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 85 users online :: 4 registered, 0 hidden and 81 guests


Most users ever online was 155 on Mon Aug 15, 2016 1:40 am

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Ignition?

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.
Sponsored 
  • Author
    Message

Ignition?

Unread postAuthor: SNDM » Sat Jun 21, 2008 2:18 pm

First of all let me introduce my project.

It is a low power copper hybrid.
(Low power because I have no idea to the strength of the copper. It is kitemarked, but other than that I don'tknow of any other ratings on it.
Looks pretty thin too.)

I need a way of igniting the Hydrogen/Oxygen mix.
I have basically an end cap in which to install the system.
It is 22mm dia size.

I was wondering what easy designs people used, which kept their launcher strong.
  • 0


SNDM
Sergeant
Sergeant
 
Posts: 84
Joined: Tue Feb 26, 2008 4:05 pm
Reputation: 0

Unread postAuthor: SpudFarm » Sat Jun 21, 2008 2:23 pm

i would be worried about DDT in a thin chamber like that..

and if it is short so DDT is no danger copper can take 4x no problem..

spark plug is the way to go
  • 0

"Made in France"
- A spud gun insurance.
User avatar
SpudFarm
Donating Member
Donating Member
 
Posts: 2563
Joined: Sat Nov 04, 2006 9:39 am
Location: Norway Trondheim area
Reputation: 0

Unread postAuthor: MaxuS the 2nd » Sat Jun 21, 2008 2:24 pm

The burst pressure of copper is over 1000psi.

I suggest you drill a hole in the end cap and using a bulkhead nut, clamp a spark plug into it.
If your chamber is too long though, it may cause DDT.

Edit: FFS spudfarm, that's the second post you've beaten me to in 30 seconds. I'm going to retire.
  • 0

Badman
User avatar
MaxuS the 2nd
Colonel
Colonel
 
Posts: 674
Joined: Sat Jan 19, 2008 3:59 pm
Reputation: 0

Unread postAuthor: SpudFarm » Sat Jun 21, 2008 2:27 pm

haha:D i am evil
  • 0

"Made in France"
- A spud gun insurance.
User avatar
SpudFarm
Donating Member
Donating Member
 
Posts: 2563
Joined: Sat Nov 04, 2006 9:39 am
Location: Norway Trondheim area
Reputation: 0

Unread postAuthor: DYI » Sat Jun 21, 2008 2:35 pm

Firstly, I think you should immediately scrap the idea of using oxy/hydrogen in such a low diameter pipe. Copper tube failures are relatively benign, even if you set off high explosives in them, but you don't want to waste time and money building a launcher that might explode on the first shot.

Use a larger diameter copper pipe to start with, at least 50mm or so. Don't make it any more than 4 times as long as it is wide. Then, you can probably go up to at least 8x (the nX system means very little with hydrogen, as the fuel takes up so much volume).

For sparkplugs, most of my designs are some variation of two copper rods passing through a 1/2" to 1/4" bushing (threads give the epoxy better grip) filled with JBweld. These designs have only ever failed when exposed to pressure of over 5kpsi and a 2km/s shockwave, so they should be good for any reasonable low mix hybrid.
  • 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: SNDM » Sat Jun 21, 2008 4:20 pm

The largest copper pipe I can get access to is 28mm.
Im having problems sourcing a union.
Im not willing to use a web order, so Im picking apart my local B&Q.

Are compression fittings alrights for this application?
  • 0


SNDM
Sergeant
Sergeant
 
Posts: 84
Joined: Tue Feb 26, 2008 4:05 pm
Reputation: 0

Unread postAuthor: MaxuS the 2nd » Sun Jun 22, 2008 4:00 am

SNDM wrote:Im not willing to use a web order


Then you will not save much money.
B&Q, are you from the Uk?
  • 0

Badman
User avatar
MaxuS the 2nd
Colonel
Colonel
 
Posts: 674
Joined: Sat Jan 19, 2008 3:59 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: SNDM » Sun Jun 22, 2008 3:36 pm

That I am.

The Far North, Scotland, as highway signs would tell me.
  • 0


SNDM
Sergeant
Sergeant
 
Posts: 84
Joined: Tue Feb 26, 2008 4:05 pm
Reputation: 0

Unread postAuthor: mark.f » Mon Jun 23, 2008 8:56 pm

Why not go with steel pipe? It'll be cheaper than copper of the same diameter (especially going into the 2" diameter range as DYI suggested), and you can install a spark plug by simply drilling a 1/2" hole and tapping with a 14 x 1.25 metric tap.
  • 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: MaxuS the 2nd » Tue Jun 24, 2008 6:04 am

SNDM wrote:That I am.

The Far North, Scotland, as highway signs would tell me.


Same, except I'm from the South East of England.
  • 0

Badman
User avatar
MaxuS the 2nd
Colonel
Colonel
 
Posts: 674
Joined: Sat Jan 19, 2008 3:59 pm
Reputation: 0

Return to Hybrid Cannon Discussion

Who is online

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

Reputation System ©'