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Jaemus
Experienced Roboteer
Joined: 01 Apr 2009
Posts: 2674
Location: NSW
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My next purchase will be an Alpha Trooper and then a Raider 35 dart drum to go with it from ebay. I'd just get a Raider but i dont like its aesthetics - it looks like a super soaker.
I also rate the Barricade, for $20 you get semi auto, get two and dual weild! My current fav.
For the same reason my 2nd next purchase would be the new Rayven - http://nerf.wikia.com/wiki/Rayven_CS-18 - hopefully all the barricade advantages but uses clips which makes reloading heaps easier and therefore it'll be greatly superior to the barricade in a nerf war.
Out of the 3 you mentioned, get the longshot. The stampede is dissapointing in rate of fire AND range AND accuracy. The vulcan is marginally better but is still uninspiring. However as a prop it's awesome.
You can voltage mod the stampede and the vulcan for rate of fire, which is win, but they will still have shit range and accuracy.
While you're at it, pick up a Nite Finder for $8. Huge power for a single shot pistol, can mod it to great effect as well _________________ <Patrician|Away> what does your robot do, sam
<bovril> it collects data about the surrounding environment, then discards it and drives into walls
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Tue Jan 03, 2012 7:03 am |
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Glen
Experienced Roboteer
Joined: 16 Jun 2004
Posts: 9481
Location: Where you least expect
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WELL i did something productive for once (a shock i know).
The propane one is useless because the tank is much too thin. Under 1mm wall. The newer ones are supposedly much thicker, but eh. My interest in tiny guns is zero. So that's in the bin.
The concept will be revisted when this baby gets made. 6mm wall steel seamless tube and a 6mm thick pipe that will get run at 500+psi. The big tube is 105mm diameter for scale.
But yeah, i crumbled and wanted something now thus i made a good ole pvc cannon. Good idea me thinks, cause the bang for buck can't be beat! The design is a barrel sealing piston valve. Super simple but super effective too. The flow rate is second only to the original design i posted and a burst disk.
First step, chop up some pipe. The abrasive saw rocks for this. The finish is like glass ^.^
This reducer fitting needs to be bored through for the barrel to go all the way through it. Normally there is a ridge in there for the pipe to butt up against. Ill come back to this part cause it caused me some grief >:C (this is actually the replacement piece being re-done)
While gluing it together it was going good, if a lil messy. But the pipe went into the reducer crooked and it wouldnt seat into the T piece (should be flush). It was made way out of spec! blarhg?! Crappy bunnings parts strike me down again.
So that cannon will be made into a low pressure net launcher In the end i gave it a test with a shonky valve made of more pvc pipe and it has quite a serious kick even at 40psi. This bodes well for the 100psi version >:3
I had to redo it all with a new piece that worked properly. The barrel protrudes a bit less than 1/2 way into the T piece and the piston will seal against it. More pics of that later. This glue is messy as hell so all the pieces got lapped and sanded smooth to ensure any stray glue didn't go where it shouldn't have. DID I SAY THIS GLUE IS MESSY?
Time to machine some delrin i got at the hackerspace for cheap. What an awesome material to work with. So easy to use and comes up with a perfect surface finish.
This is the rear bulkhead. I read the force of the piston slamming back into this piece caused pvc fittings to tear apart, so its being made from delrin. I need to machine the length of the piece so i put a spacer between it and the chuck and forced it in place with the tailstock that sits in a center drilled hole. Works sweet for stuff like this
All done. Its a real tight fit in there plus it has an O ring to seal it up. Still have to drill the mounting holes around the edges to keep it there and drill the hole in the middle for the firing valve.
Next is the piston! I've seen some pretty ramshackle piston designs work just fine online. So this one should work great (famous last words lol). Its a big ole 55mm chunk of delrin with a neoprene washer bolted to the front. There's plenty of room to tinker with this too by adding o-rings, removing weight, adding check valves etc. So that should be fun
The piston in place. I shaved it down incrementally by 0.125mm in diam each time until it moved through the bore when i blew into the back of the tube it sits in. Works very very awesome The design basically allows a little air to flow around the piston to fill up the reservoir but when fired doesn't allow enough back through to stop the valve actuating if that makes sense!
Now the tricky bit. Getting it to seal which is a big problem with most peoples cannons. Just having a solid bit of rubber flat on the piston wont work well because the barrel is never perfectly straight, has been cut at an angle.. whatever. So i made the washer bow up at the edges a tiny bit with a funky cap so it should seal whatever the case.
A little stub for the washer to locate on -
The trick of it all. The little ridge in the middle when pressed down on makes the edges of the washer flex up. This is what the aluminium cap presses down on.
The cap.
M6 stainless countersunk holds it in place. The cap also helps center the piston into the barrel.
It works!
Also had to trim the diameter of the washer down a bit. So the test piece for demons self righter gearbox came in handy. Almost suspiciously so O_O
And here the new gun sleeps as i left it for tonight. All that remains is to bolt the end cap on and work out what to use to vent the pilot volume (that's what causes the valve to open). Current candidates are a 1/2" ball valve or a modified duster gun. Ill probably use the ball valve
Oh and the data for the cannon. 400kmh for a golf ball doesn't sound too bad There are guys out there firing them at almost 1000m/s with hybrid cannons that combust 150psi mixes of gas. Most interesting
Anyway back to drinkin'. Test videos should be around tuesday if it doesn't kill me XD! _________________ www.demon50s.com - Minimoto parts
http://www.youtube.com/user/HyzerGlen - Videoooozzz
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Mon May 21, 2012 12:48 am |
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