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CPS Custom Assault Rifle

Written by JLspacemarine
Last updated on 2009-08-03


Overview

(to be completed...)

The pump

I initially built the pump out of CPVC. With the correct o-rings and some duct tape I managed to make it work with a wooden stick. Unfortunately, even if the pump shaft was more than one feet long, it only had a volume between 30mL and 40mL, which isn't much for a homemade. At least it was on par with regular CPS Super Soakers.

I bought two O-rings of different sizes that I thought they would fit the best(having a piece of CPVC at the store to compare) and fortunately one of the two rings was the right size to use. Actually, I don't remember the size...

Pump handle

^ The handle came from a fake CPS 1000; at least cheap copies can be useful for something.

Pump handle and pump tube

Pump seal and pump tube

Pump seal inside pump tube

^ The O-rings were pretty thin so I used two for the best seal possible. The duct tape improved stability and acted as a stopper.

The orange handle snapped off so I built a tracked, properly positioned handle as a replacement. The original handle was a little bit too far from the grip, resulting in an unbalanced feel when combining pumping and shooting. I'm not worried anymore about the pump volume. Even if it is only about 40 mL, pumping is easy and smooth, allowing me to pump it faster without too much force. Any change to the gun's pump diameter would have forced me to change the trigger as well anyway, so I decided to keep it like it is.

The bladder

The balloons are attached just like LRT:

Spherical rubber CPS bladder made out of balloons

Mid-way update

Well, here is what it looks like so far:

CPS 1500 (top) and CPS Custom Assault Rifle (bottom)

Side view of the nozzle, trigger, valve, and pump assembly

Angle view of the assembly, trigger valve closed

Angle view of the assembly, trigger valve open

Close-up of the trigger valve, closed

Close-up of the trigger valve, open

Using test bladders such as balloons and even a Hydro Blitz bladder, I was been able to improve the pump and the trigger a lot. The trigger actuates the ball valve perfectly now. Yep, the wire travels trough the ABS, I've drilled holes in the casing for that purpose. I've took several pictures of the building process of the trigger so I should detail its construction soon.

Final update

The result was pretty much what I expected. Major changes:

  • The trigger is now pulled by all four fingers, as the previous hook type trigger was too hard to pull with only one finger
  • Most of the gun is now painted black
  • The pump handle is now vertical instead of horizontal
  • Note that all grips are improved with bike tubing
  • The ball valve and its mechanism has now its own casing held by the laminator (ABS test cap over a 4" PVC sleeve)
Side view of the CPS Custom Assault Rifle

Front angle view of the CPS Custom Assault Rifle

Rear angle view of the CPS Custom Assault Rifle

The ABS pipe I'm using is labeled Schedule 40 but has no sign of pressure rating. The reason why I choose ABS pipe is because where I buy my parts large PVC is not available in short lengths. I've just added a strap to the gun so that it is easier to use.

View of the disassembled CPS Custom Assault Rifle

These are the parts that can be detached from the current design.

The magic between the reservoir and the pressure chamber is just a 3" PVC endcap surrounded by a one inch long part cut out of a 3" ABS coupler. The PVC endcap fits perfectly within the ABS coupler piece, and the coupler piece fits perfectly within the 4" drain pipe as well. So I just had to epoxy/cement everything inside and that's it, the reservoir is separated from the PC. (I apologize for not having a picture of this as I'm too lazy to disassemble it again.)

Here are some stats:

  • Length: Between 22" and 32" (depending on what nozzle and reservoir is used)
  • Weight when empty: 7 pounds
  • Weight when full: heavy! (it needs a shoulder strap)
  • Pressure chamber type: Spherical (75 9" helium quality balloons)
  • PC capacity : 1200 mL
  • Reservoir Type: Onboard (can be detached and replaced by a backpack)
  • Reservoir capacity: 3600 mL
  • Shots per tank: 3
  • Pumps to pressurize: 33

Shot pictures

(no pictures of the standard nozzle yet)

Nozzle laminator + endcap drilled to 7/32":

  • Maximum range: 41 ft
  • Shot time: 4 sec
  • Output: 350 mL/sec
Water gun firing, using nozzle laminator and endcap drilled to 3/8

Nozzle laminator + endcap drilled to 3/8":

  • Maximum range: 50 ft
  • Shot time: 2 sec
  • Output: 850 mL/sec

This one is on par with my CPS 2000, but has more shot time.

Water gun firing, using nozzle laminator without endcap

Nozzle laminator without endcap:

  • Maximum range: 27 ft
  • Shot time: 1.3 sec
  • Output: 950 mL/sec

This one isn't very practical as the water has trouble getting very far, but a concentrated stream that thick is always heavy-hitting and fun to watch.

Water gun firing, using the riot blast

Riot blast:

  • Maximum range: 45 ft
  • Shot time: 1 sec
  • Output: 1200 mL/sec

The riot blast is amazing. Actually it is the best riot blast I've used yet, as its effective range get past 40 feet. It has also the most kickback.

In the end, this gun is great, but its weight can be annoying. Especially when compared to my CPS 2000. My homemade has some more power, capacity and versatility, but weights a lot more. All its drawbacks make me want to build another one. Air pressure this time. A 3D concept is on the way.

Links

The entire discussion thread from the forums.

< Discuss at the SSC forums - Print this page >

< http://www.sscentral.org/homemade/cpscar.html >