Next generation rubber CPS homemade water gun planning

Guides and discussions about building water blasters and other water warfare devices such as water balloon launchers.
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Tim
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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Fri Jul 08, 2016 5:17 pm

Drench-

“...I prefer a real pistol grip...” - I agree that a real pistol grip would be slicker. Are you suggesting just a pistol grip or a pistol grip with trigger? I don’t think I could use a pistol trigger unless I were using an electric or pneumatically-actuated valve (very short travel). If I use a pistol grip without a pistol trigger, how would I mount the brake lever?

“...a bike handle is much better than a PVC pipe!” - Actually, what I have modeled for the handle is PVC pipe. Technically, it’s rigid CPVC tube for drinking water, which has the appropriate OD for a bike brake lever. I am trying to keep this as light as possible. I’ll swap it out with aluminum if it doesn’t work.

Other parts of the handle assembly shown in the wire-frame view below include a “Sit-on-Top” strut washer, a 1/4”-20 weld nut, two 25-degree spacers, a long 1/4”-20 cap screw, a 7/8” OD washer, a wedge lock washer, and a rubber handle grip. Items not yet modeled include the bolts, 0.02” shims, and nuts I intend to use to attach the handle assembly to the strut channel.

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“Like Ben, I too am rather skeptical about the choice of a plastic ball valve...” - You guys are probably right; so, I replaced the plastic valve with a compact brass one in my model. I was unfairly comparing a 5/8”-port plastic valve to standard-port and full-port metal valves. I didn’t realize 5/8”-port 3/4” NPT metal valves existed, but Specialty Manufacturing does make them.

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“How long is the blaster and how much will it weight empty and full?” - Including the laminator and 2” sweeper nozzle, the blaster is 36.5” long. So, it’s more than 2” shorter than the original Monster XL, but about 1.5” longer than the 2002 Monster XL.

If someone wanted to make this concept shorter, they could cut the PC cover and find a smaller reservoir (or use a backpack reservoir). If someone felt my laminator/nozzle setup was excessive, they could have nothing more than a 3/4” NPT drilled cap (or 3D printed nozzle) protruding from the 4” PC cover end cap. This would still allow them to jam in straws sandwiched between two screens.

At the moment, my model weighs 8.27 pounds. That’s about 1.27 pounds lighter than the Monster XL’s dry weight, but I don’t have the pump and other miscellaneous items in there yet. I don’t know how accurate this weight is. For example, the brass valve I downloaded from Specialty Mfg is one solid piece; I assigned it the SG of brass, but the ball and seats are not actually brass. The Travel Agent is not solid in real life like I have it modeled, and I don’t have to use a brake lever as heavy as the one I downloaded.

A full reservoir would add 8.82 pounds of water. I’m thinking a full pressure chamber will not hold more than 1.33 liters, which would be 2.93 pounds. With the large reservoir, it may not be necessary to “fill-pump-fill” in every situation if you are worried about weight.

“Perhaps you should test the forces created and needed beforehand...” - Absolutely; this is a MUST. The valve is the first thing I need to buy & test before buying anything else. There is one on ebay right now; perhaps I should scoop it up.

“...pen and paper still works wonders.” - With my hand-drawing skills, this is pretty much how the concept looks...

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SEAL-

“How are you planning to do the reservoir-to-PC connection? - As Ben suggested, I’ll connect it to the other end of the bladder using flexible tubing (I have the unconnected tubing adapter in the model). I’ll probably use self-retracting tubing like McMaster part number 9148T165. I’ll breach the PC cover at the end cap that abuts the reservoir. From there, I’ll use regular flexible tubing to connect to a tee or wye that leads to the reservoir and pump. I have not modeled the tee/wye or check valves yet.

“I recommend having the tubing and pump be as wide as possible” - Both volume and pressure are important. If the diameter is too small, it will take forever to fill the chamber. If the diameter is too large, you cannot build as much pressure. I would like to make a convertible pump (somewhat like this pump). So, initially, you would pump with the inner and outer pistons. When pumping gets too difficult, you would pump only with the inner (smaller diameter) piston.

“My mountain bike has this fancy ‘short reach’ brake lever.” - A shorter-travel lever would not work in this application because the valve requires a long travel to open fully.

VR,

Tim

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Drenchenator
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Re: Next generation rubber CPS homemade water gun planning

Postby Drenchenator » Fri Jul 08, 2016 5:54 pm

Good job addressing my points! I was only concerned that the design would not go as planned, so I'm glad you had already had thought through all these aspects already.

Hmm, I didn't realize that the grip was a PVC pipe. I guess it looked like bike handle due to the bicycle brake so I said bike handle. Actually PVC pipe is better; it should be lighter and easier to source. But now I just realized that you could, provided you get the right diameter pipe, put a bike grip on the grip to make it more comfortable. That would be another "next-generation" idea for somebody to try.

