Riptide CPS Prototype

[Drenchenator]

I posted this at Super Soaker Central about 2 weeks ago and figure that I ought to post this here for more comments.

I've labeled this gun Riptide DR-4. It's a cylindrical CPS water gun with a trigger, tracked pump, and casing.

At the moment, the gun has a single tube of later rubber tubing to make the CPS bladder, but upgrades can happen if I want; though I don't right now.

The casing is 1/4" thick polycarbonate. I took some of the pictures below before I took the plastic casings paper coating off and before I replaced the grip. The gun's final state is as pictured above--clear and transparent.



The gun compares well to the CPS 3000: Both are 28 inches long; both have tracked pumps; both need a backpack reservoir. But my gun weights 7 pounds empty.

Let's look at my gun's preliminary performance tests:



This data is from tests I did this morning. The gun under-performs in these tests, because the new CPS bladder twisted and bent (click for a picture), decreasing the pressure applied to the water and decreasing performance. Still, a cubic approximation of the best nozzle size predicts that a 7/32 inch nozzle produces 43 feet in range, so I'll have to try out that later. To fix the problem, I will flip the bladder around or replace it entirely; it's only a problem with the rubber bladder itself, making it very fixable.

Internally, the gun is simple:



It pumps 45 mL or 1.5 oz with each stroke. I put all the check valves at the gun's pump end, where stock soakers also place them. This placement balanced the gun well.

All parts are brass; brass saved space but added weight. PVC composes only one part, the pump.



I designed an original trigger system: a rotary trigger. Most triggers are linear triggers--they travel in a straight line--but I chose a rotary trigger because it offered more displacement (change in position) in a smaller size. The ball valve I used needed around 1 1/2" inches of displacement to fully open; the designed pressed me for space in this region, so I let the trigger's path arc to get more displacement.

Two rubber bands folded onto each other return the trigger and valve a closed position. The user feels little resistance when pulling the trigger because the trigger acts as a torque arm, reducing the force you need to pull the trigger the farther out you pull it.

Such a simple system works well. This video shows that you can pulse shots with ease.



The valve is a 3/8" brass ball valve. The trigger pushes an aluminum beam, which pushes the firing valve's arm, opening the valve and shooting water. The valve closes when the rubber bands pull back the aluminum beam and close the valve.

I made a video of several trigger cycles to demonstrate this.

[HBWW]

Looks like you may need another layer of LRT for better performance. Rest is as seen on SSC. Looks as amazing here as it does there; well done.

[isoaker]

That's one slick-lookin' homemade. How many pumps does it take to fill the PC; any idea on the approx pump volume? My only complaint is the use of opaque PVC tubing to house the PC. I suppose the opaque stuff is cheaper and more durable in the event of a PC-rupture, but considering the rest of the blaster is either metal or transparent plexiglass, the PVC tube looks a little out-of-place. Otherwise, looks like a great build and good performance, too, though as C-A_99 noted, perhaps another layer of LRT would boost its power a little more.

[HBWW]

I wouldn't say the big PVC PC case looks out of place, but it definately makes it a bit more difficult to get a feel for when to stop pumping. The transparent casing looks perfect though, effectively showing off the internals.

[Drenchenator]

Thanks for the replies and positive comments, isoaker_com and C-A_99.

How many pumps does it take to fill the PC; any idea on the approx pump volume?

The PC volume is around 2500 to 3000 mL, and the pump volume is 45 mL, so it will take around 56 to 67 pumps to get it full. But remember, that's over 2 liters in the chamber, so you won't always have to.

I suppose the opaque stuff is cheaper and more durable in the event of a PC-rupture, but considering the rest of the blaster is either metal or transparent plexiglass, the PVC tube looks a little out-of-place.

I wouldn't say the big PVC PC case looks out of place, but it definately makes it a bit more difficult to get a feel for when to stop pumping. The transparent casing looks perfect though, effectively showing off the internals.

I did look into the clear plastic pipe and tubing at McMaster-Carr, and the prices varied greatly for different sizes. I couldn't find anything with a 3.5" diameter, 3" PVC's diameter, for a reasonable price; many times, the pipe cost 20 to 30 dollars a foot. Though this gun wasn't cheap (I guess it cost around 100 dollars, but I could be wrong), I'm not spending that much money. I'd love to see the pressure chamber expand just like you guys and see when it reaches full, but counting my pumps is quite easy, and as long as I don't go over 45 to 50, I know it's not full.

But if I had the money, I would go for it.

[Fishfan]

Could you post a guide on how to make this? I'd love to make something like this, it's a lot more compact than a CPS based on Ben's design.

[Andrew]

Check dates before replying to posts. Drenchenator last visited isoaker.net on 1st November 2009.

The SSCforums thread has more information and details on this, but I don't think there was ever a guide as such.

The reason it's more compact is because he thought a lot about where to position the components. The standard CPH can be made more compact by making small variations to the design layout. At the core of the riptide design is of course a standard CPH (because they MUST have that basic layout [res-CV-pump-CV-PC-nozzle] to work well).

[Drenchenator]

Unfortunately, I don't have any pictures of the construction process, so a guide would be hard to write. I designed and build the gun simultaneously, using parts that were laying around the shop. I think I only ordered 3 parts from McMaster: both check valves and the square brass tee.

The design came together pretty quickly. I thought of a trigger system, and decided to just build it. Ben and I had so many extra parts that I just started fitting stuff together and trying it out. I was a little surprised that it came together so nicely considering I designed it piecemeal!

There is actually one part that I wish I took pictures of to make a guide. The pump is very well done. I bought 2 rubber grommets (big, thick rubber washers), drilled a hole in the end of a 1/2" wooden dowel, and fastened the grommets to the end of the dowel. 5 minutes work -- no sanding, no stretching O-rings.

There was some discussion on another thread about this gun being a rather advanced build. I agree. It was an experiment from the get-go, and I didn't design it to be reproduced. The big thing to replace would be the plastic sheeting for the casing. Wood could work, believe it or not, as long as you paint it with some kind of sealant. The next thing would be to reduce the total number of bolts and screws. I think there are 40 to 50 bolts or screws in the whole thing, which is way too many. Another potential problem is that trigger system. I'm left-handed, and the gun clearly is only designed for lefties. There are many other smaller issues, but these are the main ones that I see in the design.

[Andrew]

Check dates before replying to posts. Drenchenator last visited isoaker.net on 1st November 2009.

I find myself eating my own words!

Welcome back!

Wood would definitely work, it could be varnished, treated etc. but would weigh a lot more than a plastic casing if you wanted something of similar strength, or stronger. Personally I would prefer to work with plastic, acrylic, perspex etc. than wood, but as I said, that's just my preference.

That idea of a pump seal is quite interesting. Kinda like the stock pumps from Super Soakers.

As it was a prototype it was bound to have small issues here and there. It just needs someone to come along, build something based on it, and amend as many of the issues as possible (I might give it a go if I ever get hold of the materials and kit. Uni should have some maybe?).

[Fishfan]

I think I will attempt to build something like that. I would like something that is much easier to use than regular homemades out there. I will also address those bugs you mentioned in your prototype.