Re: Rotax RPMs

Dan_Thomas_nospam@xxxxxxxxx wrote in
news:2a304f81-8a07-42ba-a450-98ff83449971@xxxxxxxxxxxxxxxxxxxxxxxxxxxx:

On Nov 29, 3:31 pm, "Maxwell" <luv2fl...@xxxxxxx> wrote:

I haven't flown one, so I can't be certain, but I'm guessing it would
at least seriously hamper the engines ability to windmill during a
temporary fuel starvation, or carb ice situation.

If a Lyc or Continental dies due to carb ice, it isn't going to
restart either. It needs air and fuel to generate heat to get the ice
out, and a pilot who lets things deteriorate until the thing is dead
is faced with a forced landing whether it's a direct-drive engine or a
geared engine.
Continental has built geared engines: The GO-300, GO-480, the
Tiara (not too successful), and there are many geared radials. Most
have some RPM range where they're not comfortable, and some direct-
drive setups have the same due to prop resonance. The Cherokee 180
was one of them. There's a yellow arc on the tach: pass through it,
don't linger there. All will be well.
Geared engines are more efficient in terms of weight/HP ratio.
HP is a function of torque times RPM, so raising RPM gets more jam for
a small weight increase in the form of a reduction of some sort.
Gears, V-belts, timing belts, chains; they've all been employed. In
some engines it improves safety by taking the thrust and gyroscopic
forces off the crankshaft and putting them onto something more
suitable.
If it hadn't been for geared engines we wouldn't have had the
P-51, P-40, Spitfire, P-38, Lancaster, and many more. On the other
hand, the other side wouldn't have been such a threat.

Dan

Again, it goes back much further than that. Hisso had a lot of success with
their geared version of the 8VA back in '17...

Bertie
.

Relevant Pages

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