Design considerations of the BECO 2.0
Here I will describe the design and the reasons for some of the decisions
made on the design.
I have always liked the idea of having a multi-cylinder engine. When I decided
to construct an engine, without a doubt it would have more than one cylinder.
So, a 2 cylinder engine would have much less parts to make than a four
cylinder. So I decided on 2 cylinders.
Now should it be in-line, vee, or
opposed? I have always thought that an opposed engine would balance itself,
so i went with an horizontal opposed design with a double throw crankshaft.
(my first engine has a single throw crank and it needs a very large
counterweight on the crank) After reading an article in Strictly I.C. magazine (Vol. 10 #56)
about model engine balancing, I have been much enlightened. Balance in an
engine is a very complex thing, but not out of reach.
Ok, so now I have a twin cylinder horizontal opposed engine. How big should
this engine be? I thought that 1 cubic inch per cyl. (check out my
cubic inch calculator) should be good. So that
will make a 2 cubic inch engine. (33 cc) The size is not a big deal to me.
I just want to have parts that are big enough to make without a magnifying
glass. A 2 cubic inch engine is pretty big compared to most model engines
used on radio control airplanes and I do want to be able to fly this engine.
2 cylinder, horizontal opposed, 2 cubic inch, and it must be air cooled to fly
on an air plane.
I have always liked a 4 stroke engine with its valves and the sound that they
make, so it must be a 4 stroke engine.
This engine needs to run on gasoline, and not a gas oil mix like a 2 stroke
engine. So lubrication comes into the question. I want to make this engine with
an oil pump to put the lubrication where it needs to be.
If it runs on plain gas then it will need a spark type ignition with spark
That should be enough on the type of engine, so how about the construction
of the engine. I'm talking about the materials, and construction methods
in constructing such an engine.
The crankcase has to open up some way for the crank shaft to be put in.
It seems to me that it must be split right down the middle. Ok, so split
down the middle. Which way should the split go? Horizontal or vertical?
Umm... I don't know. How about vertical? Ok, split vertical. Hmm... Yes!
When split vertical the left and right sides are almost identical!
Now about the cylinders. Should they be made in one piece with the crankcase?
Yes, That should make a good engine. Well... It might be kind of difficult
to make the crankcase with the cylinder attached. How about a bolt on cylinder?
OK... bolt on cylinder and bolt on heads. That should make construction of
the parts much easier.
The crankcase, cylinder, and cylinder head should be made from cast aluminum.
These parts can be cast in my home foundry. The crankshaft will be made from
hot rolled steel and the cylinder liners will be made from cast iron.
The cast aluminum parts should be made with as thin a wall as possible to
reduce weight. This requires much effort in the construction of the
crankcase specifically. But with a well designed core for the mold, a thin wall
should not be a problem.