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High RoF WBL concept

Posted: Mon Jul 11, 2011 5:17 am
by strato_2r5
While browsing YouTube I came across this video of a T-shirt launcher:

http://www.youtube.com/watch?v=5lfytYKcecg

What's interesting about this design is that he has a pressurized "air reservoir" and a firing chamber. This way, the reservoir could be pumped up to higher pressures than for firing. Then you could have a slightly smaller PC than usual so it takes less air to get up to pressure. You load a balloon, open the ball valve to fill the firing chamber, close it, and open the solenoid to shoot the balloon. This way, you could fire multiple shots before having to repump.

Re: High RoF WBL concept

Posted: Mon Jul 11, 2011 8:22 am
by C-A_99
A regulator would be better if you'd rather have it shoot consistently instead of having the range drop in half every other shot.

Re: High RoF WBL concept

Posted: Mon Jul 11, 2011 11:57 am
by atvan
:eek: 100th post!

Anyway, realize that for a well preforming launcher, you will need about 40 psi (~2.5 bar). Then think about the fact that a standard WBL's pressure chamber is about 1/2 to 2/3 the volume of the barrel. Any shorter and you will start to lose efficiency. You could shrink down the whole barrel and firing chamber, but you would likely have to design special sabots that cushion the balloon for sudden acceleration. Think tennis ball container with a few rubber bands placed so that they absorb the initial acceleration, then push the balloon faster when their acceleration slows.

You would definitely need a regulator for this design. The pressure chamber could be done in any one of a variety of ways. One is to scale up the experimental design drenchinator posted on these forums a while back. It used a moving PC to make the design trigger activated on one trigger pull, as opposed to opening a valve, closing it, then pushing a button. I was intended for nerf, but has potential here as well.

The larger pressure chamber should be no smaller than 5 times the volume of the firing chamber, and should be twice the pressure of the firing chamber(this is an estimate, and it would warm my heart if someone who knows the math of pressures worked it out for us the volume and pressure needed in the air chamber to achieve 40 psi in the firing chamber for five shots). If you used the fill-pressurize-fill technique, this will get somewhere around 6 shots at full pressure, then a few that are weaker. Any less than this, and you might as well build a design with separate PCs.

Edit: Whoa, scary long 100th post too!

Re: High RoF WBL concept

Posted: Thu Jul 28, 2011 6:34 am
by DX
G3 Douchenator had a 3 shot air rez. However, range suffered because the middle chamber was too small and the gun was long as hell (you need to do an over-under for that). I also used no regulator, so the range sloped off by the 3rd shot. It simply had 2 ball valves, one to open the connection between air reservoir and firing chamber and one to fire. The air reservoir was pumped way high and then diluted as it was funneled into the middle chamber.

Re: High RoF WBL concept

Posted: Thu Jul 28, 2011 11:38 pm
by C-A_99
You'll need each PC to have a separate connection in an over-under configuration (if you want to avoid using a regulator), obviously. Breech load is a must at the very least. Hoppers/magazines are very tricky to get working and probably require special sabots.

Re: High RoF WBL concept

Posted: Fri Jul 29, 2011 12:25 am
by atvan
What we need is to get boltsniper interested in WBLs. He could probably throw together a semi-auto design in an afternoon.

Re: High RoF WBL concept

Posted: Fri Jul 29, 2011 12:32 am
by strato_2r5
I doubt he'd make a semi-auto wbl. More like a full auto gatling gun. :p

Re: High RoF WBL concept

Posted: Fri Jul 29, 2011 8:58 am
by DX
A true hopper wouldn't work unless the sabot is flexible...a dart bends when it is seated. Darts that are too stiff or short don't fire. The sabot would have to bend without breaking the balloon. A mag would be more promising since the sabot can be rigid and fed like some oversize ammo. Those .88's in WWII are what I'm thinking of, shells the size of a pringles can. I think those were breech-loaded. There would still be problems related to keeping the balloons in the sabots while nested in the mag. Even if the mag is the perfect dimensions, the balloons can still move inside a sabot unless you spend a lot of time making one that holds it steady. And those tend to have openings that might not feed as well as a straight can.

Re: High RoF WBL concept

Posted: Fri Jul 29, 2011 12:38 pm
by atvan
He'd prefer a full auto single barrel system that uses shels and sabots. But that might take him a few days.