6"x3" coaxial launcher [now with video!]

[Davidvaini]

looks good.. are you the older man, the younger guy, or the woman in the video?
looks good but I would like to see some damage shots

[SplatteredStarch]

All projectiles were 20 oz soda bottles filled to top then capped again. The fit of a 20 oz bottle in the 3" sch 80 pipe is as astounding. In the first video you can just barely make out where the projectile hits the tree towards the end. In the second video the camera was downrange and under the barrel, thus you see the bottle come in from the top of the frame and travel downrange. As for damage pictures, our current stand setup is highly unadjustable (only moving the truck around), and we made no effort to hit anything (rest assured we will once we get the stand correct).
@ JSR I don't quite get where your going with your post.

[STHORNE]

looks amazing. very nice work.

(as for the gun) Do you plan on giving it a paint job in the future? If so, you should probably have a poll on what to paint it, as a gun like that deserves only the best

[Gippeto]

Bloody good job!

What did you use for the piston?

[jackssmirkingrevenge]

@JSR: what's up with your discombobulated link...

Not my typical form, I know, but wikipedia would not have it any other way it seems.

JSR I don't quite get where your going with your post.

Just a little infantile humour referring to the fact that "flange" can also have a different meaning in some parts of the world, don't worry

[psycix]

I still hear a small SHHH before the BLAM so it could be pilotting faster, but it is alright I guess.

Why mount it? Just hold it with 2 men and get blasted over. xD

I'd love to see a picture of the piston.
How far does the piston travel?

[SplatteredStarch]

I like the cannon's look in grey, and it brings attention to the fact that it is sch 80 pipe, that being said if I was to paint the cannon it would be either matte black or olive drab. As for the piston we were initially trying to make a metal piston in a woodshop, with did not really work out. So we got a piece of void free 3/4" furniture grade plywood. We laminated it 4x with some super strong waterproof woodglue, and clamped it all together with wood screws. We took the blank to the bandsaw made it roughly round, and tuned the fit on a woodlathe. A couple coats of sealer was applied to keep out the moisture. Then we glued rubber sheets to both sides; one to seal the barrel, and the other to act as a bumper. As for total travel, it is easy to increase but harder to decrease, so we picked a conservative 1.5" travel for starters.


I still don't like the wood piston, and it was somewhat of a stopgap measure. An aluminum piston would be most ideal, but I have no means of manufacturing it. So if the current piston fails, I guess ill have to get in touch with a machine shop.

The air you hear venting could be the deadspace before between the qev and the blowgun. even if that air dumped faster, it can still only vent as fast as the 3/4 QEV. That was the biggest QEV I could get quickly, but if it is hindering performance, the back of the gun has 1.5" NPT female threads.

[kablooie]

Very nice cannon, it looks well-made and professional. As far as the pilot goes, I would recommend making (another) piston valve, this time in the tee configuration and using that to pilot it. They are surprisingly easy to make, and you could trigger it with your 3/4" qev, which is probably overkill, but would enable you to keep the blowgun trigger (as opposed to a 1/2" ball valve or something similar).

Again, very nice cannon, I like it a lot.

[SpudUke5]

That was the biggest QEV I could get quickly, but if it is hindering performance, the back of the gun has 1.5" NPT female threads.

Well, there are 1.5 inch qevs out there, and i have one of them
8)

They are ASCO valves but it works in the same principle as a qev. I still need to think about what i am going to do with one of these, although i was gona sell one but that still didnt happen yet.