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This is a two part Instructable designed to demonstrate how to construct 1) A hybrid potato cannon capable of accelerating a projectile to supersonic speeds and 2) A cannon mount that resembles a WWII Howitzer field piece.

This is about is powerful as it gets with this size of potato gun. The boom is like a thunder and if you aren't careful you will quickly lose sight of the projectile. It definitely packs a punch and is "just a blast" to fire.

I found most of the parts for the cannon at a plumbing supply store in town and the rest at Home Depot. Then I pieced together the mount from parts I had laying around my home.

The whole cannon can be made with no welding experience as all the parts can either be screwed together are epoxied together. The only difficulty that comes with this is that you have to fix a lot of leaks before you can operate the cannon, but this is not hard to do.

Step 1: Principles / Concepts of Cannon

         The regular potato gun that every serious DIYer has built utilizes just a regular combustion of gases at atmospheric pressure. This is the most basic of potato guns and usually the least powerful. The next most powerful type of gun is a pneumatic cannon that uses pressurized air to launch a projectile. After that comes the hybrid potato cannon which is a combination of the other two (hence "hybrid").
          A hybrid is powered by the combustion of pressurized gases. This allows for much more fuel and oxidizer to react inside the combustion chamber and it will produce much higher pressures than the other two types of potato guns. More information can be found at  http://www.spudfiles.com/spud_wiki/index.php?title=Hybrid_launcher

There are 4 major components to a hybrid potato cannon:
- Barrel
- Combustion Chamber
- Metering System
- Ignition System

Operation: The potato gun is first fueled via the metering system which injects just the right mixtures of fuel and air into the combustion chamber. The fuel mixture is then ignited by two spark plugs connected to a stun gun. The resulting combustion produces enough pressure to break the burst disk holding the gases inside of the combustion chamber and to shoot the projectile out at high speeds

Design Considerations :
- One of the most important things to consider when building any potato gun is the chamber to barrel volume ratio. Experiments have shown that a chamber to barrel ratio of 1.5 : 1 will efficiently utilize all of the guns power.
- The next thing to consider is the barrel length. The longer the barrel is the more time a projectile has to accelerate. However, the larger the barrel, the larger the chamber. So you have to strike a compromise and just decide on a practical and economical barrel length.
- For the meter pipe I got the largest pipe I could at the longest length that would fit. A meter pipe with a larger volume means that you don't have to pressure it up as high when measuring fuel. This is what I would suggest.
- When you incorporate multiple ignition sources you increase the power of the cannon. Igniting the fuel mixture at multiple points will create multiple pressure waves which will increase the velocity of the gases. I have built two ignition sources for now, but I have left room for two more.

My main resources when researching this project were:

- The next step will demonstrate how to build the barrel.

I know this is old but where did you get 4 inch schd 40 caps
If he does not respond to this comment, I will assume he was arrested
<p>hmm. looks as if he was then....no reply yet!!! wow....whatta beast tho... :)</p>
<p>I am building this! My hybrid is smaller to save money and has a different metering system, but it will be able to shatter 2 by 4s.</p>
Finally! Someone else actually built a life size propane cannon! I built mine about a year ago and have been looking for other cannons that other people have built but I haven't found any! Until now, Thank you for posting this! lt is very helpful.
Any idea about the range of this thing?
Also do you know how much the internal pressure gets to upon ignition and what exact type of pipe you used
Ive been looking at this beast for over a year now contemplating whether to build it. I would like to know how far it shoots, how much it costs, where you got the pipe, and if you can put a video up. Thanks for the answers. I really want to build it.
we want to see video of the beast in action!
Finally! Someone actually made an air cannon with a straight tank-barrel configuration! Maximize efficiency!
Not an air cannon, a real cannon, for all intents and purposes.
I am about to graduate from high school and want to build one of these over the summer before I go to college. How much money do you think you spent and how long did it take you to make this?<br>
I probably spent about $500 on this project. The metal is not cheap, but it is necessary to handle the pressures. The whole thing took me about a month to build, and another month to work out all of the bugs. If you do decide to build one, I would suggest that you find an alternative way of coupling the barrel and the combustion chamber. My way works, but I don't think it is the best way.
Apologies if you address this somewhere (at work, so I don't have time to read this as carefully as I want to) but I just have a tip that may reduce the number of leaks to epoxy. As a spudder myself and longtime handyman, I was surprised recently by this info -- surprised it never occurred to me, and surprised ever since at how few professional tradesmen seem aware: <br><br>COMPRESSION fittings only work reliably WITHOUT thread sealer (teflon plumbing or gas tape, pipe dope e.g. Rectorseal #2 etc) -- I am sure that anyone familiar with these fittings who was not already aware of this, will understand why immediately... for others, I will explain. The seal in a compression fitting is from the COMPRESSION (ah, it begins it make sense) of the collar (or nut, or olive, depending on which side of what pond you are spudding from) onto the tube or pipe. The threads on the fitting serve not to create a seal themselves, the way NPT (aka IPS, FPT, MPT) are designed to, but to create the torque required to squeeze the collar.<br><br>SO, in brief: pipe threads? Use that thread-sealant, and don't be shy! Compression fittings? Skip the teflon tape, it will just get in the way. Bonus: save epoxy for other stuff :-)
if i was to buy this from you how much would i pay (just the frame, not the spud gun)
Hiya,<br>Why not meter directly into the chamber?? you could measure it's volume and then only use the end (propane end)of you metering system. Accuracy of metering might be effected but at this size of cannon, would it matter much?? <br><br>Great 'ible though, now thinking of converting my steel pneumatic cannon into a hybrid.......<br>
When I saw this on facebook, I was like &quot;no way no way AWESOME!&quot; :D I need to make me one of these! Sir you are a true god among men! Now let's see a video of this baby in action! :D
My son has made several potato guns, some combusion, one pnumatic... but this has caught his attention! (thanks :/ lol)<br><br>Do you happen to have a video of this bad boy in action?
my gosh doesnt that seem a little to hard to make, but i do conradulate you on your amazing invention
I love the step on safety: there is none XD<br><br>Awesome project, to the true sense of the word. That's genuinely terrifying, I don't know why Howitzers weren't designed like this in the first place!
grand instructable!
What kinda range do you get out of these things?
Looks like a snazzy lookin cannon you've built there, good job.
This is AWESOME! I have 2 questions, how big is it and how far does it shoot?
The whole cannon is about nine feet long and weighs about eighty pounds. Although I haven't measured its range yet, theoretically it can shoot close to a mile
WOW! that's crazy!
I may have to get my Scouts to make one of these!<br><br>High Five for you!

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