SpudFiles

how about something like this? the one u showed me above will be too long to fit on my rack. but how would i stop the water from pouring out of the nozzle?

Personally, I think duct tape would work acceptably well to hold the water in... or saran wrap and a rubber band, or something.
It's not like you really want to only use half of a tank anyways, considering the lousy delta V (maybe 2-3 m/s) that gives you.

As an idea, I think simply drilling a hole at the bottom edge of the endcap might be your best option - it saves you fittings and helps keep the water supply consistent.

And Crazy Ivan has presented the gist of my valving idea in pictorial form.

That said, if we double the pressure to 200 psi (that's admittedly an average, so you wouldn't be able to provide that...) we find that the specific impulse (water velocity) increases to ~52 m/s.
So the speed that 3 gallons of water gets you 7.8m/s (about 30 kilometers/hour) of delta V (speed change).

Or you can simply build a gas turbine engine...like the ones on model planes. All you need is sch40 steel pipe, reducer, fittings, and a car turbocharger....some cool turbo props get bicycles to 70 mph.

I'm not sure about what cptn is proposing
but with that diagram apparently ivan still doesn't get it, are water guns allowed in your country cause its the same concept the air and water are in the same chamber the output is on the bottom with the water so when the output opens water comes out
the water and air are in the same chamber and both are behind the valve

once you get that you can consider this idea I had you can have a ball valve near the kick and a tub that leads to the back of the bike

a model jet engine uses propane, (or kerosene) and compressed air. The functionning is simple. You compress massive amount of air constantly, witht the turbo charger. You inject fuel (propane or kerosene) in right amount in a combustion chamber next to the air exhaust. The gazes are ingnited and roduce a lot of pressure. these gazes pass through the secondary rotor of the turbo charger, making it to self sustain. You can add a nozzle to increase the velocity of the gazes, and thus provide a better acceleration!
Simple yet effective design. Construction is a bit tricky, i'm making the plans....you can find most of the parts at low cost, turbo-charger in a junk yard.

iknowmy3tables wrote:I'm not sure about what cptn is proposing
but with that diagram apparently ivan still doesn't get it, are water guns allowed in your country cause its the same concept the air and water are in the same chamber the output is on the bottom with the water so when the output opens water comes out
the water and air are in the same chamber and both are behind the valve

once you get that you can consider this idea I had you can have a ball valve near the kick and a tub that leads to the back of the bike

what did u mean? u mean air and water should be in the same chamber? i am getting very confused..

CpTn_lAw wrote:Or you can simply build a gas turbine engine...like the ones on model planes. All you need is sch40 steel pipe, reducer, fittings, and a car turbocharger....some cool turbo props get bicycles to 70 mph.

i cant afford a turbocharger...

crazyivan wrote:i cant afford a turbocharger...

Ah, but can you weld?

@Crazyivan:
Remeber that this is water and not air. Any system will need to be tilted at an angle so all the water drains, and doesn't shoot both air and water out the nozzle. Although the acceleration may be enought to make the water cover the nozzle and stop air escaping. To keep the water in you could have a union and a weak burst disk.

Insomniac wrote:@Crazyivan:
Remeber that this is water and not air. Any system will need to be tilted at an angle so all the water drains, and doesn't shoot both air and water out the nozzle. Although the acceleration may be enought to make the water cover the nozzle and stop air escaping. To keep the water in you could have a union and a weak burst disk.

ok so i should put a weak burst disk at the nozzle?

jackssmirkingrevenge wrote:

crazyivan wrote:i cant afford a turbocharger...

Ah, but can you weld?

i cant weld metals too...

Too bad, a pulse jet would be totally awesome for propelling a bike (though it'd probably break some kind of vehicle noise regulations).
If you want to use gas pressure, you're better off using a piston arrangement driving the wheel if you want any kind of efficiency/sustained power.

Yeah an air and water rocket would work. Crazyvivan, the reason for using water AND air is because it compresses less than air and therefore will provide more output pressure with less input pressure. Spud

You should try and mount an impact gun to the petaal in your bike and just have it attached to a pvc air tank.
Also, a pulse jet would be much easyer and cheaper to build. Use the link to that pulsejet website to seehow a lockwood pulsejet is made. 40-50 bucks and sme time with a welder and you could have over 100lbs of thrust for a couple minutes

spudzinger wrote:Yeah an air and water rocket would work. Crazyvivan, the reason for using water AND air is because it compresses less than air and therefore will provide more output pressure with less input pressure. Spud

That isn't really the reason for using water.
If you only used air, all the air would be gone in a fraction of a second. With water, the air is used up much slower, providing more sustained thrust. Another reason is that water will give more power than air, as it is heavier.