NY wrote:
"Davey" wrote in message
news
On Tue, 15 Nov 2016 10:26:23 +0000
Mike Tomlinson wrote:

Fantastic model of a 9-cylinder radial engine, shown operating.

Part 1: https://www.youtube.com/watch?v=qjnQKXNPsk4

Part 2: https://www.youtube.com/watch?v=R71Xhrkc3EQ


I prefer the Rotary:

https://www.youtube.com/watch?v=0jHRuEkvO8E

Rotaries have always baffled me: how do you get your supply of fuel to the
cylinders without leakage where the stationary fuel tank feed meets the
rotating cylinder block. It's not like an electric motor where slip rings or
a commutator serve the equivalent purpose with electric current: in the case
of fuel, you need to prevent leakage.

I could be wrong but I think the carb would be mounted on a stationary part
of the crankcase and then the fuel/air mixture was drawn up individual
induction pipes to each cylinder


What was the advantage of rotating the cylinder block? Was is mainly that
the movement of the block though the air provides additional air currents
over the fins and allows the cylinders to be air-cooled rather than
water-cooled? Or was there any other advantage?

Just cooling IIRC.


Presumably rotaries tend to be noisier because each cylinder has its own
separate exhaust pipe - or if there is a common exhaust pipe it cannot have
such elaborate silencer because of the need to balance and minimise the
rotating mass.


Also had problems with huge torque reaction. It would significantly affect
how quickly a plane could sharply bank to the right or left in a single
engined craft.


Can rotaries be made to made with supercharging (ie a compressor to increase
air intake pressure)? I suppose it's possible if the compressor is made to
spin with the cylinder block. Turbocharging (using exhaust pressure rather
than crankshaft rotation to drive the inlet compressor) could be
"interesting" :-) In either case, you've got the problem of not being able
to have a large (and therefore heavy) air reservoir to store boost pressure
for cases where the throttle is opened on a slow engine and high boost is
needed at a time when the engine can't yet generate it.


As you say, turbocharging almost certainly not possible. No reason
theoretically why they couldn't be supercharged but given that better
engine designs were developed, not much point.


Is "rotary" the correct word for this type of engine, given that the word is
also used to describe a Wankel engine which works in a very different way.

The term was in use *way* before the invention of the Wankel so I don't
think it can be considered "wrong" in any sense.

Tim

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