Big River Turret

Build a homemade water gun or water balloon launcher and tell us about it.
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Jheart
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Joined: Sat Mar 29, 2008 6:27 pm

Big River Turret

Post by Jheart » Sat Mar 29, 2008 6:50 pm

Hey all, I'm Jackson

I'm the waterfront director at a summer camp in New Hampshire, and with the summer creeping up, and a little free time and cash, I've been meaning to tackle a project for our lake.

This summer, I want a deck mounted, turret style water cannon to attach to a ship I've been working on. Aesthetically, I could care less what it looks like, as the ship is made of scavenged catamaran parts and a bike.

It MUST be Child Safe (low risk of explosion, low pressure stream, even at short distances) and able to be operated by small children. Other than that, I'm open to anything. I'd prefer it be able to draw water from the lake automatically without the kids having to refill by hand.

I've been looking through this forum, and at all the major gun types to try and figure out where to start, but I'll admit I'm a little stumped. Assuming that I would prefer to not have a motorized pump on board, could anyone weigh in on the following ideas, and or suggest their own?

-A Piston gun, with refilling hose
-A pressurized gun that could be pumped fairly quickly using a bike pump(s) or old firetruck style teeter-totter pump
-A continuous Hand cranked (or pedal powered or pumped) water or air pressure system
-A compressed air tank refilled at the shore (enough pressure for a good water fight?)

I know this project could range from fairly simple to crazy complicated, but I would like to shoot for a good middle ground, where the kids can climb on, pump then shoot, or tandem team run the gun, and dodge water balloons that I'll be shooting from the shore : )

Thanks in advance!

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SSCBen
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Re: Big River Turret

Post by SSCBen » Sat Mar 29, 2008 7:01 pm

Welcome to SSC!

A piston gun (with input tube) or a hand crack would be your best bet. These designs do not build up substantial pressure because they lack firing valves, and their power will be limited by the strength of their user, making them most appropriate for children. The handcrank design would be more continuous because they do not need to stop like piston guns (with the right design) and usually is a variation of the piston design from what I know. I don't know much about the hand crank design, but I'll research it for you if you're interested.

Most of these designs use a wheel that moves a piston from what I can tell. I'll post a few preliminary links here and research it some more. I've never looked at these designs much before, but they should be perfect for what you want.

http://www.google.com/patents?id=uNY2AAAAEBAJ
http://www.google.com/patents?id=YPmSAAAAEBAJ
http://www.google.com/patents?id=odUdAAAAEBAJ

Once I get an idea of what sort of design you want I'll post more specific details about which parts you want, etc.
Last edited by SSCBen on Sat Mar 29, 2008 7:37 pm, edited 1 time in total.

Jheart
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Joined: Sat Mar 29, 2008 6:27 pm

Re: Big River Turret

Post by Jheart » Sat Mar 29, 2008 8:53 pm

Thanks Ben, that was obscenely fast. I looked at the links you provided, and at a couple more, as well as some videos of crank powered commercial water guns. I wasn't really impressed. I plan on arming all the kids with those off-the-shelf $10 pump squirt guns, and I'd like there to be an impressive difference between those and the raft gun.

I appreciate your offer to research cranking for me, and I'll take you up on it. I'll be spending my time doing the same. If you think that's the most practical way to get teams of kids independently shooting this thing, I believe you.

Should I also consider the idea of a pressurized gun, maybe a mounted air tank, with a bike pump or some other pressurization method? I want these kids to wield a little firepower.

akumabito
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Re: Big River Turret

Post by akumabito » Sun Mar 30, 2008 9:44 am

How about a double piston design?

I'm terrible with describing things, so please bear with me;

There are classic firefighting pumps who's design pretty much dates back to the Roman Empire. They consist of two upright cylinders side by side. The pistons are connected to a sort of teeter totter lever on the top. Water intake and output is controlled by two very simple check valves for each cylinder. When in use, it produces a steady stream as long as the levers are worked..

There are a number of advantages to a system like this;

- Ease of construction; it can be built entirely using store-bought supplies. PVC pipes for the cylinders, McMaster-Carr sells suitable 'pistons' (similar as used in the Cannon listed on the front page). Check valves can also be store bought, or made yourself. The levers can be made out of wood or metal.

- Easily adjusted; It is a pretty open ended design. You can control power in a number of ways; intake and output diameters, barrel diameter, cylinder bore and stroke, lever length, etc. Besides practical customizing, you're also pretty free in construction method to suit most budgets. It can be built almost entirely out of PVC and scrap wood if you want, or on the other end of the scale you could opt for an all-metal construction for increased longevity.

Jheart
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Joined: Sat Mar 29, 2008 6:27 pm

Re: Big River Turret

Post by Jheart » Sun Mar 30, 2008 12:49 pm

Akumabito, thanks so much for the idea. It took me a solid three minutes to sketch up an abominable copy of this concept. Is it what you were thinking? I've seen this type of fire engine, and the concept makes sense to me. Any leads on people who have attempted similar things?

Regardless, I've got the camp credit card and I'm going to head to Lowes and spend a hundo on a couple sizes of pvc, cement, and various caps, T's and elbows. The best way to get my head around this is for me to dive in and waste some time and money.
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SSCBen
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Re: Big River Turret

Post by SSCBen » Sun Mar 30, 2008 1:48 pm

Forget everything I said about crank water guns. This will simplify things.

You can make the entire handle part from PVC pipe. Make it big enough for multiple people to push on. Also, to get a good mechanical advantage you will want to extend the length of the arm to the handles from the piston maybe a few feet. Make sure the distance the handle moves is within what a kid could move and you're in business.

