Is Sch10 Stainless Steel DDT safe?

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WizardNoodle
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Tue Mar 21, 2017 7:33 pm

I am going to be making a hybrid gun in about 4 weeks, and I have a relatively low budget. The construction material will be T304 stainless steel.
I want to use Sch 10 for the construction as it is relatively the cheapest, but as I am working with a hybrid safety is #1.

The Sch 10 barrel diameters I will be using are 1-1/2" and 2.5".
1-1/2" Sch 10 burst pressure is 8605 psi and 2-1/2" Sch 10 burst pressure is 6260 psi.
The chamber will be Sch 10 3" diameter pipe with burst pressure being 5142 psi.

Chamber Length will be 20 inches (167 Cubic inches), 1-1/2" Barrel will be 92 inches, 2-1/2" Barrel will be 38 inches.
There will be a chamber fan with 51 CFM.
The fuel will be MAPP gas.

I'm sorry if this is a bit much but if someone could run HGDT with these parameters, running worst case scenarios (burst disk doesn't rupture) until the pressure reaches no more than 2000 psi and sending back pictures of what mix it reached the pressure at and pictures of what 5x, 10x, 20x, 50x, and 100x will do for me that would be so helpful as my computer cannot run HGDT.
(jack was kind enough to already run a simulation for me but I have since then tweaked the design and completely changed the material from PVC to steel)

Also, this seems a bit stupid to ask but just to be safe, I am wondering if DDT does occur, will the Sch 10 steel be able to absorb it or will I have steel shards in my skull?
Last edited by WizardNoodle on Wed Mar 22, 2017 6:41 pm, edited 4 times in total.
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mark.f
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Tue Mar 21, 2017 10:08 pm

In the future if you want to run HGDT on a chromebook, you can do this:

1.) Enable developer mode
2.) Install Crouton and any number of linux distributions
3.) Install WINE
4.) Install HGDT.

As to the question, I can't run HGDT now because I'm at work, but I'm sure somebody else will come along. Generally, you shouldn't design around your materials' burst pressures. It would be far more helpful to know the yield strengths and fudge in your safety factor from there, keeping in mind that drilling through the chamber for things like electronics and ignition will weaken it further.

Also, that chamber fan it going to get pretty beat up. What kind is it?
WizardNoodle
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Wed Mar 22, 2017 7:09 am

mark.f wrote:In the future if you want to run HGDT on a chromebook, you can do this:

1.) Enable developer mode
2.) Install Crouton and any number of linux distributions
3.) Install WINE
4.) Install HGDT.

As to the question, I can't run HGDT now because I'm at work, but I'm sure somebody else will come along. Generally, you shouldn't design around your materials' burst pressures. It would be far more helpful to know the yield strengths and fudge in your safety factor from there, keeping in mind that drilling through the chamber for things like electronics and ignition will weaken it further.

Also, that chamber fan it going to get pretty beat up. What kind is it?

Thank you for answering, at least! I have installed Ubuntu (A Linux system) on an old Windows XP in the past, and we are planning on installing the same on this Chromebook, however, the internet here is extremely spotty, so I will be able to download and install it this weekend when we are in the city house.

As for the chamber fan, I was thinking I would be using the same that was in The Jackal Baaaazooka, http://www.ebay.com/itm/Sunon-60mm-x-38 ... SwVupTmSf5 positioned at the very front of the bottom chamber, or the farthest from the barrel so less stress inflicted on the fan. (Over/Under design)
That specific fan is brushless and moves 57 CFM.


Also, is the cannon too big? I may need to downsize again as I want it to remain handheld, I don't want to be blown back 10 meters every shot...
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jackssmirkingrevenge
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Wed Mar 22, 2017 9:59 am

Quick simulation at 10X Propane:
3inchhybrid10x.jpg
As you can see, without the need for a chamber fan (pressurizing the system agitates the mixture in and of itself) you're already at ridiculous power levels, well beyond .338 Lapua Magnum.

How are you thinking of holding it exactly? Did you plan on fitting a stock or simply holding it Bogan style?

[youtube][/youtube]
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WizardNoodle
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Wed Mar 22, 2017 10:09 am

jackssmirkingrevenge wrote:Quick simulation at 10X Propane:
3inchhybrid10x.jpg
As you can see, without the need for a chamber fan (pressurizing the system agitates the mixture in and of itself) you're already at ridiculous power levels, well beyond .338 Lapua Magnum.

How are you thinking of holding it exactly? Did you plan on fitting a stock or simply holding it Bogan style?

[youtube][/youtube]
I was hoping to mold or make a stock on the 180 degree angle, with foam core covering the stock to further soften the recoil. The gun will also have a simple (detachable) muzzle brake on the end of each barrel. I also will add a grip on the top of the chamber to be able to shoot from the hip at higher mixes, or to just look badass.

Wow, those readings are nice! I was disappointed about the data until I realized that that was from the 2.5" barrel and using Propane, not MAPP!!! This upgrade to Galvanized steel certainly opens opportunities... better stop bragging to mom, she is starting to get antsy and threatening to stop the project haha.

What would the 1.5" barrel yield with MAPP and a chamber fan?
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mobile chernobyl
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Wed Mar 22, 2017 6:02 pm

Here is a link to my Sch. 10, 304 SS chamber and barrrel hybrid that I made a few years back:
http://www.spudfiles.com/hybrid-cannon- ... 23523.html

I have had it fail to rupture the burst disc with a 10x mixture once - it was kind of interesting - a "ping" sound and nothing. Kind of scary actually haha. The chamber became very hot and my spark-stalk assembly was ruined from the continuous high heat generated in this scenario.

