This launcher comes from an idea from the following email extract.
This (when it is built) will allow the pressurisation of the bottle and then release on depressurisation of the air supply line.
The diagram on the left shows the basic parts of the Copper Tube Launcher with the additional fittings that make it all function from one air line and the bottle in position (note that the 'o' ring and fins et cetera are omitted).
The copper parts (purple) are assembled as described on the Copper Tube Launcher page but omitting the cable ties, the copper ring and Jubilee clips that secure them and the plastic sleeve. The rest is as follows . . .
Fixed collar (a) is built to hold three of the latches (b) as shown in the smaller diagram at the bottom. There are three pins that secure the latches (b), allowing them to move freely. The fixed collar (a) can be made from 6mm brass or copper and the latches (b) from 3mm brass. The fixed collar (a) should be soldered onto the copper pipe and then end stop (d) is soldered into a hole made in fixed collar (a). End stop (d) can be made from 3mm brass rod but it should be remembered that it must be able to withstand the force from piston (h) at the highest pressure to be used.
Next slide spring (e) onto the copper pipe followed by sliding collar (c) which should slide freely. Into the bottom of sliding collar (c) are drilled two holes - one for piston (h) and one for the end of latch (k). Piston (h) should be soldered in place such that it is able to move up and down cylinder (g) freely. Cylinder (g) is soldered onto the side of the copper tube as is mount (j) - they may be mounted together. Mount (j) is positioned such that the end of latch (k) locates in a hole in the end of sliding collar (c) and allows for the disengaging of latch (k) and sliding collar (c) when sliding collar (c) moves upto and meets end stop (d). Lug (l) is positioned such that it holds the spring (f) in place on the side of the tube.
Spring (e) needs to be strong enough to overcome the almost neglegable friction force when latch (b) is holding a pressurised bottle in place.The cylinder (g)'s diameter needs to be great enough in order to compress spring (e) at the lowest working pressure used in addition to any frictional force derived from pushing sliding collar (c) along the tube and, disengaging the end of latch (k). The length of end stop (d) should be such that it allows enough movement to disengage the end of latch (k) whilst starting from a position of holding closed the latches (b).
If you are experimenting with different gasses in order to find the effects of the ratio of specific heat capacities of the gas at constant pressure and constant volume ( Gamma or compressability) on performance and are considering gasses with a low, you should not use Acetylene (it is dangerous enough gas as it is) NEVER PUT ACETYLENE IN CONTACT WITH COPPER. Try looking only at gasses with a high such as Argon.
Thanks to Jonathan Edge for writing to the group.