clare at snyder.on.ca wrote in message
...
On Sat, 4 Feb 2006 21:00:11 -0500, "Peter Dohm"
wrote:

The fact that it ran with a governor means that it was not at full HP.
It
is admirable for it to run that many RPM's for that many hours, but
still,
there is no indication of how long it would run at true Wide Open
Throttle,
making all the HP it could.

I suspect its life would have not been as long, if it were loaded to
it's
maximum output.
--
Jim in NC

I agree with your basic point. And also feel compelled to add that there
is
probably no way for anyone to know how much power the VW engine produced
in
the harvesting application--unless they metered torque, which would not
be
reasonable. My supposition, just from reading the post, is that at least
half of the total fuel burned was applicable to pumping losses rather
from
the work done.

However, also have problems with the wide open throttle scenario. I also
suspect that if we were to discuss the issue at length, we would find
that
we are completely in agreement; but that we insist on using different
"phraseology."

We really don't operate our Lycomings and Continentals at their sea level
maximum output very much of the time. My best guess is that, flying with
a
fixed pitch prop on a standard day, we can achieve nearly 90 percent just
off the runway and that drops gradually to less about 75 percent by
around
3000 feet msl. (My recollection on exactly were this occurs is less than
perfect as I have not flown in a long time) And 75 percent, on the
aircraft
engines with which I am familiar, ranges from about a low of about 0.355
to
0.357 HP per cubic inch of the low compression Lycoming O-235 engines
through 0.375 HP per cubic inch for the Continental O-200 and their new
O-240 FADEC engine, as well as Lycomings 160 HP O-326 and 180 HP O-360
engines, up to 0.420 HP per cubic inch on the 200 HP angle valve Lycoming
O-360. Those are all engines that really were designed to run that way,
for
which the cooling intake and baffling requirements are well documented,
and
even so many had "teething" problems which were solved long ago.

If we apply the same specific power output to a pure stock 1600cc VW as
to
the smallest Lycomings, 75 percent power should equal 34 HP; which would
result in a theoretical 45 HP engine with a take-off rating that could be
as
high as 60 HP, although 55 HP is more likely--based on a 52 inch diameter
prop turning about 3600 RPM. The slightly more agressive specific output
of
the O-200 would give the 1600cc VW a rating of 48 HP which would equate
to a
75 percent level of 36 HP.

My point in all this is that a relatively slippery aircraft fitted with a
climb prop, to conform to the ancient formula of 0.2 G static thrust
measured with a fish scale, should fly safely with an auto conversion. I
remain a fan of auto conversions, but my advocacy has its limits.

Peter




On the old Klaus combine the VW was rated at 40 HP. Actually, that is
on the later model units. The early ones were 35. (talking 1200cc).
The 1600 engine was rated at 60, IIRC.


That really does put a little different light on the matter.

IIRC, the 40 HP (1200 cc) VW developed it's full power at 3600 rpm, and the
VW racers in SCCA placed the red line on their tachs at 4500, although no
beetle could hope to maintain 3600 rpm in top gear.

OTOH, I believe that Ken Rand claimed that the prototype KR-1 could wind up
to around 4000 rpm.

I believe that the "dual port" 1600 cc engines were rated at 65 HP at 4000
rpm. IIRC, they were used in the Super Beetles, Type-3s, and some of the
transporters. However, my recollection agrees with yours that the 1600 cc
engine used in a lot of the normal Beetles had siamesed intake ports (like
the 1200, 1300, and 1500 cc engines) and were rated at 60 HP; but I don't
know at what rpm.

None of this really is any dispute regarding the often quoted thermal limit
in aircraft, since the method of cooling is so different. The centrifugal
cooling fan used by VW was/is a *very* high pressure type!

Peter