For the forty years following the
of the Wright brothers, airplanes used
internal combustion engines
Today, most general aviation or private airplanes are still
powered by propellers and internal combustion engines, much like your
We will discuss the fundamentals of the
internal combustion engine using the
Wright brothers' 1903 engine, shown in the figure, as an example.
The brothers' design is very simple by today's standards, so it is a good
engine for students to study and learn the
fundamentals of engines
On this page we present a
computer drawing of the crankcase of the Wright
brothers' 1903 aircraft engine.
The crankcase is the "body" that holds all of the other
together. It's the largest part of the engine, but must be designed to
be both strong and light. To keep the weight low, the brothers used
aluminum to make the crankcase. The crankcase was cast at a foundry in
Dayton. In this process, a mold of the crankcase is made (using sand or other
materials), and hot, liquid aluminum is poured into the mold and allowed to coolinto a solid, shaped piece. You can see that the piece was fairly intricate,
with a number of holes and webs.
Four legs were cast into the crankcase on the corners to attach the engine to
the lower wing of the aircraft.
Looking at the figure in a little more detail, there are two main parts to the
crankcase, a box-like structure to the right and a curved structure to the left
as viewed from the front of the engine.
As viewed from the front,
the box-like structure to the right of the crankcase
holds the four cylinders. The cylinders are screwed from inside the box
into the holes facing to the right.
are then screwed into the cylinders from outside the box.
The rocker arm struts hold the rocker
arms which open the exhaust valves of the combustion chambers.
Additional castings on the bottom hold
the camshafts and the
The box stucture also holds the
the water used to
the cylinders in an arrangement called a water jacket.
The cylinders are surrounded by water which is brought into the jacket by a
port on the bottom and returned to the radiator by the two ports seen on
top at the corners of the box. The water carries
heat from the cylinders to the radiator. On the top of the box, we see
the floor of the
carburetor, where gas and air are mixed on the
way to the combustion chambers. Heat from the water jacket is used to evaporate
the gasoline drops in the carburetor.
As viewed from the front,
the curved section to the left holds the
which turns the
propellers to produce thrust.
The curved section is open so that you see can inside. In operation, a sheet steel
plate was attached to the top to completely enclose the cylinder bays.
There are four bays, separated by ribs, which hold the individual pistons and
cylinders. The pistons are connected to the crankshaft by piston rods which
move in the bays. The crankshaft turns on bearings which are located
on the ribs of the crankcase. This animation, viewed from the top of the
engine, shows the installation of the crankshaft:
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