the JAUSH (in operational stage)[[[[UPDATES 28/3/2008]]]]

sniperjosh · Posted: 07/10/2007 4:27 AM Post subject:

Hi all, just thought i share my cannon with the community.

Name: JAUSH (Josh's aussie hybrid)

Description: small bore, high mixture hybrid. chamber is machined high tensile aluminium with aluminium lever coupling for attaching barrel / burst disc.
The gun features a propane metering system, air injection system, and ignition system - It has a manifold on air injection system which has 2 ports left for attaching a pressure recording gauge setup (already have 0-1150psi gauge, need a one way valve + venting valve). The air injeciton side has a dead volume on the air side of the valve, which as a result reaches the same pressure as the chamber when injecting, after each shot the valve is re-opened and it quickly vents the chamber of left over smoke from the combustion effectively.
The ignition system consists of a 100kv stungun circuit, and my own fabricated "spark plug".
There is no proper/permanent barrel(s) built for the gun as of yet, but the plans are a 75cal, 100cal, Glass marble barrel, 3/8" bearing barrel, and 1/2" bearing barrel. At the moment i have a 75cal and 100cal barrels of lengths 80cm and 200cm (2 barrels per calibre) - these are made of pressure rate PVC (200psi approx) with no re-inforcements, also a terrible example of a marble barrel is used occasionaly, they are treated as if sacrificial and the setup is only for this operational / experimental phase of the JAUSH.

Chamber: chamber is custom machined high tensile aluminium, the dimensions are: 31mm I.D x 180mm deep, with wall thickness of 11mm and rear flat wall thickness of 20mm (to account for flat walls being weaker) The overall external length of the chamber is 200mm. the chamber has 3 holes tapped into it, 2 1/4" BSP threads for propane and air injection, and a 3/8" BSP thread for my spark plug setup. The mouth of the chamber is tapped with 1" BSP threads.

As more progress on the gun is made, all observations and any useful information / new pictures / videos will be updated into this thread.

The JAUSH so far...
The gun has performed well and fired shots on all mixtures up to 5x, but the majority being at 6x, with a handfull of 7x shots also being fired. the only problem i have noticed was with a cheap gauge which is used for my chamber pressure, i was short a valve to isolate the gauge for combustion and decided the gauge was cheap enough to sacrifice - it only reads to about 200psi - it is now permanently damaged (as shown in pic). This bad gauge has resulted in poor mixture calculations once it became damaged, the only shot that was perfect after the gauge became damaged (perfect: explosion with minimal smoke) was a 7x mix, but with 110psi on the chamber gauge prior to ignition (the gauge seems to read about 20psi with no pressure now, so i attempted to compensate - but it was a big guess). the Guns explosion was clean, thought it grenaded my 100cal PVC barrel. I have a chronny but dont have the low-light setup for it, which is needed for my under-house range; I will set up the chronny soon to find some FPS figures. The gun atm seems very powerful, and i am very eager to get the chrony onto it. One thing that remains to be done is measure the volume of chamber and propane meter with water.

The gun will soon sport a timber enclosure for the bottom part of gun to hide all propane / air injection / ignition systems.

My goal / design purpose for this gun is supersonic speeds and high mixtures. Everything but the chamber itself is treat as sacrificial, and nobody can be anywhere near it when it is fired, it is simply unsafe.

UPDATES: finished housing for ignition and remote firing control box + electrical lead. Finished 1.2m marble barrel.

Today I finally did some rough testing (propane metering gauge and chamber gauge dammaged, need to be replaced). I played with 1x shots to try to roughly tune in a good mixture, as my metering gauge has been dammaged. To do this i used my chrony, doing sequentially higher volumes of propane injection, to see where the peak FPS was being achieved. @ 1x the results varied a fair bit whilst tuning it in, the highest recorded was 182 FPS, witht he average being about 160fps. I then did a single 2X shot which produced 314.1 FPS, a healthy improvement over a 1x. I then did a single 3x shot, producing 637.9 FPS. I didnt do any further testing as this was performed in my backyard (not my underhouse range) and the 3x shot was very loud, i decided to pack it all up before any neighbours got annoyed. I feel the results are good as my aim is to break the sound barrier with the 16mm glass marbles, considering i achieved over 0.5mach with a low mix, im quite confident its well in the range of this setup.

27/3/2008: Did testing with single weak burst disc at 2x mix (1200mm marble barrel). This test was still with damaged meter gauge and damaged chamber gauge. I will do testing with 2 burst disc layers tomorrow, and possibly 3 (trying to determine effects burst pressure of disc has on gun performance). These discs burst at about 20psi max, which i observed while accidentally over pressurizing the mix.

1 burst disc...

SHOT1: 487.3 FPS
SHOT2: 539.8 FPS
SHOT3: 506.5 FPS
SHOT4: 484.5 FPS

SINGLE BURST DISC AVERAGE: 504.5 FPS

2 burst discs...

SHOT1: 617.3 FPS

As you can see the 2x shot (single burst disc) a few days prior of only 314 FPS was obviously a bad mixture (too rich I think). I am confident the shots would produce more power and be more consistent with new gauges.

I will update with pics and more info when i get hold of a camera and do further testing.