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 83 users online :: 4 registered, 0 hidden and 79 guests


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

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

The Team
Administrators
Global Moderators
global_moderators.png CS

Spark Gaps: Some food for thought

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

Spark Gaps: Some food for thought

Unread postAuthor: Pilgrimman » Mon Oct 15, 2007 10:11 pm

I have read that spark gaps that use points as opposed to flatter surfaces such as spheres tend to produce longer sparks. I am wondering if it'd be practical to use extremely pointy metal objects to increase the spark length. For all you drug addicts, you might use your spare syringes! :D What I'm unsure of, however, is whether a technique such as this would have a noticeable effect on the length of the spark, or is the improvement marginal?
  • 0

Yeah, we wouldn't want to anger the bees, now would we??

I HATE YOU BEES! I HATE YOU BEES! I HATE YOU BEES!

LMAO Classic!!!! I love Family Guy!
User avatar
Pilgrimman
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 481
Joined: Thu Jun 28, 2007 1:10 pm
Location: Grants Pass, OR
Reputation: 0

Unread postAuthor: shud_b_rite » Mon Oct 15, 2007 10:16 pm

I think this is only the case with static electricity. Because a sphere or pointy surface has much more space for charges to gather on it is more likely that sparks will be attracted/emitted from it. I dont think this increases the length of a spark (the length still depends on voltage) it is just a way of getting the spark to go where you want it, this is good for a lightening rod
  • 0

Airbeds... so many different uses
User avatar
shud_b_rite
1st Lieutenant
1st Lieutenant
 
Posts: 290
Joined: Tue Jan 30, 2007 7:10 pm
Location: Auckland, New Zealand
Reputation: 0

Unread postAuthor: jimmy101 » Tue Oct 16, 2007 12:01 pm

The breakdown voltage between two eletrodes is a function of the radius of curvature of the electrodes. Pointy electrodes will spark at a lower voltage than will blunt electrodes.

So, Pilgrimman, you have it backwards. To get the longest spark possible you want dull electrodes. The optimal shape would be a big-ass sphere like those used in van der Waal generators.

But, the length of the spark probably doesn't affect the perfromance of the performance of a gun all that much. At, least with reasonable length sparks. 1/16", 1/8", 1/4", 1/2" probably all work about the same.

Of course, if you could get a 10" spark that might be useful. The tricky part with a very long spark is keeping it from sparking through the wire insulation, between connectors, though the PVC, to you ...

EDITED 17 Oct, 07, the para highlighted is backassward.
Pilgrimman was right, sharp and pointy to jump the longest possible gap at a given voltage.
  • 0

Last edited by jimmy101 on Wed Oct 17, 2007 2:29 pm, edited 1 time in total.
Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: psycix » Tue Oct 16, 2007 4:12 pm

I think a pointed electrode allows for a longer spark distance because of the electric field aroud the point.
The field will concentrate on that one point when using a needle and thus make it easier for electrons to jump over.
When using flatter electrodes like spheres for example there is only a weak electric field around the whole sphere.
  • 0

User avatar
psycix
Donating Member
Donating Member
 
Posts: 3684
Joined: Mon Jun 25, 2007 7:12 am
Location: The Netherlands
Reputation: 0

Unread postAuthor: Pilgrimman » Tue Oct 16, 2007 6:23 pm

@ jimmy

I know it won't affect performance normally, but I thought this might prove useful for hybrid ignition, since the maximum spark length shortens under pressure. The reason I posted it here is because I figured there might be more replies, as combustions could use the technique, and hybrid builders have usually dealt with this type of situation.
  • 0

Yeah, we wouldn't want to anger the bees, now would we??

I HATE YOU BEES! I HATE YOU BEES! I HATE YOU BEES!

LMAO Classic!!!! I love Family Guy!
User avatar
Pilgrimman
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 481
Joined: Thu Jun 28, 2007 1:10 pm
Location: Grants Pass, OR
Reputation: 0

Unread postAuthor: jimmy101 » Wed Oct 17, 2007 2:16 pm

Pilgrimman wrote:@ jimmy

I know it won't affect performance normally, but I thought this might prove useful for hybrid ignition, since the maximum spark length shortens under pressure. The reason I posted it here is because I figured there might be more replies, as combustions could use the technique, and hybrid builders have usually dealt with this type of situation.

Yep, it'll be much easier to get a spark in a hybrid with pointy electrodes than with blunt ones.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Unread postAuthor: jimmy101 » Wed Oct 17, 2007 2:22 pm

psycix wrote:I think a pointed electrode allows for a longer spark distance because of the electric field aroud the point.
The field will concentrate on that one point when using a needle and thus make it easier for electrons to jump over.
When using flatter electrodes like spheres for example there is only a weak electric field around the whole sphere.


I reread my previous post and psycix is correct. When you want to get a spark you use pointy electrodes. When you don't want to get a spark you use spherical electrodes.

Pointy electrodes will spark across a larger gap at a given voltage then will spherical/dull electrodes.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Sponsored

Sponsor
 


Unread postAuthor: Pilgrimman » Wed Oct 17, 2007 5:32 pm

I thought so, but I wasn't sure, and I wasn't going to question someone with 4x my post count! :D So, what's the consensus? Would using syringes or similar increase max spark lengths at a given voltage? I'm leaning towards "yes", but I'd like others perspectives based on the above posts.
  • 0

Yeah, we wouldn't want to anger the bees, now would we??

I HATE YOU BEES! I HATE YOU BEES! I HATE YOU BEES!

LMAO Classic!!!! I love Family Guy!
User avatar
Pilgrimman
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 481
Joined: Thu Jun 28, 2007 1:10 pm
Location: Grants Pass, OR
Reputation: 0

Unread postAuthor: jimmy101 » Thu Oct 18, 2007 11:49 am

Yes, using a syringe needle would increase the spark length, or decrease the voltage required for a given spark length.

Instead of syringe needles I would just use sewing pins. They are sharper and cheaper.
  • 0

Image

jimmy101
Lieutenant General
Lieutenant General
 
Posts: 3128
Joined: Wed Mar 28, 2007 9:48 am
Location: Greenwood, Indiana
Country: United States (us)
Reputation: 7

Return to Combustion Cannon Discussion

Who is online

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

Reputation System ©'