h a l f b a k e r yI think this would be a great thing to not do.
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The summary just about says it all -- connect the pedals of a bicycle to a turbine air compressor, the rear wheel to a turbine air expander, and in between add a fuel mixer and combustion chamber.
Since the expander isn't mechanically coupled to the compressor, the engine can't run without being pedaled.
This
means that if the rider wants to accellerate, he *must* pedal... he can't rely on the engine alone. This means that although he only gets a fraction as much exercise as if there were no engine, he still does his body some good.
Other types of compressors and expanders besides turbines would probably also work (pistons, wankels, etc), but they'd likely be noisier, and produce a less smooth ride.
Like this?
http://www.youtube...._1k&feature=related
Pedal control for motorcycle [pashute, Feb 24 2010]
Perhaps similar thought
VanCycle
[pashute, Feb 24 2010]
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[+] pending more detail... an itty-bitty jet-turbine perhaps ? |
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Well, *like* a jet turbine... it would have an air compressor like a jet turbine has, and an air expander like a jet turbine has. |
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However, in a jet turbine, the compressor and expander are connected by a shaft, so the compressor is powered by the expander. |
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In this idea, the air compressor is powered solely by the pedals, and all of the mechanical power produced by the air expander goes to the rear wheel. |
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Couldn't the functionality of this be done by messing with the govenor on a moped? Ie slaving the motor power to the pedal input torque & speed? It might be more efficient that way too... |
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He wants to replace(partially at least) the shaft-compressor with a human powered version. Dunno what an "expander" is though. |
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That is, if [goldbb] is a "he". I think we're both taking liberties to make this assumption. |
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s'true, but "he/she" sounds as cold as "it" and saying "she" unknown would put a crimp in my sexism. |
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I like the idea though, freeing up the power requirements of the compressor stage; wonder what kind of human:turbine power ratio you would get. |
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small scale jet engines have quite considerable rpms at the compressor stage : i.e. 15.000-100.000 rpm. You'd need some serious gears (~ 1:1000) to achieve that. To have a jet enginge roar (or, at that size, squeal) in concert with my pedalling would be worth it, though. |
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If using a turbine compressor would require too high a gear ratio to get the desired rpms, then perhaps using some other type of compressor, pistons for example, would work better. |
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Assuming you could get the efficiency somewhere in the 35% band from the fuel, this sounds like a brilliant idea! |
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I was wondering how to teach people how much fuel they're using when driving by how much power they're requiring. This is brilliant, although is admitedly more suited to a bike. |
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In terms of worrying about airflow, all you need to worry about is the mass flow and pressure ratio you want to run at the cyclist's cruising ability on the pedals, meaning you can use whatever pump you like, be it turbo (axial, radial or other) or displacement (piston, gear or other) based. |
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For town riding, you may want either a very reliable stop-start system to keep everything rolling without the pedals for 60s at idle. |
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[goldbb] Here's a bun from me. [+] (I don't see any
MFDs here.) |
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I still wonder if the weight of this 'device' would be
justified. |
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After searching the web, I've found that the big stuff used in gas combined cycle (turbine exhaust used to run a steam plant) power plants has about 50% of the power from the turbine used in the compressor stage, so you'd get a doubling of power, allowing around a 40% increace in speed (assuming square law losses sqrt(2) ~ 1.4). I suppose the only problem is how quick you use the fuel! |
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