Brass Barrel Manual Bleed Sprinkler Valve Nerf Homemade
First let me state that there is nothing original in this homemade other than the overall design and ergonomics. Others have used sprinkler valves before and there's nothing very sophisticated about this gun.
This gun is, however, a whole lot of fun and can be built quite easily for a little over $30. Parts list follows, unless noted otherwise, all items were purchased at Home Depot.
2 9/16" K&S Brass Tubing (Ace Hardware) 1 19/32" K&S Brass Tubing (Ace Hardware) 1 Chrome Push-in Tire Valves 4pk (Kragen Auto Supply) 1 3/4" Orbit Watermaster Inline Solenoid Sprinkler Valve 1 1.5" x 9" SCH40 PVC 1 3/4" x 24" Threaded SCH80 PVC Riser 1 3/4" x 6" Threaded SCH80 PVC Riser 1 1.5" PVC Endcap 1 1.5" PVC 45 Degree Bend 1 1.5" - 3/4" Flush Bushing w/ Socket Fittings 1 3/4" PVC 45 Degree Bend 1 3/4" PVC Socket to Female Threaded Adapter
A word or two on glue will be necessary at this point. Not all glue is created equal and for this gun you absolutely must use the right glue or you will experience pain beyond description when the gun detonates in your hands. All socket type PVC joints in this gun must first be treated liberally on both surfaces with purple primer, then covered completely but not excessively with PVC cement. It must say "PVC Cement" on the can. Make sure the pipe is pushed all the way to the bottom of the socket. Let it cure for 24 hours before you pressurize it. Really.
All threaded connections on this gun must be sealed by first wrapping the male threads in a single layer of teflon tape, then screwing together firmly.
Here are the parts needed for the air tank assembly. The small piece of SCH80 is cut from one end of the 6" Riser. I cut it an inch past the threads to leave enough pipe to glue into the bushing.
The placement of the air valve reflects my attempt to avoid small radii curves but leave the endcap valve-free to use as a stock. I settled on the left side of the 1.5" 45 bend as a reasonable location. Making sure to avoid the socket areas where the pipe and bushing will interfere, I drilled a 1/2" hole through the fitting and cleaned it up with sandpaper. A little silicon spray on the snap-in valve and a lot of pushing/tugging got it into place. No goop/epoxy/whatever required - the fit is airtight all by itself.
The finished air tank. Note the valve placement and the 3/4" threads peeking out of the reducer bushing.
Here are the parts for the barrel adapter. Once again I used the threads and about an inch of pipe from the other end of the 6" riser. You can use the middle part of that riser in place of the regular 3/4" SCH40 I used to connect the fittings - there's no difference.
Here's the barrel adapter all glued and assembled. The female end will connect to the barrel, the male end will connect to the sprinkler valve.
I couldn't take this picture till the next day because you don't want to go ripping those little threaded riser sections out of their sockets. While waiting 24 hours for the glue to cure I got bored and dressed up the tank a bit. The sprinkler valve has arrows indicating flow direction. You'll want them to point away from the tank obviously. I'm not using the solenoid leads on the valve because this is a manual bleed implementation but have decided to leave them in place in case I use this valve in another project.
Here is a picture to demonstrate the ergonomics and use of the manual bleed lever. Imagine the endcap is pressed against my right shoulder - my right hand naturally rests in the position shown. The small black lever under my index finger is the manual bleed. I flip it down and the air gets dumped out of the first stage area, opening the valve very quickly. This lever is the reason I bought the Orbit valve - most other brands either have no manual bleed or have a screw-type manual bleed knob. This implementation gets the valve open MUCH faster than a ball valve but doesn't require the 3 9-volt batteries and switch usually required for solenoid valves.
With the air delivery system complete I started on the barrel. I was concerned about using two 12" pieces of brass to form a 24" barrel but it's difficult to find 36" K&S brass tubing so I did everything I could to make two pieces act like one. First I got out my (.45 caliber - pretty good fit) gun cleaning kit and used brass polish and cotton cleaning pads to carefully polish the inside of both pieces of 9/16" brass. I then rounded the inner edge of the rear end of the frontmost piece of brass so that darts wouldn't catch on anything sharp at the join area. At that point, it's a simple matter of sliding 6" of 19/32" brass over the two 9/16" pieces, centering it over the join area, and using electrical tape to secure it. I was careful at this point to insure that the two pieces of 9/16" brass were very tightly held together - the 19/32" piece takes care of the alignment.
Here are two crappy pictures of the porting I did on the muzzle end of the barrel. Ignore the SCH80, it's just in the picture to illustrate the relative fit of the brass in the PVC. The porting is a two-row staggered slit design with 6 slits per row. When mounting the brass in the SCH80 I wrapped the brass in electrical tape until it was a snug fit, but left the front 3" of the barrel tape-free to allow the ports to exhaust through the gap between the brass and PVC. The picture DOES NOT illustrate the final position of the brass as I pushed it back until it was flush with the front edge of the PVC.
Since the barrel screws into a female adapter to 45 bend combination, the brass can extend about 2.5" beyond the rear end of the threaded riser. To take advantage of the decrease in length and remove that dead air space, I cut 2.5" off the front end of the barrel, including the threads on that end of the riser.
I decided to attach my barrel securely with teflon tape and muzzle load with a ramrod so I needed a physical block at the back of the barrel to prevent the dart slipping into the 45 bend. I cut a slot across both sides of the very back end of the brass and strung a small piece of 18 gauge insulated wire across the opening. It's not big enough to impede air flow significantly.
This gun tends to annihilate darts rather quickly unless fired into a hanging blanket or some other backstop designed to stop them gently. The accuracy is very good compared to Nerf guns but the very high velocity exposes even the smallest flaws in darts. I'll be updating this article with more information as I try other barrel and dart types in an attempt to get this thing accurate enough to be worthy of a scope.
|All images and content © Kevin Davis 2004 - Hail Eris! All hail Discordia!|