10 replies to this topic

[GeneralPrimevil]

Well, I finished one of my homemades. This one utilizes a barrel sealing piston coaxial valve. I have yet to fire it, but will over the weekend (have to wait for a quarter of a cement can to set and make new Stefans). Well, on to the cannon.

First off, it is about three feet long with a 32.5" barrel. By using GGDT (made by D_Hall over at spudtech.com/forums), I was able to create some numbers. I will see how accurate my inputs were when I test it. It needs to set for three days and I finished it about two horus ago, so... Anyway, pics!


That is the chamber/valve body and barrel, suspended from a $300 lifetime warrantied vise so that the glue poured into the reducer bushing will set evenly. I poured a quarter to half inch of cement down there. I had to re-adhere the barrel after I had already cemented the whole deal to the chamber. Since it wasn't far enough in the first time, the bond had to be broken (did that within a minute) and redon. Wow, that muzzle break is really white. That's what I get for hand sanding it with 100 and 240 grit sandpaper.


That was my first attempt at doing the bushing on the barrel. The bushing needs to be a whole 'nother two inches closer to the muzzle (the hand in that photo, which isn't mine by the way. Looks the same...).


There's some random stuff with the chamber/valve body without barrel adapter and coupler attached. The coupler is behind it on the table.


That's the piston. It is made of 1 1/4" PVC fittings: a ground down bushing plug and a coupler.


There's the piston sealing face. It is made of 2.214mm thick reinforced rubber sheet, industrial super glue holds the sealing face to the piston, then it is held in securely by the ridge on the inside of the coupler. Yes, the bushing plug was put in upside down. There is a paint cross-section of the piston here.


That is the removeable pilot/fill valve. I plug it into a compressor when I need it filled, then unplug it and open the blowgun to fire it. Since the whole deal is removeable, I can breach load and/or remove the piston without having to break any joints.

Well, that's all for now. I'll edit this later with ranges and whatnot.

edit: There...I finally read all of the post again and fixed the errors and things which I messed up on the night before. Picking up the cannon today after school to let it dry at my house. Then I will charge it to 40 psi and try it out on Saturday. How many layers of cardboard would be necessary to simulate what would be ballistically safe for Nerf at a hundred or so feet? Three? Four? I'll just add more until the dart doesn't penatrate or something...

Edited by GeneralPrimevil, 30 March 2006 - 06:51 PM.

[davidbowie]

Overall it looks pretty nice, but you might want to rethink piloting a valve that large with a blowgun.

[GeneralPrimevil]

Okay, I have time to do stuff now, 'til I go to sleep...

Remember Mr. Plow, was it? and how he made that one cannon out of 2" Sch80 with a 3/4"? barrel, he used a blowgun. I don't need major power here, since I will be using it as a Nerf gun. However, if there are problems with the valve opening, then I will use a ball valve and mount this thing to a tripod. Otherwise, I wanted ergonomics, just as whatshisname wanted aesthetics. I might get a 3/4" sprinkler valve or use a 3/4" two-way washing machine solenoid valve instead...

Okay, after the cement sets and I prove that it works, this thing will get three-six coats of ruberised undersealer (smooth to rougher finishes each coat) to give it a nice, solid grip with gloves, bare hands, whatever.

Another reason why I had to fill the 2" to 1/2" slip bushing: I didn't remove the stop lip on the bushing propperly which created a 1/64" gap on one side of the barrel. By completely filling the bushing and using no more than 40 psi, there should be an airtight seal by the time all of it hardens. I was tempted to put PVC dust in with the cement, as well, but didn't...

Hey DB, is there any reason why the piston should not open from what you can see? As far as I know, no one has made a piston like how I did, where the coupler goes over the barrel then a plug seals against it. I'll make a Paint image later...

I will recheck all of my numbers with the actuals now just to make sure...MV to 246 and ME to 22.9. Wow, big difference...still five and a half times as powerful as a singled AT3k with two and a half times the projectile velocity, or at least compared to my AT3k. Those are just numbers. Real stuff will be discovered in a few days; however, if those numbers are right, I see a 3/0 mega Stefan going a couple hundred feet if it doesn't spin out first. Will I have to make heavier Stefans? This thing is like SM5k or more at it's power level. Perhaps modified Super Soaker? So if it were anything like my Super Soaker was, then half ounce still will spin a little bit. Unfortuneatly I don't want to go that high, so lower pressure? I'll experiment when it's done hardening...

With how that is set up, I could almost use another manual piston valve to open it, such as an oversized RF20 firing valve. Then I could make it look like something, perhaps an NTW-20 or an RT-20...they both have big cylinders behind the barrel. Or, if I really tried, I could make another like the WA-2000...

Edit: I guess world.guns.ru won't let me steal their bandwidth...well, Google image search those three weapons to see more...

Edited by GeneralPrimevil, 29 March 2006 - 10:26 PM.

[davidbowie]

We'll see about that blowgun. That's great if it works, and you can change it if you need.

Hey DB, is there any reason why the piston should not open from what you can see? As far as I know, no one has made a piston like how I did, where the coupler goes over the barrel then a plug seals against it. I'll make a Paint image later...

I don't think this really needs a paint image, all you did was use a coupler for the sealing face. My coaxial has this, simply because I'm rubbish with a hacksaw when it comes to square cuts. I don't see why it shouldn't open, except maybe the pilot valve issue.