I just checked the forum and apparently I never posted this, but I did show it off at a water war. The last update I made on Cloudburst before I put it aside was to install an AK47 pistol grip (just the grip; the trigger was an entirely separate system). This greatly improved the feel of the trigger and helped with the gun's handling. I don't know why I didn't post a picture of that online, but it certainly it something easy to do to greatly improve your firing hand's experience. (I don't have a picture of it with me at the moment, but I could post one in 2 months time.)

Still, I don't think it would be the right idea for your design, Tim, because yours really needs that bicycle hand-brake to fit properly, but I do think using a real pistol grip is a worthy addition for next-generation designs.
The Drenchenator, also known as Lt. Col. Drench

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Re: Next generation rubber CPS homemade water gun planning

Postby SEAL » Fri Jul 08, 2016 9:02 pm

I actually had a concept CPH where the water entered into the back of the chamber and exited the front. I'd like to see how it works in practice.

I wonder what the optimal pump diameter is. I think the SS 300 has the biggest pump of any stock soaker, but it also has three huge PCs. I'd imagine that total PC volume would factor into this. I'd love a blaster that I'd only have to pump once for full pressure, but I don't know what that would require.

The point of the short reach lever is that it still pulls on the brakes the same as a regular one. Although now that I think about it, my bike also has different-looking brakes than normal, so perhaps the extra travel comes from the brakes themselves, and not the lever. But I'm going to shut up about it because my knowledge of bicycle technology is rather poor, haha. Short travel levers would sure be great for tap shots though. They feel awesome to use.
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Tim
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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Fri Jul 08, 2016 9:08 pm

Hey Drench,

"...you could...put a bike grip on the grip" - I do have a rubber bicycle grip modeled in the screenshots that is over the CPVC. It's not very apparent because I didn't model in any texture on the grip. Above the gold brake lever clamp is the black external 25-degree spacer. If you zoom way in, you can see a thin beige haze between the spacer and the clamp - that's the CPVC tube. Immediately below the lever clamp is the rubber handle grip, notice the diameter below the clamp is larger than the diameter of the spacer above the clamp.

I was thinking about using McMaster part number 9729K21, but perhaps I could use something fancier like the grip below, but in black.

Image

EDIT: Hey SEAL - Sorry I didn't see your post earlier. V-Brakes require a longer pull than other types of brakes. Perhaps you have disc brakes or something or perhaps you have a type of brake lever that I have not considered. Can you tell me the brand and model of your levers so I can check them out?

VR,

Tim

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Re: Next generation rubber CPS homemade water gun planning

Postby SEAL » Sat Jul 09, 2016 6:23 pm

^No, I don't have disc brakes. Those use a hydraulic system I believe, like car brakes. I actually wonder if you could use hydraulics to actuate the trigger valve. But that's probably needlessly complex.

Unfortunately my bike is at my parents house so I can't look at it. I know it's a Trek Single Track ### (the number is like 930 or 950 or something), and I believe the levers are made by Shimano. The brakes are apparently called cantilever brakes.
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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Mon Jul 11, 2016 4:43 pm

Quick update. I was able to find a thin LDPE paint masking cap with the correct dimensions to keep the LRT/GRT centered...

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Re: Next generation rubber CPS homemade water gun planning

Postby SSCBen » Tue Jul 12, 2016 6:31 pm

All, just wanted to make a quick reply saying that I have read the replies here but haven't had the chance to sit down and hammer out one of my own. Hopefully will get the chance soon.

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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Sun Jan 29, 2017 11:17 pm

Yes; I need to work on the valve, and I'll likely change the design below to include TheSoaker's 12-volt 100 PSI pump, but I figured I'd drop a screenshot of my 3D model's current state...

Image

VR,

Tim
Last edited by Tim on Mon Feb 06, 2017 7:17 am, edited 4 times in total.

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Re: Next generation rubber CPS homemade water gun planning

Postby TheSoaker » Mon Jan 30, 2017 12:55 pm

If you are going to use the pump I found, Use a LIPO pack to power it. You'll save a ton of weight and you would get more power out of it than if you were to use lead acid.
super soaker cps 2000......SUPER SOAKER CPS 2000!!!!!!!!!1!!!1!!one

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Tim
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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Wed Feb 08, 2017 10:54 pm

TheSoaker - I'm not sure if I will use LiPo, but I'll definitely use a Lithium technology for its superior energy density. The problem with LiPo packs is that I cannot find any in the necessary dimensions. I want to hide the battery in the strut channel (the "backbone" that everything mounts to). I believe I can do this if I use a LiNiMnCo Battery Pack.
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VR,

Tim
Last edited by Tim on Mon Feb 20, 2017 10:29 pm, edited 3 times in total.

