CPH M1

[wetmonkey442]

So last summer I had a lot of fun building a super compact APH. It has some major issues, but I also think that the design was a step in the right direction for homemade water guns. This summer I am going to try to build a CPH with the same utilitarian design philosophy. I started this thread because I just ordered the LRT and a couple check valves from McMaster. I am going to keep a build log on this thread, but I will probably only be able to update it on weekends.

I've been contemplating the design for a few months now, and have been considering some of the more specific issues over the last couple of days. The most obvious concern for me is the pump design. I have never been satisfied with my attempts at homemade pumps, and I usually end up scavenging a pump from a broken Super Soaker. Well, I finally think I have a good grasp on how to deal with the issues that I've experienced in the past. I'll try to build up a version of it this weekend to show you guys.

This whole build is going to be very tight, and completed with precision and expert craftsmanship. I've got a lot more experience working with PVC than I did 8 years ago when I built my first APH. I have all of the tools I need and I'm sparing no expense for parts, etc. (although I did decide to ditch the 24k gold case with inlaid diamonds ).

Alright, let's get ready to roll!

[SEAL]

wetmonkey, is it just me, or do you always come up with a new homemade every spring (although we're into the beginning of summer now.)? In 2010, the year I first joined, you were making that weird-shaped APH, last year you made those compact APHs, and this year, you're making a CPH. Do you get an urge to build around the same time each year?

I'm looking forward to seeing your project unfold. You should bring it to our next war if it's good.

[atvan]

Are you using those tubing check valves? I have always wanted to see those used to make a compact homemade, just because they are tiny and don't have to be lined up all rigidly because they attach to the vinyl tubing.

[mr. dude]

although I did decide to ditch the 24k gold case with inlaid diamonds

Well there goes the project

Anyway, I look forward to seeing this happen!

[DX]

I can't wait to see what you do with the pump. Homemade pumps are my least favorite part about making water guns and are usually the weakest link in what I build. My most recent APH ripped a pump off from a broken Blazer. I'm definitely looking forward to this new pump design.

[atvan]

Mine doesn't leak at all. The nerfers really got it right, putting teflon tape under the O-ring to bump it out. I believe it worked flawlessly for Andrew (the other one) as well.

The are way to many people on here with the same names. It gets confusing.

[DX]

There are 2 Andrews, 2 Bens, and 2 Roberts. That's not too bad...(but the pun is). Usually my problem is needing the rod to get smaller rather than needing the O-ring to get bigger. Nothing I find seems to work with 1/2" PVC. The one seal I got to work very well was on a wooden dowel when it was dry. That doesn't work when it expands, and cutting a groove takes a lot of experimentation to get the seal perfect when the dowel is saturated. It's to much of a hassle, and I'd like to ditch wood for another material.

[atvan]

My wooden pump worked fine the first time after adding the teflon tape.

2 Andrews, 2 Bens, and 2 Roberts walk into a bar…

ftfy

[wetmonkey442]

@DX: See that is exactly what I am aiming to solve. It's pretty hard to cut grooves into a dowel that are perfectly straight. Even the slightest imperfection can lead to an uneven distribution of stress on the o-ring (or whatever sealing material you're using) and lead to leak and tears over time. My pump will be featuring nylon spacers in order to make sure that the o-ring is situated in a perfectly round groove. It will also be using a thin metal rod instead of a wooden dowel. I've got the whole thing pretty much planned out, I might make a Home Depot run later tonight.

@atvan: Yeah, I'm gonna try out those hose barb check valves and see what they're all about. If they work well, it's gonna go a long way to making homemades more compact.

[wetmonkey442]

Here's a short video detailing the beginning phase of the pump construction: http://www.youtube.com/watch?v=PVJtiske ... ature=plcp

[wetmonkey442]

The completed seal:

[SEAL]

There are 2 Andrews, 2 Bens, and 2 Roberts.

I think there are actually 3 Andrews...

wetmonkey: I enjoyed watching your video. I'd like to see how the pump turns out; whenever I get around to making my CPH (which will likely be more of a heavy cannon.), I want to make a homemade pump, and I want it to be at least as good as my APH bike pump, so if your method works well, I may copy it...

[HBWW]

Nice pump seal. I didn't go quite as far with the nut and bolt concept for holding the o-ring; all I had was an inset-hex head (whatever the proper name for it was) screw 3/8" thick and 3/4" to 2" long. A 3/8" x 5/8" O-ring goes on the end and the rest goes into a 1/2" rod.

Now, the hollow 1/2" aluminum rod is about 7/16" and doesn't fit tightly with the 3/8" diameter of the screw, so I use epoxy to hold it in. Unfortunately, this means it is not perfectly centered.

My alternative is to use epoxy putty and a 1/2" x 5/8" (something like that, more or less) o-ring and put the seal right on the rod. I never really tested it that far, but I'd imagine its considerably weaker. Regular epoxy would probably be better, but it's not as controllable when applying. You can't make a large, flat, even area that supports it.

