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My 2nd one. (With some probs) :(

Built a combustion cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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My 2nd one. (With some probs) :(

Unread postAuthor: GeoNet » Mon Jan 06, 2014 6:48 pm

OK guys. Hello. Im pretty new in this forum (but not new to combustion cannons), so I will make my topic as constructive as possible.

My spudgun in its full glory

This is my 2nd combustion launcher and it is insane (for my live experience). The power coming out is like 5 times bigger than my last one although the volume of combustion chamber in my 1st gun wasnt enormously lager. So I assume that my other improvements were pretty much helpful to increase its power.

Ok I will try to show its parameters:
-100mm diameter and 600mm length for combustion chamber (so volume is like 5.19 liters, if my math is right ah and - spark component volume)
-50mm diameter and 1000mm length for barrel (extendable)
-12 V fan for faster venting
-20 KV and around 2Hz sparker with 2 sparks inside (ordered on ebay as grill igniter)
Spark gaps inside combustion chamber

And so I guess that rest of it is obvious.
-Maybe something that is worth attention is my handle where the sparker is attached. It is pretty much 50mm tube mounted through the 100mm one... The way I mounted sparker to this tube will stay a secret (obviously duct tape was used there) because it is a giant mess inside there.
cool-fancy handle/trigger

-Ah and of course I did use 2 screws to hold spark component in place and also used to carry spark inside combustion chamber (pretty coll huh? :idea: ) well you can see that wires inside look pretty messy but it is not at all... just screws attached to wires that are attached to spark gaps that are attached to each other. :)
wiring/spark component holder screws

So that was my informative part here! Thank you for your attention and im looking forward to see comments from you guys!
And sure I cannot make credit for any of this gun parts. More or less I copied 90% of technology from this Norway sick bastard nolife gunner dude (FYI this was meant to be hilarious not hateful ), whose introduction is unnecessary. I think...

Ok and now we come to part where I have to say I have 3 serious issues:
1) My spark dosent jump over frequently as it should! Every time capacitor is fully charged in sparker, it discharges regardless of fact that it does not have place to jump over and make spark. So many people would say that I have bad isolation and it has short-circuit somewhere, but I say big and fat NO! Originally I wanted to put in 3 sparks, but I bailed that idea because it just didnt jump over enough times to call it a normal spark. So I made it only with 2 sparks. But still... Sometimes even wihtout being inside my gun, it still liked to discharge without spark (ah forgot to mention that it should jump around 2 cm in length, but I have max 0.7cm space between both gaps together) So till now I assumed that all screw resistances are making my max spark gap smaller. Am I right or wrong?
Here's a vid that shows exacly how it like to jump over only sometimes. (when im filming this, im just holding my camera and spark button - no finger or hand movement. Later moved my head off light so you could understand what the hell are you looking at! :D )


2) End of combustion chamber has been blown out for 2nd time that makes it pretty sensitive spot in my gun and im thinking of better idea for holding it together. So conclusively I have brutally distroyed 2 fans that I was mounting in for too damn long. Previously I used 3 wood screws and chamber didnt handle my guns rapid explosion. Should I use more of them? Because Rest of connections are with same 3 screws and I can't see problem there.
Ripped cap

Here is pic with cap and how screw holes are ripped apart!

3) And the last one is about back handle movement.
Handle moves that way after each shot

In here you can see that after each shot, my guns handle is moving towards because not only combustion chamber is braced to handles but also barrel is braced to handle aswell so it wouldnt move around freely. It wouldnt be such a problem, but fact is that it moves on spark screw and it can harm wiring. I was thinking of putting some kind of pipe between both handles and so it wouldnt move so much!

I am really really looking forward to hearing from you guys! Please comment it. Say what you liked and what you didnt like so much, so I can be more objective for upcoming projects! And any kind of suggestions will be greatly appreciated.

Ok! So that's about it! It turned out to be pretty long topic (at least for me :D )

P.s. You have to excuse my bad English grammar mistakes. English isn't my 1st language... :roll:
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Re: My 2nd one. (With some probs) :(

Unread postAuthor: mark.f » Tue Jan 07, 2014 12:29 pm

1.) Some more details on your sparker would be helpful. If it is a BBQ igniter electronic type, there are multiple connectors, of which a few are "hot" and one is a common ground. If you're attaching your two wires to the connectors that are both hot, they could be at almost the same or a much lower potential than between a hot and ground.

2.) Those fittings are pretty thin, and wood screws really aren't the best solution. Machine screws can actually clamp the pieces together and have a higher tensile strength. 1/4" bolts can handle about 200 pounds in tensile so you would need around 8 to be on the safe side (assuming 120 PSI peak combustion pressure).

3.) Your idea seems like it would work... also, adding some rubber between where the pieces of pipe contact the chamber would as well, along with generally increasing the clamp pressure.

Good luck, hope it all works well. That norway bastard needs no introduction, although he doesn't post here much at all. :wink:
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Re: My 2nd one. (With some probs) :(

Unread postAuthor: GeoNet » Tue Jan 07, 2014 7:38 pm

1) Ok so My igniter is from triple A battery DC to 20KV AC coonverter with 4 ends at bottom seperated in two pairs...
As I tested out, between each pair there is about 1 cm long spark. When I put those two in chain (I really didnt know the right term for this one), they make 2x longer spark... Just like i would put 2 1.5 v batteries together to get 3 v. Here is a ling to exact product I ordered in ebay:
http://www.ebay.com/itm/Battery-Spark-I ... 2554f98a84

2) Thanks! I was thinking of just doubling screw ammount, but I think I will do like you say.

3) Ah clamps is the right term! :) And rubber is pretty good idea! Thanks!!

Well I assumed he isnt that much into spuds because of his inactivity in youtube aswell, but I will carry his knowledge legacy with my head held up straight in my country (I hope I didnt offend anyone, because I really dont know where he got info about this type of spud)

When I will finish it, I will put some pics in here and vids in youtube...
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Re: My 2nd one. (With some probs) :(

Unread postAuthor: dart guy » Thu Jul 24, 2014 6:11 pm

Clean out adapter may be a better idea, that idea with screws was pretty dumb. If you think about it the big clean out adapter has a huge surface area to hold things together, 3 or so screws realy don't have what it takes.... I bet that if you where to make it like a metered combustion like system you could just glue the end cap and then have a one way valve to fill it ( king of random made a tutorial on it) but make sure there's a coupling over the area where you drill the hole for the valve( apperently it is unsafe to drill through single walled PVC )
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