SpudFiles

Well the time has come to replace the old water rocket launcher..

I basically have the design complete.. But I thought I'd post here just in case I've missed something.

First of all, the hold-down/release mechanism. This is the part I'm the least firm on, so suggestions are welcome.
Swing arm mechanism
Poppy launcher
Clark cable launcher
And the U-pin launcher..Sorry, don't have a link for this one.

Decided things already are a double o-ring seal, pneumatic trigger, schrader valve and a quick connect and BV. A pneumatically triggered safety venting BV, 150 or up to 200 psi guage, launch tube. Basically all the works.

A pneumatic triggering box (with a length of pvc to actuate each function (air chamber)). Eg. a switch to launch the rocket, one to dump pressure, etc.

Any thoughts/queries/etc.eh eh ehh?

none of the above.
Unless you are using a special nozzle, go for a hose quick connect, as they have a decent sized port, and will make a very simple launcher.
The ziptie one is sketchy as hell, so I would go for everything else over that.
The one made out of a cut up soda bottle cap also doesn't seem that secure...

The problem with the hose quick connect is that you don't get any guidance in the first foot or so of the launch. Most tube based launchers give a much more stable initial flight than do hose quick connects.

At launch the rocket is, aerodynamically speaking, flying backwards. Any thing you can do to keep it from turning around will help the launch.


Back to to OP. I would go with the Clark type launcher though all three appear to work fine.

I take it you have never done any model rocketry in your life...
I kind of took it for granted that you would have a launch guide rod. I can't see any rocket of any type working too well without a guidance system.
Just glue a straw onto the side of the bottle, and attach a 3' metal rod onto your launcher, and you will have no troubles.

I personally don't like any thing else for rockets than on board propulsion, preferably combustion.

What does that even mean?

What I think you mean is that you prefer to have motor, and nothing else, so that in theory it will fly the highest, but in reality it sucks because you didn't put all of the stuff on it that makes it fly well, or makes it interesting.

I understand the need to keep weight down, but a 1" section of straw actually has zero mass when compared to a liter of water, and causes the rocket to fly at least 100x higher.

Also, fins are generally usefull...

Rather than use a guide rail (as in regular model rockets) the best option is to use a launch tube. The reason for this is because then in the first foot or two of flight, you are essentially powering the rocket with a pneumatic ram, which is of course much more efficient than the rocket. So you get a nice, guided speed boost at the beginning of the flight with next to no penalty, and then when the tube leaves the rocket's nozzle it can actually start to act like a rocket.




I've done some thinking and I believe it would be possible to do if you used a garden quick connect setup. You would just need to get some brass tube that fits snugly into the nozzle, and attach that to the mechanical part of the connecter. Perhaps use epoxy to attach it to a short section of hose, then shroud that in pvc and use a bit of hose sticking out the end to attach the connector.

Lentamentalisk wrote:I take it you have never done any model rocketry in your life...
I kind of took it for granted that you would have a launch guide rod. I can't see any rocket of any type working too well without a guidance system.
Just glue a straw onto the side of the bottle, and attach a 3' metal rod onto your launcher, and you will have no troubles.

True, Lenta knows what he's talking about. Also instead of a straw, it is possible to get a piece of copper pipe that fits within the quick connect. This gives the rocket a bit more kick from the ground as well.

I didn't list a reduced launcher, as I already have a perfectly functioning one.

After the launcher was completed last night (clark cable with steel ties) it took a hammering and ended up separated from the base in order to use a length of cell core as a launch tube for a bazooka style launch.

Rather than a pressure guage we decided to set the compressors reg to the pressure we wanted, or use the sch. fill which had a guage. A hose quick connect was also added (with a bv) to allow water filling on the launcher.

The night went well, we ended up losing 2 double bottle rockets (launched vert. with a tube!) to roofs over 100m away.. We have the power to rebuild it..but I don't want to spend a lot of money

Apologies for the double post, but recently using firefox I receive an error message very often while posting or editing, usually editing. I'll edit this information into the first post when it's working again.

