Advice on Building Truck-Mounted Water Cannon

[Major Mallet]

Hello everyone,

I am brand new to the forums and would like to run an idea past everyone. I am looking for help in designing 2 truck-mounted water cannon - one in the front of the vehicle and one mounted in the bed of the truck. The goal is to build a truck that resembles an LRDG vehicle from WW2 (http://blindkat.hegewisch.net/lrdg/lrdgvehicles.html) with two very powerful water cannon in place of the machine guns.

The only design limitation I have is that I want to make the guns look as much like .50 cal Browning machine guns as possible. Further, I would like to get about 50’ of range and safety and durability are extremely important. Where do I begin? Thoughts anyone?

[Silence]

Welcome to the forums! I'll move this topic to the Homemade subforum, as we might be getting into depth...

I believe there was a thread about a Lada Niva somewhere, and a simple search should bring it up. It's a bit late now, so I'll do the search tomorrow. Are you actually doing this to a Pink Panther, or to a different vehicle?

As Ben said recently, a CAP system would unleash the maximum potential for a vehicle-based turret. It would have a lot of power, and the car would provide the mobility, space, electricity, and such that would otherwise be a limitation. Money is a bit of a problem with CAP systems too. Check out Ben's SuperCAP thread and m15399's CAP explanation (I can provide a link tomorrow) if you're interested.

If you want something that has a more flexible design and that isn't as awkward or expensive, you could easily hook up a water pump (connected to the car's battery, of course) to a large, powerful latex rubber tubing (LRT) chamber. The pump would constantly fill up the chamber, and the chamber would allow for output greater than the pumps, although not constantly. This design would lack the sheer power of CAP, though.

And finally, if you want to have something more conventional and less vehicle-based, then it's probably possible to design a large homemade soaker in the shape of a Browning. The second option I suggested seems the best, though.

Also, you can build a water balloon launcher (WBL) extremely easily--and that can be attached to an air compressor. I don't know of any that use air compressors as opposed to bicycle foot pumps, but it would be really powerful. With an air tank or something along the lines of what I'm currently discussing in my automatic-WBL thread (I can also provide a link to that...), you can easily create a powerful artillery system.

[Major Mallet]

Thanks for the prompt reply. The vehicle I am thinking of modifying would be a Chevrolet C-1500 work truck (2WD – 6 cylinders). I will be removing the roof, windshield, doors and airbags. Granted, it will not look exactly like an original LRDG truck but I think with the right paint and accessories (a few jerry cans, sand channels, chains, etc) I should get 80% of the “look” I want. I was hoping to get away for under $600 for the water-cannon parts. I would sacrifice range for simplicity and safety.

I found the links you referred to – thanks. I grasp the CAP system but don’t know how the LRT chamber would work. Also, what water capacities / PSI would you recommend for the CAP system? Finally, would you suggest running both guns from a central system or having separate systems for each gun? Any other ideas / thoughts?

[Drenchenator]

Also, what water capacities / PSI would you recommend for the CAP system?

I would recommend at least 20 liters of water (5 gallons), but more would be better. I have a pretty good idea for a fairly simple air pressure based system. Air pressure systems would be most suitable for this kind of stuff. Even though latex rubber tubing expands like mad, it still won't provide enough capacity. 40 to 60 PSI should do the trick, especially if you this is a regulated (CAP) system. Do you have access to an air compressor?

Finally, would you suggest running both guns from a central system or having separate systems for each gun? Any other ideas / thoughts?

It would be easier to have one central system but with multiple outputs. You should at least share the air source; there is no need to not share it.

Here is my idea. It would be a little expensive but extremely effective. Basically, it has 4 very large water/pressure chambers. One central ball valve fills all four. Each chamber has a capacity of about 10 liters (2.5 gallons) for a combined 40 liters (10 gallons). The guns are powered by a tank full of compressed air. A regulator will regulate the pressure for all four chambers. The bottom will contain the "outputs". You can build as many as you want, just make sure that every chamber is connected to each other. Each gun will be connected by tubing (haven't decided what kind yet) to the pressure chambers. All that a gun would need to work is a valve and nozzle, so it would be easy to make them look like real guns because all you would need would be the bodies.



If you build a "Super Soaker Gun Truck", would you mind making a guide of sorts? This is a fairly common request (Ben says that he gets a lot of emails about stuff like this).

[Major Mallet]

Drenchenator,

CAPACITY: I was thinking 20-40 gallons of capacity. Perhaps 20 gallons under pressure and 4 five-gallon jerry cans in reserve.

