SpudFiles

This is a quick project i thought up for my four day weekend. i got a shock pump the other day and I've been dieing to use it. The gun has a 1/2'' pvc chamber. A 7mm aluminum barrel and it is about 2' long. I ran the pilot along the chamber to reduce the profile and I actually like the way it shoots a lot. It feels like a wand or a sword, lol.

Here's some pics:





And a vid:
[youtube][/youtube]

looks good
Kinda like my mini coaxial that I havent finished yet
And for the vid you have to do the url not the embed code
And any pics of the piston

Running pressure?What does the GGDT say about it shoots at X amount of pressure?

Could you get a picture of the piston up?Looks like a neat little project.Could I get some damage pics?

Sweet, there are few aircanes in the Beeman collection, they were very popular with poachers as they were powerful enough to take down medium sized game while being abe to be carried discreetly.

The chamber volume is a little large for a shock pump, my suggestion would have been to have half the length of PVC as the chamber, then have the other half as an integral silencer.

Video doesn't work btw...

Besides poachers using them, I've also heard of their use in attempted assasinations by shooting poison bbs and other things of that nature.

origin unknown wrote:I've also heard of their use in attempted assasinations by shooting poison bbs and other things of that nature.

You're thinking of the umbrella gun used in the Georgi Markov assasination.

thanks, um if i take it apart again I'll try to remember to take a picture of the piston. Jack do you think shrinking the chamber will decrease performance a lot?

homedepotpro wrote:Jack do you think shrinking the chamber will decrease performance a lot?

If your decrease in chamber size is accompanied by a corresponding increase in pressure, then performance will increase.

I had done a little design exercise with an imaginary launcher on GGDT, these are the results I got:

20 inch chamber at 50 psi - 406 feet per second

10 inch chamber at 100 psi - 537 feet per second

5 inch chamber at 200 psi - 684 feet per second

2.5 inch chamber at 400 psi - 830 feet per second

1.25 inch chamber at 800 psi - 958 feet per second

0.625 inch chamber at 1600 psi - 1006 feet per second

All the time, we're talking about the same quantity of air, because we're doubling the pressure but halving the volume.

So a small metal chamber at shock pump pressures is better than a large PVC chamber at compressor pressures

That being the case, are there advantages to having a fairly large chamber? I can see one problem being if you are using PVC, you can't get to the higher pressures, but is there any other reason why it would be advantageous to have a large chamber?

I'm not a physics major or anything, but I would imagine with such a small chamber, barrel size couldn't be too large; thus limiting your types of ammunition.

I love your launcher, but i loved your vid also.
you have a knanck for illustrating the benefits of higher pressure.
10/10

mega_swordman wrote:That being the case, are there advantages to having a fairly large chamber? I can see one problem being if you are using PVC, you can't get to the higher pressures, but is there any other reason why it would be advantageous to have a large chamber?

For a given pressure, the larger the chamber, the more power you're going to get, but it comes to a point where the power advantages are not worth the inconvenience of having a bulkier chamber that takes more time to fill, as well as the louder shot. GGDT is a good way to determine the cut-off point where the power stops increasing.