Re:Cruise speed

["Hyndes, Keith" <KHYNDES@xxxxxxxxxx>]

I do not know origin of the R&T 2500 fpm, but here are some interesting 
comparisons:

1. 2.3 litre 4 cylinder car engine bore/stroke 96 X 80 MPV = 14.7 m/s
(2893 fpm) @ 5500 rpm.
2. 3.0 litre 10 cylinder F1 engine bore/stroke 80 x 60 MPV = 30.0 m/s 
(5904 fpm.) @ 15 000 rpm.
3. 131 litre 12 cylinder MLW diesel bore/stroke 228 x 267 MPV =  
10.7 m/s (2106 fpm) @ 1200 rpm.

Comments. The F1 engine will only (needs only) last ~500kms, despite 
exotic materials.
The big diesel is surprisingly fast moving, especially considering the 
weight of the moving parts, and that it will sustain full revs for most
of 
it's life.
Even if wear and reliability was acceptable on a fast reving car engine,
drivability, noise and cost would be against it. It would be easier to
make it
larger, or to turbocharge it.
I take off my hat to all the carmakers who achieve >100 bhp per litre on
a production road engine. 

	Cheers
		Keith

Response to:

I will try one more time. I think Mr. Fred D. was on vacation the last
time
I asked this. Does anyone know the basis of the 2500 fpm piston speed
index
used by R&T in the 50s and 60s to establish max cruising speed of a car?
Why did it disappear from usage? Is it still valid or has modern
technology
superceded it? 

Having some experience with limits and fatigue in the helicopter
industry,
I suspect that there is an rpm beyond which one is encountering
accelerated
wear or fatigue. I asked a friend of mine at the Nevada Auto Test Center
who replied that the manufacturerers knew the answer but that I wouldn't
stand a snowball's chance of getting it. He also added that the engines
weren't the limiting factor anyway, that the transmissions were the
problem. Of course, he was speaking of automatics. Apparently, automatic
transmissions haven't advanced as much as I thought they had.

I invite response. One person did reply previously to speak of max
piston
ring speed as a  limit but didn't amplify.

Rube Erickson 

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