The basic idea is that you want to launch a rocket from a tube, just like the bullet from a gun. Because of the rocket fins a real tube is sort of out of the question and the drag of the tube against the fuselage would probably be to big to actually let the rocket fly high. So digging around on George Katz website: Aircommand I found a great launcher. I decided to make things a bit more simple, because I only use tree types of bottles and thus am able to make sure the diameter of my rockets is always the same.
An overview of the lancher.
I use tree aluminium U-shaped parts as vertical guide rails. I use three aluminium struts of a bigger size as tripod legs. And I use double flat struts to keep the guide rails straight. The three guides are connected to a MDF rectangle that is big enough to hold more stuff than the legs alone.
Detail of three struts.
Finally I got a brass Gardena compatible coupling. These are somewhat hard to get here In the Netherlands, and I got one from Gamma (it actually is Gamma Brand, and I never saw it before!) (Gamma = compare: Home-Depot).
I stuffed a small aluminium pipe through the coupling. The aluminium pipe is made wider on the side that stays inside the coupling.
I did that by mounting it in a drill and sticking in a brass part that you would usually stick on a airhose to pump up a rubberboat. Anyways, the pipe is wider in the coupling so it can’t fall out, I sealed it with a small rubber ring. To make sure that the pipe doesn’t work itself out of the coupling I filed a small indent in a circle in the aluminum pipe and wound a piece of steel wire around that which I twisted in on itself, thus sealing the pipe.
Bottom of the launch-plate.
The alu-pipe sticks through the launch-plate and a standard pressurehose coupling (normally used to connect a water-tab to a pipe) fits on perfectly, these things are water and air tight. A small piece of rope is connected to the brass ring of the brass-coupling and comes out on the bottom in a loop. The loop is caught by an L-shaped piece of steel that is used as trigger (see two photo’s below). The pulling cord is not yet in place but will be on the most right hole. The pulling direction is downward in the photo.
L-shaped trigger.
The elastic band pulls the trigger back after use so that the brass coupling can reset itself after launch.
Detail of the rope coming from the brass coupling through the baseplate looping around a pin in the L-shaped trigger.
Pressure meter.
The pressure meter is putt on a T-shaped brass part that serves as a connector for the pressure hose coming from the pump (right side in the picture above). Inside is a Dutch Bicycle Valve (DBV) which just sticks out on the left side thus preventing water entering the pressure meter.
Exploded view of the valve section.
Valve assembled in a rubber ring.
Rubber ring inserted in adapter.
Finished valve assembly.
Part of a fuselage in the launcher.
Fully assembled rocket (without camera for testing purposes) ready for launch.
The next possible launching day will be saturday, August 29th. I’ll hopefully test both the launcher, the new ripstop nylon parachute and the dampened magnetic trigger. So thats going to be hilarious!