river gun/stream machine

Build a homemade water gun or water balloon launcher and tell us about it.
Locked
fatalnrg
Posts: 1
Joined: Mon Jun 05, 2006 6:39 pm

river gun/stream machine

Post by fatalnrg » Mon Jun 05, 2006 8:15 pm

Hello everyone,
I am trying to improve on a water gun I made for rafting wars on the American River (anyone here from Sacramento?). Every year there are major water battles out there when people get drunk and rowdy. The design of my gun is based on the NRS Stream Machine. These are often weak and break fast. My design uses PVC pipe for the shafts and seals.

Here is the "blueprint":
Image

I'm experiencing several serious design problems.

First of all the piston part leaks when I try to suck water out of the river. I'm thinking its because I used a suction cup screwed to the end of the handle. It fits tight but im not sure I centered it right and the material is too soft to suck up such a volume of water. In any case, I'm looking for an alternative piston/suction material. Any suggestions?

Next, the water often leaks through SEAL B. I drilled a hole through the PVC cap just big enough for the handle/pushrod to slide through the seal with allowable resistance. Still the water shoots out the back through the seal when I draw water! The drill bit and the pushrod are listed at the exact same diameter. How can I possibly improve on this seal?

Finally, I made a few efforts to design the best nozzle. Small nozzles (1/16") often required too much force to draw/shoot and took too long to fill. Large nozzles (1/4")do not cover enough ground when I shoot. Medium nozzles (1/8") have good propulsion but force the water in all directions when I apply enough force. Is there a specific way to drill a nozzle that will give greater accuracy?

Thanks in advance to anyone who can help me answer any of these questions. I apologize for the weird terminology.

User avatar
DX
Posts: 1780
Joined: Wed Feb 04, 2004 1:00 pm

Post by DX » Mon Jun 05, 2006 8:40 pm

The nozzle problem should go away when you create a better seal. I made a piston pumper gun that uses the kind of seal drawn here: http://www.geocities.com/m15399/pumps.html

I've found that O-rings are the best way to make the seal, water gun manufacturers themselves use O-rings for perfect seals. If you get the right OD and ID, the seal will be good enough that no water drips out the back whatsoever. I've found the best nozzle to be 1/4" and it gets ranges from 48-54 ft.

Image
Mess With the Best, Get Soaked Like the Rest!

2004 Red Sox - World Series Champions
2007 Red Sox - World Series Champions!

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Mon Jun 05, 2006 8:47 pm

Wow, never heard of the sport/hobby, but we do have several Californians and at least one Sacramento member (is it Baghead? I'm not sure...). There's a stickied locations thread under the Off Topic subforum, and some members put their locations in their header.

Use the standard O-ring procedure people use in their homemade pumps. Basically, take an O-ring with an OD slightly larger than the tube's ID and and ID the same as your pump shaft's OD, and use electrical tape stacked on both sides of the O-ring to hold it in place. Here's a link to Ben's pump article. The only seal you'll need is an O-ring attached securely to the pump shaft--don't worry about what is currently "Seal B."

To solve your intake/outflow problem, I suggest the use of two openings. Have a tee near the end, and in the fork that sticks out from the others, have a check valve and a very large orifice. Then, stick both openings in the water and draw out some water, and when you squirt, everything will go through the small, unsealed opening. You could also build a full-fledged homemade...

EDIT: Didn't see Duxburian's post. Note that the ideal nozzle orifice often depends on the internal pressure (which can vary for pump-action models because of the varying strengths of different users), so you should just experiment. If you used a screw fitting to be able to use multiple nozzles, then there's nothing wrong with having a large nozzle for "special situations." You can also buy the Lanard X-Stream Blastmaster 660 from Sears, and it's an effective and reliable pump-action blaster, though it has its own reservoir.

Sean
Posts: 2
Joined: Mon Jun 12, 2006 9:32 pm

Post by Sean » Tue Jun 13, 2006 10:31 pm

Hmmmm.....

What if we took the design below and used it as a pump? Plug the nozzle end into a manifold with check valves at either end. One end going to the water supply and the other of course going to the CPS.

After seeing the article on howstuffworks.com I couldnt help but wonder if one could mimic the same design on a larger scale. The problem I was running into was the CPS....what would I use in place of a small balloon? I thought of all kinds of things, hot water bottles, whoopie cushions, latex gloves, inner tubes, vollyball bladders. The practicality of using any one of these of course remains to be seen. I like this pre-charge idea because I could draw from the river on the up stroke and pressurize on the down stroke.

User avatar
SSCBen
Posts: 6449
Joined: Sat Mar 22, 2003 1:00 pm

Post by SSCBen » Tue Jun 13, 2006 10:55 pm

CPS homemade water guns already have been made if that's what you were referring to. You use latex rubber tubing for the CPS chamber. Some people also have reported success using bike inner tubes or balloons, but I wouldn't use those.

Locked