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karan_s

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I am designing a compressed air engine for a project. A little stuck with calculations.

I need to work out how long the engine will run at its top speed using a air pressure which is supplied from a compressed air tank.

Compressed air pushed down a piston which is connected to a camshaft. As the piston reaches bottom, a slot opens allowing the air in the chamber to escape and for the piston to come back up again.

A second piston will eventually be added which helps the first piston come back up using the air that is released.

For now I am just doing calculations for the first piston.

Weight of go kart including driver and tank: 200kg

Compressed air pressure pushing piston down: 8 bar

Max engine speed: 1500 RPM - 17 MPH max driving speed

Piston stroke: 60mm

Piston bore: 62mm

Crankshaft radius: 19mm

Weight of piston: 100g

Min acceleration to top speed: 6 seconds

Could someone please explain how long this engine would run on a 500L tank of compressed air? This is assuming that the air is supplied at a constant pressure.

I have attempted it below but do not think its correct and am not sure what to to next.

1500 rpm = ω = 157 rad/s

α = ω/t , t being the time needed to reach the max rpm.

α = 157/6 = 26.16 rad/ sec^2

I = 1/2(200)(0.019)^2 = 0.361 Kgm^2

τ = I x α = 0.361*26.16 = 0.94437 Nm

τ = F x r

0.94437 = F x 0.019 So, F = 49.703N

Thanks in advance