On Sat, 3 Aug 2013 23:25:49 +0100, Chris Holford
wrote:

In article , Ed Huntress
writes
On Sat, 03 Aug 2013 11:28:44 -0700, pyotr filipivich
wrote:

"Jim Wilkins" on Sat, 3 Aug 2013 08:13:42 -0400
typed in rec.crafts.metalworking the following:
"David Lesher" wrote in message
...

A Hellcat, powered by a 9 cyc. 450HP radial aircraft engine,
could do 60 MPH full out and these did just that. Imagine
those 40,000 lbs going 60 mph up a narrow road....


This 15,000 lbs at 30-40MPH was about all I could handle on narrow,
winding Bavarian back roads, the Ultimate Driving Machine's native
habitat:
http://en.wikipedia.org/wiki/File:M-...p_Van_pic1.JPG
The Romans built straighter, wider roads for foot and wagon traffic.
One road across an open field meandered in sync with a stream a few
hundred meters away, as if following an ancient land boundary.

They were fun in a Jeep or my VW, though once a convoy of British APCs
forced me to dart into the wood when we met in a corner.

Coming down a twisty mountain road as passenger in a heavily loaded
5-ton I watched the tach hit 5000 RPM, twice the redline. I suppose
the engine can survive whatever full scale on the tach is, right?
jsw

Depends. One thing if you are using the engine as a large
air-compressor "brake, another thing if you are trying to get power
out of it at that RPM.
Your Mileage (engine hours) will vary

Not much difference. Limits on rpm are mostly a matter of mechanical
accelerations -- piston accelerations, valve accelerations,
accelerative force vectors on rotating parts -- not of force applied
to pistons from combustion.

Isn't there a risk of flywheels bursting at extreme overspeed?

Yes. That's what I meant by my arch description, "accelerative force
vectors on rotating parts." I didn't want to risk the wrath of the
obsessives by mentioning "centrifugal force." g

ISTR hearing of British tank transporter vehicles having this problem if
the brakes failed going down a steep hill.

Flywheels can blow up. Drag racers used to blow them up with some
regularity. Covering them with a protective shield was an early use
for Kevlar.

A lot of guys were relieved when they moved engines to the rear, where
the flywheel and the ring-and-pinion were well clear of their
testicles. d8-)

--
Ed Huntress