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Stage1 - 120X CLGG

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Stage1 - 120X CLGG

Unread postAuthor: DYI » Fri Aug 29, 2014 11:53 pm

Stage1 is my first foray into the development of a combustion light gas gun, and has several design features not seen before on Spudfiles. First, the specifications, interspersed with the relevant pictures:


Chamber: 1.525" ID x 3.5" long, 1.5" long taper from 1.525" to 0.800". 2024-T651 aluminum with 1" thick walls (this is a chamber I made about 3 years ago which was a convenient fit for the project)

Image

Barrel: 0.760" ID x 85" long. 1" OD DOM tube.
Operating pressure: up to 12000psi.
Fuel mix: oxygen/hydrogen only. Pre-ignition pressure up to 1750psi. First shot used 90:10 hydrogen/oxygen at a pre-ignition pressure of 1714psi.
Fuel meter: 2 inlets, for unregulated hydrogen and oxygen, both with 10000psi needle valves. Gauge is 0-3000psi, +/-0.25% over full range. Connection to the chamber is also a needle valve. Currently uses 3000psi unions for disassembly. All hoses are PTFE lined and rated for oxygen service to 3000psi.

Image

Image

Ignition: finely adjustable spark gap mounted on machined high pressure pass through. HV supply is a standard battery operated barbecue igniter. Note that the version pictured here is last year's, and has been slightly improved since, but is functionally identical.

Image

Breech: 3-part design allowing the disc or shear skirt to be clamped without rotation. For harder skirt or disc materials, 0.03" thick machined Delrin gaskets are used. The breech can accommodate assemblies up to 0.155" thick, and has a short tapered region immediately downstream of the disc or skirt to prevent the torn edges from obstructing the flow.

Image

Image

Projectiles: shear skirt design (can also take burst disks). I've used these before, but haven't posted them. The 7075-T6 aluminum slug shown is drag stabilized by way of a drilled out tail, and its shear skirt is designed to release at 9000psi.

Image

Performance: predicted at 1110m/s with a 14.4g projectile, using the GALE code with empirical calibrations. Although I attempted to chrono the first shot, the Chrony was blinded by the flash, for reasons that will become apparent when you watch the video. The breakwire device I mentioned a few years ago is still in the works, due to a major difference of opinions between its designer and Customs.

Image


Of particular note here is the fact that this appears to be the first hybrid on Spudfiles using an oxygen/hydrogen mix. Also of note is the (still terrifying) unregulated gas supply, the high pressure breech connection which allows the barrel to be evacuated or purged with hydrogen, and the fact that I'm igniting a mix at 1700psi precharge using a $20 barbecue sparker.

For the first (and currently only) shot, the spark gap was near the center of the chamber, and set to a width of 0.003". The mix ignited immediately upon pressing the igniter button. The projectile for the first shot had a mass of 14.4g, of which 7.67g was recovered after the shot. Due to a leak elsewhere in the vacuum system, the original plan to pull a vacuum on the barrel was scrapped in favor of simply purging it with hydrogen, which is nearly as good in terms of performance gains (about 10% over an air filled barrel, at this speed).

This is in the discussion and not the showcase for a reason: it is very much a work in progress, and there are still a lot of kinks to be ironed out of the system before it can be considered fully operational. The central functions, however, appear to work properly. The name stems from the fact that this launcher is both the first stage of my CLGG development program, and the first stage of my upcoming 2-stage light gas gun design. It is also my first major step back into the hybrid world after the 2008 mishap.

Finally, the video: Here it is

The violet-white flash 4 frames after the first appearance of the muzzle flash is the projectile hitting the target. The range from muzzle to target is 3.5m, and the frame rate is 1200 frames/s. Accounting for drag, the projected muzzle speed of 1100m/s is near the center of the possible range given by the video.
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Re: Stage1 - 120X CLGG

Unread postAuthor: MrCrowley » Sat Aug 30, 2014 2:15 am

That's an amazing piece of engineering, looking forward to any updates. Why is it that you're shooting inside? I'm surprised you're allowed to!

Not sure how accurate HGDT is at those pressures but it's interesting to see that it estimated a muzzle velocity of 930m/s using only MAPP gas and not hydrogen/oxygen. Perhaps that lends a bit of weight to your own estimation.
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Re: Stage1 - 120X CLGG

Unread postAuthor: POLAND_SPUD » Sat Aug 30, 2014 5:08 am

Nice. Really really nice.
Do you live in an apartment ? You are doing in indoors so it seems to me that you do.
Neighbours calling for police in 3..2..1..

lol I hope they won't but I can imagine what they would think when they saw all of that plus those two tanks of hydrogen and oxygen
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Re: Stage1 - 120X CLGG

Unread postAuthor: DYI » Sat Aug 30, 2014 7:25 am

I don't live in an apartment, and no one outside of my house can hear anything noticeable during these tests, as they're done in a basement. Moving everything outside is just too much trouble, especially on systems that aren't complete yet.

