What started as this
evolved into this
and finally was fabricated into this
And this pic gives you a better idea of it's scale!
The cannon was dubbed "10 gallon" originally because the chamber volume was to be appx 10 gallons of air. I splurged a little later on and it is now appx 11 gallons of air. Originally the air tanks were to be 6 feet long, and now they are 7 feet long.
Primary ammo will be 20-24oz soda bottle's filled with whatever may end up in them. Also soda can's fit with a very light layer of wadding, the same goes for the 16.9oz water bottles that are ever so common these days.
The cannon uses a 4" cross where the normal "Tee" would be on all the t-valve cannons. This allows me to draw air in from twin straddling air tanks instead of one big air tank.
The valve is pretty much your typical piston valve, Only it's a hearty 3 full inches of porting. To make it I started with two 3" to 2" bell reducers, cut down quit a bit to reduce the overall length - Then for the sealing surface I used a trimmed down Suction Cup pick up device like they sell at Harbor Freight for $3 and it works GREAT! It's about 4.25" in diameter originally, and is made of a decent durometer rubber that is designed specifically for sealing in air (or creating a vacuum), so I thought hey why not? I took my time in fabricating it and ended up with this.
Piston weight came to around 1lb 4oz. To provide a sufficient bumper for this (a major concern of mine, as my last "large cannon" failed catastrophically due to a faulty insufficient bumper) I ended up using two 1" pieces of radiator hose for a car - with different sized slits in each piece to allow a "progressive" bumper effect.
Now this cannon weighs almost 150lbs or more (havent put it on a scale yet - haven't found a big enough "bathroom scale" lol). To allow myself to adjust the angle of firing this beast, I decided right away I WASN'T going to jamb stuff underneath the front of the cannon like oh so many people on here doing - mainly because I wasn't looking to lift all the heft of this beast every time I wanted to change the angle.
To solve this - I purchased a scissor jack like the kind they put in cars for changing spare tires.
Which I later modified into this to allow mounting points to attach it to the frame.
The pivot, lifting arm, and scissor jack are all best seen in action in this picture
So there you have it - from imagination - to completion... all in 2 years! I was able to draw this complete cannon up in SolidWorks, a CAD program and from there I was able to see what would work - and what wouldn't before I ever assembled anything. I will now work on painting it, and recording damage shots!
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), and will really reduce some of the strain from your shooting sessions, although maybe not time...