In the past, I've also tried CPVC spacers and wooden dowels. All of the years I spent doing that were nothing more than wastes of time and parts; nothing ever worked properly for more than a few pumps. My latest pump, however, (the one with the screw, o-ring, epoxy, hollow aluminum rod) has been pretty solid and has lasted at least 3-4 games and several PC cycles. If anything, it's the CPH bladder that's the problem. LRT broke and I replaced it with balloon layers that keep snapping off one by one. I will need to continue working with it and perhaps use different balloon sizes.

Wetmonkey, what did you do to make/get the plastic part around the screw that holds the seal?

[marauder]

This is great. I hope you take lots of pictures of how you put the pump together. I will probably put a link to this thread/your videos on Hydrowar when you're finished. The video is good, I'm jealous of your toolshed and work shop. Part of the problem with having a little college apartment is there's really no room for that, but one day!

[wetmonkey442]

Wetmonkey, what did you do to make/get the plastic part around the screw that holds the seal?

I used two nylon spacers that were ground to fit inside the 1/2" PVC pump shaft. I then turned each spacer while filing a 45 degree angle at the top lip. By placing the spacers on the bolt so that both of the grinded angles were facing each other, I effectively had a plastic cylinder with a "V" shaped groove running around it. I then rotated the whole assembly while using sandpaper to deepen the groove, stopping every 15 or 20 seconds to dry test the o-ring into the pump shaft.

The goal was to make a pump seal that was water tight, even at high pressures, but that also had a small sealing face (to reduce friction and make the pump easier to move). Really, this is no different than cutting a groove in the end of wooden dowel, except that this process ensures that the groove is centered and is (more or less) perfectly circular. I wanted an even-distribution of force on the o-ring along the entire circumference of the seal. Dry tests indicate that this should work pretty well, but I won't know for sure until I set up the actual pump with a pair of check valves.

[Andrew]

I believe it worked flawlessly for Andrew (the other one) as well.

It did until the wooden pump rod snapped (nothing to do with the o-ring groove, it was the holes drilled for the pump handle bolts combined with an enthusiastic friend). I used a brass rod second time round, and a homemade lathe to cut the groove evenly, with a file to smooth out the bottom of the groove.

I like the idea of using nylon spacers, brass isn't easy to cut grooves into, and the drill took a little bit too much punishment (when used as a lathe headstock and spindle) for my liking. If I had access to a proper lathe, I'd be much more comfortable using a single piece brass rod, but until then this seems like a much easier and more reliable method.

How are you planning on connecting it to the rest of the pump rod? Are you thinking of drilling a hole into a metal rod and tapping it to the same thread size as the bolt?

I believe it worked flawlessly for Andrew (the other one) as well.

The are way to many people on here with the same names. It gets confusing.

Yeah, sorry about that. I used my name on SSCentral because I couldn't think of a good enough username. Came to iSoaker.com and (even though I already made an account a while before) thought I might as well continue using it to avoid confusion (well that worked didn't it! ). Now I can't change it so I'm pretty much stuck with it.

If everyone has and uses usernames it's much less confusing.

[wetmonkey442]

How are you planning on connecting it to the rest of the pump rod? Are you thinking of drilling a hole into a metal rod and tapping it to the same thread size as the bolt?

I will most likely use a threaded coupler to connect the bolt to a much longer thread 1/4" galvanized rod that I picked up. I will cover the remaining threads in tape so that the pump rod moves smoothly through the pump cap at the end of the shaft. The only reason I'm doing it this way, instead of drilling into a wooden or metal dowel, tapping the hole, and connecting the bolt (as you suggested) is that I can't ensure that the hole that I drill will be perfectly centered (lack of a drill press, etc.). To reiterate, I think an even distribution of force across the sealing surface is the most important part of a successful pump seal, and centering the movement of the seal around a rod that is static in two axes will go a long way towards ensuring this even distribution.

[wetmonkey442]

My LRT and check valves arrived last night. I can't wait for the weekend so I can make a trip to Lowes to pick up the remaining parts.

The in-line tube valve is brilliant it's SO small and looks like its going to work perfectly. Well, it worked great with me blowing air through it, so I can assume it'll work well for water to. I guess time well tell. Meanwhile I need to figure out a way to layer this LRT. It is much thicker than I imagined it would be...

[wetmonkey442]

No work today since I'm out of town. I'm gonna swing by Lowes on the way home tomorrow and pick up the remaining pieces. I'll do a try fit and take a picture to show you guys what the final product will (hopefully) look like.

[atvan]

That is amazing. The nice thing about pumps is that they can be easily replaced, and because they are probably the thing that could use the most advancement, that is nice. I might make one of these if ( when) I make a CPH, but more likely than not my APH will borrow it for full time use as well.

Also your vice is exactly the same as mine…