Determining the forces on the crankshaft
Determining the forces on the crankshaft
(OP)
hi,
I am trying to calculate the shake, inertial and moment force acting on the crankshaft. The reciprocating motion of the piston+pin+small end of the conrod creates these forces. Still I need the right formula to figure out the correct numbers. Also, if these are for a 4 cylinder engine, do I need to multiply these force values with the number of cylinders?
Thanks in advance.
I am trying to calculate the shake, inertial and moment force acting on the crankshaft. The reciprocating motion of the piston+pin+small end of the conrod creates these forces. Still I need the right formula to figure out the correct numbers. Also, if these are for a 4 cylinder engine, do I need to multiply these force values with the number of cylinders?
Thanks in advance.





RE: Determining the forces on the crankshaft
Cheers
Greg Locock
RE: Determining the forces on the crankshaft
RE: Determining the forces on the crankshaft
Start with the formulas for the geometry (crank pin relative to centerline, rod position and angle relative to crank pin and piston relative to rod) then use the F = ma and T = I omega formulas to solve for the reaction forces at the crank pin. You will have to use scales to find the rods mass center and the compound pendulum formula to find the rod moment of inertia.
Minimise the main bearing loads by varying the balance mass (at half the stroke distance) until the integration of the crank loads over a revolution are zero. That gives one cylinders loads.
Shift these loads by the angle of each crank pin and multiply by the distance from the engine reference center in 3D space. From this you can calculate the location and force required by balance shaft(s) to minimise vibration.
If you want to be elegant, add in the forces and moments of the valve train components.
RE: Determining the forces on the crankshaft
RE: Determining the forces on the crankshaft
I still can't understand what your actual problem is, at least for simple cases.
Cheers
Greg Locock
RE: Determining the forces on the crankshaft
Jonathan T. Schmidt
http://www.schmidtmotorworks.com