Force at Crankshaft Pedal
Force at Crankshaft Pedal
(OP)
I want to preface this with the fact I got a C- in dynamics!
I'm trying to analyze a flywheel with a crank attached. A simplification of the design would be a bicycle pedal, crank arm, and a flywheel. All I need to do is calculate the force at the pedal, but just can't do it.
I know the flywheel/crank moment of inertia via 3D modeling, I can measure angular velocity. I know all the geometry, so R is known. What I'm missing is an understanding of momentum & forces apparently. I know that torque = I*w, but I am assuming the angular acceleration (w) is constant. (I can evaluate bearing friction after I figure out the basics.) I have come to understand that torque is only necessary to change (angular) speed. That was a revelation (makes sense though), but it doesn't help me find the force I'm looking for.
My question is: What am I missing? Is there no actual force on the pedal? (Experience tells me your foot is pushed by the pedal, but of course that slows down the bike/flywheel.) Or is there something in momentum that I need to understand better? Or do I have to assume an angular acceleration if I want to find a force? Although my immediate goal is to find the force, I really want to understand the concept I am currently missing.
I'm trying to analyze a flywheel with a crank attached. A simplification of the design would be a bicycle pedal, crank arm, and a flywheel. All I need to do is calculate the force at the pedal, but just can't do it.
I know the flywheel/crank moment of inertia via 3D modeling, I can measure angular velocity. I know all the geometry, so R is known. What I'm missing is an understanding of momentum & forces apparently. I know that torque = I*w, but I am assuming the angular acceleration (w) is constant. (I can evaluate bearing friction after I figure out the basics.) I have come to understand that torque is only necessary to change (angular) speed. That was a revelation (makes sense though), but it doesn't help me find the force I'm looking for.
My question is: What am I missing? Is there no actual force on the pedal? (Experience tells me your foot is pushed by the pedal, but of course that slows down the bike/flywheel.) Or is there something in momentum that I need to understand better? Or do I have to assume an angular acceleration if I want to find a force? Although my immediate goal is to find the force, I really want to understand the concept I am currently missing.





RE: Force at Crankshaft Pedal
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Force at Crankshaft Pedal
I guess momentum in real-life and engineering have a big disconnect in my brain.
RE: Force at Crankshaft Pedal
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Force at Crankshaft Pedal
I'm working on stopping force (no freewheel/freehub) rather than pedaling force, thus the 2 factors I mentioned. And it's actually stationary (thus the flywheel), so not even the momentum of the bike is in play, just the flywheel.
RE: Force at Crankshaft Pedal
RE: Force at Crankshaft Pedal
Ted
RE: Force at Crankshaft Pedal
https://www.edx.org/course/advanced-introductory-c...
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?