large burst disk hybrid build(Update September 2017)

Harness the power of precision mixtures of pressurized flammable vapor. Safety first! These are advanced potato guns - not for the beginner.
wdr0
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Wed Jan 28, 2015 8:33 pm

Hey, I did actually do that test, just did not get anything up because it was not quite as exciting as previous tests. The sphere was rather loose in the barel so did not seal as well and there fore had less energy. It did split the oak log it was fired in to. but only penetrated about 3". Currently I am working on getting hydraulic cylinders to add to the breach so that it can be easily opened and closed and the bolts will no longer be required. Eventually hydraulic elevation and possibly traverse are a possibility, and idealy a built in compressor with the whole thing on a trailer. Eseentialy the idea is to have the whole thing powered by an engine so no outside power is needed and have the movements mechanized as it really is a beat to lift all the parts back in line after it fires.
wdr0
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Fri Feb 27, 2015 11:42 pm

Progress is being made, I got these two giant hydraulic cylinders for only $75 each and they look almost new. They will serve to both open and hold the flange where the burst disk is placed.
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these are the cylinders wrestled into the car, atleast 5ft long and over a hundred lbs.
these are the cylinders wrestled into the car, atleast 5ft long and over a hundred lbs.
wdr0
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Wed Sep 02, 2015 10:25 am

I realize there may not be anyone who can answer but I'll ask any way. I have a question for those with metalworking experience/knowledge. I am considering attempting to build a piston valve for this cannon and was thinking I might use a section of a compressed gas cylinder (something like a 125 cf nitrogen cylinder)for the piston housing. What I'm wondering is if those cylinders are a reliably weldable alloy of steel? Also I am aware of the safety aspects of working with a cylinder that may have flamible residue or gases. I would appreciate any input, Thanks!
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matti
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Thu Sep 03, 2015 3:25 am

wdr0 wrote:I realize there may not be anyone who can answer but I'll ask any way. I have a question for those with metalworking experience/knowledge. I am considering attempting to build a piston valve for this cannon and was thinking I might use a section of a compressed gas cylinder (something like a 125 cf nitrogen cylinder)for the piston housing. What I'm wondering is if those cylinders are a reliably weldable alloy of steel? Also I am aware of the safety aspects of working with a cylinder that may have flamible residue or gases. I would appreciate any input, Thanks!
You can get hydraulic cylinder pipe from steel pipe sellers, same pipe that is used to manufacture the cylinders. That has very good roundness and surface quality also it's very good to weld. (Or you could cut a section of some used hydraulic cylinder)

I would not use gas bottle, they are made by forming from sheet metal and welding could stress it and also it would probably deform when welded.
wdr0
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Thu Sep 03, 2015 9:37 am

That was my concern. Problem is there are no steel suppliers where I am, at least not without a trip. Cutting a portion from a hydro cylinder might be my best option if I can find a large enough one.
amit chawla
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Tue Sep 22, 2015 5:04 am

where r u from??? i m working for steel supplier company....
wdr0
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Thu Sep 21, 2017 5:04 pm

hello all, update here, this project has been on hiatus, moved at the beginning of the year. I was able to do some work durring a visit home with the help of some freinds. The remaining work should be completed before November by my freinds with test firings of the new arrangement in early novemember. Here is the current progress.
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Chamber and shocks for recoil test fit
Chamber and shocks for recoil test fit
Trailer with pivot mount for elevation
Trailer with pivot mount for elevation
Beam for slide and chamber on trailer
Beam for slide and chamber on trailer
Drawing of fully assembled unit
Drawing of fully assembled unit
Slide mount drawing for chamber
Slide mount drawing for chamber
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Fri Sep 22, 2017 8:01 pm

May be a bit late to the game but....

Large projectiles go a very long ways when elevated even slightly. VERA only elevates about 5 degrees but I get "first impact" points about a mile downrange. The point being that you may want to re-evaluate the angle of the dangle on that gun mount to make sure it is compatible with the realities of your firing range (whatever they may be).

All that said... GOOD WORK! Hate that I missed all the updates from about page 2 to current.
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wdr0
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Fri Sep 22, 2017 8:21 pm

The implications of the high elevation range were indeed discussed. I did decide to allow for that much range mainly because many of the other areas where I may fire from are not flat and the increased range will allow for firing at a basically horizontal trajectory even if the trailer is facing down hill on an incline which is fairly likely. We are aware and have taken into account the long range abilities and possibility of projectiles passing out intended target. Thanks for thoughts and interest!