COMPRESSOR: As for a compressor: I was going to purchase either an electric or gas model. Leaning towards gas in that I will not have to fool around with integrating the compressor to the vehicle electric system. However, gas compressors are expensive and would easily eat up the entire $600 budget if purchased new. I have to give that more thought.

Before selecting a compressor, I want to double check my actual requirements. I thought I saw an article on the site that dealt with calculating the pressure requirements. I could not find that specific article - can anyone give me the URL for that?

GUIDE: You asked if I would post a guide about building this system. I certainly would. I am in the planning stages right now. Coming up with a total price for the project. My first guess is that it will be about $4,000 in actual expenses plus a lot of labor. Should I decide to go for it, I will post a guide here as well as start a blog detailing the entire project (how I modified the truck, painted it, post videos of the guns in use, etc.). After all, your community is helping me put this together. The least I can do is show it was done.

QUESTIONS: What are the advantages of using multiple water/air chambers? Why not one large chamber?

Thanks for the detailed reply - I appreciate it.

MM

[joannaardway]

Normally, higher diameter pipe has a lower rating, and is very much more expensive for each cc of capacity.

4 narrower chambers should be better rated.

I could help with some maths on the pressure/compressor required, but I'd need some information to get started.

[Drenchenator]

Normally, higher diameter pipe has a lower rating, and is very much more expensive for each cc of capacity.

I would not worry about the rating. My drawing was using schedule 40 4" PVC, the same kind that Ben uses in both SuperCannon II and SuperCAP. Most compressors can't obtain pressures higher than 150 psi; 4" schedule 40 has a rating of 220 psi, well over the absolute maximum that can be produced.

Also, larger diameter pipes are significantly cheaper per unit of volume. If you are going for volume, go for larger diameters. I did some quick math, and if you buy 10 foot lengths of both 3" and 4" schedule 40 PVC, 4" would definitely be the best for our purposes. 3" PVC gets 39.58 cubic inches per dollar, while 4" PVC gets 49.42 cubic inches per dollar (prices from McMaster). That's a whole 10 more cubic inches per dollar, making it substancially cheaper for the same volume.

In other words, 4" PVC really is optimal for our purposes when you are building large scale projects (like this and SuperCAP).

CAPACITY: I was thinking 20-40 gallons of capacity. Perhaps 20 gallons under pressure and 4 five-gallon jerry cans in reserve.

It seems that 20 to 40 gallons under pressure is quite viable from my experience. It would also be good to have some backup just like what you said.

QUESTIONS: What are the advantages of using multiple water/air chambers? Why not one large chamber?

The main advantage would be the increased capacity while maintaining a high enough pressure rating. Plus extremely large pipe is very expensive, so it is easier to use multiple smaller chambers. You may also need multiple air tanks too, but this is a bit less important. If you use an air pressure regulator, you can charge a 15 gallon air tank to 100 PSI and shoot for as long as you want if you use a fairly low or moderate pressure (40 to 60 psi).

Before selecting a compressor, I want to double check my actual requirements. I thought I saw an article on the site that dealt with calculating the pressure requirements. I could not find that specific article - can anyone give me the URL for that?

I am going to have to get back to use on this. I am pretty sure that there is something like this on the site (not the forums) but it would probably be a bit outdated. I can check in a while. I don't have the time at the moment.

[Silence]

Wow, the ideas have been flying! You sound dedicated to the project, which almost certainly means completion. I might as well congratulate you in advance.

Anyway, with $600 you can do pretty much anything. It sounds like an electric compressor wouldn't be too much of a problem; and I recommended way above a gas compressor.

Pressure isn't a problem, but price is--when you get to 6". If you want more power, then you have to maximize the base area of the PCs--because that's more contact between the pressurized air and the water surface. For example, after getting a lot of 4" PVC, it's better to have many smaller pieces than to have a couple tall pieces--and it would be a lot less awkward.

It doesn't really matter whether or not you store water separately, so you might as well put it together unless you have other concerns such as height or the like. I would definitely recommend a central system, and it looks like the Drenchenator's idea would be perfect. A few suggestions, though:

--For the air tanks (yes, you might as well have multiple ones. On the other hand, that isn't too necessary since you have an air compressor, unless you plan on unleashing a ton of water at once. I'd go for a cheap compressor and a lot of volume worth of air tanks), you can take multiple ones, mount them on the sides of the vehicle, and paint them. That would solve part of the looks issue.

--If you're going to have separate water tanks, I would only suggest that for one reason: filling up individual soakers and water balloons. Truly invaluable, IMO, but don't count on it to refill the main tank. It will sure be a beast!

