylinder horizontally opposed (boxer) engine with the propellor directly connected to the crankshaft.
CAD drawing of boxer engine:
My first idea was to make a wax model with very precise dimensions by using a wood model made very carefully on a wood lathe. I hollowed the center out of the wood model and made holes at various locations and I attached a plate with a tire valve. I would dip the wood model in molten wax and build up a coating then use compressed air to pop the wax model off the wood model. Since the outside of the wood model was made very carefully and would form the inside of the engine cylinder I thought that it would be possible to cast a very acurate bore so I wouldn't need an engine lathe and I could just use a ridgid hone to finalize the dimensions of the engine bore. I made wax rings to attach to the wax model for the heat fins.
Wax melting pot:
Wood patern and wax model:
Wax heat fins:
One thing I would do differently is to wash the wax model in detergent to remove the oily residue so the ceramic slurry would adhere better.
Ceramic Slurry:
I had problems with getting the wax model off the wood model and became fustrated so I abandoned this particular approach and decided I needed a lathe. Now I would be tempted in not buying a lathe and just do the casting and have a machine and engine shop do the machining/boring but since I was so involved with this project I decided to buy a lathe.
I have the classic "Charlie Brown" furnace using a propane torch, an iron pipe crucible inside a 5 gallon pail inside a garbag can.
Some have suggested that it would be better to use a steel liner rather than chrome plate the bore. The problem is that most steel liners still need to be machined. If the liner was pre-machined and cast in place I am worried about the adhession between the two as I've heard this can be a problem. Another option is that the liner could be pressed into place but that requires machining both the liner and the bore.
| My first casting. |
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| The narrow throat caused a void in the casting. |
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| This was an attempt to make the con-rods with an open face sand casting. |
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| Some turning that reduces the diameter of the casting. |
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| Drilling the cylinder bore. I then use a boring bar, then a boring head in the tail stock, and finally a ridgid hone. |
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| My first machined casting. A little rough around the edges and some porosity. |
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| Drill bits and boring bar. |
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