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At 03:36 PM 6/3/2005, you wrote:
Bill Dube wrote:
As a rule of thumb, if you double the reversing load, you decrease the the cycle life by a factor of 100. For a car engine connecting rod in an airplane, you are not only (at least) doubling the load (torque) you are also doubling the RPM, so the connecting rod will have a MTBF 200 times shorter in the airplane than in the car.
Bill, I THINK you just answered a question I've had, but haven't asked.
On switching from the 3 planet to the 6 planet gears in the C6 gear set. I was wondering about what happened when you doubled the reversing loads on the sun and ring gears. You've double the reversals, but halved the load. If I have it right, this rule of thumb would say that the cycle life would increase by a factor of 50?
You understand how it works. You would have to put a lot of other factors in to get the real lifespan, but you have the central concept correct.
Fatigue damage is exponential with load (stress, actually.) Most folks don't get the full meaning of this.
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