Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 36 users online :: 3 registered, 0 hidden and 33 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: Bing [Bot], Google [Bot], Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Poured Concrete Hybrid Chambers

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
Sponsored 
  • Author
    Message

Poured Concrete Hybrid Chambers

Unread postAuthor: DYI » Tue Apr 01, 2008 6:45 pm

Today I was casting concrete around the breach of my SCTBDC after the incident on Saturday, and suddenly had this thought:

What's to stop someone from casting reinforced concrete around a relatively weak ABS pipe to make it into an exceptionally strong hybrid chamber?

Here's the method: Get a suitably sized pipe, put on whatever fittings you want for fueling, ignition, etc... Put that inside a large stovepipe (6", 8", whatever is needed). Suspend the chamber pipe a few inches up, and cut holes in the side of the stovepipe to run through whatever pipes are attaching your ignition and fueling to the outside world, then epoxy the space around the holes. Built a rebar/steel mesh cage, then pour in the concrete, creating a pipe with walls about 2" thick that won't break unless you set off high explosives inside it.

Advantages:

Low cost, high availability - anyone can get concrete, anyone can get drainpipe and stovepipe, and anyone can get rebar.

High strength - you could also reinforce standard SCH 40 steel for much higher mix capability, and you could make a weak DWV pipe into a 10x hybrid chamber. ABS pipe or similar should take the direct shock off the concrete as well, and a layer of something else could be added if needed to increase shock absorption.

Insulation - most of the power in any combustion gas gun is heat. The less heat that is lost, the higher the power. ABS and concrete are far better insulators of heat than steel or aluminum

Ease of construction - no sparkplugs required, as the chamber material is an electrical insulator, and the wires are simply epoxied into holes in the stovepipe, as the concrete provides the strength

Disadvantages:
Weight. That's all I can think of, really. Concrete weighs about 2.4g/cm<sup>3</sup>, roughly similar to aluminum. Since most hybrids of the size this would be practical for aren't handheld, it shouldn't be too much of a problem, as long as the chamber is wheeled.

What I'm hoping for here is response from the black powder gun crowd on how well this will work, how thick the concrete will need to be, and how to create the reinforcements to offer the most, well... reinforcement.

As with all my theory topics, I ask that if you have nothing useful to contribute on the actual question, you refrain from responding at all. If all you want to do is comment on how heavy it will be, keep it to yourself. I've already ran those numbers, and they really aren't impossible to work with.
  • 0

Last edited by DYI on Tue Apr 01, 2008 8:52 pm, edited 1 time in total.
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: mark.f » Tue Apr 01, 2008 8:05 pm

I dunno...

Concrete has good strength under compression. As far as I know, it's not that great for tensile strength.

McMaster probably has some useful numbers to crunch.
  • 0

User avatar
mark.f
Donating Member
Donating Member
 
Posts: 3464
Joined: Sat May 06, 2006 11:18 am
Country: United States (us)
Reputation: 21

Unread postAuthor: DYI » Tue Apr 01, 2008 8:26 pm

I know that concrete has poor tensile strength. I also know that it's used to reinforce black powder guns, so there must be a way of making it useful for this app. I believe the trick lies in the layout of the mesh inside the concrete. What I want to know is how to do this properly.
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: D_Hall » Tue Apr 01, 2008 9:00 pm

Biggest problem will be getting bubbles out of the mix (assuming you aren't going with some massively monolithic pour).



edit: And if it were me, I'd just go with a fiberglass/epoxy wrap.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1759
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: DYI » Tue Apr 01, 2008 9:02 pm

Biggest problem will be getting bubbles out of the mix (assuming you aren't going with some massively monolithic pour).


So... Any ideas in that regard?
And what would you consider massively monolithic? :lol:

And a fiberglass/epoxy wrap isn't really an option for what I'm thinking of.
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: ammosmoke » Tue Apr 01, 2008 9:05 pm

You might be better off using firebrick mortar or something. It is much finer. And, to improve tensile strength you can mix in glass fibers from fiberglass. It has been shown to greatly improve strength.
  • 0

<img>http://www.speedtest.net/result/309559995.png</img>
User avatar
ammosmoke
Brigadier General
Brigadier General
 
Posts: 1011
Joined: Wed Sep 27, 2006 10:57 am
Reputation: 0

Unread postAuthor: D_Hall » Tue Apr 01, 2008 9:20 pm

DYI wrote:
Biggest problem will be getting bubbles out of the mix (assuming you aren't going with some massively monolithic pour).


