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Doesn't shoot very far

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Doesn't shoot very far

Unread postAuthor: thesuffering » Wed May 23, 2007 8:56 pm

okay, so we followed the instructions from spudtech.com, loaded it up...and well it shoots approximately 20ft...i know we can acheive more...what could i be doing wrong? how much propellant (aquanet hairspray) should be used? how far should the potato be loaded into the barrel?
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Unread postAuthor: ShowNoMercy » Wed May 23, 2007 8:59 pm

The projectile should be put all the way down the barrel, and I have no idea what amount of aquaspray you should use. This is why we build pnuematics, ease of operation.
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Unread postAuthor: jackssmirkingrevenge » Wed May 23, 2007 8:59 pm

posting a few more details/pictures of your launcher will help you get more relevant advice.
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Unread postAuthor: Pete Zaria » Wed May 23, 2007 8:59 pm

@TheSurffering,
Welcome to the forums. Hope you stick around.

Believe it or not, most people use way too much fuel in aerosol guns - a half-second spray is frequently enough, but it depends on the size of your chamber. The reason you're not getting much distance is that your air/fuel mixture is not optimal. Try less fuel and see if thats better. If not, try more, but I'd bet you're using too much rather than not enough.

I recommend avoiding hairspray - it leaves gunk inside the chamber after awhile. Aerosol deodorant is better, but carb cleaner / engine starter fluid is the best. Of course, metered propane is accepted as the gold-standard for combustion spudgun fueling.

The potato should be loaded as far as it'll go without falling into the chamber. Most of us put a mark on a stick for the right distance, or put a screw at the bottom of the barrel to prevent the potato from going through into the chamber.

This site has a HUGE amount of info available - use the Search box and check the Wiki whenever you have a question. If you don't find an answer there, ask us!

Peace,
Pete Zaria.
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Unread postAuthor: thesuffering » Wed May 23, 2007 9:05 pm

jackssmirkingrevenge wrote:posting a few more details/pictures of your launcher will help you get more relevant advice.


here are the specs we followed
10" of 4" SCH40 PVC water pipe (chamber body)
36" of 1 1/2" SCH40 PVC water pipe (barrel stock)
4" PVC coupler
4" x 1.5" PVC bushing (if not available combine two, like 4x3 and 3x1.5)
4" PVC FSxFNPT adapter (clean-out adapter)
4" PVC MNPT threaded plug
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Unread postAuthor: kingjames488 » Wed May 23, 2007 10:24 pm

From the reasons I know of that cause that...

1. not very air tight

cause- bad joints, lose amunition

solution- use a sabot or cut the potato better, If it's a construction problem your gonna have to either struggle with patching holes or toss it and buy materials for a new one...



2. bad fuel-air ratio

cause- using too much or too little fuel

solution- use more/less... unfortunatly it's hit and miss



3. bad c:b ration (chamber to barrel)

cause- a bad design

solution- build a better one...



what did you try to shoot??
how big is your barrel/chamber exactly??
what fuel did you use??
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Unread postAuthor: thesuffering » Thu May 24, 2007 8:56 am

we played with it yesterday, and realized our problem....

we werent loading the potato very far into the barrel, it was only at the tip....as soon as we loaded it properly the potatos flew at least 100+ yards. Im thinking bigger and better guns are to come :twisted:
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Unread postAuthor: ShowNoMercy » Thu May 24, 2007 9:27 am

Thats good to know, try and make some pnuematics, they are more fun and much more easier to use. But if you prefer combustions then build on. Try and get some propane fueled ones. :wink:
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Unread postAuthor: thesuffering » Thu May 24, 2007 9:45 am

im definately happy with it...and it was a good learning experience....
two days ago, when we were initially building it, we tried test firing, and nothing....took off the barrel to check for spark and looked directly over it (really really really dumb thing to do) well i got spark....and a fireball to my face....after burning my eyes, burning off my eye lashes, and almost my eye brows, i gained a lot of respect for saftey with these things. i really dont know what i was thinking when i did it, but it was the first and last time that will ever happen. burning your eyeballs causes a lot of pain....good thing it wasnt too bad according to the dr.
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Unread postAuthor: ShowNoMercy » Thu May 24, 2007 9:48 am

What were you thinking? That has to be the dumbest thing to do ever! Ok enough flaming, but yeah dont do that again. As if I need to tell you that.
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Unread postAuthor: jackssmirkingrevenge » Thu May 24, 2007 9:59 am

if it has a barrel, the basic rule of thumb is never, ever, EVER look down the barrel. There is no prestige in earning yourself a Darwin Award.
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Unread postAuthor: thesuffering » Thu May 24, 2007 10:25 am

ShowNoMercy wrote:What were you thinking? That has to be the dumbest thing to do ever! Ok enough flaming, but yeah dont do that again. As if I need to tell you that.


hah....i deserve it. i really wasnt thinking.
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Unread postAuthor: kingjames488 » Thu May 24, 2007 7:03 pm

lol, I look in the back, at the highest angle possible to check my spark...
I need a better one, thats my prob is my fuel isn't ignighting.
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Unread postAuthor: SpudBlaster15 » Thu May 24, 2007 7:21 pm

I think we should compile a list of people who have burned themselves after attempting to check the condition of their ignition setup. I have read similar stories at least 50 times. :lol:
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Unread postAuthor: VH_man » Thu May 24, 2007 7:31 pm

Yeah. i dont know anyone who made a combustion and HASNT done that. mabey there are some on this fourum, but.....
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