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Zephrous
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I have been boggled by something for a while now. It pertains to the forces acting on two cranks in an opposing piston engine.
So let's just assume the pressure remains constant in the cylinder(for simplification). Now half way through the cycle one piston is acting on a 3" moment arm with a sin of 1(90deg), the opposing piston is also acting on the other crank, with a 3" moment arm of sin of 0.5(30deg).
Let's assume the internal gas pressure is 200psi and the surface area of both the pistons is 5sq.in. So 1000 lbf is acting on each piston. Now this is where I get confused...
Is the combined torque magnitude(if the cranks are geared together) compounded? Or how is the total torque output calculated?
So 1000 lbf on a 3" moment arm with a sin of 1 is 250 lb-ft
1000 lbf on the opposite crank with a sin of 0.5 is 125 lb-ft
Since they are geared together what is the final torque output value? Is it 750? That seems wrong...It's wrong to me because to me it's like if they compiled the forces, it would not agree with energy conservation laws. That would be like, the same spring pushing on two moments with a sin of 1 would equal 2 sin total...what the heck am I missing here? I understand that if the forces stay the same, then the only difference is the distance traveled by the pistons. So the GASES are doing 2x the work(roughly), so the work would be more, but the torque would be the same with two cranks the same size(if the moments were 90degrees on both)versus a single crank right?
I don't care about the HP/power/work values. I'm only looking to understand the torque output. Single moments I understand, but double? I can't seem to find any information regarding this process!
Thanks.
So let's just assume the pressure remains constant in the cylinder(for simplification). Now half way through the cycle one piston is acting on a 3" moment arm with a sin of 1(90deg), the opposing piston is also acting on the other crank, with a 3" moment arm of sin of 0.5(30deg).
Let's assume the internal gas pressure is 200psi and the surface area of both the pistons is 5sq.in. So 1000 lbf is acting on each piston. Now this is where I get confused...
Is the combined torque magnitude(if the cranks are geared together) compounded? Or how is the total torque output calculated?
So 1000 lbf on a 3" moment arm with a sin of 1 is 250 lb-ft
1000 lbf on the opposite crank with a sin of 0.5 is 125 lb-ft
Since they are geared together what is the final torque output value? Is it 750? That seems wrong...It's wrong to me because to me it's like if they compiled the forces, it would not agree with energy conservation laws. That would be like, the same spring pushing on two moments with a sin of 1 would equal 2 sin total...what the heck am I missing here? I understand that if the forces stay the same, then the only difference is the distance traveled by the pistons. So the GASES are doing 2x the work(roughly), so the work would be more, but the torque would be the same with two cranks the same size(if the moments were 90degrees on both)versus a single crank right?
I don't care about the HP/power/work values. I'm only looking to understand the torque output. Single moments I understand, but double? I can't seem to find any information regarding this process!
Thanks.
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