And as may be noted I mentioned multiple other plans at various times in previous posts, I tend to constantly come up with new ideas and directions with my projects until I have the chance to execute something, this is why the ultimate result may only contain some or even none of the previously mentioned plans
Last edited by jrrdw on Sat Sep 23, 2017 7:27 am, edited 1 time in total.
Reason: Double post.
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Tue Sep 26, 2017 4:26 am

D_Hall wrote:"first impact" points
I imagine that implies that the projectiles continue to bounce along the desert floor... what a sight that must be :D

wdr0, great job with this build! Always nice to see size limits being pushed.
hectmarr wrote:You have to make many weapons, because this field is long and short life
wdr0
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Sun Nov 12, 2017 12:40 pm

last weekend all conceivable major work was completed. Painting and some minor adjustments are the only thing planned at the moment, however a fail to fire incident did occur, which may provoke further work. Initially multiple shots were planed, but the fail to fire occurred on the second attempted and due to time constraints we were unable to take much time to investigate or prepare for subsequent firings.

At the moment still have no confirmed reason for the fail to fire. I have a few hypotheses though.
My first is that all previous shots had been conducted successfully but with the chamber In essentially a level condition. The fail to fire occurred when the cannon was aimed at a significant downward angle. My thought is this may have caused the propane to all settle at the forward end making for a mix that would not support combustion.

My second is the chamber seemed quite warm, maybe even more so than after the first shot. Even though heating would of occurred from compression of the added air I'd think that would have been counteracted by the venting of the chamber after the failed attempt to fire. So possibly had incomplete combustion at a lower than required pressure to rupture the disk. I realize just now a way to check for this would be to see if the disk is bulged at all( did not remove it after the attempt, will have that done when possible)

Lastly my metering system could very well be off and we essentially got lucky the first shots. Regardless I'm going to have my freinds investigate and see if this was a fluke or a new issue that has arrisin. There is video which I will post once it is sent to me. The first shot went perfectly, the cannon stays stable and the improvements have reduced recoil to an entirely reasonable level.
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Sun Nov 12, 2017 10:23 pm

jackssmirkingrevenge wrote:
D_Hall wrote:"first impact" points
I imagine that implies that the projectiles continue to bounce along the desert floor... what a sight that must be :D.
It's really not that impressive. A big poof of dust. A delay. Another poof of dust farther away. A smaller delay. Another poof of dust.... Generally 3-5 poofs before the poofs are too small to see from a couple miles away. Drive out. Find the first impact mark. Start walking.... Find the projectile 1/2 mile later.
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Sun Nov 12, 2017 10:52 pm

wdr0 wrote:...
My second is the chamber seemed quite warm, maybe even more so than after the first shot. Even though heating would of occurred from compression of the added air I'd think that would have been counteracted by the venting of the chamber after the failed attempt to fire. So possibly had incomplete combustion at a lower than required pressure to rupture the disk. I realize just now a way to check for this would be to see if the disk is bulged at all( did not remove it after the attempt, will have that done when possible)
...
I've had a FTF scenario where it 'combusted' but did not burst the bust disk - definitely a hair raising scenario when going to investigate.
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Mon Nov 13, 2017 7:08 am

wdr0 wrote:My thought is this may have caused the propane to all settle at the forward end making for a mix that would not support combustion.
Unlikely, given that the mixture is pressurized. If the chamber was warm then a burst disk failure... failure is the most likely explanation.
hectmarr wrote:You have to make many weapons, because this field is long and short life
wdr0
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Tue Nov 14, 2017 6:29 pm

Luckily I had planned for venting the chamber withought a known combustion for both this exact reason or if a leak occurred durring fueling. I have a electric ball valve now installed on the cannon and then a vent off my fueling manifold. So I can vent the chamber entirely remotely. I will have my freind check on the condition of the disk as soon as I can and get the videos up as soon as I have them.

This is the most recent fueling set up. Controls for the actuated valve on the left and firing on the right. Air and propane are the two quick connects, the brass fitting is the hose to the cannon(just a standard garden hose). Lower left is the vent.
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IMG_3347.JPG
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