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 38 users online :: 4 registered, 0 hidden and 34 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Metal Chamber and Ignition

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
Sponsored 
  • Author
    Message

Metal Chamber and Ignition

Unread postAuthor: Grignacke » Mon Mar 07, 2011 11:20 pm

Hey guys, have you all ever had problems with steel chambers and high voltage ignition sources? What sort of insulation do you use?
  • 0

User avatar
Grignacke
Private First Class
Private First Class
 
Posts: 33
Joined: Sun Jun 20, 2010 3:26 pm
Reputation: 0

Unread postAuthor: Lockednloaded » Tue Mar 08, 2011 12:02 am

epoxy works well, but standard spark plugs can also be found in standard NPT threads
  • 0

User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Unread postAuthor: JDP12 » Tue Mar 08, 2011 12:04 am

or, you can usually get spark plug thread taps as well if you need to
  • 0

"Some say his pet elephant is pink, and that he has no understanding of "PG rated forum". All we know is, he's called JSR. "
User avatar
JDP12
Major General
Major General
 
Posts: 1943
Joined: Fri Mar 30, 2007 8:34 pm
Reputation: 0

Unread postAuthor: jackssmirkingrevenge » Tue Mar 08, 2011 12:39 am

  • 0

User avatar
jackssmirkingrevenge
Donating Member
Donating Member
 
Posts: 24225
Joined: Thu Mar 15, 2007 11:28 pm
Country: Holy See (Vatican City State) (va)
Reputation: 66

Unread postAuthor: Moonbogg » Tue Mar 08, 2011 2:00 am

I used a spark strip for my metal chamber. I supportd the spark strip with screws, and then fed the wires through another set of holes. The rubber coating of the wires is enough to prevent shorting. Epoxy was used to seal the holes and not for shielding.
  • 0

User avatar
Moonbogg
Major General
Major General
 
Posts: 1375
Joined: Mon Oct 13, 2008 10:20 pm
Location: whittier, CA USA
Reputation: 0

Unread postAuthor: motorfixer1 » Tue Mar 08, 2011 7:15 pm

On my all metal launcher, I drilled out steel 1/4m x 1/8"f reducer bushings and fed two electrodes through with .015 nomex around the outside and .045 fiberboard inbetween the two electrodes. I filled the remaining cavity wit PC7 epoxy and ran the whole assy. through a 30" of mercury vacuum chamber to remove voids while curing. Voids in high voltage insulation materials cause internal shorting and carbon tracking. Extensive research was done to get to this point with regard for pressure testing. The Spark bushings would easily withstand 150 psi air pressure and thread into the chamber via 1/4" npt half couplings welded to the sides of my chamber. Most folks have never ran their combustion launchers through any sort of pressure testing. If you have ever had a ball jam in your barrel you would know why this is so important. Check out my build pics if you are intersted. Happy Building, hope this helps.
  • 0


motorfixer1
Sergeant
Sergeant
 
Posts: 91
Joined: Wed Jul 07, 2010 5:28 pm
Reputation: 0

Unread postAuthor: Grignacke » Tue Mar 08, 2011 10:00 pm

So epoxy can, Moon, can withstand hybrid-level pressures, and an additional set of holes wouldn't weaken the chamber too much? (The cobras seem fine :P )

I may consider a similar, albeit less equipment requiring method, motor...
  • 0

User avatar
Grignacke
Private First Class
Private First Class
 
Posts: 33
Joined: Sun Jun 20, 2010 3:26 pm
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: Moonbogg » Thu Mar 10, 2011 1:08 am

Grignacke wrote:So epoxy can, Moon, can withstand hybrid-level pressures, and an additional set of holes wouldn't weaken the chamber too much? (The cobras seem fine :P )

I may consider a similar, albeit less equipment requiring method, motor...


The epoxy I use is only to surround the wire as it feeds through the hole. The epoxy has very little surface area. It just fills a tiny gap around the wire to make it air tight. The epoxy is not relied on in any significant way. Rubber cement would also work for this purpose. I would not fill a large hole or use the epoxy as a major part of the chamber and expect it to withstand the punishment. Some people do that, but I wouldn't trust it. I use it as a sealing compound only.
  • 0

User avatar
Moonbogg
Major General
Major General
 
Posts: 1375
Joined: Mon Oct 13, 2008 10:20 pm
Location: whittier, CA USA
Reputation: 0

Unread postAuthor: Lockednloaded » Thu Mar 10, 2011 11:52 am

I'm using an NPT spark plug for my hybrid ATM, you just have to look around for some standard threaded sparkplugs if you don't want to use epoxy
  • 0

User avatar
Lockednloaded
Major General
Major General
 
Posts: 1558
Joined: Thu Sep 03, 2009 9:38 pm
Location: Texas, USA
Reputation: 0

Return to Combustion Cannon Discussion

Who is online

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

Reputation System ©'