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Launcher Systems

The launch system I use is a Gardena Release mechanism.

Below are my updates which apply to the launcher system.

Cable-Tie Launcher

posted 23 Apr 2011, 08:27 by Andy Lakin-Hall   [ updated 23 Apr 2011, 09:11 ]

Just for fun, and for use at small scale demonstrations in restricted areas I have built a small cable-tie type launcher.

This features a champagne cork, bored through with an air hose and sanded down to fit snugly inside most bottle necks.

This is mounted in turn on top of a column of PVC plumbing pipe, which forms the frame and structure of the launcher.

The base of the PVC pipe is clipped to a rectangular frame of timber as weight.

On the very top of the cork is a flap of rubber, cut from a bicycle inner tube. This acts as a simple valve, and prevents most of the water leaking back down the pipe.

Six medium sized cable ties are arranged in a circle around the vertical PVC pipe, and these are held in place by tape to allow adjustment. They are aligned so that when a bottle is pushed onto the cork tightly, the heads of the cable-ties fit just over the protruding ring around the bottle neck.

The larger diameter length of pipe slides up and down on a spring cut from a 2-litre PET bottle. The spring pushes up the pipe, which in turn holds the heads of the cable-ties against the bottle, clamping it in place.

The lower end of the spring is resting on a purple disk, which is actually the plastic lid from a tub of drinking chocolate. I cut a hole in this with my compass cutter so that it is a very snug fit around the vertical PVC pipe. This allows me to vary the tension on the spring by raising or lowering the purple disk. This disk is also supported underneath by a PET bottle lit, again cut through to fit snugly onto the vertical PVC pipe.

An air hose runs down from the cork, through the PVC plumbing pipe and out through a hole. All the air pressure is held inside the air hose, not in the PVC pipework, so I do not have to worry about leaky joints, and the whole construction can be taken apart easily to replace bits if required.

At the other end of the air hose is a Presta valve, which came from a bargain-bin bicycle tyre. This has enough rubber moulded around it to fit snugly inside my air hose. This is held in place tightly by a tiny jubilee clip.

The nature of the cork means that it will only hold pressures of about 40psi before leaking like a sieve. This means that rockets from this launcher are not able to be pumped up to seriously dangerous pressures. It also means that a small bottle of up to 1.5-litres can be pumped up to launch pressure with only a few pumps on the Joe Blow. This means that it is quick to set up, quick to pressurise and quick to launch, as well as only likely to launch a rocket a little way, which is great for using in a small area.

Here is a 1.5-litre tapered bottle mounted on the launcher. This bottle is intended just as a test rocket, so it has tiny fins and no nose cone. In flight it tumbles only slightly less than the bottle would without fins, but it did the job of testing the launcher really well. Now I have got a working launcher of this type, I can design a better small rocket to launch from it.

MkII Launcher

posted 24 Aug 2009, 10:32 by Andy Lakin-Hall   [ updated 8 Apr 2011, 02:04 ]

I've been working for a while now on a new launcher.
There were several problems with the old one, which lacked a launch rail.
I had also had problems with the connection between the hose release and the upright air pipe going wonky after a couple of launches.
I found a brass Gardena release in the hardware shop, and soldered this directly onto a copper pipe.

This new connector was reassembled and mounted onto a new baseboard using a similar type trigger mechanism as before; a light pull on a string pulls out a hinged locking block, releasing a longer spring lever, which in turn pulls down two cables fixed to the Gardena release.

Lock and Release
Cables on Gardena Release

Full Assembly

The complete assembly includes a pressure gauge, a non-return valve and release valve for emergencies.

Pressure Gauge 
Non-Return Valve
Pressure Release Valve

For a launch rail I decided to use a length of curtain track which was fixed to an aluminium support.

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