What causes rod failure?

[Digsy]

Originally posted by Chris Wilson

Basically, yes, hence my "obsession" with Cosworth and Omega pistons and a general dislike of US made ones. Rod length also plays a part, particularly in reducing skirt friction, hence a longer rod with the pin higher up the piston can gain power, particularly at high RPM's. It's a lot more complex a subject than it initially appears.

 

This is why a short stroke is good too (right, kids? )

 

Part of the equation for piston acceleration contains the term "r/l" whith is equal to stroke / 2 x rod length (or crank throw / rod length). So for piston acceleration, and therefore inertia loads, long rods are good, and short strokes are good because either will decrease the r/l ratio.

[Chris Wilson]

Originally posted by Rob

Isn't the whole of F1 about reducing piston mass to facilitate an increase in RPM?

 

More valve train mass, with pneumatic vave actuation although there is talk of direct solenoi valve operation in testing. Of course, piston mass and all rotational and reciprocal inertia is a curse and addressed as best as technology and regulations allow.

 

They should allow 2 strokes....

[Keith C]

So how about if you don't want to increase rpms, but achieve more power through, basically, more boost (a simplification)? Is the main benefit of forged pistons their weight or their strength?

[Adam W]

Yep, what Keith said I'm keeping the rev limit at 6500rpm but I want to run as much boost as my fuel octane will allow! What is classed as "mega boost" these days Chris? I have ARP rod bolts which offer some reassurance I guess, and forged pistons, albeit american ones, so they may be lighter than standard ones.