Dual Overhead Cam Internal Combustion Engine
SPECIAL NOTE: We have two very similar internal combustion engine models: this dual overhead cam model, and a single overhead cam model that is somewhat less expensive. Which should you get? If you want the model that most clearly and simply illustrates how these engines work, get the single overhead cam model. It allows you to see all three pistons operating simultaneously from a single view, and is easier to assemble. If you are specifically interested in the dual overhead cam design (which is a higher-performance racing style of engine), then get version on this page.
Here you see one of our more ambitious models: a complete, detailed 3-cylinder, 4-stroke internal combustion engine. It’s got everything! Crankshaft, pistons, valves, cams, timing gears, and a “starter motor” to make it run. It even has a working old-school distributor and LEDs that light up to simulate spark plugs.
The gears have engraved index marks that let you accurately align the cams to synchronize the opening and closing of the valves with the motion of the pistons, and with the firing of the spark plugs.
On a personal note, this model represents several advances in our model-making capabilities. The crankshaft is beautifully made by photolithographic 3D printing (which makes strong, translucent parts much more attractive than ordinary 3D printing). The distributor contacts are precision-milled from electrical brass sheet. And the entire wiring harness, including battery pack, switches, motor, and chassis wires comes pre-assembled (no soldering or wire cutting/stripping required). Even the batteries are included, along with all tools required for assembly.
Here you can see the model in action being driven by its build-in “starter motor” (actually a small electric motor positioned where the starter motor would be, driving the flywheel):
Looking straight at the back of the engine you can follow the 4-stroke cycle. Starting with the piston at top dead center with both valves closed, the strokes are as follows:
Intake stroke: the blue intake value is open, and as the piston moves down a mixture of fuel and air is sucked into the chamber.
As the piston starts to move back up both valves are closed and the fuel-air mixture is compressed.
Just before the piston reaches top dead center again, the spark plug fires, igniting the mixture. This begins the power stroke, when energy is delivered to the crank shaft by the gas pressure pushing down on the piston.
When the piston reaches the bottom the exhaust valve opens and the piston returns to the top, completing the exhaust stroke, and leaving the engine where it was at the beginning of step one.
Notice that the crankshaft makes two complete revolutions during a single 4-stroke sequence. That’s why the timing gears at the top of the engine, which drive the distributor and operate the valves, are twice as big as the timing gear on the crank shaft. There is a 2-1 gear reduction between the crank shaft and the cam shafts.
Your model will arrive attractively packaged with all the necessary parts and tools. It does not require any special model-building skills. A detailed, step-by-step assembly video is available on our instructions page.
