S2 Marauder: 12-shot Semi-automatic ...
Phil Pilgrim (PhiPi)
Posts: 23,514
... rubber band gun! Here it is:
I was in an ecumenical mood, it being Easter and all, and made this thing out of wood AND plastic. (Erco and Matt, I now pronounce you ... compatible.) The wood is 2.7mm 3-ply doorskin from EdenSaw; the plastic, 3/32" acetal copolymer (similar to Delrin), and a couple pieces of clear acrylic. Everything was laser-cut. The servos are the GWS Naro units that Parallax carries -- really nice mini servos, just perfect for this app. One servo operates a cam that's coupled to an escapement, which turns entirely from the force of the stretched rubber bands. One back-and-forth motion feeds and fires the next rubber band on the star wheel. The other servo operates the tilt mechanism. Here's a view of the guts:
Loading it requires a short program to cycle the escapement while you pull back on the star wheel. It's not too bad, though, since you can reach three slots at a time to load them.
Here's a short video of the thing in operation:
[video=vimeo;39991872]
Any questions?
-Phil
Addendum (10 Apr 2012): Attached are assembly instructions for the kit, along with a sample program.
I was in an ecumenical mood, it being Easter and all, and made this thing out of wood AND plastic. (Erco and Matt, I now pronounce you ... compatible.) The wood is 2.7mm 3-ply doorskin from EdenSaw; the plastic, 3/32" acetal copolymer (similar to Delrin), and a couple pieces of clear acrylic. Everything was laser-cut. The servos are the GWS Naro units that Parallax carries -- really nice mini servos, just perfect for this app. One servo operates a cam that's coupled to an escapement, which turns entirely from the force of the stretched rubber bands. One back-and-forth motion feeds and fires the next rubber band on the star wheel. The other servo operates the tilt mechanism. Here's a view of the guts:
Loading it requires a short program to cycle the escapement while you pull back on the star wheel. It's not too bad, though, since you can reach three slots at a time to load them.
Here's a short video of the thing in operation:
[video=vimeo;39991872]
Any questions?
-Phil
Addendum (10 Apr 2012): Attached are assembly instructions for the kit, along with a sample program.
Comments
Very nice design.
I can haz filez?
Rich: Yes, eventually.
-Phil
I have just a few hours before I leave for CA, just barely enough time to laser one out.
Oh, gosh; sorry, man. My intent is a measured release of a few samples first, before the files themselves are released. That's what I meant by "eventually." 'More details later.
-Phil
I had done one several years ago from G10 fiberglass on the CNC mill, that was attached to a webcam. People accessing the site could aim and shoot at some targets I had set up -- or at me, if I was in the shop. The idea of adapting it to the S2 has been brewing for awhile, and the laser cutter makes it feasible to build them more quickly and easily. I didn't begin working on it in earnest, though, until a couple days ago. Getting the escapement clearances right was the hardest part. With the mill and G10, everything was spot on dimensionally. With the laser, I had to fatten things up a bit to account for the "kerf". (The first couple units went "full automatic" as a consequence of too much clearance.) In the webcam design (a one-off unit), the servo was oriented differently and used a standard servo horn with a wire linkage to operate the escapement. I knew this was not easily reproduceable, and that's when I came up with the cam approach. The tilt mechanism is brand new, since the webcam had its own pan/tilt. The gear involutes were designed in Rhino and imported to Corel as DXFs. Also, the webcam design made copious use of spacers and standoffs, which I did not want to have to include in any kits I put together. In this design, the wooden bulkheads replace them, although everything is held together with screws, and nothing needs to be glued.
-Phil
Awesome video. I know exactly how much time went into choreographing and testing: way too much, but the results speak for themselves!
I'm sure you'll be getting two thumbs up from Cowbody Coder.
Jim
Phil -
I must have one! Way Cool Dude:cool:
-MattG
Unless I stay up all night....
I'm with Matt - I want one too!
I think we need to make sure at least one of these shows up for every expo. I'm sure OBC will appreciate it.
Also, Matt & Jessica, you two get along okay and can share, right? Right? (Say yes.) I've also sent an extra kit and a pre-built unit with your names on them. You'll see them tomorrow.
-Phil
That is just AWSOME!
But we expect no less from you..cutting edge and all that
Jim
-Phil
Just coming back online after Easter...
This is totally cool!!!!!!!
Phil, I hope you or Parallax will be selling kits on-line?
This is way cool!
Servos are for suckers.
Truth be known, the escapement mechanism would be easier to load with a single-acting cam and a spring, instead of the double-acting cam that I employed. The star wheel and escapement would have to be tweaked a bit, so that rotating the star wheel backwards would force the cam to retract against the spring, then snap back like a ratchet.
Well, for lazy people like me, at least, who don't want to drag relays or extra electronics into the equation.
-Phil