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New Aluminum Claw Launcher

New Bottle and Launcher

Last Update: April 18, 2006

Highest Launch to date: Approximately 300 feet

After reading countless sites dedicated to Water Rockets and launchers in particular,

I decided to fabricate my own with off-the shelf hardware supplies,

galvanized pipes and all steel, aluminum and cast hardware

This is my HOW-TO

I wanted a quick release mechanism but didn't want the hassle or the problems associated with building the release mechanism. The water-hose quick-release mechanism seemed the most reasonable, but there were two problems. In Canada, the 28mm bottle cap is the standard. This cap is much too large to fit inside the standard garden-hose adapter. Secondly - I didn't like the idea of a plastic garden-hose coupler.

A trip to the hardware store netted a brass quick release which works great with the plastic male quick couplers. As far as fitting them into the bottle caps - a few minutes chucked into my drill press Initial testing at 30PSI and hand-held launched a 500ml plastic beer bottle about 50 feet straight-up.

There are several companies who manufacture quick-release couplers
There are brass and plastic. Many are interchangeable
As I said before, in Canada, our garden faucet threads are too small to fit outside the 28mm PET bottle caps
For this reason, I had to modify a cap so the quick coupler would fit inside
After cutting a hole in the bottom of a bottle cap which would fit the nozzle, I had to modify the nozzle
I found a bolt which closely matches the diameter of the nozzle and added tape to make a snug fit
Then I chucked the cap into the drill-press (I don't have a lathe) to cut and trim the bottom
I slowly trimmed (with the drill-press on medium speed) until the plastic disc was snug in the bottom of a plastic cap
With a few wraps of PTFE tape on the bottle threads it seals fine. I've tested at 60lbs with no air leaks

I drilled a hole in the cap for the new nozzle With a longer bottle cap (which I haven't found yet) I might even try
a rubber washer on top of the nozzle, to seal against the bottle
With remote pressurization, however, I'm not sure if it would make much difference

Shot of all the components Pipes, fittings, tools and PTFE (Teflon) tape Click the image for a detailed bill of materials

Assembly begins
Here is the bottom support 'T' under construction
Ensure you wrap all pipe ends with a good 4 layers of PTFE Tape
The first 'T' is assembled with two 6" pipes and end caps
This is then attached with a short pipe nipple to another 'T' which will form the upright
If you are going to use pipe mounts like I have, you will need to install them before the pipe caps

The upright pipe
The brass check valve (below) ensures water does not get to the bottom of the assembly
It's also another fail-safe for back-pressure to the air line
The ball shut-off valve is probably not necessary
I installed it for testing and/or to shut-off air supply to the bottle if needed

The brass check-valve - open and closed
This isn't a spring-return check-valve like the pneumatic one on the air side
It's not what I wanted, but it was cheap and in-stock
It works fine for my needs

The 'brains' of the outfit
The brass quick coupler, with integrated shut-off
With nothing attached, air flow is restricted
With the combination of air pressure in the upright pipes and this valve,
no water should enter the piping system

I thought about using electrial ground clamps for water-pipes as a release mechanism
They work well and were inexpensive
If you look carefully, you can see I seperated two pairs of clamps
The part with the 'screw' for attaching a ground wire has been used for the top
This screw will conveniently hold the aircraft cable I'm using for activation
I did have to use longer screws than came with the clamp to go around the brass coupler

Here is the other pair of ground clamp pieces
I drilled-out the threads on one of each of the clamps
The twin eye-bolts were threaded into a cut piece of a coupling nut
I had to grind-down the threads on one of the eye bolts to get it to lock-in
and line-up correctly with the other one
The assembly was then locked around the base of the launcher
A horizontally pulled cable can now activate a vertical pull on the coupler mechanism

The air inlet has been added with another short section of pipe and my step-down fittings
There is another brass check-valve just after the air fitting
Again, this is both a safety fitting and to prevent any water from back-flushing the line
Don't forget to put the mounting bracket on first, if you use the same style as shown

A pair of 'T's was used to create a pressure-guage and pressure-relief mount
The pressure guage is large enough to read the pressure from a distance
Another eye-bolt is mounted to the mounting plate to allow activation of the pressure relief
Many sites claim an ordinary pop bottle will withstand 150PSI of pressure (a little over 10Bar)
The pressure relief is rated for 150PSI. I don't plan on going any higher for now

The mounted eye-bolts for the launch release
These will allow for a change of plane for the vertical release
into horizontal motion from the pull-wire

Here we begin the mounting process
Using hanger-style mounts for the pipes, I mounted the first one
with an eye bolt. This eye bolt will form a change of plane
for the pressure relief valve

The back pipes are mounted with the same hangers
I'm using aluminum for a number of reasons
1) It's easy to machine
2) It's light
3) It won't rust

Close-up of the leveling feet I designed
I found some rubber, tapered caps
A shouldered 1/4" x 20 bolt, two washers and a nut were added
They are threaded into tapped holes in the aluminum base

The bottom of the aluminum mounting plate
I used three mounting feet
A tripod platform is much more steady than 4 feet on unlevel ground
The rubber should grip well enough to allow for triggering
If not, I may have to add weight or another ground mounting system

The mounted Rocket Launcher
I don't have the pressure relief line added yet,
But the twin lines have been looped around a steel eye
Another cable will be prepared for activation
I have an air cylinder - but I'm not sure yet if it will work as well
as the manual pull method

The first set of launches
We're only getting about 50 feet
I need to investigate why we're losing so much thrust at take-off
This is my first attempt with a fin sleeve attached
I'm at probably 110PSI

My second attempt, without the fins
I didn't get much difference in height

I put a little less water in and put the fins back on
Because I was using an air tank,
the pressure was now down to about 90PSI

A 2L bottle launch
About 80PSI and about 100ml of water
Next time out - I have to measure the water more carefully
I didn't keep track except by eye


Heeding much advice from more qualified wrocketeers,
I have created a more 'rocket' like device
It's two bottles taped together
With an easter-egg nose cone glued to a bottle cap
If I understand the calculations and the terminology,
My center of gravity is now higher than the center of pressure

I'm also planning on testing a new launch system
Modeled after the Bristol sport-cap launcher
I'm cheap. I had this cap from a dish-detergent bottle
With a very slight modification, the cap fit perfectly
into a brass compression nut I had in my junk drawer
I also had some other fittings in my junk drawer so I could simply
attach this assembly to a brass quick connect
With no modifications to my garden-hose coupler, I can add the
new launch assembly and run some tests

The completed assembly. Sorry for the focus
I had this up to 70PSI while testing
It didn't self-launch, nor lose pressure
I'm hoping for 80 - 100PSI launches with this cap
I haven't seen other references to a dish-detergent quick release
Perhaps this is a first ??

More Launch Photos Coming Soon
The launch stream looks good . . and the wrockets flew pretty straight
But I really didn't get a lot of height
I kept lowering the water volume and that helped a little
An empty 2l bottle at 80PSI seemed to go almost as high as one
with 100ml or so of water
More research needed
eMail wrocket@mikesheppard.net any questions

Launched on Easter Weekend with the new rocket designs.
The two 500ml bottles spliced with the green egg nose-cone and the corrugated plastic fins flew for 4 - 5 seconds and reached probably 300 feet. It flew down range in the field probably 500 feet. It was a very cool launch.
I also flew another two-bottle splice, this time 1 litre bottles. I used 4 struts and a circular fin. It hit about the same height as the 500ml bottles.