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The launcher

Well, after the flogging the stationary launcher copped doing launch tube shots (large id cellcore guide) I decided to build a smaller, lighter, better handheld launcher and throw the larger launcher on the backburner until I have supplies for a booster launcher (1 main, 3 boost..).

It uses a clark cable design with a launch tube and o-rings to seal. A DWV fitting is used as the hold down collar. Originally, the design was going to use a pressure guage, but instead we decided to run the compressor air line through a high quality air reg and simply set that to the required pressure.

The air inlet is a quick connect, which can be replaced by a schrader valve if required. The first (RED) ball valve opens the airline and fills the rocket to the pressure the reg is set at. The second (ORANGE) valve is a safety. It's set to dump the pressure quickly in case of rocket fatigue/stress. If you wanted you could add a hose barb for remote fill, guage, second launch tube...whatever to the port. It's set up like that for safety. Pressure rated 1/4" id pipe connects the valve assembly to the launch tube.

The new rocket

A new rocket was built after loosing my two best rockets to rooftops, each over 100m away (for reference, they had no chutes, were shot vertically and there was a fair amount of wind). This one is constructed from 1.25L bottles rather than the larger, draggier 2L bottles. (also, to what I've seen 1.25 resists more impacts/pressure). They were robinson coupled (bottom to lid) for maintenance/repairs. Another bottle was pressurised and thermalformed, then cut up and used as a nosecone. A shroud hides the neck, and streamlines the rocket. Large fins were cut from corflute (basically corrugated plastic-imagine plastic cardboard. Brilliant stuff.) and filament taped on for maintenance. The rocket was then finished up in red and yellow, with a silver shroud (spray cans).

And the pictures...











And hopefully I'll get a flight video up when jimmy gets here to shoot some rockets!


(waits for flaming about the cellcore launch tube and DWV collar)

What are you fins made out of,Until no i have only used solid propellant rockets with R-candy but this is slightly more legal and so i am thinking of maybe build a few(though i like to pump bottles up to 150psi anf then quickly unscrewing the cap, goes about 40 or so meters).

John; my fins are made out of a kind of plastic called "corflute". It looks like a white, corrugated cardboard. It's often used a lot in signs such as for sale signs on houses (real estate). It's very strong, crash resistant, glues and paints easily and is cheap and easy to use.

Well, following on from this thread I think I have a chamber. After tearing the coffee machine to pieces I got a huge stainless steel tank with extremely thick walls (I feel kind of sad that it will only be seeing below 150 psi...regardless it will be hydrotested.), a motherload of valves, pipes, nozzles, fittings etc..A pop off valve which is likely set too low for this, and a guage (unsuitable for this, will go into a propane fueling rig..).

Well, it has a lot of ports in it! hopefully I can find a use for each one.. Would be nicer than plugging them. All together, there's 8 ports! 6 Large ports, 1 medium and one small port. In the small port I'm going to screw in a tee and add a schrader and presta valve to it. One port will be used for a guage, one for an emergency valve (to purge pressure). It will have both a clark cable (or similar) and a quick-disconnect (water) launcher. One port will have a tee, with two ball valve leading to each of the launchers. Each one will have a pipe going to the bottom of the chamber (bottom half filled with water) with a tee and a ballvalve for each. Filling on the stand!. Needless to say two more ports will be used for either launcher, and a ballvalve for filling/removing water and then a quick connect to the compressor. The water filling may be given a miss.

As for the nice big stainless tube, I'm not sure. It will either be disposed of, used as a cover around the launcher (for firing rockets that have signs of damage) to reduce risk to the shooter or perhaps a guard for pressure testing. It's rolled, not drawn so a pressure application is out of the question.

The port near the bottom where the heating electrodes are will most likely be plugged with epoxy.










Any input?