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A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Synchronous multiple Gardena release

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
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dongfang
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Synchronous multiple Gardena release

Post by dongfang » Sun May 24, 2009 4:53 pm

Hi,

I am working on a winged rocket, with four 8 * 1/2 liter bottle stacks comprising the fuselage and power plant... each of the four stacks will have a male Gardena as its nozzle, and I will need a launcher that can synchronously release 4 female Gardenas.

Does anyone (Batkiter?) have experience with such a set-up? My particular worry is this scenario:

- All Gardenas release, except one
- The rocket turns / bends over the Gardena that is still attached
- That remaining Gardena breaks
- The rocket flies off horizontally, smashing whoever & whatever happens to be in its way

Do multiple synchronous Gardenas behave well? Experience? Designs for the part that should trigger them all at the same time?

Can anyone think of a solution for my worry? A high ring wall or an underground silo are not options :)

Regards
Soren



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rockets-in-brighton
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Re: Synchronous multiple Gardena release

Post by rockets-in-brighton » Sun May 24, 2009 5:12 pm

dongfang wrote:Hi,

I am working on a winged rocket, with four 8 * 1/2 liter bottle stacks comprising the fuselage and power plant... each of the four stacks will have a male Gardena as its nozzle, and I will need a launcher that can synchronously release 4 female Gardenas.

Does anyone (Batkiter?) have experience with such a set-up? My particular worry is this scenario:

- All Gardenas release, except one
- The rocket turns / bends over the Gardena that is still attached
- That remaining Gardena breaks
- The rocket flies off horizontally, smashing whoever & whatever happens to be in its way

Do multiple synchronous Gardenas behave well? Experience? Designs for the part that should trigger them all at the same time?

Can anyone think of a solution for my worry? A high ring wall or an underground silo are not options :)

Regards
Soren
I think you are unlikely to succeed with this, for the reasons you state, and the best you could do is reduce the effects of a misfire with a protective screen of some sort.

It would be far better to have a single point of release but I don't have a ready design for a suitable release. Could you give us more detail, perhaps show us the layout of the stacks - are they arranged in a line side-by-side, or around a core? How are you pressurising the whole system - do the stacks form a linked pressure system or are they independent?

If you have a core tube, could you fix a gardena to the bottom end of that and use it as the hold-down for the whole system?


Cheers
Steve
Rockets-in-Brighton
WEB: http://groups.google.co.uk/group/rockets-in-brighton

dongfang
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Re: Synchronous multiple Gardena release

Post by dongfang » Sun May 24, 2009 7:23 pm

Hi,
Could you give us more detail, perhaps show us the layout of the stacks - are they arranged in a line side-by-side, or around a core? How are you pressurising the whole system - do the stacks form a linked pressure system or are they independent?
The bottle stacks will be arranged in a quadratic pattern, as seen from the end. 2 pairs of 2 over and under the wing.

I plan to have a linked pressure system at the launcher. I might even add little tubes connecting the air parts of all stacks, so the water will automatically level in the 4 stacks.

A single 9mm Gardena would deliver far too little thrust. If I need a single attachment, I will have to S-bend four PVC pipes and connect each from a bottle stack to a common core pipe. With epoxy to seal maybe. Something like the exhaust manifold on a motor. It will be a bit difficult to design/fly a plane with heavy parts on the tail. Standard plumbing like elbows, tees and wyes will not do. They are too heavy and lose too much pressure in high speed flow - I have tried :)

But I have seen pictures (Batkiter's, I think) of a rocket with half dozen or so side boosters, all set off at the same time with Gardenas. I also recall having seen booster rockets by Air Command on Youtube. How do they do that....?

Regards
Soren



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U.S. Water Rockets1
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Re: Synchronous multiple Gardena release

Post by U.S. Water Rockets1 » Sun May 24, 2009 9:02 pm

dongfang wrote:Hi,

I am working on a winged rocket, with four 8 * 1/2 liter bottle stacks comprising the fuselage and power plant... each of the four stacks will have a male Gardena as its nozzle, and I will need a launcher that can synchronously release 4 female Gardenas.

Does anyone (Batkiter?) have experience with such a set-up? My particular worry is this scenario:

- All Gardenas release, except one
- The rocket turns / bends over the Gardena that is still attached
- That remaining Gardena breaks
- The rocket flies off horizontally, smashing whoever & whatever happens to be in its way

Do multiple synchronous Gardenas behave well? Experience? Designs for the part that should trigger them all at the same time?

Can anyone think of a solution for my worry? A high ring wall or an underground silo are not options :)

Regards
Soren
We have personally seen another water rocket designer successfully launch a 3-nozzle gardena rocket. The way he did it was to add an external spring to each gardena that pulled it down with a pin or wedge of some type that held it in the closed position. The triggers were all connected with a rigid piece of plastic that yanked them out at the same time. It worked over several successive launches until a parachute failure ended his day.


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rockets-in-brighton
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Re: Synchronous multiple Gardena release

Post by rockets-in-brighton » Mon May 25, 2009 2:50 am

dongfang wrote:Hi,
Could you give us more detail, perhaps show us the layout of the stacks - are they arranged in a line side-by-side, or around a core? How are you pressurising the whole system - do the stacks form a linked pressure system or are they independent?
The bottle stacks will be arranged in a quadratic pattern, as seen from the end. 2 pairs of 2 over and under the wing.

I plan to have a linked pressure system at the launcher. I might even add little tubes connecting the air parts of all stacks, so the water will automatically level in the 4 stacks.

A single 9mm Gardena would deliver far too little thrust. If I need a single attachment, I will have to S-bend four PVC pipes and connect each from a bottle stack to a common core pipe. With epoxy to seal maybe. Something like the exhaust manifold on a motor. It will be a bit difficult to design/fly a plane with heavy parts on the tail. Standard plumbing like elbows, tees and wyes will not do. They are too heavy and lose too much pressure in high speed flow - I have tried :)

But I have seen pictures (Batkiter's, I think) of a rocket with half dozen or so side boosters, all set off at the same time with Gardenas. I also recall having seen booster rockets by Air Command on Youtube. How do they do that....?

Regards

Soren
By having the active nozzles pressed into seals but not held down - the hold down may not have to be an active nozzle at all.


Cheers
Steve
Rockets-in-Brighton
WEB: http://groups.google.co.uk/group/rockets-in-brighton

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Spaceman Spiff
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Re: Synchronous multiple Gardena release

Post by Spaceman Spiff » Mon May 25, 2009 10:25 am

If you do it that way you can get rid of the gardenas from the pressurized nozzles totally and replace them with your own o-ring seals and launch tubes.


Spaceman Spiff
"What goes up, must come down"

dongfang
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Re: Synchronous multiple Gardena release

Post by dongfang » Mon May 25, 2009 10:49 am

Hi,

I agree it could be elegant with separate nozzles and attachment points. I could even use something less expensive than Gardenas then, like a mix of 16 and 20 mm PVC plumbing. But it would require a pretty strong structure to hold down 4 bottles. Maybe the manifold solution would be no heavier anyway then...

Hmm I guess I could try build a dummy manifold, and see how heavy it will get. I liked the idea of using springs to make the Gardenas default-detached instead of attached. Ideally, I would like something that could be remote triggered with a servo.

Regards
Soren



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