--The layout of the PCs can be as flexible as you want it. I would go for propping up a row of tubes, perhaps along the side of the truck or somewhere, or just making multiple short tubes (more powerful, too) and putting them in the middle. All the air tanks would connect to the central system, and then a couple of huge hose (with strong Jubilee clips) would lead to the two main guns. The guns can be of practically any design; just make sure they're mounted, or the recoil would be really, really excessive.

--Add a WBL or two up front. For their air supplies, connect a couple of hoses from the central gun system (not the water part--just the air) to separate PCs (for conservation of air; it's not exactly necessary) and then have those fire. You can easily modify a solenoid valve for the WBLs and put a trigger or two anywhere in the vehicle, so firing them will not be a problem at all. I know Pink Panthers had grenade launchers; I have a book somewhere.

[Major Mallet]

OK, you guys have given me a lot to think about. Here is where my thinking takes me currently:

I think I will go with an Electric Air Compressor like this one:

http://www.toolbarn.com/product/makita/MAC700/

Multiple water/air tubes also sound like the way to go. I would like to mount the tubes inside the truck bed just behind the driver and passenger (front gunner) positions. How effective would two banks of 4-6 tubes about 3-4 feet high and 4" in diameter be?

I did not want to mount anything on the outside of the truck because I will be mounting sand channels on the sides of the bed. Also, the truck will have to be transported by tractor trailer from the assembly site across the country. I don't want any items that could get damaged on the exterior of the vehicle.

I am going to pass on the water balloon launchers at the moment. This first round of gun manufacture will keep me occupied for a while.

Also, I thought at first to build the .50 cal bodies out of PVC but now think I will have them manufactured out of metal. This should dramatically increase the durability of the units, negate the effect of recoil, and make them easier to place on swivel mounts.

Three more questions: How long will the typical CAP system retain pressure after you pressurize the system? I know the answer is a direct function of how tight the connections are - I just was wondering what your field experiences have been.

The air compressor I listed above - enough to get the job done? I would like each gun to produce a 50' blast of water.

Finally, let's talk safety. I have read where some of the guns built have cracked or "exploded" under pressure. I very definitely do not want that to occur. In your experiences, where are the trouble areas? What safety precautions would you recommend? I am assuming that the tanks are the biggest concern. If that was the case, would you encase them in a wood or steel container that could contain the PVC fragments that might come from a mishap?

Again, you guys have been great - I love the ideas and input I have been getting.

[Drenchenator]

Multiple water/air tubes also sound like the way to go. I would like to mount the tubes inside the truck bed just behind the driver and passenger (front gunner) positions. How effective would two banks of 4-6 tubes about 3-4 feet high and 4" in diameter be?

That seems fine. Just make sure that the tubes are upright. This means that the air input and filling area must be on the top because the air floats to the top.

Three more questions: How long will the typical CAP system retain pressure after you pressurize the system? I know the answer is a direct function of how tight the connections are - I just was wondering what your field experiences have been.

As long as there is no way that the pressure would leak out, the gun could technically be charged indefinitely. But when you are working with flexible tubing (which you would need to use since you are building seperate guns), leaks will occur. But if you tighten the tubing clamps well, this should not be a problem. Expect the system to retain the pressure for extened periods (3 or more hours) unless it somehow develops a leak.

The air compressor I listed above - enough to get the job done? I would like each gun to produce a 50' blast of water.

This air compressor will definitely get the job done. Pressures of about 40 to 60 psi should definitely get 50 feet in this case.

Finally, let's talk safety. I have read where some of the guns built have cracked or "exploded" under pressure. I very definitely do not want that to occur. In your experiences, where are the trouble areas? What safety precautions would you recommend? I am assuming that the tanks are the biggest concern. If that was the case, would you encase them in a wood or steel container that could contain the PVC fragments that might come from a mishap?

The only thing that I can recommend is that you PVC cement the chambers well. Many people complain of "leaks" and then say that they pressurized it 30 minutes or an hour after gluing. Make sure to first use primer, wait, and then cement, and wait at least one day. Encasing the chambers in wood seems unnecessary to me, but you can take whatever precautions you want. From my experience, if you glue the gun together well, there should be no problems. Other trouble areas include threaded attachments, and tubing barbs and clamps. Make sure that you use teflon tape (thread seal tape) on every threaded attachment. Tubing barbs can leak and even cause the tubing to blow off if they are not clamped down well enough. My only recommendation is to periodically check and tighten every clamp after each use of the gun. If the tubing blows off (especially the tubing connecting to each gun), the gun can literally turn into a massive water rocket.

