POLAND_SPUD wrote:I meant that the distance ammo has to cover while it is being fed from the magazine and pushed to the firing position makes you use an air cylinder that has the same stroke lenght as that distance...
consequently, any 'deadspace' there is makes you use a cylinder that is longer for that exact lenght... so acctually the overall lenght is increased by (2 * lenght of an unneccessary deadspace)...
if ammo has to go 4 cm through the tee this means that the cylinder has to have 4 cm longer stroke and this makes the gun (2 * 4 cm) = 8cm longer
There is very little dead space in the design as I said previously. I think I could possibly use a 3 inch stroke cylinder instead of the 4 inch one I am using right now, but that'd be cutting it close. It's definitely worth investigating.
I hadn't quite thought about the "extra" length from the longer air cylinder, but that's correct. Something to keep in mind for prototype 2...
On a similar note, I had considered putting the air cylinder on top and using a linkage of sorts to push the darts, but that was more complicated than I would have preferred. It's another idea worth considering (err... reconsidering).
john bunsenburner wrote:Ok something totally different to gun lengths:
You where talking about different kinds of fam darts, why not make 2 or 3 mags all with different darts, and you just use the best one for each situation, that would look pretty cool and maybe be really useful. It sounds like a powerful gun, i guess even foam darts can hurt so watch out, it would be a pitty if either some one took the gun away or if you hurt some one. Do some testing and show damage pics. Otherwise iahve to say once more great gun, good job...
p.s. I truely wonder what would happen if you used that thing on ply woad at maybe 250psi with lead slugs, if you decide to change your mind about using other kinds of ammo, and do what i just mentioned please get a camara first, we all would love to see the gun in action killing some ply woad...
The only major difference between different foam darts is the caliber, and making an effective weapon that can use different diameter projectiles would be difficult. Though, different weights are possibilities too, though I'd just choose whichever weight worked optimally at my typical operating pressure.
The foam is necessary for a good seal, but I could make lead weighted foam darts and see how that works with the pressure cranked up... it should be spectacular.
Ragnarok wrote:Looks great to me so far. Obviously, it still needs the finishing off and cleaning up, but that shouldn't press you unduly, having seen your previous water gun work.
Actually, I hadn't heard anything about your work in some time, but seeing this, it's still looking good.
Sorry, my posts in the showcase almost always end up being boring sounding praise, because I don't often have many questions to ask to spice up the posts.
Praise can't hurt, so keep it up.
I'll probably post some of my future water gun designs here too so watch out for them. I've been planning some interesting things with them lately.
How about "Great minds agree this is the most reasonable way to do it"?
That's it exactly.
cheeseboy wrote:magnificent, I worked my way on to spud gunning from nerf gun modifying nerf guns but I could never make something like this, how many darts can you fit in the magazine and how many can you shoot with a full chamber before having to repressurize?
The current magazine will fit at least 10 darts.
The plan is to make a higher capacity magazine eventually where I should be able to hold 20+ darts. That's on the drawing board... I choose a proved reliable method for the initial build.
POLAND_SPUD is correct. I have a paintball regulator I intend to use with either HPA or CO2. I have an HPA tank but have been considering using CO2 too. If I did use CO2 I'd change the PVC pressure chamber to metal, but aside from that I should be good.
I think I did the math earlier and my HPA tank could have had over 400 shots with a larger pressure chamber than what this build has. To increase the air use efficiency I intend to decrease the pressure chamber volume beyond it's currently small state too, but I'll need to make a model of this gun before deciding on that.
To summarize my current thoughts for changes for prototype 2:
- use a dual action air cylinder with an air spring to reduce the length, and potentially use a shorter stroke air cylinder
- put a sleeve of plastic around the barrel to prevent dents
- use less sizes of brass (It is not obvious but I have 4 different sizes of telescoping brass in this system... 3 would be possible but I didn't have the right size drill bit to allow for that.)
- potentially use a different directional control valve, possibly with higher flow
- consider a smaller QEV to reduce weight (the Cv values are all extraordinarily high for Nerf so it may not make a significant difference in performance)
- make model of this gun to minimize the pressure chamber volume and pressure for maximum range
- make a higher capacity magazine
- add retractable/adjustable/removable stock
- stain the handle and add grip tape (I might go for a prettier wood too)
- add trigger of sorts (I'm still considering various options)
For a trigger I'm considering various options. What I intend to do now is make some sort of linkage from the trigger area to the DCV. I also could use tubing to move the DCV closer to the trigger area, but that would increase the pilot volume and I'm afraid the DCV's flow might be too low to work optimally (though I doubt it because the additional volume would be so small). I also could use a different DCV I suppose. I'll need to do some more research into that.