SpudFiles

[center][/center]i have some problem with my spud gun. if i'm not fill the chamber with much fuel it doesn't work. and sometimes the igniter spark doesn't work. can you help me to fix my problem? my chamber make from pvc pipe 1,5 diameter and 17 inch long.
you can visit my blog and i hope you comment for how to fix my problem
but my spud gun not bad for launch marble.

The small chamber volume will be a problem with aerosol spray. A typical potato launcher has a much larger chamber volume, and even that is tricky to get just the right amount.

You will need a fuel metering system.
http://www.spudfiles.com/spud_wiki/inde ... Fuel_meter

I haven't used the syringe method, but the other two. Any will work, it just depends on what you have lying around, or what will be the cheapest.

thank you. but is this the problem? maybe i put the screw for igniter too far from fill port? or i make chamber too long then the barrel too short? i use methylated as my fuel

this my blog : http://www.marblespudgun.blogspot.com

[youtube][/youtube]

For science!

Looks good! As others have mentioned, using a better fuel and a way to measure the correct quantity will give more reliable performance. A chamber fan will also help with fuel mixing. Since it is such a small chamber, you can also use something like a small air pump with a check valve to vent the chamber in between shots.

EDIT: http://www.spudfiles.com/combustion-can ... c1713.html

ok thank you sir. i will try it. but i'm still confused about the function of chamber fan. is that function for blow the air from outside chamber? or make the chamber to be cold temperature? hehe. sorry. it's my first time make spud gun.

thank you sir but i'm still confused about the function of chamber fan. is that for blow air from the outside chamber or make chamber temperature to be cold?

Looking it up is an option ( I'm being friendly about this because I don't want gunfreak flaming you, also is he a mod?)

satriyo wrote:thank you sir but i'm still confused about the function of chamber fan. is that for blow air from the outside chamber or make chamber temperature to be cold?

A chamber fan is used to mix up the fuel air mixture and to exhaust the burnt gases after firing the cannon.

@dart guy No gun freak is not a mod.

owh ok. thank you sir. yesterday i try to make fuel injection, but it's not powerfull. so you have idea for make injection fuel system?

satriyo wrote:owh ok. thank you sir. yesterday i try to make fuel injection, but it's not powerfull. so you have idea for make injection fuel system?

JSR wrote:[youtube][/youtube]

yesterday i try it. but it still not powerfull sir

Start exspiermenting with different fuel mixtures, a little less, a little more...As CS stated above it may be a chamber volume issue.

When you say "not powerfull" what are you getting out of it now? Does the marble roll out of the barrle and drop to the ground at your feet? Will the marble go through a piece of wood?

The only issues with fueling are getting the right mixture (which is easily done with a syringe like you have already done) and getting that mixture to be homogenous (which is the purpose of the chamber fan). If you haven't installed a chamber fan, that could very well be your problem. If you are using butane as a fuel, multiply your chamber volume (measure it by filling with water and measuring) by 3.13% (since injecting fuel displaces air with syringe fueling, that's a little lower than 3.23%) to get the volume of butane gas you need.

Knowing your chamber volume accurately is another issue with small chambers.

A mixture fan can come from a number of places but finding one that will fit in 1.5" pipe can be tricky. A small PC cooling fan might be able to fit... look for one on an old graphics card or something similar, since you want a brushless fan (PC cooling fans are brushless and don't produce sparks). You can cut the cage off of the fan also. If you can't find a brushless fan/motor a small toy motor or motor from the vibrator in a phone running on the rated voltage or less doesn't produce a whole lot of sparks which could ignite your mixture and can be sealed up without worrying about them overheating for short run times.

Good luck with your project!

actually i mean not powerfull is, fuel in the chamber is not make total combustion. every i'm shoot marble it has rest. so this is the problem. i can shoot twice until three times on single fill chamber. hehe it make me confused. i'm put 2 igniter spark in my chamber. i'm put 2 igniter spark because i hope it can make total combustion. please help me sir