I need some help

[Rafael de Oliveira]

I have to build a small toy car for the fluid dynamics subject, the car must be moved by a water jet, we can´t use compressed air or chemical reactions, but we can use mechanical means to push the water to the outside of the water tank, anyone know where I can find anything which could help me with this work.

Thanks a lot

[flynfrog]

a water tank and a block of wood?

look at a jet ski maybe what is the goal longest distance fastest

[Ciro Pabón]

Flynfrog, with all due respect, I think Rafael de Oliveira is a person in need of a simpler solution. Anyway, following your lead, I give these three "designs":

Simpler solution: you could try to use the parts of a second-hand spresso machine: it has a pump and a boiler. Or you could settle for an ordinary coffe maker. Those things can boil water for you, are not hard to find, and have an unidirectional valve that can take the temperature. I would throw in a light battery and a transformer for (I guess) really short runs, or you can make your own electric boiler to substitute the 120 volts heater and avoid the transformer weight. The tubing is light and all you need to build is a good nozzle.

Besides, for a steam car made in Brazil, it would be nice to be able to make some coffe while it runs... I would baptize this car, appropriately, the "Cafeteira"...

Complicated solution: I guess there are other means to propel water away from your car, even if I have a hard time trying to figure out. You ask for something else behind chemical reactions or compressed air... I do not know if you've heard about the Estes's hydrogen rocket (I haven't until ten minutes ago): it seems it generates the hydrogen from water (by electrolisis?) and then burns it. You can even "precharge" the car by plugging it into an electric outlet, if you figure out a way to store the hydrogen.

Complicated, but what a project, man... I guess you will thrown your car's thermal efficiency through the roof by "burning" the water. I wonder if your teacher has thought about it... This car should be called "Burning Ipanema", of course.

Out of this world solution: now, if we use the hydrogen to burn rubber like in Burt Rutan's SpaceshipOne (I'm just joking here, please)... or throw in a little liquid oxygen and develop a pulse detonation wave engine (PDWE), we could left the "Flynfrogger" car in the dust, with the McLarens, where it belongs, and that before the wind-tunnel analysis... I don't have a name for this design, yet, I guess you can help.

[Mikey_s]

I think the key to the project is that you need to think about devices to store energy. My first thoughts are clockwork (springs, transmission, propellor/impeller to 'pump' the water through the jet).

Gravity is another means (but might make the craft unstable) - could be solved with outriggers

It's an interesting poject anyhow, I never did anything like that whe I was at school.

How about using a rubber balloon filled with water - that'll propell the craft.

I also like Ciro's heated water concept.

Can you give us more inf about the project briefing?

[zac510]

Ciro, that reminds me of a little boat we had when we were kids. If my memory serves me, it had a metal 'chamber' underneath sat a candle you would light. This would heat the chamber and the gas exiting out the back would somehow propel the boat.

Sounds like a simpler version of your 'cafeteria' solution

[flynfrog]

Flynfrog, with all due respect, I think Rafael de Oliveira is a person in need of a simpler solution. Anyway, following your lead, I give these three "designs":

Simpler solution: you could try to use the parts of a second-hand spresso machine: it has a pump and a boiler. Or you could settle for an ordinary coffe maker. Those things can boil water for you, are not hard to find, and have an unidirectional valve that can take the temperature. I would throw in a light battery and a transformer for (I guess) really short runs, or you can make your own electric boiler to substitute the 120 volts heater and avoid the transformer weight. The tubing is light and all you need to build is a good nozzle.

Besides, for a steam car made in Brazil, it would be nice to be able to make some coffe while it runs... I would baptize this car, appropriately, the "Cafeteira"...

Complicated solution: I guess there are other means to propel water away from your car, even if I have a hard time trying to figure out. You ask for something else behind chemical reactions or compressed air... I do not know if you've heard about the Estes's hydrogen rocket (I haven't until ten minutes ago): it seems it generates the hydrogen from water (by electrolisis?) and then burns it. You can even "precharge" the car by plugging it into an electric outlet, if you figure out a way to store the hydrogen.

Complicated, but what a project, man... I guess you will thrown your car's thermal efficiency through the roof by "burning" the water. I wonder if your teacher has thought about it... This car should be called "Burning Ipanema", of course.

Out of this world solution: now, if we use the hydrogen to burn rubber like in Burt Rutan's SpaceshipOne (I'm just joking here, please)... or throw in a little liquid oxygen and develop a pulse detonation wave engine (PDWE), we could left the "Flynfrogger" car in the dust, with the McLarens, where it belongs, and that before the wind-tunnel analysis... I don't have a name for this design, yet, I guess you can help.

woudlnt splitting and buring the water be a checmical reaction though ?

if not hydrogen fuel cell plus a solar cell it wont be fast but it should go till there is no more light asuming you recycle the water

[Ciro Pabón]

woudlnt splitting and buring the water be a checmical reaction though ?

Flexiwings accusations? Our team abides strictly by the rules, I must say. I found it is a "chemical change", not a "chemical reaction". I believe the point 5.5.2.3.3.1.a of regulations states it explicitly, but wait till the FOMCTIBWE (Federation of Manufacturers of Car Toys Impulsed By Water Engines) settles it in September...