So... Any ideas in that regard?

Vibration is the normal tool, but I don't know if you've got pneumatic vibrators available to you.

And what would you consider massively monolithic? :lol:

If you can pick it up, it isn't monolithic.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1759
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Sponsored

Sponsor
 


Unread postAuthor: DYI » Tue Apr 01, 2008 9:28 pm

Well, I do have lots of glass fibers around.

I knew about the pneumatic vibrators, I'm looking for some sort of slightly more ghetto way around the problem that doesn't involve horrendously expensive equipment.

How thick do you think the walls of a concrete casting around a 4" SCH 40 ABS pipe would have to be to make it safe for 10x or so, assuming that I don't have any specialised tools to make the casting with, but do use rebar and glass fibers?
  • 0

Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.
User avatar
DYI
Lieutenant General
Lieutenant General
 
Posts: 2861
Joined: Sat Jul 07, 2007 8:18 pm
Location: The People's Republic of Canuckistan
Country: Turks and Caicos Islands (tc)
Reputation: 9

Unread postAuthor: benstern » Tue Apr 01, 2008 9:31 pm

To overcome the tensile strength problem you can prestress it.

Another disadvantage:
maintenance - what if you need to change a fitting or spark gap?
  • 0

User avatar
benstern
Donating Member
Donating Member
 
Posts: 909
Joined: Wed Sep 21, 2005 8:24 pm
Reputation: 0

Unread postAuthor: Rokmonkey » Tue Apr 01, 2008 10:11 pm

Hmmm, my roommate has taken Strength of Materials course, I take it next semester, I'll ask him. But for background, what's the approximate pressure spike, and constant pressure within a hybrid chamber?


He can make concrete to pretty much any specification.
  • 0

Last edited by Rokmonkey on Tue Apr 01, 2008 10:41 pm, edited 1 time in total.

Rokmonkey
Corporal
Corporal
 
Posts: 73
Joined: Wed Feb 28, 2007 10:03 pm
Reputation: 0

Unread postAuthor: D_Hall » Tue Apr 01, 2008 10:24 pm

DYI wrote:How thick do you think the walls of a concrete casting around a 4" SCH 40 ABS pipe would have to be to make it safe for 10x or so, assuming that I don't have any specialised tools to make the casting with, but do use rebar and glass fibers?

Well, for something like this (ie, almost pure tensile stress) really it's the steel that's going to be absorbing all the stresses. The concrete just forms a convenient matrix to transfer the forces to the steel. Just think in terms of what a (say) 3/4" diameter bubble does to localized stress transfer. Now ask yourself what you have to do to make that 3/4" bubble either go away or become insignificant.
  • 0

Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
D_Hall
Donating Member
Donating Member
 
Posts: 1759
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Reputation: 6

Unread postAuthor: MrCrowley » Tue Apr 01, 2008 10:45 pm

I skimmed over the basics of this thread, but would it be better to have a gap between the concrete and chamber? You may of mentioned this and I just missed it, but it seems logical to me :)
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: ammosmoke » Tue Apr 01, 2008 10:54 pm

What, so it forms a sort of wall of air to absorb shock? Sounds kinda cool. But air is a pretty good insulator so...
  • 0

<img>http://www.speedtest.net/result/309559995.png</img>
User avatar
ammosmoke
Brigadier General
Brigadier General
 
Posts: 1011
Joined: Wed Sep 27, 2006 10:57 am
Reputation: 0

Unread postAuthor: MrCrowley » Tue Apr 01, 2008 10:57 pm

I dunno just seemed like a good idea at the time :D

I must of thought of it from the logic that the tighter you pack something that goes boom, the bigger boom you're going to get 8)

...Which we don't want in this case :roll:
  • 0

User avatar
MrCrowley
Moderator
Moderator
 
Posts: 10207
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand
Country: New Zealand (nz)
Reputation: 4

Unread postAuthor: bigbob12345 » Tue Apr 01, 2008 10:58 pm

another way would be to build a chamber around the combustion chamber and pressurize it with air which would put stress on the outside making it not blow...maybe
This may have already been mentioned but...

Like a triggered burst disk, it uses pressure to make the burst pressure higher
  • 0

User avatar
bigbob12345
Major General
Major General
 
Posts: 1516
Joined: Sat Dec 01, 2007 9:13 am
Location: Mercer Island,Washington
Reputation: 0

Next

Return to Construction Materials/Ammo Discussion

Who is online

Registered users: Bing [Bot], Google [Bot], Yahoo [Bot]

Reputation System ©'