Posted: 04/06/2010 12:30 PM Post subject: copper combustion cannon
Joined: 23 Nov 2008 Posts: 183 50.87 Spud Bux
Copper combustion cannon:
As I’ve Already built pneumatics and a hybrid I thought I’d give a straight up combustion a go. This is a bit of a spare parts cannon, the only parts I bought for it were the chamber fan and piezo sparker, the chamber is the aluminium suppressor from my first pneumatic and I chopped the barrel up for ammo, most of the rest is copper pipe which I had lying around. The main aim here was for something compact and quick and easy to shoot, thus the use of butane over propane as it's available in a much smaller canister. Power was a secondary concern but I was pleasantly surprised by the destruction I managed to achieve
The 38mm chamber fan is mounted directly to the end cap (acetal), ignition is a piezo sparker with two gaps in the spark strip.
The chamber fan is powered by a rechargeable 10AA battery pack, a bit overkill but I will be using it in another project. The grip is a piece of copper pipe with polymorph moulded over the top and an aluminium base plate.
The fuel meter consists of the valve on the fuel canister, a regulator, meter pipe and ball valve.
There is a bike pump to assist in venting the chamber.
The breech is o-ringed with aluminium spacer rings to hold the o-rings in place.
Ammo consists of 1” aluminium tube (1/8” wall) filled with hot glue with a wrap of tape for a good fit
Yeah the breech is probably the nicest feature, very smooth and easy to operate. No machining anywhere here, the breech is just a matter of finding the right sized o-ring that fits between the two tubes. The ali spacer rings are cut from tube just thinner than the o-rings, it didn't quite fit over the barrel so I cut it open the rings to fit over and epoxied them on.
Oh also what is the bore size and barrel length?
bore is just a tad over 1" (26.2mm) can't remeber how long the barrel is, about 1.2m I think.
You should start filling the Al tube with lead, at least partially.
It did cross my mind, however they already weigh in at 50grams
Unfortunately just filling one of these would probably use my entire lead spply, and that stuffs expensive enough at the moment that people around here will steal it off your roof if you're not careful.
Very nice design and construction. I love how you edited the video to give the illusion that the shots were fired in rapid succession. You're probably going to get a lot of "omfg dude is that thing semi auto?!!?!?!?!?!?" type comments on YouTube.
I notice there are some who are surprised by the power. It is amazing what an optimized combustion can do isn't it...
Yep, especially considering the modest size and slightly weaker butane gas, mind you the 50gram profectiles certainly help
I love how you edited the video to give the illusion that the shots were fired in rapid succession. You're probably going to get a lot of "omfg dude is that thing semi auto?!!?!?!?!?!?" type comments on YouTube.
LOL I like to cram in as much destruction into the shortest time as possible, nobody wants to watch a target for half an hour before anythng hits it . Of course when I finally get round to building an actual semi, nobody will believe it.
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