Pneumatic Water Rocket.

[Thursto]

Well i have posted one of these designs before on here. This is for my school semester project, its a pneumatic water rocket. it has 2 "rocket engines" the main body and fins.

it will be mounted on a base, with quick release brass hose fittings.
It will be actuated by a pull motion of a cord with a handle, which pull a plank down on rods (to keep it straight etc) on the plank the brass female couplings will be fixed so when you pull it should pull both at the same time. i might even rig up a spring actuated piece to do it.

Well enough chit chat here is some specs:

"engines" x2

Length: 40cm
Width: 2"
Material: Pressure rated PVC
Nozzle port: Li'l bigger then 1/4"

Main body:

length: 70cm
Width: unknown at this point

nose cone:

length: 30cm
Width: same as main body (but coned shaped, so main body thick at base)

Launch pad:

Dimensions unknown.

Release mech:

Brass hose fittings (see pics for details)
Pull actuated (possibly spring, not sure yet)

Fuel:

100psi
have to work out water ratios.

enough crap heres some pics...









Note that 2" PVC is just for reference not actualy length

same with the PVC in this one









What i am wondering is will it propell into the air?

Do you think it would work?

It will have stabalizing fins

what should i do for a parachute technique???

And what should i change or what do you think will fail?

any modifications i should make?

Thanks heaps in advanced

[ghostman01]

ahhhh i finally understand how it launches lol, wow that took a while for me to get but i think to picks of the brass water bit helped alot. As for your power , im pretty sure it would propel your rocket as long as it is as light as possible , and i think a higher pressure like 150psi might cut it quite good, im pretty sure 40mm can handle that because its really thick

[Thursto]

hahah yeah just got all the photos up. Yeah as to weight with all the brass and seeing so Pressure PVC is heavy and the main section is going to be DWV bigger then 50mm (engines of 50mm not 40mm ) it might be quite heavy but i think the size of the engines will make up for it. also wen it first takes off the water will add more weigh but i sure as hell hope this works.

oohh and btw if no one minds, im going to use some of the replys in my investiation and designing process.

and no im not making you do the project for me, more like opinions, and your thoughs on how it will work.

thanks a bunch.

[ghostman01]

ah ok yeah i mis read the specs .... ;lenght: 40mm width 2"
thats what stuffed me up lol, is this like a school project i cant remember, i could only think it is after you said you have to do an investigation or was that investiation....

[Thursto]

Yeah it is, we are undergoing a MYP IB coarse, (middles years program international baclarat) or something like that, we are like one of 3 schools in SA that do it.

But its called a persoanl project n has to be like 4000 words in length. not that bad considering we have like half a year to do it, but most people (including me) are only just starting to get stuck into it.

Thursto.

[ghostman01]

wow the biggest ive had to write up to now is 1000 words and i got away with only writing bout 700 or so lol

[Carlman]

what about a 1.5L coke bottle as your chamber instead? it can hold pressure and it will be lighter than pvc.

[Thursto]

But that is too basic, this is suposed to be an "adavcned" sort of rocket, and i was thinking this would would better with 2 engines.

other words coke bottles are out fo the question. to basic.

thanks anyway.

[psycix]

Sorry to spoil your fun, but I think it will give a bit dissapointing results.

1: Having two engines your rocket WILL tumble over and go crazy
Unless you use an gyroscope and a microchip controlled thruster regulator, one engine will always be more powerful then the other and it will get a big chance of failing.
Once it got speed, then its possible because then the fins can pull it straight.
I recommend HUGE fins to get this thing fly straight.

2:PVC is too heavy, a coke bottle will perform better even if its an lower pressure