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Posted: Sat Mar 15, 2008 10:35 pm
by C-A_99
I'm planning on another pneumatic launcher, one with a fairly reasonable ROF, onboard pump, 2" barrel, and most likely a modified solenoid valve. Here's a diagram of the design.


The primary purpose of this launcher is for direct-fire sniping. I'm trying to design it so that not many pumps per shot are needed. (40-60 PSI should suffice just fine for loads of that size)

Now I need to know the practicality of this and to get some ideas and advice here. Some potential difficulties include:

-Finding something for the breech, and the proper O-rings needed.

-Getting the pump to be onboard.

-Modifying the sprinkler valve.

-(Probably the easiest) Getting the whole structure together; it should be held and handled like a typical gun/blaster. The extra pipe in the back will work almost like a stock (I might actually attach a stock on), and the actual vertical space taken up by the PC, pump, and firing valve should be less than in the diagram. (I might also do some lateral shifts with both the PC-valve and pump to further compact the design, as well as use flexible tubing for some transitions instead of PVC)

-The fact that the balloons will probably pop in the hopper, perhaps when they're just above the breech.

-If the operator is an idiot and doesn't lock the cocking handle, the breech will be launched back when the trigger is pulled. This actually may not be a bad thing if it doesn't launch it back too much, then I could put a spring on the breech and make it semi-auto-ish, I say ish because re-pressurization is still required.

Now, I'm guessing someone will suggest using a rotational breech instead. (to lessen the chance of cook-off, to improve airflow, and to avoid using unecessary space) However, those seem to be difficult to design and I want to stick with this type if I can get it to work.

Re: New WBL

Posted: Sat Mar 15, 2008 10:55 pm
by Silence
I'm not sure what you mean by "cook-off"...

There's nothing wrong with the design, and it should be fairly easy to pull off. The worst-case scenario is that you get some dimensions wrong and the pieces don't fit to create a seal. But that's unlikely. :cool:

O-rings will be a bit of a problem. At the point where the sabots enter the barrel, half the tube must be cut off. When the plunger slides through, the O-ring on the open side is going to expand. Getting it to squeeze back into the barrel requires either a sanded rim (acting as a wedge) or a slanted cut where the hole comes back together.

Just create a regular pump. You can incorporate the intake valve into the end of the rod, but that's also simple enough.

Re: New WBL

Posted: Sun Mar 16, 2008 1:30 am
by C-A_99
Ok, I should've just said pop, when the balloons pop before being fired. (as opposed to cook-off, which I believe often implies muitiple rounds going off before being fired)

For the rims, is the plunger is going to try to pop out when it moves over the half-cut area? I suppose a possibility for avoiding the pop-out is to have a larger diameter PVC tube connect the barrel to the plunger holder. (for the lack of a better term.) The whole thing is basically 2 2" pipes connected by another pipe of larger diameter as opposed to one 2" pipe with the half-cut. If I do this, I'll have to make the rim slant a bit more for the sabots, but it shouldn't be a problem due to the sabot design. (info on my sabots below)

I have had horrible luck so far with custom built pumps. My first configuration is a 1/2 metal rod, 3/8 ID, 1/2 OD O-rings, into 1/2 PVC. Then I tried a 3/8 wooden rod with 3/8 ID, 5/8 OD into the same PVC. I have gotten the first configuration to work by grinding up the O-rings with a dremel, but never did that for the other rod. Either way, I can't see a way of creating an air intake into the rod. (especially for 3/8 wooden dowels)

The actual sabot's will be slightly lengthier than shown. They will probably be yoplait cups trimmed accordingly, perhaps with some duct tape wrapped around. (similar concept to the Snake-Eyes sabot, if not the same thing.) With this design, I shouldn't have to worry about slanting the breech rim for sabots, the slant will only be necessary for the O-rings.

