Arizona Pneumatic question

I'm interested in setting up quad 1/4" Arizona cannons. I'm just not sure how to do it. Would one Accumulator tank work four all four, or would it be better to have two and have two cannons per accumulator? Would 3/8" I.D. hose deliver sufficient air to the cannons? Hopefully someone much more educated on these aspects of RC combat can help

 

3/8" I.D. seems like a bit much. most cannons I have seen are run on the smaller 1/16" I.D. stuff also 4 barrels on one accumulator should be fine as long as you have the right size accumulator.

 

Would one accumulator provide enough airflow to fire them all at once?

 

yup. We have a guy in WWCC who has armed up to 7 secondary barrels for his montana on a single accumulator. Also, another gent has his dunkerque's quads armed and is working on his Alaces which has quad 1/4" turrets.

 

For Arizona-style cannons, you need to have a separate accumulator for each valve because they will not all open exactly simultaneously. If you try to run all four valves off one accumulator, one MJV-2 valve will open first, draining pressure from the other valves and reducing their effectiveness. End result is most likely one round penetrating, two dents, and one round that doesn't even make it that far. For best results, you really need to have one accumulator per cannon. *note* I have not personally tested this, just discussed the results with someone who attempted two Arizona cannons from one accumulator.

For the hose, are you referring to a "remote accumulator" cannon, where the accumulator and valve is physically separated from the breech/barrel assembly by several inches of flexible hose? If so, 3/8" is sufficient, as long as you don't kink it. If you're just looking for a hose from the gas system to charge up the accumulators, 1/16" ID is plenty. Remember, you're limited to a 8-second ROF with 1/4" cannons.

 

My mistake my brain was reading Indiana Style cannons

 

I should also point out that a single MJV-2 valve only provides sufficient airflow for a single barrel, whether it be .177" bb or 1/4" ball bearing. I did experiment with a single MJV-2 firing a custom-made twin .177" bb cannon, and it was nowhere near enough airflow. I later found a few higher-flow alternatives, but never got to test them.

 

Thanks for clearing that up Kotori. I am planning on using remote accumulator cannons. Should a 4 cubic inch accumulator be enough to fire the cannon with enough pressure, or would I need to go bigger. Also, how would I get all four cannons to fire at once? Solenoids to a firing board?

 

Each MJV valve is operated by an MPA-3 actuator. You can operate all four cannons with a single MAV-3 poppet or solenoid valve with three T fittings, or an X and a T fitting. Either way, you just take the one input from the poppet and branch it off to all four actuators, and that'll work them all.

I don't know if a 4-cu.in accumulator is enough. I can tell you that 1.5 to 2 cu.in. is good for a regular cannon, but I've never actually tried the remote accumulator design before.

 

I'd like to see if a simpler setup would work. Here's the basics of what I'm thinking:

V1:


V2:


As it sits, I like V2 better, it provides a straighter airflow, with less likeliness to kink when the cannons rotate since it's right bellow the cannon. I'm not sure if this would work, and any feedback is welcome.

 

Tug, that sounds very similar to the designs I put up in my cannon build thread awhile back.

 

One thing's sure, you'll need some very high-flow solenoids to directly fire a Big Gun cannon. The remote accumulator system also reduces your efficiency rapidly as the length of the remote line increases.

 

Would 25-30 SCFM be enough airflow, or would 60 be better? Also, would it be possible to mount the magazine onto the bottom of the deck, and have a hose leading to the cannon with a bit of extra so that the cannon can still rotate? I'm interested in seeing your idea Tug, do the accumulators rotate as well?

 

Well, thinking about it a bit more, it would probably be easier to build an Indiana cannon with a large solenoid to fire it instead of a ball valve. I've found this one that has a Cv of 4.5, or a SCFM of 270 at 100 psi.
http://www.ebay.com/itm/1-2-Brass-Electric-Solenoid-Valve-12-VDC-Water-Air-Fuels-Gas-VITON-SEAL-B21V-/300714222574?pt=LH_DefaultDomain_0&hash=item4603f6e3ee

 

Did a basic sketchup model of the modified Indiana styled cannon:

 

270SCFM sounds good, but I don't know what the average buna-ball valve's max flow rate is. I used to think that 22SCFM/barrel was enough based on MJV-2 cannons, but I tried doubling that with a 50scfm quick-exhaust valve for a twin .177" cannon and it was woefully insufficient. Other concerns include actuation speed and overall height of the cannon. Maximum flow rate isn't the only reason Buna ball valves are used so often in Big Gun cannons.

 

You can get away with lower pressures if you work to fit each turn the gas has to make with a good radius. 90 degree edges are a no-no if they can be avoided. The gas simply departs from the surface and goes turbulent, slowing it down. If you could create a rounded turn coming out of that accumulator, your pressures will remain higher and with better velocity.

I do like where the exit from the accumulator is. With a shape much longer than its width, the gas has to travel longer, on average, to get to the breech. By cutting into the center as in the drawing, you have more gas within a short trip to the breech than otherwise. The shock wave hits harder.

 

Interesting how it's not a linear progression. That's got me thinking I should go with this one instead with a Cv of 12, which will hopefully be enough.
http://www.ebay.com/itm/1-NORMALLY-OPEN-Brass-Electric-Solenoid-Valve-NPT-NO-ONE-YEAR-WRRANTY-/110909094291?pt=LH_DefaultDomain_0&hash=item19d2b27993
If the cannon is to tall, I'll move the solenoid to the end of the accumulator on an elbow fitting, and hopefully that will lower it enough. I'll find out the height limit once my plans come in.

 

The length of the cannon from the bottom of the accumulator to the top of the magazine is 8". The accumulator is 3", the solenoid is 3.25", and the magazine is 1.75". I'm thinking of making the accumulator more like this to save space:

Here's a quick drawing with the curves put in to direct airflow:
Note: this isn't to scale, just a basic representation, can't get the hang of curves in sketchup yet.




One thing I do want to ask, Would it be a good idea to place the solenoid right under the cannon barrels, so that the gas goes straight up into them, or would it have the issue of the middle cannons being way more powerful than the outer ones?