Before I get started on the design. I must say that it was'nt soly my creation. The base model of the air cannon I got from Curt Graber on youtube. Please visit his tutorial video on the base model. CLICK HERE for Curt Graber's origninal base model.
Step 1: The Base of the Design
The base model is a potato cannon on its own. I will briefly describe how it works, but for more description, you can visit Curt Graber's videos.
Ok to start, this is a very simple design, one of the most effective BUT, SIMPLE designs.For a potato cannon. If any of you have built potato cannons before then you know that the faster the valve opens the more efficient the cannon can be. Well this model uses a varient of the diverter type of valve. the valve is very simpilar to a piston valve but without the weight of the piston that casues a loss of efficiency. This model has the efficiency that is extremly simpilar to a burst disc, wich by the way is the best it can get and its reusable.
The main valve is made up of a diapram disc that moves backwards to allow the inner chamber to release all the air. When the air hose is attached and air starts moving in, it moves around the diaphram into the large pipe around the barrel. There is a rubber drain hose that is clamped over the back of the barrel which servs as the seal keeping in the pressure also holding the diaphram in place. As soon as the trigger valve is activated, the air pressure suddenly becomes less than whats in the air chamber pushing it backwards. the moving air keeps pressing the diaphram backwards as the air escapes the barrel.
If this isn't clear enough, plese visit this video and build tutorial HERE, but this instructable isn't about one of these cannons, but 19 of them!!
Step 2: Adding 19 Barrels to Make It Rapid Fire Full Auto.
I should say before I get into the experamental deisgn that i haven't built this yet, but it works exactly the same as what has been built and the operation of the componets seem promising. NOW saying that, im asking for those experiences fellows on their input for this design variation.
I recomend if sombody were to build this before i do that they would only add 1 or 2 cannons to the series testing the concept before adding 19 of them
Allthough this design is not your typycal $20 weekend build, it is reletivly cheap and easy to build
Let me start with the opertion of the seperate cannons in the series. the only change needed when adding cannons to fire in the series, is the addition of a exaust to every cleanout cap and the only one with a trigger valve being the initial cannon. For explanation simplicity, im going to talk about only 2 cannons. each cannon will have 2 exaust connections. each one will be used in the pressurization of the cannons. when the air hose is connected, the 2nd exaust connector will send air to the next cannon. as they pressurize every cannon will fill simultaneously acting as one air chamber. the last cannon in the sequence needs only a single exause port to fire and to pressurize.
Now lets talk about firing.
when the trigger valve is activated the first cannon will fire, BUT that 2nd exaust connector will bleed air. which is the only necessity for fire sequence. because every cannon uses the same type of valve they pressurize simultaneously, but the series of exaust connectors cause the sequence of triggers.
it takes a fraction of a second for the diaphram to react and time for the air to leave the small exaust ports. so this is what causes the delay for the machine gun effect.
The edition of multible cannons will heavily increase the importance of no leaks. if a couple of the high number of connectors leak, then the cannon will not get to full pressure.
Also the seal that presses against the diaphram will need to be lubricated reguly to all the cannons to get to full pressure. Above you can see the direction of the pressurization of chambers, but when the trigger valve is activated, the direction of air flow will reverse in sequence starting with the one connected to the initial cannon.
Step 4: The Overall Effect of 19 of These Cannons
The Fire rate of the cannons can be adjusted by changing the exaust size or pinching each exaust hose equaly.
Now, i plan to build these 10 feet long and 1 1/2" barels. 1 1/2 inches will allow for a potato, but will also allow giant spears to be used as ammo. Another issue would be reusable/cheap ammo. spears would be reusable as long as they didnt expereince too heavy of impacts. Ice is used alot with potato cannons, but why would i use ice when i can make pykrete. They melt, so you dont have to worry about the firing range being littered.
if you can imagine this is a beast of a potato gatling cannon, not gatling gun but gatling cannon. 19 700+ ft/sec projectiles that weigh a couple ounces is some serious power.
to compare.......i built a potato cannon once that was about 1/5 the power of this and it fired a fence post 6 inches into a tree (UNSHARPED).
please visit Curt Graber's Youtube channel.
Also here's another youtuber that built the same cannon and fired 500 ft/sec potatoes.
If you've read this far then im sure that your intrigued, so your input will be greatly appreciateed on the design and operation of the cannon.