No doubt about it, piston valves are high-power. This is kinda the point where it stops being a nerf gun and starts being a spudgun. This is definitely much more powerful than a SM5K, titan, etc. You have to make the stefans heavier to keep from spinning out, thus they hurt way too much, possibly maim or seriously injure.
It's nice, but I see no use in nerf.

[GeneralPrimevil]

10 psi on GGDT gets me to AT3k limits. However, I highly doubt that valve would open at 10 psi.

I am intent on making this thing Nerf legal, even if I can't shoot at anyone within a hundred twenty feet of me. Well, there we go...15-20 psi gets it to where I'd need it (twice as powerful as AT3k) where I could use it at that distance...maybe. I'll just test it on soft, inatimate targets at varying distances with varying darts. I don't think I have to put a cone in the back of the FBR with a hot glue gun tip for the increased SA for the air to hit. This thing would already have enough power, considering it's a sprinkler valve on growth hormones and anabolic steriods...

The pilot thread (in the rear bushing) is 1/2" NPT, so I could put anything on there.

[GeneralPrimevil]

Well, I like double posting when I have new information. This information is new for this forum.

I tested it (dry fire excercise) at 20 psi. Well, all the pressure vented out the pilot. Okay, relube the piston and try it at 40. Almost the same thing. A slight bit of pressure was felt at the end of the barrel. I blow through my trombone twenty times as hard as the air was coming out of the barrel. Okay, now 80. The valve opened after a 60 psi pressure drop. Still, I have more lung power. Now time to tweak the piston. So I reduced its weight by almost an ounce, or 22%. Now it looks like Swiss cheese. Well, hopefully that does the trick. I'll check again tomorrow. Then I'll make four or five of each varying weight Stefan, if it works, to find out how (then what) it likes to spit at people. Also, I will take video documentary of the first test shots, because I can.

Oh yeah, it looks like \/below\/ when fully assembled, without muzzle brake.


What is the interest level to find out how I did that porting? Should I make a how-to guide or writeup of my style?



Oh yeah, Hey DB, if you read this, give advice for the piston on either forum.

[davidbowie]

As I said... try a bigger pilot valve.

With the right pilot, it would probably open at 10 psi.

No offense, but porting isn't a huge scientific advance. It's a very handy skill, but I think most of us can figure out how to drill holes in stuff.

[GeneralPrimevil]

Yeah, but I remember a long time ago (before you came here?) when one of the more artistic members was ranting about the shitty hole patterns (or lack there of) that people were using for silencers and assorted other stuff. Since then, I haven't seen many silencers or whatnot. Also, the thing Zero sent for the silencer on this site is really pointless if a proper hole pattern and spacing cannot be achieved to maximize outward flow to reduce the pressure leaving the front of the silencer. I'll just real quick make what I mean...



The valve opened with the same speed/pressure drop as the original only with a lot less lubricant...
I'll go throw a ball valve on there and see what happens; however, I really think that the .1" total equalization gap has something to do with this. The pilot (realizing I messed up on the math, resulting in 33.233ci, larger than the chamber) is 7.09543 ci...if that is too big, some round wood stock will fix that.

Edit: Replaced silicone on the piston with Vaseline, removed any liquid silicone left in the chamber. Now the valve will only open at pressures less than 40 psi. Well, time to try it with Teflon on the PVC and a Stefan in the barrel. I highly doubt it'll shoot, but if it does, well, I should have a vid of it.

Edited by GeneralPrimevil, 31 March 2006 - 09:17 AM.

[euphemism]

Your gun links don't work and I think it's hilarious. The reason it is hilarious is that the URL was changed by the word filter. Just take a look at the URL and you'll see.

[Carrtoon]

Yeah, but I remember a long time ago (before you came here?) when one of the more artistic members was ranting about the shitty hole patterns (or lack there of) that people were using for silencers and assorted other stuff. Since then, I haven't seen many silencers or whatnot. Also, the thing Zero sent for the silencer on this site is really pointless if a proper hole pattern and spacing cannot be achieved to maximize outward flow to reduce the pressure leaving the front of the silencer. I'll just real quick make what I mean...



The valve opened with the same speed/pressure drop as the original only with a lot less lubricant...
I'll go throw a ball valve on there and see what happens; however, I really think that the .1" total equalization gap has something to do with this. The pilot (realizing I messed up on the math, resulting in 33.233ci, larger than the chamber) is 7.09543 ci...if that is too big, some round wood stock will fix that.

Edit: Replaced silicone on the piston with Vaseline, removed any liquid silicone left in the chamber. Now the valve will only open at pressures less than 40 psi. Well, time to try it with Teflon on the PVC and a Stefan in the barrel. I highly doubt it'll shoot, but if it does, well, I should have a vid of it.

Here's a pic of the silencer I use on my LBB. It uses an MDX bottle and is on the top of the picture:



Anyway, that homemade is absolutely stunning. I never would have come up with that system! Very nice!

[GeneralPrimevil]

I didn't come up with the valve. I don't really know who did since piston valves are really old.

I think this would be more "stunning" if it actually could fire. I tried a larger valve (1/2" ball) and, well, the piston never opened. The dart went further when I used the force of the piston closing on the barrel. Well, time to try something else.

Okay, I think this is going to be dead pretty soon. Time to start work on another homemade...*cough* SNAP...