Half a croissant, on a plate, with a sign in front of it saying '50c'
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Air Dynamic Vehicle

A nonaerodynamic vehicle.
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An air powered bicycle can be made by using a motor from an air tool, such as a ratchet, and attaching this to the drive wheel. A pair of bellows can be used to replace the pedals, and provide platforms to stand on and use the rider's body weight to compress and pump air.

The air is pumped into a very large trailer full of two liter pop bottles. Because each bottle takes up approximately half a cubic foot (1/8m), fifty of these bottles contained in the trailer is twenty-five cubic feet. As each bottle only weighs a few grams this is only a very light trailer, even with hoses and caps included. This powers the bicycle once a critical pressure has been established.

rcarty, Aug 17 2013

Chainless Challenge http://hydraulicspn...chZone-Accumulators
See the pneumatic one [mitxela, Aug 17 2013]

Sail bike http://www.treehugg...ike-with-whike.html
Just put the air bottles in the sail. [pashute, Nov 11 2013]

Planet Mechanic (2011) make a feasible pneumatic bike https://www.youtube...watch?v=43q70bKOsks
[pashute, Sep 01 2014]

This one by three students led to the new Peugeot hybrid to be out by 2016 https://www.youtube...watch?v=NBeky4EuyBc
[pashute, Sep 01 2014]

[link]






       Hmm, we must then consider the aerodynamics of the rider. Not to mention the RSI caused to thousands of workers in Guandong Province from using bike pumps, as they will inevitably corner the market.   

       You'd get a bun, for 1 in 10 bottles containing helium so the rider the rider has a 10% chance of cursing that careless driver sounding like a chipmunk.   

       All profits to go towards equipping chipmunks with some little back-pack tanks containing a gas so dense it make them all growl like grizzly bears when vexed.
not_morrison_rm, Aug 17 2013
  

       I looked into using air tools as steam or compressed air motors, and was disappointed to discover that they are very inefficient; probably because they are built for compactness and power, and almost no-one cares or notices the low efficiency. Does anyone here know of a small, reasonably efficient, off-the-shelf motor, for [rcarty]'s and similar uses?
spidermother, Aug 17 2013
  

       As a sometimes truck mechanic I notice the inefficiency of the air tools, however since all the tools run on the same airline, the most efficient ones are likely the largest air ratchets, the small air ratchets exhaust far more air than they use. But yes, heavy duty power equipment trades are not very focused on efficiency outside a certain range.
rcarty, Aug 17 2013
  

       I think you'd have much better luck using a small hydraulic motor powered directly by the foot bellows. Use the larger tubes in the bicycle's frame for the reservoir and ditch the trailer altogether. You'd have to finagle some sort of hydrostatic transmission andor a secondary reservior that gets filled and pressurized when coasting down hills. Hmm, with a sensitive valve you could use it as a dynamic brake...   

       I'm posting this.
Alterother, Aug 17 2013
  

       [+] the overall math works, but //each bottle... 1/8m, fifty... twenty-five cubic feet// doesn't by almost an order of magnitude.   

       You end up with 100L(duh), or about 3.5 ft2 of pressurizable volume. And 2-litre bottles are supposedly good up to 6-7 atmospheres.   

       Long story short: 48kJ which is enough to get you moving right along.
FlyingToaster, Aug 17 2013
  

       Oh right, about those numbers, I was working off a drawing I made and some rough numbers I wrote down. <laughs nervously> I wanted to describe a really big trailer. Ok for a trailer with fifty pop bottles, the bottles would form a rectangle to try to stay inside the aerodynamic profile of the bike. Consider the bottles square, 1 bottle is 10cm wide and long, and 30 cm tall. A good length for the trailer would be 1m so that's ten bottles. and a good width would be 50 cm, so that's 5 bottles. A second row could be added for 100,and maybe a third for a total of 150 bottles. That's a total volume of 0.45m^3
rcarty, Aug 18 2013
  

       Never mind, somebody got there before me.
Alterother, Aug 18 2013
  

       Forget numbers, numbers are for precision and accuracy. If I build this I don't want anything to be precise or accurate about it, I want it to be the transportation equivalent to that thing William Shatner in the old Star Trek made to shoot that slow green scaly costume guy that was following him through the desert, that's on every night at 3am before the irritating noise making rainbow comes on TV. Ultimately fulfilling two requirements, 1. used to kill space aliens, and 2. allowing me to say that I once had one, that I made, but it broke.
rcarty, Aug 18 2013
  

       Why the obsession with pop bottles? Why not a balloon? A simple valve or two could control the in/out pressure, assuming the ballon could not do that inherently by informed selection of material, thickness, size, and shape.
the porpoise, Aug 21 2013
  

       Odds on he got the idea from an episode of Mythbusters, who in turn got the idea from one of those wacky Japanese game shows.
Alterother, Aug 21 2013
  

       or you could make your own in-house version of the hyperloop using only an office chair, a long office chair shaped tunnel and several gazillion bottles of compressed air, in the manner of the busy lizzie Nazi superweapon/Gerald Bull contrivance.
not_morrison_rm, Aug 21 2013
  

       //Why the obsession with pop bottles? Why not a balloon? A simple valve or two could control the in/out pressure//   

       Pop bottles, unlike balloons, make superb pressure vessels. And (to use an electrical analogy) controlling pressure using a valve is like controlling voltage with a resistor - pure waste.
spidermother, Aug 21 2013
  

       An aperture valve is the thing to use. It uses restriction instead of blockage, minimizing backpressure. One of those little plastic thumbclamps on an IV tube is a simple example, but the kind I have in mind is the funnel-shaped kind (I don't know what they're properly called) used in high-pressure pumps like those powering Vegas fountain shows and really huge gritblasters.
Alterother, Aug 21 2013
  

       //It uses restriction instead of blockage, minimizing backpressure//   

       I don't believe you*. Any device that restricts flow in a tube creates a pressure difference. Since energy is directly proportional to pressure, there is a corresponding energy difference. Work is done on the restriction by the fluid. Unless that work is put to some use (as in a turbocharger), it is wasted as heat.   

       * As a practicing philosophical skeptic, my goal is not to believe anything at all, so that's not as harsh as it sounds.
spidermother, Aug 22 2013
  

       Well, the example I have to go by was deep in the innards of a gritblaster so big you could literally drive a train through it, and was several years ago, but it was explained to me that it was better than a gate valve for such-and- such reason and I thought it was all very interesting. That's all I got.
Alterother, Aug 22 2013
  

       It's probably about laminar vs turbulent flow, and efficiency of converting pressure to kinetic energy. It would only make a big difference if the constriction were near or at the end of the pipe.
spidermother, Aug 23 2013
  

       Yes, that's exactly the kind of thing I mean. Thank you.
Alterother, Aug 23 2013
  

       Shape the air storage container like a large sail, and you can use the wind as well. Sea linque.
pashute, Nov 11 2013
  
      
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