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Re: Next generation rubber CPS homemade water gun planning

Postby TheSoaker » Thu Feb 09, 2017 12:29 am

That seems like a perfect battery to use for this haha. When this is done it'll be like the Scorpion on steroids! I'm looking forward to seeing the updated 3D model and soon after the finished product!
super soaker cps 2000......SUPER SOAKER CPS 2000!!!!!!!!!1!!!1!!one

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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Fri Feb 10, 2017 8:21 pm

TheSoaker,

I don’t have time to update the model for real at the moment, but I’ve lobbed the pump in there so you can get an idea of its size in relation to the blaster….

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I didn't even know the Scorpion existed. Now looking at this blaster on isoaker.com, I found it amusing that isoaker said "The Scorpion gives a glimpse at potential next generation water blasters..." Here we are, about a decade later, contemplating picking up where the Scorpion left off in a thread called "Next generation rubber CPS homemade water gun planning".

Are there any other blasters like the Scorpion?

VR,

Tim
Last edited by Tim on Mon Feb 20, 2017 4:45 pm, edited 1 time in total.

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Re: Next generation rubber CPS homemade water gun planning

Postby TheSoaker » Thu Feb 16, 2017 2:22 pm

Looks good! I don't think there any other water blasters like the scorpion, it's one of a kind!
super soaker cps 2000......SUPER SOAKER CPS 2000!!!!!!!!!1!!!1!!one

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Re: Next generation rubber CPS homemade water gun planning

Postby SSCBen » Thu Feb 16, 2017 11:27 pm

Tim, I think you're on a great track so far. Sorry for the delay. I had forgotten to reply here after reading through everything.

The firing valve is nice. Based on the experiments you've done so far, I think you're on the right track. I had meant to mention in the other thread (seems I never posted there) that the water hammer issue might be reduced if you use rubber tubing instead of a garden hose. The tubing could act like an accumulator, absorbing the pressure instead of ejecting the water. Though, you did say an extra seal fixed this.

I'm afraid my understanding of seal technologies is insufficient to offer much other advice. I look forward to what else you can figure out in March.

The pump fits very nicely on top. Almost looks like you designed it that way from the start. I'd like to see how well this works. If the energy storage of the batteries is adequate then this could change the hobby a lot. I'd be careful to avoid overheating the battery. We have a battery fire expert in our research group, and it seems that batteries placed without regard for the heat transfer from their location can be very dangerous. This might be a reason to prefer a more conductive strut channel rather than the fiberglass one you picked. Also, consider using some sort of conductive paste to mount the battery. These ideas might be unnecessary, though, so do some tests to see how hot the battery gets in typical and extreme use cases.

Tim wrote:"I think a 4.25 inch ID tube is way too big." - The large OD allows me to put the valve inside the PC cover. Maybe I'll just build up the bladder to a larger OD. I'm thinking I might try to use Gum Rubber Tubing (GRT) instead of LRT. Sling shot enthusiasts use LRT and GRT interchangeably. They admit the LRT has a little better performance initially, but the GRT has much greater durability and longevity. I can get the bladder to a 2.75" OD with just three layers of GRT. Maybe a smaller OD than this would be okay because GRT is more durable.


GRT also is a good idea. I recall being very dismissive of GRT back at SSC, but I do not think I had good reasons to dismiss the material.

SEAL wrote:I'm looking forward to seeing how this GRT stacks up to LRT. I've always been kind of skeptical of CPHs because it seems like every single person who's built one has had the PC rupture.


How frequently does this happen? I had the PC of my CPH rupture once, but it was only because I lent it to someone else who overpumped it.

Replacing the bladder is not hard, and probably should be done every once in a while anyway because the bladders will wear out and become weaker.

Tim wrote:At the moment, my model weighs 8.27 pounds. That’s about 1.27 pounds lighter than the Monster XL’s dry weight, but I don’t have the pump and other miscellaneous items in there yet. I don’t know how accurate this weight is. For example, the brass valve I downloaded from Specialty Mfg is one solid piece; I assigned it the SG of brass, but the ball and seats are not actually brass. The Travel Agent is not solid in real life like I have it modeled, and I don’t have to use a brake lever as heavy as the one I downloaded.


I've had the same concerns for my designs before. I'd be interested in seeing a comparison of the weight predicted by the provided information and assumptions to the final actual weight.

SEAL wrote:I wonder what the optimal pump diameter is. I think the SS 300 has the biggest pump of any stock soaker, but it also has three huge PCs. I'd imagine that total PC volume would factor into this. I'd love a blaster that I'd only have to pump once for full pressure, but I don't know what that would require.