MrCrowley: how did you simulate that on HGDT? I get one of those famous "invalid procedure call or argument" rats nest graphs when I try to run it.
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Re: Stage1 - 120X CLGG

Unread postAuthor: MrCrowley » Sat Aug 30, 2014 7:41 am

DYI wrote:MrCrowley: how did you simulate that on HGDT? I get one of those famous "invalid procedure call or argument" rats nest graphs when I try to run it.

Chamber dimensions as given, barrel dimensions as given, MAPP gas 120x with a single ignition point, burst disk failure 9000PSI with the same diameter as the barrel, projectile info. as given. Got chamber and barrel burnout warnings but it modelled it successfully nonetheless. I assumed burst pressure was given by the following "its shear skirt is designed to release at 9000psi".

I was expecting one of those rats nest errors to be honest. Haven't used it in awhile but I think I entered everything correctly.
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Re: Stage1 - 120X CLGG

Unread postAuthor: jrrdw » Sat Aug 30, 2014 8:08 am

What program did you make that video with? Or a Photobucket link would be better...
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Re: Stage1 - 120X CLGG

Unread postAuthor: DYI » Sat Aug 30, 2014 12:04 pm

MrCrowley, those are the same parameters I used when I got the rats nest. Which version are you running? I have v0.5.4.

Jrrdw, the video was just thrown together in WMM last night. I don't have my own computer set up at the moment, and didn't see the point in going to any trouble making a video for a single shot. This launcher should see more use around Christmas time. I'm not sure what you mean about the Photobucket link. That's what I have in my post.
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Re: Stage1 - 120X CLGG

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Re: Stage1 - 120X CLGG

Unread postAuthor: MrCrowley » Sat Aug 30, 2014 3:55 pm

Running the same version, here's a screenshot:
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Re: Stage1 - 120X CLGG

Unread postAuthor: jrrdw » Sat Aug 30, 2014 4:20 pm

DYI wrote:Jrrdw, the video was just thrown together in WMM last night. I don't have my own computer set up at the moment, and didn't see the point in going to any trouble making a video for a single shot. This launcher should see more use around Christmas time. I'm not sure what you mean about the Photobucket link. That's what I have in my post.


http://vid813.photobucket.com/albums/zz ... _test1.mp4

DYI Video_0001.jpg
This is what I get when I open the video link.


DYI Video_0002.jpg
When I close the player I get this.


DYI Video_0003.jpg
When I paste the link in the Photobucket search field I get this.


Is anyone else having issues watching the video7
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Re: Stage1 - 120X CLGG

Unread postAuthor: MrCrowley » Sat Aug 30, 2014 4:24 pm

Nope, works for me fine. Maybe WMM is some how associating the link with its program? Perhaps try another browser.
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Re: Stage1 - 120X CLGG

Unread postAuthor: D_Hall » Sun Aug 31, 2014 12:00 am

Nice!

One comment/question though... If the ultimate goal is a 2SLGG, why bother with Stage 1? A plain ol' propane/air gun (or O2 if you so desire) should work perfectly fine for the first stage of a 2SLGG.

And yeah, one of these days I'll get off my ass and rewrite HGDT. Alas, life.... Maybe when the kid goes off to college?
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Re: Stage1 - 120X CLGG

Unread postAuthor: DYI » Sun Aug 31, 2014 5:24 am

Propane air would definitely be adequate for the first stage of a LGG, but there are two project branches at play here, and one of them is the eventual development of an oxy/hydrogen CLGG. It seemed more convenient to incorporate them into one build, considering that the scales were the same, and this gun can be run on oxy/propane with a slight modification to the fuel meter if desired.

I probably won't actually run oxy/hydrogen in this gun when using it as the first stage of a 2SLGG, as the high pressure fueling would introduce more hassle than it was worth at that point, and the performance is predicted to be nearly identical below 1200m/s or so. I've actually done pretty extensive modeling of 2SLGGs with my 1D ALE code, and successfully predicted the performance of various guns in the literature with it. After I incorporate chemical kinetics (not exactly a small task, I know), it should be a useful validation tool for predictions made with 0D codes like HGDT.
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Re: Stage1 - 120X CLGG

Unread postAuthor: jrrdw » Sun Aug 31, 2014 8:30 am

MrCrowley wrote:Nope, works for me fine. Maybe WMM is some how associating the link with its program? Perhaps try another browser.


It seems I have codac issues with the .mp4 extension. So I grabbed Quicktime Player and that worked.

@DYI... :P

http://youtu.be/lidFipyLG8k?t=1m35s
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Re: Stage1 - 120X CLGG

Unread postAuthor: Juggernaut12121 » Sun Aug 31, 2014 5:02 pm

This is one of the most beautiful things I have ever seen.....
I now have a new life goal :D
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Re: Stage1 - 120X CLGG

Unread postAuthor: mobile chernobyl » Sun Aug 31, 2014 8:58 pm

Your testing environment may raise a few eyebrows... but who cares!

Your work is a huge advancement in "amateur" CLGG's and an inspiration to keep pursuing this hobby!
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