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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.
Last edited by sniperjosh on Fri Mar 28, 2008 3:22 am, edited 7 times in total.
i like it alot thats a Cam lock isnt it? i didnt know that you could use those for burst disks how well do they work compaired to a union?
very very nice gun is this your first?
Im a pneumatic marble sniper fanatic, tho this is my first hybrid, i pretty much fnished it apart from 1 ball valve and a hose clamp about 8 months ago, a few days ago i decided to finish it since I was bored . Im glad you like it . Yes it is a cam lock, it works a dream for burst discs, Ive done plenty of 7x mixes (90psi air prior to ignition), and the burst discs have sealed perfectly, u'll notice in the pics the camlock held them inplace during the firing, not once has one of them sliiped down the barrel. I only used a steel union once ages ago in an experimental combustion laucnher, it leaked stupidly, PVC ones look liek they would seal nicely but i myself dont feel liek buying a new union all the time as i doubt PVC really has a chance against fast pressure spikes of high mixtures.
the whole time i have used the bottom cut out of disposable plastic cups, cheap ones, cost me $5AU for 100, so its 5cents / shot
they wont blow @ 2x, havent tried them @ 3x, they blow at 4x , and highest ive tested so far is 7x.
2x makes around 140-150psi combustion, but thats only for a minimal time length, id say they will hold about 120psi continuosly.
Have you done any damage shots yet? What is the estimated burst pressure of the chamber? What kind of ball valves are you using to separate the meter from the chamber? Most brass ball valves are only rated to 600psi.
P.S.- I love how the gauge's needle is bent from the pressure spike.
redacted will be a 4" bore, 10x oxy/fuel hybrid using 1 cubic foot of 8" SCH 80 steel chamber
Last edited by DYI on Fri Apr 04, 2008 8:51 pm, edited 1 time in total.
Jesus you would want some hearing protection in that shooting range!You would have no ears drums left after a few shots.
Nice cannon,the chamber is Aluminium right?Is there any powder residue left on the inside of the chamber after shooting?Because usualy a layer of oxide on the chamber.
wow, beautiful hybrid, man, now I'm starting to miss spudguns:(
Current project: Afghanistan deployment
Homedepotpro, I dont fire it from upstairs, and its very loud, but the brick walls and pillars seem to muffle the sound alot, i fire all day and it bothers no neighbours or anything and isnt loud at all to anyone standing in my backyard .
DYI, I have only been firing some lightweight pine wood slugs, they punch through 5/8" chipboard easily at 5X +, the chipbaord is laminated and highly compressed - its not crap stuff. I did some figures to estimate the burst pressure of the chamber a while ago, but i simply have forgotten / neglected to re-do the calculations - i think its over 10000 psi (but i really do forget anything specific). The chamber was designed over-strength to be better equipped for possible detonations. The brass ball valves are only the standard ones, i think 600psi is what they are rated too, as i said before, in its current state all but the chamber is considered sacrificial - i dont trust anything but the chamber not to explode (as stupid as that may sound) So i like to be in a safe position when it is fired. Once it is in its complete stage i will run ball valves with around 2000psi rating atleast. Another weak point is the lever coupling, it is aluminium, it will be replaced for stainless for the main reason that i trust stainless more than aluminium, but that part of the gun will remain sacrificial unless i decide to machine a complete flange system myself at a later date. I also love how the gauge is damaged, its my fave pic of the gun, and really gives you a sense for its power .
rna_duelers, I havent checked for that as of yet, ill let you know when i do (gun is still under the house, i get home from work and cant be bothered crawling in there to unhook it all and crawl out with it). The loudest shot so far was the one that destroyed the barrel, but i dont wear hearing protection at the moment - I think if i was located down range of the gun it woudl be painfully loud though
Frank, cheers dude - im glad i have re-sparked your interest
thanks to all the comments / questions guys, keep them coming
That's a neat hybrid. I can imagine people brushing their teeth and then all of a sudden hearing a nice THWAP under their feet.
BTW, I did the same thing to a gauge like that. It was a cheap Ashcroft gauge with a little copper coil thing which held the needle. The coil untwisted a little and now the gauge is stuck on 60 PSIG. I've got a ball-valve between it and the new one.
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