You need to figure out how much you want to trade off pump volume for pump force. Then it's a matter of finding the sweet spot. For me, I think larger pump volumes are okay because I'm stronger than the kids even older Super Soakers were designed for.

I might add more later when I have more time...

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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Sat Feb 18, 2017 12:00 am

TheSoaker,

Thank you for the feedback. Do you (or anyone else reading this - isoaker? mr. dude? soakinader? anybody?) have photos of the Scorpion’s internals?

Ben,

You’re totally right about rubber tubing acting like an accumulator – even the garden hose does this. I did not add an extra seal to alleviate the problem, I removed the redundant seal. As before, the pressure upstream of the inlet-side seal accumulated in the garden hose. I think the problem was that the pressure in the valve body downstream of the inlet seal could not relieve through the firing nozzle until I compromised the outlet seal. I could have removed either the inlet seal or the outlet seal to eliminate the water hammer.

I removed the outlet seal because I was thinking I’d have pressure working on a smaller surface area to separate the seal and gate. Yes; less “total” surface area, but not less “net” surface area (not less force). If I had removed the inlet seal, pressure would be applied to the entire area within the inlet body seal, and pressure would be applied to the area within the outlet body seal minus the area within the outlet seal. But what if I altered the shape of the inlet body seal so the area within it was equal to the area of the outlet body seal minus the outlet seal? I can employ the same o-ring for the inlet body seal, but make the groove hour-glass shaped instead of slot shaped. I’ll have clearance for this if I remove the redundant inlet seal groove. Would this help me achieve a near-equilibrium across both sides of the gate or am I thinking about this wrong? Although I can’t find any examples of the embodiment I am proposing, the gate valve patents I am reading emphasize techniques in which to transform pressure seal applications into zero-pressure seal applications.

“The pump fits very nicely on top. Almost looks like you designed it that way from the start.” – I agree; it looks really good there. Thankfully, the pump is self-priming and can be run dry for short periods while you prime or as you run out of water. That position will put the wires in an excellent spot, but will put the plumbing connections in a less-than-ideal spot. To resolve this, my contact at Seaflo USA has confirmed that he has US stock of the optional pump body in the sketch below. The 90-degree elbows swivel so I can better route the inlet and outlet tubing rearward.

Image

“…it seems that batteries placed without regard for the heat transfer from their location can be very dangerous…do some tests to see how hot the battery gets in typical and extreme use cases.” - I’ll keep this in mind, and testing/monitoring is a good call. I’m hoping the FRP strut channel will provide shade from the sun while allowing ample ventilation because the bottom of the rail is open. I fear that metal strut channel might conduct heat from the sun to the battery pack on hot days.

“I recall being very dismissive of GRT back at SSC, but I do not think I had good reasons to dismiss the material.” – Perhaps I should not be so dismissive of LRT.

“I'd be interested in seeing a comparison of the weight predicted by the provided information and assumptions to the final actual weight.” – I can’t wait to see that either.

VR,

Tim

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Re: Next generation rubber CPS homemade water gun planning

Postby SSCBen » Sat Feb 18, 2017 11:04 am

On the battery heating issue, I should also point out that battery fire are rare and hard to reliably reproduce, so you might not see one no matter what you do. Another issue to keep in mind is to not have anything pushing hard into the battery. The contract point can help initiate an internal short.

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Re: Next generation rubber CPS homemade water gun planning

Postby Tim » Sun Mar 05, 2017 1:28 am

Ben,

Good points regarding battery safety. Batteries with Lithium chemistry can be dangerous if not used and protected properly. Some of these Lithium chemistries are safer than others by default. The LiNiMnCo chemistry combines the safety and low resistance of Manganese with the high energy of Nickel and Cobalt.

Lithium-based batteries are found in modern laptops, phones, power tools, and many other electronics. Similar to these consumer electronics, the LiNiMnCo battery pack that I'm proposing already includes a protection circuit module that prevents over-charge, prevents over-discharge, limits discharging current, and avoids damage from short circuit or reversed polarity. Li-Po battery packs for RC cars, planes, and boats do not have built-in protection modules. Despite the presence of the protection module, an appropriate charger must be used with the battery pack. Additionally, the discharge current limitation is above the pump's recommended fuse amperage rating. Regardless, an inline fuse should be employed on the positive DC circuit.

Yes; punctures must be avoided to prevent fire. RC Li-Po batteries rarely come with a hard shell. The Li-Po batteries in a mobile phone are also soft-shelled, but protected by the phone's enclosure. Although the pack that I identified is made of hard-shelled cells, I must still consider the risk of puncture when determining placement.

VR,

Tim


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