SpudFiles

I had been watching some potato cannon videos on Youtube (by MushiYoshi) and I finally decided to build one of my own. I took down the specs for his potato cannon and simplified the design significantly.

It is made from 1X 5'x2" barrel, 2X 90* 2" street bends, 1X 4" to 2" reducer, 1X 2'x4" combustion chamber, and 1X 4" screw on end. As an ignition system, I used a standard $10 BBQ grill ignitor from The Home Depot. All the pipe, which was sch-40, was bought at Lowe's. The total price was around $35.

I actually have made a video of this combustion style cannon in use on Youtube. The link is

<a href="http://s614.photobucket.com/albums/tt22 ... LE0098.jpg" target="_blank"><img src="http://i614.photobucket.com/albums/tt22 ... LE0098.jpg" border="0" alt="Photobucket"></a>

<a href="http://s614.photobucket.com/albums/tt22 ... LE0104.jpg" target="_blank"><img src="http://i614.photobucket.com/albums/tt22 ... LE0104.jpg" border="0" alt="Photobucket"></a>

Custom Potato Cutting Tool-A small segment of 2" SCH-40 pipe inside a 2" connector. I have sanded the end of the pipe down to about a 45* angle. I just push a potato through it, and then push the potato down the barrel with an old broomstick.
<a href="http://s614.photobucket.com/albums/tt22 ... LE0111.jpg" target="_blank"><img src="http://i614.photobucket.com/albums/tt22 ... LE0111.jpg" border="0" alt="Photobucket"></a>

Before anyone starts slamming you, there are a coupla things you need to make note of...

Those 90's are not pressure rated, and the 4" chamber is cell-core(not good for pressure rated use) it has a rating on it, but it's basically thin pvc on the outside, thin pvc on the inside, and foam filler in between...

But, welcome aboard, and take the advice from the peeps on here, most will not steer you wrong...

jeepkahn wrote:Before anyone starts slamming you, there are a coupla things you need to make note of...

Those 90's are not pressure rated, and the 4" chamber is cell-core(not good for pressure rated use) it has a rating on it, but it's basically thin pvc on the outside, thin pvc on the inside, and foam filler in between...

But, welcome aboard, and take the advice from the peeps on here, most will not steer you wrong...

I know the 90's aren't pressure rated, but I am looking at it right now and the 4" combustion chamber is undeniably solid PVC, and it says "Charlotte Pipe TrueFit System 7400 4" PVC TYPE 1 SCH 40 ASTM D-2665," and continues on to say that it is rated at 220 PSI @ 23*C. It is definitely pressure rated. It is not some weak cell-core!

PaulsAirsoftArmory wrote:

jeepkahn wrote:Before anyone starts slamming you, there are a coupla things you need to make note of...

Those 90's are not pressure rated, and the 4" chamber is cell-core(not good for pressure rated use) it has a rating on it, but it's basically thin pvc on the outside, thin pvc on the inside, and foam filler in between...

But, welcome aboard, and take the advice from the peeps on here, most will not steer you wrong...

I know the 90's aren't pressure rated, but I am looking at it right now and the 4" combustion chamber is undeniably solid PVC, and it says "Charlotte Pipe TrueFit System 7400 4" PVC TYPE 1 SCH 40 ASTM D-2665," and continues on to say that it is rated at 220 PSI @ 23*C. It is definitely pressure rated. It is not some weak cell-core!

You must have one of the good Lowes,,, The ones around here stock cell core on anything over 3"...

BTB, your build DOES look good aside from the 90's...

Picture just after a firing of the cannon:
<a href="http://s614.photobucket.com/albums/tt22 ... t_0001.jpg" target="_blank"><img src="http://i614.photobucket.com/albums/tt22 ... t_0001.jpg" border="0" alt="Photobucket"></a>
It has a surprising amount of recoil, comparable to shooting a Beretta semi-auto 12 gauge at Boy Scout camp. It is also accompanied by a HUGE amount of noise!

I know the 90's aren't pressure rated, but I am looking at it right now and the 4" combustion chamber is undeniably solid PVC, and it says "Charlotte Pipe TrueFit System 7400 4" PVC TYPE 1 SCH 40 ASTM D-2665," and continues on to say that it is rated at 220 PSI @ 23*C. It is definitely pressure rated. It is not some weak cell-core!

The pipe may be pressure rated, but that doesnt tell anything about the fittings used. Those are DWV.
The sockets of these fittings are shallow, and because of this lack of depth there is not enough contact area for solvent welding.
Im not saying that this WILL cause a fail, but I will say that IF it fails, the DWV fittings are the ones which will. Do not expect this cannon to last for years.
Now it is generally accepted that it is relatively safe to use DWV for spray and pray cannons, but it is certainly NOT RECOMMENDED.


For the rest, its a nice cannon. I would normally highly recommend a chamber fan, but thats not a good idea with this chamber. You know what to improve next time.
Also it may be a better idea to put the BBQ ignitor though a place where a fitting overlaps with the pipe. This will cause the hole to go though TWO layers of pipe instead of ONE.

I'll throw in this little part as well:

If it fails, it will do so at the elbows, not simply because they are non-pressure rated, but because that is where most of the stress from the recoil will be absorbed at. To remedy this, add you a barrel support, one that connects the chamber to the barrel.

If you keep shooting it as is, and you do not reinforce it, assuming the recoil is as you mentioned, it WILL eventually fail.

I've only fired it about 10 times, and I have already designed a barrel support for it, I am just waiting for my dad to build it at work when he has some spare time.

Is an inline design with just a reducer a better design?

Nice build but as others have pointed out the elbows aren't pressure rated and neither is that bell reducer or the clean out cap although if it fails it will just fly out toward the range.