h a l f b a k e r yBaker Street Irregulars
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Suppose instead of the usual single engine, single propellor small aircraft you used a single engine mounted in the rear of the plane, similar to a seaplane. Instead of a single propellor you have belts or a driveshaft with gears extending along the wing that drives 2, 4, 6, 8 or more cheap ass little
plastic pusher propellors.
Combined, they generate the same amount of thrust as a single ordinary prop. The advantage is they can turn slower to create the same thrust, and thus won't create as much noise as a single prop, especially if you stuck a muffler on the engine (this is a big deal if you live near an airport).
Another advantage is that they can be made out of lightweight plastic instead of expensive and heavy steel or wood. If one breaks in flight, no problem, you have more. If for some reason you have a prop strike they shatter like wood so you don't need to tear down and rebuild the engine.
Disadvantage: more complicated and probably more driven weight than a usual prop, although it could be offset by the lighter plastic.
Carbon fiber driveshafts
http://www.acpt.com...ft/driveshafts.html
[+mw+, Jun 28 2006]
Even better
http://www.jet-man.com/actuel_eng.html#
Many small jet engines. [cyber_rigger, Oct 15 2007]
[link]
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[+mw+] can you please break your idea into paragraphs so that I may read it. |
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I'm sure the plane would look great, but
I'm equally certain that this is bad
science.... |
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i thought you needed bigger fans to get
the same amount of push at a slower
speed. putting lots of little propellers
on the front of the wings in order to
reduce the weight isn't going to work
because of the added weight of the
drivetrain would probably make up for
the weight saved in lighter props. |
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i don't like the idea of weakening the
props. it would be easier to replace
them, but in flight, you can't really get
to them, and if one breaks, what's to
stop the others from following suit. |
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i agree with [xenxag] that this would
look pretty cool, but would probably
end up falling like a rock. |
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Airplanes usually have multiple engines incase one or more of them fail. |
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Having lots of belts and/or shafts will complicate the mechanics of the plane, which would require much more maintenance. |
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If you turn the propellors at a slower speed, then that would also make the plane fly slower. |
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[BJS], i'm pretty sure that the planes
suggested here don't have backup
engines. the phrase /single engine, single
propeller small aircraft/ is a pretty good
tipoff. |
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The trouble with small propellors is that
they have to spin very fast to get the
same speed through the air as the tips of
large props. (oh... tcarson already said
that_ |
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I love it - already baked by the Wright Bros! I hadn't thought of that. What gave me the idea was the DeHavilland Dash 7 (en.wikipedia.org/wiki/Dash_7)
which was a multi-engine, quieter than usual design. tcarson & st3f are right, it would need bigger propellors. I disagree about the maintenance though - driveshafts take very little if properly designed. |
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[+mw+], you're assuming that the
driveshafts are kept in good condition
by the owner of the plane. this isn't so
much of a problem for commercial
airlines, but private parties might not
be as meticulus. |
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add to that the fact that airplanes stay
in use for much longer periods than
cars, and you've got problems that
could result in drivetrain failure.
whether this was the fault of the plane
manufacturer, or just the owner, this
would be bad publicity for you. |
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another thing, you haven't yet
addressed the problems with weight.
the driveshafts can't be made out of
anything but metal if you want them to
hold up, and adding more bits of metal
to the internals of a plane makes it so
that you need to turn the prop faster,
and make the wings longer. |
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Carbon fiber? Already baked in driveshafts for race cars and garbage trucks - (see link)
Probably pretty expensive though. |
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For maintenance, even small planes have to pass annual - adding inspection/lubrication to the list of required items for the aircraft would take care of it. |
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1. Belts are inefficient, and would be very difficult to maintain in winter weather conditions. |
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2. You don't want to break a prop mid-flight. It's liable to break others as well. Instant incredible balance problem that can really tear the plane up. Also, be on the lookout for flying propellor blades. You really don't want to be anywhere near them when they fly apart. They can shred the fuselage without much bother. |
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3. Carbon-fiber driveshafts would be very very hard to balance and manufacture. Terribly costly. |
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The smaller propellers would have a higher Reynolds number and be less efficient. |
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It's not smart to put a 'cheap ass' anything on an airplane. You're paying for good materials so that they don't break in mid-flight. [-] |
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//If one breaks in flight, no problem,// |
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Um, it's a big problem since the plane will fall out of the sky if the propellor breaks. |
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Um, no. If just one breaks, this design will have a lot left. It'll fly slower, that's all. And if they all break, the plane will glide down to the ground, not fall down. |
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