Quote:
Originally Posted by serialk11r
The peak acceleration is a fixed ratio between 2 different rods.
I don't want to add units to this since it'll have some stupid pi^2 and crap everywhere, but the ratio of peak accelerations is 1.0267.
I think the rod length on the FA is closer to 130mm though, so for fun let's see what the ratio between a 130 and 138 rod are. Okay it's 1.01462.
So it appears that as far as rod strength is concerned, a longer rod doesn't help too much, as peak acceleration and forces are at TDC when the rod is at angle 0 with the piston. So it should be the friction and combustion that a longer rod is good for. I don't know which one is more important though. The effect of combustion is going to affect thermodynamic efficiency, but I don't have any idea of how fast the charge burns.
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C'mon... give me a g value... please... (le whining) At 7000 and 8500... We can find weights on comparable pistons, pins, and rods, then we can play with imaginary reciprocating components until pricing comes out. Without g, can't figure out the load on the rods and how thin/thick of a cross-section to resist it.
If I remember I'll try to find an article on rod design (stiffness vs cross-section of H or I beam, etc...) I have and post up some of the math stuff that I don't understand. I would imagine as we increase the rod length, stiffness becomes more important...
(I want an 8500 rpm limit on this motor...)