Depending on what chromebook you're using - look into the Galium OS distro of Linux - I use it in dual boot fashion on mine and it's regularly updated and optimized for the HW of a chromebook! Also with the chromebook - highly recommend dual booting - you'll find that you don't really need the full blown OS all the time, and Chrome OS is pretty slick at the end of the day - VERY good driver support for stuff like wireless home devices (i.e. chromecast).
WizardNoodle
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Wed Mar 22, 2017 6:36 pm

mobile chernobyl wrote:Here is a link to my Sch. 10, 304 SS chamber and barrrel hybrid that I made a few years back:
http://www.spudfiles.com/hybrid-cannon- ... 23523.html

I have had it fail to rupture the burst disc with a 10x mixture once - it was kind of interesting - a "ping" sound and nothing. Kind of scary actually haha. The chamber became very hot and my spark-stalk assembly was ruined from the continuous high heat generated in this scenario.

Depending on what chromebook you're using - look into the Galium OS distro of Linux - I use it in dual boot fashion on mine and it's regularly updated and optimized for the HW of a chromebook! Also with the chromebook - highly recommend dual booting - you'll find that you don't really need the full blown OS all the time, and Chrome OS is pretty slick at the end of the day - VERY good driver support for stuff like wireless home devices (i.e. chromecast).
That sounds like a fun experience... and if it didn't burst then, I am reassured in this cannon's integrity.

Funnily enough, we are actually already going to do a duel boot, we already have a thumb drive with 128 Gigabytes! We have to wait until the weekend for the downloading/installing part, which we have not done yet...

Also- I have found your Supersonic Day x videos before! It's weird to actually talk to the person who made the same videos I was awestricken watching... over and over...
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mobile chernobyl
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Wed Mar 22, 2017 11:01 pm

Interestingly enough - that gun initially started out as 'something I want to hold' - it quickly turned into not that haha.

Glad you enjoy the videos - Hopefully I can get back into making them in the future (aka shooting REAL spud guns, and not just boring cartridge fed AR's and AK's lol).
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Thu Mar 23, 2017 9:59 am

mobile chernobyl wrote:Interestingly enough - that gun initially started out as 'something I want to hold' - it quickly turned into not that haha.

Glad you enjoy the videos - Hopefully I can get back into making them in the future (aka shooting REAL spud guns, and not just boring cartridge fed AR's and AK's lol).
Yeah, I want the gun to be as mobile as possible, cam couplings and all. I just realized I would always need to have an air compressor nearby, is it possible to hook up a bike pump to the meter and pump through there? I want all the recharging/loading systems on the gun. I'm not going to drag an air compressor around during the apocalypse, that's for sure!

I suggest making spud gun videos with a few shots of blowing up watermelons in high-speed, people really like that instead of hard drives for some reason. Also, keep the titles as descriptive yet click baity as possible, definitely will get more views. More views = more people exposed to spud gunning = more members on spudfiles = boost in spud progress = closer we get to sending a tater to the moon!
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mobile chernobyl
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Thu Mar 23, 2017 1:09 pm

WizardNoodle wrote:Yeah, I want the gun to be as mobile as possible, cam couplings and all. I just realized I would always need to have an air compressor nearby, is it possible to hook up a bike pump to the meter and pump through there? I want all the recharging/loading systems on the gun. I'm not going to drag an air compressor around during the apocalypse, that's for sure!

I suggest making spud gun videos with a few shots of blowing up watermelons in high-speed, people really like that instead of hard drives for some reason. Also, keep the titles as descriptive yet click baity as possible, definitely will get more views. More views = more people exposed to spud gunning = more members on spudfiles = boost in spud progress = closer we get to sending a tater to the moon!
It certainly would be possible to pump up the combustion chamber with a bike pump after you have injected the low-pressure initial charge of Propane/Fuel - I probably should have supported this feature in my design as most of my test shots were 'remote' in the sense that it was hard to get a 20A circuit to kickstart my compressor most of the time!

A Simple adapter could be made by sticking with a standard air chuck adapter on the gun air-inlet side, but then making a combination of these two parts:

Quick Connect adapter:
Schrader valve with threaded base:

For lower volume/higher mix ratio designs I always wanted to use an HPA tank from paintball - and for more exotic mixes I always wanted to use a scuba tank with a calculated Nitrox mix.
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Thu Mar 23, 2017 1:17 pm

mobile chernobyl wrote:
WizardNoodle wrote:Yeah, I want the gun to be as mobile as possible, cam couplings and all. I just realized I would always need to have an air compressor nearby, is it possible to hook up a bike pump to the meter and pump through there? I want all the recharging/loading systems on the gun. I'm not going to drag an air compressor around during the apocalypse, that's for sure!

I suggest making spud gun videos with a few shots of blowing up watermelons in high-speed, people really like that instead of hard drives for some reason. Also, keep the titles as descriptive yet click baity as possible, definitely will get more views. More views = more people exposed to spud gunning = more members on spudfiles = boost in spud progress = closer we get to sending a tater to the moon!
It certainly would be possible to pump up the combustion chamber with a bike pump after you have injected the low-pressure initial charge of Propane/Fuel - I probably should have supported this feature in my design as most of my test shots were 'remote' in the sense that it was hard to get a 20A circuit to kickstart my compressor most of the time!

A Simple adapter could be made by sticking with a standard air chuck adapter on the gun air-inlet side, but then making a combination of these two parts:

Quick Connect adapter:
Schrader valve with threaded base:

For lower volume/higher mix ratio designs I always wanted to use an HPA tank from paintball - and for more exotic mixes I always wanted to use a scuba tank with a calculated Nitrox mix.
Yes, the part of my cannon that will seem most complicated to me will be the fuel/air meter... is it possible to make an all in one meter with two adapters, one a quick connect and the other whatever connects to a MAPP gas tank?
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