On a side note, I'll be sure to write up an article on this because I think a practical, easy to build WBL is something the online community has be somewhat lacking with in a while. Most of the articles around I see pertain to high power, low ROF WBL's, and I don't find a lot of those designs practical. (While something like the Douchenator is easy to build, I regret not using an under-over design instead, which would've been much more practical.) However, all that will depend on how well this particular design works out.

Re: New WBL

Posted: Tue Mar 18, 2008 7:12 pm
by C-A_99
Well, anyone have anything else to add? One of my friends claims he has a better breech design and either way, I'm still looking to possible improvements that aren't excessively troublesome to implement. I'll be building this during spring break, when there's time, so I want to finish all the pre-planning now, then see how some parts fit when im shopping around next week.

Re: New WBL

Posted: Tue Mar 18, 2008 8:07 pm
by SSCBen
You might want to try a pre-made pump. Pumps for basketballs and soccer balls have worked great for me in Nerf guns, so I'd imagine they'd work great here too.

Re: New WBL

Posted: Wed Mar 19, 2008 12:08 pm
by WaterWolf
Its good to see more people working towards battle-practical launchers.

I have two words of warning for this current design:
"Clip" and "Valve".

I too had been planning to build my launchers using a clip system, but after a lot of designs and experimentation, I decided that the clip was going to be more trouble than it was worth. Instead I took a step back in my design, building a breech-loader and figuring out an easy way to carry WB-Shells so that I could load quickly.

As for the bolt-action clip design above, the one problem I can see with it now is that when you slide the bolt forwards, the back end of the next carriage is likely to drop down a bit and catch on the PVC pipe, causing the system to jam.
I have encountered this exact same problem in one of my prototypes.

To fix this, you can either switch to breech loading, or make the entire bolt out of just that PVC pipe, with a big hole cut in the bottom of the front end to allow air flow.

Next, the valve:
In my past experience with modified solenoid valves, they accelerate the balloon so fast that it bursts before exit.
This was only tested on 75-mm balloons however, so it might still work with 50-mm since smaller balloons don't pop as easily, but its just something to keep in mind.

Now for a little design change in the name of ergonomics:
It order to give this launcher a good handle, take that piece of PVC between the firing barrel and that elbow just after the valve, then lengthen it to about six inches.
Place your trigger mechanism there and the launcher now has a solid handle which makes the design less top-heavy to hold.

One other issue:
The pump in its current spot looks like it might be susceptible to snapping off, so I'd put a support piece between the end of the pump casing and the PVC elbow above it.
Now you've got a stronger design, less prone to damage.

Hope this helps and good luck.

Re: New WBL

Posted: Wed Mar 19, 2008 9:51 pm
by C-A_99
The diagram isn't very exact; I might opt to switch some joints to flexible tubing instead, and the final design should have the barrel resting well on the PC. As for the possibility of jamming, is it possible to correct this by removing the head of the load pusher as well as creating a slope-up to gently push the round above the loaded round upward? (that was not worded very well, what I mean is, first, the piece that directly pushes the sabots in will not have that groove, and the plunger itself will slant, or cone in at the front to push the above sabot and balloon back into the mag)

Now, after looking at the breech system, it looked like it was too hard and complicated to design and build, so I decided to create this simpler bolt. Even if magazine use causes jams, I can load the rounds in manually.

As for the valve, would it be more effective to go with a lower PSI? Or is it better to switch to a pull valve? I don't want to use a ball valve due to the unnatural feel of opening them with a torque arm. (which negatively affects accuracy)

Thanks for the tips though. I just need to be sure on the jamming.

Oh yeah, for future reference, magazine refers to anything that feeds rounds into the chamber (much more commonly by spring than by gravity) and clips actually "connect" the rounds together, without actually "pushing" the rounds in. (Such as in old rifles with built-in mags, the clips are loaded in. Today, they are still used for loading individual mags.) A Nerf example of a clip would be the magstrike and powerclip while a mag would be the Longshot or Recon. Just something I want to clear up as many people use the terms magazine and clip as if they were interchangeable.

