SpudFiles

I'm planning to make a combustion cannon, and all of the designs on the internet has the fuel (hairspray or deodorant) load from the back. Is there anything wrong with putting a t-joint or a ninety degree bend on the back and loading through that? Or were those designs made so it would be easier for a newbie to build/fire?

Of course you could. If you're using an aerosol fuel the mixing may be less reliable though.

would a fan (mostly) fix that problem? It would only need to be mixed enough to ignite when sparked, correct?

Yes. If your installing a fan you could go the whole nine yards and add a spark strip and metered propane injection.

geniusbomberman wrote:It would only need to be mixed enough to ignite when sparked, correct?

Depends, if you're talking about "spray-n-pray" type performance than any BOOM is good.

If you are talking about getting the most out'a the gun then no, the performance will be much better with well mixed fuel and air.

Why would you want an elbow or T to fuel through? How would you imagine that making fueling easier?

If you don't want to fuel through the cleanout you can just install a schrader (tire tube type) valve and fuel through that. If you remove the valve stem you can insert a syringe needle through the schrader. The screw on cap for schraders can easily handle the pressure the gun generates when fired.

I don't know about metered injection of a first cannon, but if you have a good HV ignition and a fan, definately use them. They add a lot of power.

Biopyro wrote:I don't know about metered injection of a first cannon,

Why not? It only costs about $5.

I remember how shocked I was at the power increase I saw when adding a chamber fan and 3 gap spark strip. Seriously, it was no joke. My first cannon gave off like a low pitched "POOM" with really disappointing power. I remember a tennis ball only flying about 75-100ft max. I thought metered propane cannons were just over hyped and just sucked by nature. After rebuilding the same style cannon with the upgrades, the blast turned into a very loud and very sharp sounding BANG! The range of the cannon was completely surprising to me and caught me off guard. I thought I had really built something unique and unusually powerful somehow lol.

Moonbogg....
I suspect the biggest boost in performance came from the fan. Mixing is that important. Proper fuel ratio and air movement during firing help but not nearly as much as good mixing.

jimmy101 wrote:Moonbogg....
I suspect the biggest boost in performance came from the fan. Mixing is that important. Proper fuel ratio and air movement during firing help but not nearly as much as good mixing.

Yeah I totally agree. I can just immagine the gas floating about in a concentrated lump after injection without a fan.