Mike,
Pretty impressive credentials. Recalling the history from that
article I mentioned, the specs included several things, and there
would have to be some not reported in the article. Since it had
to be carried by 2 soldiers, small and light would be a priority.
I can't remember the GPH specified for the pump, but that would
have put a minimum requirement for horsepower from the motor.
Since it had to run unattended for 24 hours, low fuel consumption
would also have been important. They probably also specified that
it run on pump gas, ruling out a 2-stroke, since back then, you
always had to mix the oil and gas first. Coventry settled on the
all-Aluminum SOHC configuration as being optimal. A stationary
engine like this one probably did not need torque over a wide
range of RPMs. It was probably tuned for efficiency and reliability
rather than max performance. I don't know all the mods one would
have to do to a fire pump motor to make it a race car motor. The
article indicated that it was usually cheaper to rebuild a motor
that was originally built by Coventry as a race motor than try to
do the conversion from a fire pump as was done to the first ones.
The fire pumps were mounted in a tube steel frame that does look
suspiciously like a roll cage, but I'm sure that's coincidence.
That's how the soldiers carried it around, by the frame.
Simon
Mike.Savin@nokia.com wrote:
>
> Gentlemen:
>
> As a mechanical engineer, and an engine designer
> myself, It seems to me that a good transportable, light-weight
> efficient engine would not necessarily be different in design
> from an engine designed to power a racing car.
>
> All the industrial engines I've seen done in the US, I
> feel have had cost and reliability as the number one consideration.
> There have certainly been many rugged engines built here, but
> with relatively low power output compared to displacement and
> heavy construction.
>
> What parameters did the government specify when asking
> for a fire pump engine? (and, perhaps, the person in charge of
> specifications wanted a racing engine for his special?)
>
> I'll have to tell you, though, if I was given the job today, I
> would design a 2-stroke-cycle engine to accomplish the task.
> (In fact, I've recently designed a new, unusual two-stroke
> 4 cylinder engine that with some modification, would perform
> well either as a racing engine or a generator powerplant, for
> example.
>
> -- Mike Savin
>
> PS: My credentials are, among others includes: Designed steam engines
> for automobiles, buses, many experimental and production engines
> for McCulloch corp., had my own company producing speed equipment
> for kart and motorcycle racing. Have designed, built and ran two
> unusual experimental engines on karts. One engine I built won an IKF
> National Championship (1975). Helped develop the turbocharger
> systems for the Buick V6 and Mercedes 300SD autos while doing
> some work for AiResearch.
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