>
> Date: Mon, 8 Nov 93 21:42:59 PST
> From: David Brady <dmb@Synoptics.COM>
>
> All this talk about engine mods has me thinking about an interresting
> formula proposed by Dr. Fred Lanchester in this months issue of
> "The Classic Motorcycle" Fred says that there's an upper limit to the
> speed at which any engine can rotate without self destructing, and here
> it is:
>
> RPM Limit = 4000/( S x .00656 )
>
> S equals stroke in millimeters
>
> At a sustained spin of "RPM Limit" the engine will certainly suffer
> broken rings, pistons, connecting rods etc. The formula considers the
> inertial loads of a piston at a mean speed of 4000 feet per minute, and
> assumes normal steel and aluminum forgings and castings. Most manufacturers
> allow for a 10% tolerance in their redline specifications.
Thanks for the formula!
It seems a tad optomistic though. According to this formula, my 3.5L Rover V8
should be capable of 8574 RPM!!! (WOW!) I guess It could in pure race trim.
Most motorcycles have much higher hp/displacement than automotive engines
anyways. (as well as higher redlines)
One flaw in the formula is the lack of accounting for rod ratios. Two engines
with different rod ratios and the same stroke will have vastly different
redlines.
Kevin
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