[Silence]

You're dealing with a lot of power here--an immense amount, probably the most powerful water gun ever created (besides a firehose)--but common sense should make sure nothing bad can happen. Don't let the pressures get too high, especially since that isn't needed; and use strong tubing clamps. The Drenchenator has provided tons of other useful information, namely waiting a while after gluing (twist the glued joints) and using Teflon tape.

This sounds like an incredibly huge project, with tons of money and time--even transporting the truck across the country? Whew. Anyway, with that kind of thoroughness, I doubt anything could go wrong.

[Major Mallet]

Yes, this will be a project. At his point I am determining if I can assemble the budget and team I need to execute it. I have spoken with folks who can help me fabricate the metal gun bodies and mounts so that should not be an issue. I have contacts at local automotive dealers so obtaining a suitable used truck is taken care of. You guys have been a big help with the mechanics of constructing the guns. The only general questions left to answer are how will I raise money to build this monster and how will I transport it. Fortunately, however, I believe I have solutions for those issues as well.

So, I will have some time next weekend to draw up my first detailed schematic and parts list for this system. I am considering adding a third (smaller) gun to the rear of the vehicle as it would both look cool and allow me to get better water coverage. I will post the schematic here for all of your review and comments.

A couple of more questions for you guys:

Safety – The gun mounted on the hood of the truck (to be operated by the passenger) should probably not be the same power as the bed-mounted gun as it would be very easy for a person to get their head next to the barrel when firing. Also, I think I will have to have some sort of “guide” for the bed-mounted system so that it can not depress at an angle that would allow it to hit the heads of the driver and front gunner.

Joannaardway – you offered to do some of the math. What specifics do you need to help me determine the exact requirements of the system?

Again, thanks for the input. You guys have been a big help.

[Silence]

Sounds great then. But I have one comment to make: anything is safe if used carefully, but everything is dangerous when used carelessly. In other words, there's really no need for safety measure of the type you just pointed out--nothing can stand in the way of stupidity. On the other hand, if everybody uses common sense and does not aim at a person's head at point blank range, then nothing could go wrong. Those precautions seem a bit excessive, and if there are people who you think could cause problems, then you just shouldn't be letting them be the gunners (or the driver, for that matter ).

[joannaardway]

I'll need to know:

Pressure you intend to use.
Size of chamber, and intial fill of chamber
Diameter of the largest nozzle you intend to use
What's the longest time you intend to use it for in one go? (or, what's the maximum amount of water you're going to use at once?)
And, how large is your "capacitor tank" going to be?

That's all I can think of right now.

[Major Mallet]

OK, I have had some time to further refine the plans.

PLACEMENT: I think I will go with three guns instead of two. One will be mounted on the hood of the vehicle in front of the passenger. The second will on a fixed mount in the bed of the truck. The new third gun will be mounted on a two position swing arm. The swing arm will pivot on the passenger side of the truck where the tailgate used to be (near the right rear tail light). When traveling, a “gunner” can cover the rear of the vehicle – this would not be as easy with a two gun system. When firing on a “fixed” target, the arm will pivot parallel to the right side of the truck bed. This will allow all three gunners to simultaneously fire on the target. How? Imagine an overhead view of the truck pointing at the 5 o’clock position. All three gunners should be able to cover a target located at the 6 o’clock position.

SYSTEM: I think 4’ pipes are going to be too tall and get in the way of the bed-mounted guns. I am leaning towards using Drenchenator’s idea in 3 separate systems consisting of four, 3’ tall, 4” PVC water containers and one, 10 gallon 125 PSI air tank each. I will use a single, electric air compressor to fill the tanks.

GUN BODIES: An actual .50cal Browning MG measures 65” long while a 30.cal measures 48” long. I think I will have to scale the water gun bodies down to make them a bit more manageable – perhaps 3/5ths to 4/5ths scale. Thoughts?

SAFETY: I agree with SilentGuy when he says: “anything is safe if used carefully, but everything is dangerous when used carelessly.” The issue for me is that I will be in an environment with a lot of people I don’t know. Obviously I will know the crew, but I won’t know many of the recipients of my hydro-assault as well as other passers by. What concerns me is someone may attempt to use the guns or wrestle them away from the operators. I would rather err on the side of caution than see someone get hurt.

QUESTIONS: OK, here come the math issues. How would I calculate how many seconds will each gun fire on this system? Can you mathematically estimate how far the water will travel? Assume that each gun has an 8 gallon water capacity (if my volume calculations are correct), will fire at 40-60PSI and have a ¼” nozzle at the barrel. Any opinions on increasing/decreasing PSI or nozzle size? Will a 10 gallon tank be sufficient for the task?