The piston part can be made with 2 inch pipe or 1 1/2 inch pipe (both schedule 40, which is normal pipe). If you want to use a pre-made seal from McMaster-Carr (part number 9411K14), go for 2 inch. If you want to use a homemade seal, go for 1 1/2 inch and basically follow this guide but with your design in mind: http://www.waterzooka.com/download/waterzooka.pdf

If you use the McMaster-Carr seal, you'll need to buy some 1/2 inch diameter allthread, which is a long threaded metal bar. You should also buy a rubber fender washer, two normal washers, and some epoxy to seal up everything there. This basically will make one side of the piston I used in Supercannon II, which is all you need.

You will need 4 check valves to use the two chambered design here. I'll edit in a picture later with where to put them. You can buy PVC check valves from most home improvement stores or save some money with smaller ones from McMaster-Carr (part number 7757K43). Edit: Don't get the smaller ones I just listed. They'd reduce your flow. Go with the 3/4 inch PVC ones. This will be more expensive, but give significantly better performance.

Some other parts you'll need include PVC threaded male adapters (the part the nozzles screw on in the APH), PVC threaded caps (the nozzles in the APH), any sort of tubing that can handle pressure, and tubing clamps. Get tubing larger than the diameter of your nozzle at the very least for this design. If you have small tubing, your flow will be very limited. Garden hose would be perfect here. If you buy garden hose with threads, there should be special garden hose to PVC adapters. The garden hose thread is 3/4 inch NPT, which should work with a 3/4 inch threaded female coupler too, but I don't know if it will seal well. Most hose attachments have a rubber seal and you'd want to find something with that. If you buy garden hose without threads (just the tubing part), you can use a 3/4 inch tubing barb and a tubing clamp to attach it to PVC pipe.

Messing around with PVC and plumbing parts is the best way to get a feel for the building process. I've actually got a good amount of my ideas from looking at what was available in stores.

Let us know if you have any other questions. If you can, take pictures while you build the water gun and make a write-up. The more guides we have out there, the more people we help. ;)
Last edited by SSCBen on Sun Mar 30, 2008 4:05 pm, edited 1 time in total.

akumabito
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Re: Big River Turret

Post by akumabito » Sun Mar 30, 2008 3:10 pm

Jheart wrote:Akumabito, thanks so much for the idea. It took me a solid three minutes to sketch up an abominable copy of this concept. Is it what you were thinking? I've seen this type of fire engine, and the concept makes sense to me. Any leads on people who have attempted similar things?

Regardless, I've got the camp credit card and I'm going to head to Lowes and spend a hundo on a couple sizes of pvc, cement, and various caps, T's and elbows. The best way to get my head around this is for me to dive in and waste some time and money.
That's the very thing I'm talking about! :D

Only comment about the picture would be that the lever bar would be straight, so that the cylinders work in opposite directions. i.e. one would be sucking, the other blowing, and vice versa when the lever is pushed down on the other side.. but anyway, the basic concept is sound.

I'm thinking you could probably find some benchmarks for various waterguns on this site and forum. Just find the output you think would be most appropriate, then calculate the theoretical output of this design, using a few design variables until you get a pretty close match. I am sure Ben, or others who know more about the technical details can help you with that.

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Silence
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Re: Big River Turret

Post by Silence » Sun Mar 30, 2008 9:23 pm

Good idea, akumabito! I haven't actually seen pumps like that, but they might have been shown in old movies or pictures that I've seen. Also, you're right in that the two pumps will alternate shots instead of working at the same time - but that's not necessarily bad.

You might as well use a wood rod for the lever with some type of bushing for the axle. Also, if the check valves still restrict flow too much, you could use a pressure chamber and a trigger valve.

Jheart
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Joined: Sat Mar 29, 2008 6:27 pm

Re: Big River Turret

Post by Jheart » Tue Apr 01, 2008 1:45 pm

So I've done a little shopping, and I'm attaching a picture of what I bought, with some rough labeling.

I think I can rig up the gun and turret just fine, I've had enough experience with hardware to do that.

But I need a little help with the piston and shaft design. I bought a 2 inch T-Y fitting (pic included) that I though I might be able to use at the bottom of the piston shaft. I want to try and find reducers to fit the check valves I bought, to avoid having to drill a 1/2 inch hole for each.

Any Ideas? Am I going to lose all kinds of pressure by going from a 2 inch piston shaft to a 3/8 inch hose to a 1/2 inch barrel?

Also, I think that the pvc designer program would be an awesome help, if I could just get it to on on Windows Vista....
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akumabito
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Re: Big River Turret

Post by akumabito » Tue Apr 01, 2008 2:40 pm

...I would think that if the volume displaced is equal, you ought to have far higher pressure using a narrow barrel. Though in most cases, you will not be able to pump the same quantity of water through it in the same amount of time exactly because of that reason - it'll take a lot more force to push the water through.

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SSCBen
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Re: Big River Turret

Post by SSCBen » Tue Apr 01, 2008 2:46 pm

Your potential flow will be severely reduced by the 3/8 inch tubing. I would suggest something higher like 3/4 inch garden hose or simple 3/4 inch tubing. The 1/2 inch PVC pipe is fine (the actual ID is 0.622 inches) as well, but it won't perform as well as the 3/4 inch tubing.

I'll post more of a response with some stuff about reducers, etc. when I get back from class. I'm leaving right now. ;)

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SSCBen
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Re: Big River Turret

Post by SSCBen » Sun Apr 06, 2008 3:48 pm

Have you started building anything yet? I haven't heard anything about this in a few days.

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