I hope I'm not late for the discussion! I feel like some holidays from my lurking job
and right on time to see the Automatic fire craze catch up. I almost thought I was the only one.
First: I didn't know that youtube name's "ukiliheal" was posting around here! I guess I need to lurk archives some more...
Second: I've been analysing and experimenting with his design for a time now. I guess I must come out of the closet about that or something...
Third: Your machined parts are really nice-looking. But I recommend you to use lighter materials for pistons (less inertia, less impact, less noise, ect.). I.E. Plastics. I've been using Nylon on my builds.
Now the real replies:
kustomkb wrote:
I will need a stronger spring and probably change the piston to Delrin or something, because the bronze piston makes it feel like a bloody jack-hammer! -Very realistic for sure.
Better get more lubricant. I guess that's obvious, but I'm not seeing it in your pictures. You could also try floating o-rings (also not sure if you're using them). And, again, lighter parts will make for less "stuckiness" due inertia.
POLAND_SPUD wrote:
Seriously why waste time trying to tweak it when you can provide pulsed air supply for it with a solenoid valve. The added advantage is that you can have adjustable ROF and no compromises are needed
I hate it when people put batteries on things that would very well work just mechanically (pneumatically, in this case).
This ties to my next point:
kustomkb wrote:
Mr Smith has a PVC tank in between the air supply and the valve. Is there any need for this if you are running from an air compressor. A bit of a reservoir charging up while the gun is firing?
I bet you already know the answers about this, but I'll elaborate my thoughts so that it might give you some insight.
If I understand this question properly, you wonder why there is a secondary air chamber (I call it chamber to distinguish from the "reservoir", I.E. the air source). It is aparent that you don't really understand the function of a regular spud gun. All spudgun with QEV action (or similar, like the sprinkler valves) have a chamber which fills from a reservoir before shooting with a desired amount of volume to be dumped into the barrel. In Mr. Smith's design, it works as the following:
Valve closed->reservoir fills chamber.-> chamber pressure reaches the pilot release valve's trip levels.->this valve releases pilot volume, therefore triggering the main valve.->chamber pressure flows into the barrel.->because pressure is too low in the chamber now, both valves close.->risen->repeat.
In this design, the larger the chamber volume, the slower the rate of fire (it takes more time to reach tripping pressure). This is why using electronics is redundant (please take notes POLAND_SPUD). The higher the reservoir pressure the faster the chamber fills=higher ROF. Obviously, lowering the release valve's trip pressure, the higher the ROF although it costs muzzle velocity. It is my personal liking to have a very low ROF (I like my shooters manageable). But just increasing the chamber volume makes the launcher inefficient (wasted air from the reservoir which doesn't really propel the projectile) as in any pneumatic gun (although this is a debatable matter; think of this as fine-tuning a guitar). There are trade-offs, but then there are lots of options. It is advisable to use a pressure regulator if you wish. It makes the fine-tuning easier and can only add efficiency.
I could now throw up the maths I've come up about this, but better keep the post shorter until further needs.