Re: New WBL

Posted: Thu Mar 20, 2008 12:39 pm
by WaterWolf
As for the possibility of jamming, is it possible to correct this by removing the head of the load pusher as well as creating a slope-up to gently push the round above the loaded round upward?
That might work, but I think that a cleaner solution would be to make the entire bolt out of that PVC pipe, then cut a large hole in the underside of the bolt at the spot where the air input pipe enters.

Now when fired, the air moves up though the hole in the side of the bolt and out the barrel.
Now, after looking at the breech system, it looked like it was too hard and complicated to design and build, so I decided to create this simpler bolt. Even if magazine use causes jams, I can load the rounds in manually.
Sure, a manually loading bolt system should work just fine.
As for the valve, would it be more effective to go with a lower PSI? Or is it better to switch to a pull valve? I don't want to use a ball valve due to the unnatural feel of opening them with a torque arm. (which negatively affects accuracy)
I agree that ball-valves are not the way to go for an accurate launcher.
Lower PSI would work, although it would limit you to less range, bigger pressure chambers and longer barrels. But as I said, I never tested a modified solenoid valve on 50-mm rounds, so perhaps they might work due to the fact that they are filled less.

I've got a modified solenoid valve that I could test on my Duxenator with a 2" barrel. I can do some tests for you and post the results.
Right now though, I don't have a good carriage for 2" balloons. But I just need to buy some Styrofoam cups and I'll be able to make a 50-mm Snake-Eye.

Yesterday and today I have been working on building a pull-valve gun, which seems to be a pretty good valve system for WBLs.
If you want to install one in your design, here's what I would do:


Re: New WBL

Posted: Tue Mar 25, 2008 4:57 pm
by C-A_99
Ok, thanks a ton for the ideas; I'll be gathering the parts today. For the sake of finishing the launcher faster, I'll go with the modified solenoid valve for now, the only issue being that I may not be able to convert it to a pull valve later. (I got the idea of how to build this, but finding more stuff that'll seal will be a pain)

I won't be putting the hole in the plunger for firing because that'll create sealing problems. As for sealing the plunger itself, I might have to use endcaps for the end of the plunger, and then slip something on the other end to hold the O-rings in place.

Yesterday, I picked up some stuff, the only stuff which pertains to this being a bike pump. Unfortunately, the best pump I could find for this did not come with a pressure gauge so I'll need to put one onboard. (which is probably a good idea anyway) Originally, I was planning on a direct connection where the schrader valve is glued into the PC, but I'll have to add some parts to it. Getting the PVC to connect like that as shown in the diagrams will be a challenge, and the joint from the firing valve to the chamber will be even worse. (especially since I don't have any drills larger than 1/2) Any suggestions here?

Re: New WBL

Posted: Tue Mar 25, 2008 9:24 pm
by Silence
What are you looking to do? If you're connecting a pressure gauge, use a metal reducer to go from 1/2" to 1/4" or 1/8" threads, then screw in a gauge. You may need a pipe nipple or something.

Re: New WBL

Posted: Thu Mar 27, 2008 6:53 pm
by C-A_99
For the pressure gauge, it'll be sticking out of the connection that connects the PC to the bike pump. (There will likely be a T-joint around here)

For the back of the PC, if I use reducers, then create the 90-90 bends from there, it will likely take up too much space (and would not work with the pull valve suggested above, which I'm still considering), which is why I went with the direct connection. If I use a T joint for the firing valve to barrel connection, it'll be worse since there will be problems with certain sabots getting in.

I suppose this is easier to illustrate with pictures, which I'll try to get up asap.

Edit: I just got most of the parts except for the blow gun and all plunger parts. I'm probably going to get the PC directly attached to the pump (for easier handling) and will therefore have to set it to a bizzare length, unless I can find a better way to attach the pump. I also got a 1/2" tee for the PC to barrel, but some work needs to be done to prevent the balloons from sliding down the tee. (perhaps I could rotate it to the side but that would require some redesign) It is however, still possible to go with the original design, given I find a way to attach the PVC that comes from the firing valve directly into the barrel. For plunger/breech O-rings, I'll have to find them on McMaster.

