The up tube is designed to be small so that you can drill or ream it to 3/16" for a nice smooth passage. For the magazine portion, make sure your machine bridges well. Speed, layer thickness, and cooling may all need to be modified to achieve good bridging. I don't believe PLA will be a viable material for pressurized guns. First it is more brittle than ABS and will result in an abrupt failure under pressure. Second, the ability to melt the printed part with acetone is critical. I've pressure tested printed plugs made from ABS. Even with what I thought was a well calibrated machine and what looked like a solid print, it leaked air.
now on a 6/7 success rate with the cannons. and i have figured out how to do a triple configuration with the bic in my Yamato which fixes an issue i introduced trying to use antfarms. print rate of 2 cannons every 9.5 hours is handy (printing a mirrored pair) and using a t fitting that i cut off the ends i get 3 cannon parts from one fitting with minimal modification. printed 2 BIC at 5% infill they come out at 38g Printed 4 BIC at 50% infill BIC and they come out at 40g but have significantly more strength planning on making about 14 bodies so i have spares that are fast to swap out if something goes horridly wrong.. that and Yamato will use 7 of them and I still have other boats to build. for 3 guns i just need about 6" copper tube 1 compression tee fitting 3 1/8 90degree 6mm push fittings (worked decent with straight but had to make a mod for the hose) 3 spring and piston set. 1 nylon bolt. (100 already cut) View: https://www.amazon.com/gp/product/B005U98PDK/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1 as always great design and love using it
I switched back to my older Solidoodle 2 which prints well in ABS and after scaling to 103% in slicer, I have nice BICs to experiment with. Instead of waiting 2-3 hours for each iteration to check my print settings I cut a chunk out of the middle of the BIC that has one loop of the magazine feed tube in it. It's easy to test the up-tube ID with a pin and roll a BB though the single turn to see how it came out. If people are interested I can post that up.
Surprised you had to scale it up 3%, but at least you got them to print. Let us know how they work for you.
I've now printed and assembled one of these (and acetone rinsed), and am working to get it to feed reliably. The photo in the Overview shows it mounted with a decent down angle. How well did the cannon in the photo work? Mine is being a little challenging. With the bottom open bb's roll down the magazine and out the bottom very smoothly. With the interrupter and threaded bottom port installed it always fires the first bb but does not like to fire the second without shaking (oddly, backing out the interrupter did not seem to make a difference). It fires best horizontal but a fresh refill of the CO2 bottle has helped some. I am gluing a small rare earth magnet to the indention in front of the interrupter tee section and will test again....
OK. So the small, cylindrical neodymium magnet at the tee seemed to do the trick. Fired 50 bb's as fast as I could squeeze, and even at 20 degree down angle). -- It's "weird" to tweak without the usual sharp percussion (normal brass elbows) to listen too.. the curved plastic arc inside at top has more of a plastic rattle sound.. but the bb's were coming out barrel so fast I could not see them so I think I am satisfied. I'll test outdoors on a target tomorrow, while I print one of the mirror-image BIC's (going for drop-in twins!)
Out of curiosity, has anyone had issues with failure at the barrel assembly/plastic connection? I have not had good experience with CA, and no experience with Loctite retaining compound. I have noticed some of the 3D printed Big Gun cannons use pins and grooved barrels to make a solid mechanical connection - is this out of an abundance of caution, or the result of past failures?
Yes, I have had issues. CA is brittle and will fail. E6000 is too thick, and has trouble actually getting into the gap. Both red and blue loctite also have difficulty getting into the gap. The best results I got was to rough up the barrel insert with super-coarse-grit sandpaper, and then glue it in place with a slurry of ABS and acetone. Even that sometimes failed, so I drilled and pinned the insert in place. This was difficult to do, so ultimately I designed my own cannons based on the BIC. My most recent designs based on the original BIC now include a threaded barrel nut printed as part of the cannon. Much stronger and more consistent.
No, not at all. My oldest ones I glued with slurry of ABS/acetone My current ones just E6000 black I always sand the short piece of copper tubing with rough sandpaper first and use dremmel cutting wheel to make a few groove/indentions - all to give the glue places to "grab" the copper *I do always use a droll bit (in hand) to make sure the top is round and will fit the 1/4" copper tube (my abs sags just slightly at top). My recent ones I have taken to reversing things. I put the threads on the barrel! I then solder the nut on the end of the piece of copper tubing. When I push that into the ABS cannon, the nut goes flat against it and has more surface area to hold glue (back of nut, not just the copper tube). The BIC's have become the best cannons on my ship (reliable and hard-hitting.. not a common situation with me and cannons, lol). Morenao (and now Rivadiavia) are both 100% BIC's BrianK
