Douglas E. Dempsey
Bellvue, CO 80512
970-221-0261
shearbond@aol.com

  big SNIP

If you want HOT!!, try trailer towing at WOT up long grades as speeds of less
than 50 mph at near sea level elevations, as major auto mfgrs. do in testing.
 Would you want, or do you believe your auto should, fail catastrophically
under these conditions??

    SNIP

Doug Dempsey

  Doug,

Bill Freeman wrote:

If you actually run the numbers, trailer towing at (USA) high speed up steep
grades is not much of a load at all.  It is essentially impossible for an
American
car to extract max rated HP from the engine for more than a few seconds
in most cases or even up to a few minutes in some cases  (stoplight Grand
Prix and short top speed runs).  Top speed runs are the only way to get
a car/truck to max HP and this is extremely rare to do for more than
a few seconds or minutes, unlike Germany.   If you run the numbers a heavy
sport-ute hauling a heavy trailer up a steep (6%) Interstate at 70 mph is
pulling in
the ballpark of 100 hp depending on the assumptions.  Considering that a
lot of the bigger engines are rated in the 250-350 hp range, this is not much.

On  "aircooled vs water cooled", the issue is design effort (aircooled is
harder) and packaging (watercooled is more flexible).  You can move your
primary heat exchanger away from the engine and do some slick diffuser and
duct design to help the overall system drag.  Plus, as Paul said, we are stuck
with the water cooled Mazda as the only reasonable basis to work from when
developing an A/C rotary.

OTOH, what kind of piston aircraft holds the ultimate speed record for
piston-prop aircraft??    An aircooled F8F which has a REALLY draggy
wing designed to come aboard a carrier at 60 mph or so with a really
pussycat stall.  The F8F uses a very nice external diffusion cowl which
is actually VERY much more efficient than most folks think, because it
looks simple.

External diffusion gets little respect, altho it is sort of an analog of the
latest technology linear aerospike rocket motor that does its expansion in
the free stream, thereby gaining much efficiency and eliminating the cost
and weight of the duct (nozzle).

Appreciate your good comments.

Bill

Good work Bill. Well done. Thanks.

Paul Lamar
 
The AirCraft Rotary Engine NewsLetter.              Powered by Linux.

http://home.earthlink.net/~rotaryeng/            http://www.linux.org