APG-2 (Air Propelled Grenade, version 2)

[Davidvaini]

okay, I see it now, the barrel is connected to a 2 inch coupling on the outside, with a reducer on the inside, it keeps reducing down to 3/4inch. While the 2 inch coupling is used for another 2 inch pipe that is used for the 2 to 3 inch piece... and then its 3 inch that holds surrounds the sprinkler valve..

[mark.f]

That whole valve section is a little voodo-ish. I'm guessing the reducers aren't really attached at all to the barrel and chamber significantly but just sit on top of the couplings, or maybe are merely glued to the "lip" left by the bushings after gluing into the 2" couplings.

If you want to know for sure, you'll have to hear it from Squirrel, though.

[Secret Squirrel]

so just making sure but...
The barrel is 2", the sprinkler valve is 3/4" and the chamber is 2 inch. what size for around the sprinkler valve?
externally, can you say from left to right in your picture what each pvc part/size?

Sure, from left to right is a cut down 3" to 2" bell reducer, which is attached to a ground down reducer bushing into which the quick disconnect is threaded. I ground off the octagon shaped part of the bushing so the bell reducer could be attached to it. Then there's a coupling, followed by 18" of 2" pipe for the chamber. Then there's a coupling with a similarly ground down 2" to 3/4" bushing. The 3/4" part of the bushing leads to a short length of 3/4" pipe and a 3/4"npt male adapter, while another 3" to 2" bell reducer is attached to the outside of that reducer. The sprinkler is attached to the threaded adapter, and a cut section of 3" pipe forms the shroud. The barrel end is constructed exactly the same way, just without the coupling and reducers on one end.

The sight is mounted on the 3" shroud on a tie from a broken piece of Lionel O gauge track, that just happened to be the perfect size for a rail.

If that block of text isn't understandable, let me know and I can make a diagram.

[Edit] Mark got it exactly right. The bell reducers of the shroud sit on the lip of the bushings. The tail piece was done the same way. The bell reducers were cut down an inch or so too, so they would bottom out on the lip of the reducers, giving DWV fittings an even shallower socket depth

[motoman807]

You've inspired me to make something like that. Simple but very cool and effective