jackssmirkingrevenge wrote:Thanks for the comments clide, since this design is essentially the same as your GB-semi breech with the exception of spring location, I was wondering if you ever observed the same effect.
I'm starting to come to the conclusion that this is going to be too hard to fine tune - as it is, the bolt starts to cycle way before the projectile has had time to leave the barrel - and I should start pursuing the pop-off-valve-in-the-pilot-chamber approach to "pulse" the air fed to a blow-forward breech.
Right, as it is now the bolt will start trying to close as soon as it is open. One way to get around this would be to make a disk in the larger diameter area, and put some vent holes on the other side of the disk so pressure doesn't build as the bolt moves forward. Once the bolt unseals from the rear tube, the disk in the larger diameter area will be exposed to the pressure and will hold the bolt forward until there is a certain pressure drop. You would want the surface area of the disk to be at least bigger than the surface area of the bolt, and the bigger it is beyond that, the more pressure drop required before it closes. Say you make the disk twice the surface area of the bolt, then the valve bolt will start to close at about half of the pressure it initially opened at is left. I was working on concept a bit like this that lead to the GB Semi, but I think it was a poor choice for me to start at golf ball scale. At your scale I think the idea could work.
A small chamber with fed by a flow controlled blowgun would give you power and allow for an adjustable ROF.
Of course with your construction methods, such a design would leave the bolt unable to be removed for service, but if you also put the springs on the outside with a method like I mentioned above then you could adjust those.
I could draw a picture if you don't quite get what I'm trying to explain.
Also, I found a video that I had sent to chewy about the auto cycling Slider bolt. I'll try to post it in a bit because it does sound pretty cool.
Edit: Here is the video. Of course that is way too fast to be any good, but that is mainly because of the weak spring...It wasn't built or intended to do this so that is why the spring is weak. Sounds like a little engine.
http://video.google.com/videoplay?docid ... 9687&hl=en
The bolt is hard to see as it cycles so quickly, I hope this won't be a problem when it comes to feeding ammunition. I'm going to experiment with a stiffer spring to see if I can slow it down a little.