Oh, zac510, it is "cafeteira", like in "brasileira", not "cafeteria". Do not make wrong decals, please...

[Mikey_s]

...wouldn't Zac's candle also be a chemical reaction?

[Ciro Pabón]

...wouldn't Zac's candle also be a chemical reaction?

You know, this kind of thinking is what has ruined this sport... at this pace, piston engines will be banned in 2007, alleging that fuel and oxygen burning is also a "so called" chemical reaction, which reduces the Otto cycle to a test tube.... I laugh at your ignorance, merchants of confusion! Let the manufacturers shine through, I beg you!

The "european" candle solution is naive and outdated, of course. It is like these 1.000 cc engines they use. You have to use an electric heater, with a displacement of at least 8.000 cc and a supercharger if you want to be in the american ANASTCIBWEOA (American National Association of Stock Toy Cars Impulsed By Water Engines of America), like any brazilian (except Fittipaldi, Senna and Piquet, misguided souls) would do. Just look at Helio Castroneves...

[zac510]

Sorry, I read it wrong..

[Crabbia]

I'd say if it has to be mechanical means and it has to a water jet tthen my solution would be as follows.

It goes along the line of those old elastic band model jets like this one...

but instead of being in the air it is bolow the water surface and its you can have a shroud around it (a plasitc tube with could so the trick) to jet the water backwards. The rotor could be at the inlet of the pipe and the fixed end ot the elatisc can be at the end of the pipe.

[Ciro Pabón]

I'd say if it has to be mechanical means and it has to a water jet tthen my solution would be as follows...

Who are you going to believe? Crabbia, that bet on Italy winning the World Football Championship since the beginning, or me, that bet on Brazil?

[Crabbia]

i'm surprised u remembered...
Hey my suggestion was a rank outsider but i think sunday proved that even relative unerdogs can have their day
My family and i are just surfacing now from a week long hangover

[flynfrog]

...wouldn't Zac's candle also be a chemical reaction?

You know, this kind of thinking is what has ruined this sport... at this pace, piston engines will be banned in 2007, alleging that fuel and oxygen burning is also a "so called" chemical reaction, which reduces the Otto cycle to a test tube.... I laugh at your ignorance, merchants of confusion! Let the manufacturers shine through, I beg you!

The "european" candle solution is naive and outdated, of course. It is like these 1.000 cc engines they use. You have to use an electric heater, with a displacement of at least 8.000 cc and a supercharger if you want to be in the american ANASTCIBWEOA (American National Association of Stock Toy Cars Impulsed By Water Engines of America), like any brazilian (except Fittipaldi, Senna and Piquet, misguided souls) would do. Just look at Helio Castroneves...

this has to be the best post in the history of the forum thanks for the laugh

[Ciro Pabón]

i'm surprised u remembered...
Hey my suggestion was a rank outsider but i think sunday proved that even relative unerdogs can have their day
My family and i are just surfacing now from a week long hangover

Did you hear, Rafael? He admits it and he thinks we've forgotten. What a cynic, spending a week partying around it, while our tears are still visible on our green-and-yellow painted cheeks... c'mon, Crabbia, take your un-brazilian designs to Ferrari, in ITALY, where they belong, with Massa and Rubens... Copersucar forever!

Back to thread, I guess a boiler would be more efficient. Crabbia design has the advantage, cited by Mikey_s, of storing the energy outside of the water.

Actually, my "proposal" on splitting hydrogen has less efficiency than a steam boiler like the one zac510 remembers.

For example, ataching the batteries that "Burning Ipanema" needs, directly to an electric motor and to a propeller like the one Crabbia suggest (the "Santos Dumont" water car, I'd call it, to keep the brazilian nicknames) gives more energy to the propeller than the energy available on "hydrogen" fuel created by electrolysis with these same batteries. Just remember to keep the propeller tip speed under the speed of sound, like ultralight airplanes do (you have an RPM limit here) and keep the flow high enough to avoid cavitation...

But, you know, is "power to the wheels" what ultimately counts.

I'd guess (and I might be wrong) that boiling the water gives it more speed than simply propelling it away with a fan, and burning the hydrogen gives it even more nozzle speed, so I wonder which one is the best "basic" design.

For a "dragster" I'd guess the rubber band can deliver the energy quicker (it has more power) but on the long run, the hydrogen should beat it (it is a more efficient way of delivering the energy), so I'd use it if I were looking for "raw terminal speed".

Apparently, hydrogen delivers a lot of energy in the form of a jet when combusted, if you can circumvent the "flexiwing-chemical-reaction" argument presented by flynfrog:



Of course, there is a problem with the high temperature of the hydrogen (and it produces a lot of NOX, so you'll need a catalytic converter on your "street legal" version). Oh, and remember the Hindenburg! I would keep a safe distance to the pits...

I would love to test this kind of water car in front of your teacher (that probably wants you to learn other things about fluids besides electrolysis): imagine, you put some batteries and a gallon of water in your car and then the thing sprouts a blue flame in the back and zooms away!