Ignition Question

[Rukus]

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

[hi]

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.

[pyrogeek]

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)

[hi]

pyro geek was talking about burst disks.


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

[TwitchTheAussie]

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.

[Rukus]

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

[jimmy101]

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.