Subject:
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Re: Rotary Engine Help
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Newsgroups:
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lugnet.build.military
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Date:
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Thu, 1 Nov 2001 22:10:40 GMT
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Viewed:
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313 times
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In lugnet.build.military, George Haberberger writes:
> In lugnet.build.military, William R. Ward writes:
> > I don't know much about how radial engines work - at the BayLUG meeting, Mark
> > Benz gave me four Technic gears (the kind with 24 bent teeth, for meshing at
> > right angles with other gears) and told me to put them on the propeller shaft.
>
> In a radial engine, the cylinders are just arranged in a circle around the
> crankshaft, and the propellor is either attached directly to the crankshaft,
> or attached via a gearbox. I think most WWII radial engined airplanes had
> the propellors attached directly to the crankshaft. So, with a 13 cylinder
> engine, some cylinders are compressing, some igniting and providing power,
> some exhausting, and some intaking. The sparkplugs and valves are near the
> top of the cylinder, at the outside diameter of the engine. The engines are
> aircooled, so they have lots of cooling fins.
>
> The toughest part in Lego is that radial engines have an odd number of
> cylinders per bank, 7, or 9, or 11 or 13 (IIRC). I found it hard to arrange
> pieces to get the correct number of cylinders, so you may have to use 8 or 12.
>
> For Lego Models, the Bi-Wing Baron, http://guide.lugnet.com/set/5928, has
> four cylinders, but does suggest a radial engine.
That's a pretty clever design. Maybe I can do something with that.
> The rotary engine is even stranger, and died out in the 1920s, IIRC. In the
> rotary engine, the crankshaft is stationary and the cylinders rotate around
> the crankshaft. The propellor is attached directly to the cylinders. A
> rotary engine had so much rotational inertia that it made for a tricky,
> nimble plane (Left to itself, rotary planes would bank and turn to offest
> the engines rotational movement. Taking your hands off the controls on a
> rotary plane could be lethal). The mechanics are even trickier than a radial
> engine.
Another type of rotary engine? The one I know of is called the Wankel Rotary
Engine, and is something completely different - it has no cylinders or pistons
at all. I'm unclear on exactly how the Wankel engine works, but it's quite
unlike traditional engines. Mazda produced a variety of cars using this engine
under the "RX" label, the most famous being the RX-7 sports car. They also
produced pick-up trucks (remember the "ROTARY POWER" on the back of the
tailgate in the '70's?) with these engines. I don't think they still make any
cars with this engine; I believe the RX-7 was discontinued a few years ago.
Anyway, your description of the rotary engine is probably what led to the
suggestion of putting a Technic gear on the propeller shaft. But I don't think
that the PB4Y-2 had that type of engine; it sounds like that was a WWI era idea.
I would guess that the reason for having the engine rotate with the propeller
would be to avoid the need for a heavy flywheel. Early internal combustion
engines required a big flywheel to keep momentum between firing of the
cylinder(s), and that design of a rotaty engine would probably weigh less than
a conventional engine of the day. Just a guess though.
> I built a model of a DH2, with a rotray engine,
> http://www.frontiernet.net/~ghaberbe/legodh2.htm . I should take better
> pictures, this MOC still exists.
Very cool model; I'd love to see better pictures. It's hard to see how you
modeled the engine, for example.
--Bill.
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Message has 2 Replies:
 | | Re: Rotary Engine Help
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| (...) In the Wankel engines, the cylinder is a shallow ellipse )maybe a circle) amd the piston is a triangular thing that revolves inside the cylinder. Due to the funky geometry between the cylinder and piston, you get intake, compression, power and (...) (23 years ago, 2-Nov-01, to lugnet.build.military)
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Message is in Reply To:
| | Re: Rotary Engine Help
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| (...) Bill, In a radial engine, the cylinders are just arranged in a circle around the crankshaft, and the propellor is either attached directly to the crankshaft, or attached via a gearbox. I think most WWII radial engined airplanes had the (...) (23 years ago, 1-Nov-01, to lugnet.build.military)
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