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 71 users online :: 4 registered, 0 hidden and 67 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

Ignition Question

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

Ignition Question

Unread postAuthor: Rukus » Sun Aug 05, 2007 7:41 pm

Hi guys....just signed up for the forum. I've been reading allot of old posts, picking up several good tips.

My new gun: 4" x 24" PVC Schedule 40 Chamber, 2" x 72" Schedule 40 PVC barrel.

I was testing it the other day and the first 2 spuds went way the heck out there....maybe 100 to 150 yards. Not positive on the distance as I fired them out into a lake from our cottage lawn.

After the second spud i kept getting bloopers where they would only go like maybe 50 yards. I started messing with different amounts of Aquanet Hairspray thinking I had to rich a mixture. I tried both increasing and then decreasing. Same problem Boopers. I found that my ignitor (BBQ sparker) had a bad wire. I have a single BBQ ignitor at the rear of the cannon. It the kind that you would install in a grill. Its mounted from the side where it goes through the rear fitting and the pipe. I brought the wires out through a small hole and plugged it.

The question I have is can ignition cause poor performance with a spud gun? It sounded a few times like it really didn't ignite well when I got the rash of Bloopers. I cant get a tazer here in NY, so I figured I'd build a ignitor with a car ignition coil and give that a shot.

Second question, what kind of distances should I expect with my rig? I"m using Aquanet Hairspray. Does Propane make that big a performance difference for me to bother building the metering rig?

Thanks in advance....appreciate any help you guys could add :)
  • 0


Rukus
Private
Private
 
Posts: 5
Joined: Mon Jul 30, 2007 12:24 pm
Reputation: 0

Unread postAuthor: hi » Sun Aug 05, 2007 10:38 pm

the bbq is NOT the problem.

if it ignites then it ignites, period.

its the mixture. its has to be just perfect or it wont work.

do you have a blow torch? you can spray propane directly into the chamber. hairspray in my opinion is the worst stuff to use because it makes the chamber all goopy and it isnt very powerful.

if you arent ready for propane, use AXE deoderant. its a little better than hairspray and it doesnt goop up the chamber as much.

the other thing is that because the chamber is so big, it probably isnt mixing up very well.

i know the gun is 8 feet long, but try this-

spray about half the fuel in, then put the cap on and wait about 5 seconds, then spray the rest in. that should make it mix a little better.

good luck.
  • 0

"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
User avatar
hi
Major General
Major General
 
Posts: 1619
Joined: Thu Feb 01, 2007 9:28 pm
Reputation: 0

Unread postAuthor: pyrogeek » Sun Aug 05, 2007 11:18 pm

Installing a chamber fan and/or switching to a better fuel like propane or butane, maybe even MAPP would greatly improve performance.
Also, if you are just shooting spuds, putting a smaller diameter barrel and using shorter sections of potato will give longer distance. Dual ignition would possibly help. I think it would give higher velocities, but I don't have a chrono or anything to test with. If you want a taser, go smuggle one in and just transfer the components into a project box, nobody can say anything then. If you need help with that, I'm sure something could be worked out. Just don't mess with car ignition systems or flybacks out of TVs or CRT monitors. They're dangerous and we don't need anyone dying from spud guns.
Burst discs will also help, but will make the gun very loud. I still need to get around to making some up for mine, I have yet to try them.

Any questions, email me at timbabeu2005 at* yahoo.com
* (@ symbol removed to prevent spam)
  • 0

I'm weird, I know it, you don't need to tell me.

pyrogeek
Lieutenant Colonel
Lieutenant Colonel
 
Posts: 457
Joined: Sat May 13, 2006 7:43 pm
Location: moline Illinios
Reputation: 0

Unread postAuthor: hi » Sun Aug 05, 2007 11:21 pm

pyro geek was talking about burst disks.


i found that those aluminum cup cake holders work well for 2'' barrels.
  • 0

"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote

you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
User avatar
hi
Major General
Major General
 
Posts: 1619
Joined: Thu Feb 01, 2007 9:28 pm
Reputation: 0

Unread postAuthor: TwitchTheAussie » Mon Aug 06, 2007 1:58 am

Actually Ive found that residue building up on the spark plugs can be a problem. I dont have aquanet tho so I really cant pass judgment but like Hi said the mix has to be perfect.
  • 0

Raise your horns if you love metal.
spudgunning is like sex, once you've tasted, you can't wait til next time.
-
CpTn_lAw
User avatar
TwitchTheAussie
Brigadier General
Brigadier General
 
Posts: 980
Joined: Tue Feb 06, 2007 3:23 am
Reputation: 0

Unread postAuthor: Rukus » Mon Aug 06, 2007 6:05 am

Thanks for the suggestions guys. :)
I'll try getting a small fan in there and see if that helps out as was suggested. I'll also try spraying half the propellent and then giving a second shot later on.

Regarding the smaller diameter barrel question, wouldn't that push my
C:B ratio too high and actually loose distance?

Regarding the distances. Is there any idea as to how far this might throw a tater?

We have a small island at the lake that is like 300 or 400 yards away. It would be fun to be able to hit that from the cottage :)

Thanks for the replys. Nice to find a place to get help and suggestions :)
  • 0


Rukus
Private
Private
 
Posts: 5
Joined: Mon Jul 30, 2007 12:24 pm
Reputation: 0

Unread postAuthor: jimmy101 » Mon Aug 06, 2007 9:57 am

Like others said, the problem is not the ignitor, it is either the mixture or the mixing.

There is a simulator for basic combustion guns; EVBEC.

For your gun dimensions and assuming a 100g (3.5oz) spud, EVBEC gives 412 fps muzzle velocity.

Now, if Joanna (hint, hint) would release her latest trajectory calculator you could use that to estimate the optimal launch angle and maximum range.
  • 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
 


Return to Combustion Cannon Discussion

Who is online

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

Reputation System ©'