There is a bunch of info and 3D models at the link above, along with pictures and Youtube videos. We have lost baseballs over the horizon at 110psi, and knocked down a tree at with one at 100yds. The tree was old and rotten, but still was hilarious to see happen.
Most of this is typical plumbing fittings from Menards, and our 3D printed piston valve could be made by other means like typical wood and rubber construction. 3D printed projectile sleeves work great.
Just wanted to share this here, figured it was your sort of stuff.
Re: Coaxial can cannon, with 3D printed parts and projos
Re: Coaxial can cannon, with 3D printed parts and projos
Posted: Wed May 30, 2018 6:15 pm
by Schlauncha
Sorry about that. I've updated the link in that second post.
We need to debug some valve problems (since going to 4" barrel recently) but now that we've got a Galaxy S9 which can do 4x higher-speed footage, I'm hoping we'll be able to get a better idea of how these projectiles are doing as they leave the barrel - if they're getting any spin.
In the meantime, here is some footage of projectiles from the 3" barrel:
[youtube][/youtube]
Re: Coaxial can cannon, with 3D printed parts and projos
Posted: Thu May 31, 2018 6:06 am
by jrrdw
Nice rifling tool! Do you change the depth of the cut by changing the position of the cutters? If it was mine I'd do away with the muzzle break, looked to me like it's throwing the rounds low. Very nice build, impressive!
Re: Coaxial can cannon, with 3D printed parts and projos
Posted: Thu May 31, 2018 9:59 pm
by Schlauncha
Yes, the different "rungs" hold the pipe cutter discs at progressively wider spread, so after the first few times pulling it through to establish the rifling grooves, it can keep cutting deeper yet. I am not sure how effective the grooves are at trying to spin the projectiles, they may just be too little and too smooth. I want to try 3d printing truly rifled 3" bore tube sized to fit within 4" bore tube to be structurally pressureworthy, so the first two feet of barrel gets the projectile spinning before it keeps accellerating down the remaining smoothbore length.
Regarding the muzzle brake, it allows for a cross bar to have leverage for tightening the barrel during assembly, as the 6" pipe threads join it to the coaxial pressure chamber. And it looks like a tank which is cool. But I think I actually need to go to a straight muzzle with cross-drilled holes, "ported" as the gun term I believe would be, so that any excess pressure behind the projectile is vented BEFORE it leaves the guiding of the barrel, otherwise this puff is rushing past the projectile at the first chance it gets after the muzzle, causing fin-stabilized projo's to get flipped around off-aim before having to straighten themselves back out. This is where high-speed footage will really help show us what's going on.
Also, though maybe unclear from the camera angle / lens warpage, we were firing this with the cannon horizontal per a bubble-level, and the cannon was rigidly strapped to a trailer (like you'd haul a big atv or mower on) hitched behind an ATV in Park. If we ever gave it a slight angle upward, we couldn't count on those trees stopping things from disappearing over the next hill. I really don't know our power levels or range, but GGDT says the 400 gram cans of pop should have muzzle velocity around 400fps, with more muzzle energy than a 12ga 3" deer slug. I believe it.
Here are snapshots of the GGDT results calculating for a 400g projectile (a can of pop) being fired from the cannon with the 3" barrel and 4" barrel we've built, and with a 4" barrel if it was longer:
