SpudFiles

I built this cannon a couple of months ago because I had some spare cash and nothing to do with it, so I decided to build my first combustion. Before, I built a sprinkler valve pneumatic and a high pressure spring loaded ball valve pneumatic. Ever since I've built this cannon I've now been mainly interested in combustion cannons. I just love the easy power and quick refueling (no bike pump hassle). So here are the basics of my cannon:

Specs
Chamber: 3" ABS w/ DWV fittings
Barrel: 1 1/2" ABS
Fuel: Metered propane
Ignition: Duel spark Chamber Short w/ BBQ igniter
Venting: 2" Ball valve and 60mm fan w/ 9v power supply
Ammo: Round white potatoes or Purple potatoes

You guys are probably wondering how I attached the ball valve so here's my explanation... the ball valve is PVC cemented to a 2" piece of PVC pipe which runs pass a modified 2" ABS bushing. On the other side of the bushing inside the chamber, is the other half of the ball valve that was sawed off. This is cemented onto the 2'' PVC pipe on the other side of the modified ABS bushing. This can be thought of as securing a bolt by screwing on a nut on the other side of a piece of wood. The 2" PVC pipe is glued to the the ABS bushing surrounding it with JB Weld.

One thing I like what I did was how I stored all of the electronics. I managed to stuff the BBQ igniter, fan switch, 9v battery+holder,and the ignition and fan electrodes. I did all this without having a spark from the igniter jump, by dividing the entire pipe with a bit of thin poplar wood. To secure the electrodes (small bolts that go into the chamber) I had to drill on the other side of the pipe so I could use a screw driver and that is why I have a section of 1 1/2" ABS pipe over the electronics tube.

About the propane meter... The operation is a little different because you open the first valve and fill it to about 66psi, then you shut it and open the second one. I made it just a tad bit bigger so 66psi is the optimal meter pressure. This helps on colder days.

Here are the pictures:
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With there being no handle on the gun, it might look as if it would be awkward to hold, but actually it is held like a rifle. I put the ball valve against my shoulder, then put my left hand on the propane tank and with my right hand I reach for the BBQ igniter.

Not a bad effort, especially for your first combustion!!

The chamber/electrical pod/propane tank "bunch-up" looks, well, like a bunch-up...missing a defined structure. The pressure gage looks like it isn't readable in the position it's in and the big ball valve air inlet in the rear is way overkill size wise.

However, my guess is that your shots are consistent and powerful if your meter is designed correctly. A longer barrel, maybe another foot or 2, no more for practicality reasons only, would offer another noticable performance increase.

starman wrote:Not a bad effort, especially for your first combustion!!

Agreed, a sterling effort.

In fact, I would agree with all of Starman's points. The only thing I would personally add is it would probably benefit from slightly more ergonomic handles.

very nice indeed, although maybe you could have gone for a cheaper smaller ball valve but it looks very well made for a 1st combustion.

Thanks for the quick responses!

Ya the ball valve was definitely overkill, but I had it laying around and it made for a comfy shoulder stock. I also didn't plan out the position of the propane tank and electrical pipe to well, but if I build a huge combustion (hopefully) I will take these things into account.

Looks very good! Although I have one suggestion:

3" SCH-40 (ABS, PVC, whathaveyou) make a great holder for propane tanks. If you were to integrate the propane tank holder and electronics holder into some 3" ABS, then clamp that on the side of the chamber, it would look better in my opinion.

Good job either way!