Breath-powered engines

Both of these engines can be operated with nothing more than breath to supply the compressed air.

The engine on the left is a fully double-acting steam engine with cam-driven piston valve. The bore and stroke are 1/4". Flywheel is 1/2" diameter. Note the power take-off pulley on the crankshaft. A bit optimistic if you're not an opera star or play the sousaphone in a symphony orchestra.

The engine on the right is an entirely different design. It's valveless. Note that the axis of the flywheel is not in the same plane as the cylinder midline. This causes the very thin piston to tilt in the cylinder as the flywheel rotates. When the connecting rod is on the lower side of the rotation, the piston is orthogonal to the cylinder and the air supply powers the piston. When the connecting rod is on the upper side of the rotation, the piston is tilted and the air supply blows right past it and out the open side of the cylinder. This action makes it an incredibly inefficient engine but the design has the advantage of being ultra simple for the novice engine builder to attempt as he hones his skills.

The coin in the foreground is a US nickel, 0.833" in diameter.

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