SpudFiles

looking for insight. ive only made a couple of potato cannons one of which burnt off my eyelashes, one eyebrow, and half of my facial hair.

ive made a proposition with a few of my friends and it seems a competition is in order.

im looking for pocket aces.

i know the ratio of accelerant to oxygen is fundamental but i dont know what these formulas may be. im not walter white and i am no chemist. i was considering a 50/50 combustion chamber where i could just turn a valve and sufficient mixture is complete. but hair spray seems.......uncreative. (it also messes up your contacts because its uber sticky) i was considering propane. but that seems a bit overkill. im afraid of the chamber exploding or the volume depleting combustibility, ive noticed my grill dosnt like to start sometimes when there is too much propane.

(oh i plan on covering it it duct tape to minimize shrapnel and to make it look AWESOME!)

i dont need PVC shrapnel in my neck. so something too intense is out of the question even with scheduled 80 PVC. BUT I DO have a cracker. or rather a whipped cream whipper. if you dont know what that is its an apparatus that allows you to "crack" or release nitrous oxide cartridges. so i have that option at my disposal

im thinking this may be precisely the upper hand i need but im afraid of the explosive potential. then again i could be entirely wrong that this is a sufficient catalyst for some explosive force. mind you anytime i pretend to be smart its shit i learned from bill nye when i was 12.

so basically my concept is the standard potato cannon. but i intended on separating the combustion chamber into two parts with a valve. im also unsure of what accelerant would be ideal. even butane (lighter recharge canisters) seems like an option but like i said id like some more experienced opinions so i dont have to set up some test shots from a considerable distance behind some plexiglass

ready go.

Metering propane is not going to blow your cannon up. Search for a thread on syringe metering. There's more than enough info on this site to suit your needs. I would also add a chamber fan to mix the fuel well. Most accelerants you would work with wouldn't produce enough power with a normal air mix to blow up a normal PVC cannon. Also, a 50/50 mix is 10+ times too much fuel for the amount of air. The "explosive limits" for propane is 2.37–9.5% fuel to air.

thanks for the advice. how about the nitrous in conjunction with another fuel?

and FYI "Sarcasm is the body's natural defense against stupid." mockery is the word your looking for sarcasm has many more applications.

I wouldn't use an oxidiser other than atmospheric oxygen in a PVC launcher. And there's better oxidisers than N₂O around.

If you arena't aware, MrT has that in his sig, he wasn't directing it to you.

DekuScrub wrote:thanks for the advice. how about the nitrous in conjunction with another fuel?

and FYI "Sarcasm is the body's natural defense against stupid." mockery is the word your looking for sarcasm has many more applications.

That's a specific quote from a t-shirt sold by Wal-Mart, but yes it has many more applications.

Assuming your friends don't really know what they're doing, you won't need anything fancy to beat them. Just use a good chamber fan, multi-point ignition, metered propylene, and a design which you've roughly optimized in HGDT.

What DYI said, though a meter and patience (to let the fuel mix fully, in place of a chamber fan) will get you 95+% of the way to the maximum performance for a given gun geometry and ammo. The choice of fuel has relatively little affect on the gun's performance.

The Spud Wiki has all the info you need. For fuels see:
http://www.spudfiles.com/spud_wiki/inde ... n_Spudguns

For metering (from simple to complex) see:
http://www.spudfiles.com/spud_wiki/inde ... Fuel_meter[/url]

Edit: An often overlooked simple mod that'll boost performance is to put a slight bevel on the inside of the muzzle. Put a full bevel on the outside to act as a spud cutter for loading the ammo. The slight inner bevel cuts the spud a hair too big, which boosts static friction (and sealing) and that boosts performance.

awesome you guys rock, i still waanted to see what the nitrous would do tho