Re: New WBL

Posted: Thu Apr 24, 2008 8:44 pm
by C-A_99
Well, in case anyone was curious, its been almost a month but the project is still slowly progressing. I now have just about all the parts, including 1 7/8" ID, 2 1/16" OD from ACE hardware. I need to measure the dimensions and plan cuts so the plunger and everything all fit together. Unfortunately, the blowgun I got is only 90PSI (I prefer a higher rating for safety; we're going to have to put a 60PSI limit on this)), but it should suffice.

Now, slight issues with the plunger. There are 2 possibilities here.

The first possibility is to use some 1 1/4" (which has an OD of 1 5/8") pipe that connects to a shorter 1 1/4" pipe through a coupler, then put the O-rings on the shorter pipe, then close it with an endcap. Afterwards, something to fill in the empty space will be necessary. The fittings for 1 1/4" just fit well into the 2" pipe and provide a good movement balance. (i.e. the plunger won't wobble around)

The second possibility is to use a piece of 1 1/2", who's OD is 1 7/8", just right for the O-rings. Then, I'd have to use a file to create the grooves, as well as a cork to plug it up. However, I will need to find a way to keep the plunger lined up so everything isn't resting on the O-rings.

I suppose I'll go with the first method for now since I have all materials necessary. Before this, I didn't suppose I could use a file to create the grooves.

I'm starting to reconsider what WaterWolf suggested for the air transit. Instead of using the rod that sticks out, having a transit hole in the plunger would conserve space and allow much more room for the bolt to move. Plus, the gap where the air comes in is larger than I expected.

Overall, the inability to stick pipes into other pipes is causing most of the reason the design is not going as planned. I don't really like the options I have right now with having to use large fittings that take up a lot of space, but I guess I don't have a choice.

Re: New WBL

Posted: Thu Apr 24, 2008 9:19 pm
by Silence
You could take some cues from Nerf homemades. Check out the various plunger systems. Also, they often use nesting brass tubing - it comes in increments of 1/32" with 1/64" wall thicknesses, so it slides smoothly within itself if you buy the right sizes. Brass is heavier than you'd expect, though.

Re: New WBL

Posted: Tue Jul 15, 2008 3:21 am
by C-A_99
The designing is still progressing. After a close look at the waterzooka, I'm quite surprised on the similarities between their plunger and my bolting system. If I got the O-rings from waterzooka, which are designed to seal with 1-1/4" and 2" pipe, it should've worked out. However, I can't figure out OD's and thicknesses in fractions from the information they give (1.6" ID x .21" cross section), so if someone could help me out with that, that'd be great. Either way, I need it to fit and seal on 1-1/4" pipe on the inside and 2" pipe on the out.

It seems like I've been using a lot of incorrect terms for this whole thread. Lots of instances where I used "breech" instead of "bolt" and "magazine" instead of "hopper". (though I know for sure it definately isn't "clip" since the loads aren't connected together by any means) I'm probably still wrong on the bolt too...

Anyways, aside from the o-rings, I should be cutting out the hole for where the balloons come in tomorrow. However, what I have right now seems to be restrictive on sabot length. Plus, I haven't tested materials (cups) for sabots yet.

Re: New WBL

Posted: Tue Jul 15, 2008 2:45 pm
by Silence
1.6 is 8/5
1.18 is 59/50, or 6/5

Unfortunately, increments of fifths of an inch are rare. McMaster-Carr part 4464T345 is similar in size, but it's not likely you'll find anything with that exact thickness. If necessary you could use an O-ring that's smaller in diameter but stretched to fit.

If you create a "triangle" with the barrel, PC, and pump, with all three flush against each other, you could have a tracked pump handle over the barrel. Just a thought.