On Jan 14, 4:55*pm, "Peter Dohm" wrote:

I am really not dissagreeing with you--as the pressure system that I am
thinking of would use a VW type cooling fan to augment the ram air pressure.
That would be a rather obvious source of added weight and an easily visible
use of power--and would never be popular.
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The trouble with the coaxial blower mods was the SAME as with the
turbo people, in that there simply was not enough fin area for the
increased density/flow to do much good. Everyone seemed determine to
get "60hp" sixty mythical horsepower from an engine that in its most
powerful configuration only produced 57bhp @ 4400rpm.... and you only
got to pull that for something less than 5 minutes.

So you increase the displacement to something seriously silly and
USING THE SAME HEADS & FIN AREA start pulling as much as 85hp(!!) from
that configuration... and wondering why things weren't working right.

Maximum SUSTAINABLE OUTPUT of the '1600' (displacement 1584cc) under
Standard Day conditions was something like 36bhp, whereas PEAK OUTPUT
can be just about anything you're willing to pay for. It doesn't blow
up (although it can) but it blows your bhp right into the porcelain
fixture.
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Interestingly, the guys I knew who broke cranks (amoung other interesting
problems) were also flying KR2s--although they were based in Florida.
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When you talk 'broken cranks' and VW's you gotta define which TYPE of
'broken crankshaft' you're referring to, because there are TWO
distinct cases. In the FIRST CASE, ANY VW crankshaft, cast, forged
or billet,....can, will and has... displayed the 'classic' fracture
failure, in which a fracture is initiated in one of the internal
threads of the PULLEY HUB, the peaks of which may approach to within .
058" of one of the corners of the Woodruff Key keyway cut into the
NOSE of the crankshaft. (As you may know, the Woodruff Key is a
segment of a circle, as is it's keyway. Unlike a SQUARE key, with the
Woodruff, which is far easier to fabricate, if you want a KEY of
substantial length and width then you must be willing to accept a
KEYWAY of significant DEPTH. This is what allows the keyway to
approach so closely to the internal threads. Another factor here is
that, unlike British or American thread-forms, METRIC threads come to
a sharp POINT. These factors COMBINE to virtually guarantee the
formation of a crack in the nose of the crankshaft.) The crack then
progresses along the corner of the Woodruff keyway cut until it
crosses over to the Stress Relief groove which completely encircles
the nose of the crankshaft. Once it reaches that point you may as well
tighten your straps and punch the locator beacon because you're about
to turn into a glider.

This situation was discovered by the British firm of Ardem who sought
-- and RECEIVED -- certification for the Converted VW. They worked
out the critical load was something on the order of 27 bhp, and the
maximum amount of time was around 200 hours. And that's what they got
certification for. T.O. power limited to 3 minutes; tear-down &
magnaflux inspection REQUIRED at 200 hours. Once they got all the
paperwork out of the way they even allowed Prince Phillip to hop one
(ie, license-built Druine 'Turbulent' powered by the Ardem 4C02, a VW
engine converted for flight that was rated at 30.7bhp @ 3000 rpm (but
only for about one minute).

Then we have the Clyde's Buggy sand-cast crankshafts. Clyde's (sp?)
is better known today as 'CB Performance' but it's the same shop just
a different name. I believe Clyde's last name is Tomlinson but I'm
going back forty years and more... Anyway, the owner's son went to
Brazil and began importing all sorts of stuff, including
crankshafts. Rex Taylor used some of those crankshafts -- which
happened to be castings -- in some of his engines and their failure
effectively put Rex out of business. But it also fostered the
Conventional Wisdom that ALL cast crankshafts were bad. Which is
kinda strange when you think of it because the Big Three have been
using cast cranks in their biggest engines since Jeeter was a pup. In
fact, what you're running into here is the fact that a crankshaft
fabricated using the Lost Foam process is actually superior to a
forging, which is why you find cast cranks in some of the best racing
engines. But Volkswagen owners didn't get the benefit of those
properly cast cranks until they started coming in from China. Prior
to then we had some cast cranks that were so bad the thing could
shatter if it fell off the bench.

The reason a MODERN casting is superior to a forging has to do with
the manner in which the casting is allowed to cool. A modern-day lost-
foam CAST CRANKSHAFT is allowed to cool at a carefully controlled rate
so that the internal grain structure of the crank comes out denser
than in a forging. Another advantage is that many of the high-
strength alloys simply cannot be forged! But one of the funniest
things you'll hear about cast cranks is that they are LESS EXPENSIVE.
Due to the price of today's fuels it actually costs MORE to produce a
a high-quality cast crankshaft. Using casting methods, you CAN produce
a cheap crank but the real reason to go with a casting is to take
advantage of the casting's denser grain structure.

Those early cast cranks were junk, pure and simple. Dropping one
could cause it to break like a piece of glass and using one in an
airplane engine was little more than corporate suicide. There is
simply no way you can compare those early sand-cast crankshafts with a
modern-day casting, such as used by Volkswagen and Ford.

Most American pilots aren't familiar with the 'flying club' system
found in Europe and most other places in the world. One reason the
clubs enjoy an enviable safety record is because they are required to
have a certified A&E on staff. aren't aware of is that flying clubs
are REQUIRED to have a certified A&E on staff. Which brings up an
interesting point about VW engines converted for flight. A majority
of those engines were used to power flying club hacks, with a long
waiting list that covered the entire flying season.

Remember the tear-down and inspection requirement for the Ardem
engines? Specifically that bit about a Magnaflux inspection every two
hundred hours? The truth is, a Magnaflux inspection cost MORE than a
new crankshaft. As soon as the airplane was taken off flying status
and began to undergo is winter maintenance schedules, the engine was
torn down in order to receive a NEW crankshaft. Depending on how many
hours the flying club's planes accumulated over the summer, you could
count on it having a NEW crankshaft every two years. With that in
mind it's easy to see why broken crankshafts simply were not an issue
with any of the club's VW powered aircraft.

-R.S.Hoover