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 53 users online :: 6 registered, 0 hidden and 47 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Compressed air spark gaps

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

Compressed air spark gaps

Unread postAuthor: Moonbogg » Sat Jan 03, 2009 5:23 pm

In a 3xi chamber, would the spark gaps have to be closer than at atmosphere? Is there additional resistance due to the thicker air? Can it be figured out without trial and error?
  • 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: Sticky_Tape » Sat Jan 03, 2009 5:30 pm

the sparkgaps do need to be smaller I discovered that in my mini it was hard to get 4x to ignite.
From the spudwiki hybrid cannon page:The ignition of a hybrid gun is more difficult than a normal combustion, as the length of a spark is roughly inversely proportional to the density of the gas. This necessitates the use of high-powered ignition source such as a stungun, flyback circuit, or other high-voltage source; grill igniters frequently won't jump a spark gap in pressurized fuel/air environments.

You can use piezo sparkers for hybrids I did. But you have to keep the spark gap small and use low x mixes.
EDIT: Yeah sparks are fun but you can also use steel wool and a 9volt batterie it was done before by daccel I think.
  • 0

You can tell how awesome a cannon is by the pressure used.
http://www.spudfiles.com/forums/high-pr ... 12803.html
xnt rnm ne z ahtbg
User avatar
Sticky_Tape
Brigadier General
Brigadier General
 
Posts: 1175
Joined: Thu Jan 31, 2008 6:35 pm
Location: Sydney, Nova Scotia, Canada.
Reputation: 0

Unread postAuthor: Moonbogg » Sat Jan 03, 2009 5:38 pm

OK thanks. I might get a more powerful stungun and also shorten the spark gaps. I will be using 3 gaps, I think this ought to work.
  • 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: Hotwired » Sat Jan 03, 2009 7:00 pm

Double the pressure halve the distance of the spark gap.

...and so on.

When you get to the pressures where you really can't be bothered trying to measure a spark gap in fractions of a millimetre you can go from high voltage low current arcs to low voltage high current glow wires.
  • 0

User avatar
Hotwired
Lieutenant General
Lieutenant General
 
Posts: 2599
Joined: Fri Oct 13, 2006 5:51 am
Location: UK
Reputation: 0

Unread postAuthor: Moonbogg » Sat Jan 03, 2009 7:26 pm

Hotwired wrote:Double the pressure halve the distance of the spark gap.

...and so on.

When you get to the pressures where you really can't be bothered trying to measure a spark gap in fractions of a millimetre you can go from high voltage low current arcs to low voltage high current glow wires.


Awesome. Thanks for that tip. First time i've heard that.

Edit...will the sparks still be as effective if they are super tiny? As long as there are 3 of them, I would think it would be good still.
  • 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: daccel » Mon Jan 05, 2009 12:13 am

Don't quote me, but I'm sure as long as the sparks are there they will still work, just marginally slower ignition rate.

Yes, I used steel wool and 9v to ignite 8.5x mix. The downside is it has to be replaced each time.

How high a mix can you go before a stungun or similar circuit becomes ineffective?
  • 0

User avatar
daccel
Donating Member
Donating Member
 
Posts: 238
Joined: Thu Oct 11, 2007 9:51 pm
Location: BC, Canada
Reputation: 0

Unread postAuthor: jimmy101 » Mon Jan 05, 2009 5:41 pm

Moonbogg wrote:t...will the sparks still be as effective if they are super tiny? As long as there are 3 of them, I would think it would be good still.

A spark is a spark. Big-ass spark, tiny little spark, doesn't make much difference. You need less than 1mJ to ignite propane in air. The propane either ignites or it doesn't. Adding the extra 100mJ of a big ass spark doesn't make a bit of difference considering the combustion process is going to be generating thousands of joules.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3127
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Sponsored

Sponsor
 


Return to Hybrid Cannon Discussion

Who is online

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

Reputation System ©'