• So, does it Sew?

    polyfractal • 03/16/2019 at 12:01 • 0 comments

    Yep! :)

    Here's a quick video showing the patcher sewing through a few different thickness of leather.  I also cover the needles I'm using, since they are a bit non-standard.

    The leather I tested on was probably ~4oz oil-tanned pullup leather.  The second test was 4 layers totaling about 8mm of thickness.  The leather is moderately supple...not super tough, but not super limp either.  I should have grabbed a few pieces of thick tooling leather but didn't think about it at the time, sorry :(

    Test thread is #69 polyester, needle is 134-35 / DP-35 LR chisel point in size 120/19.  This replaces the 15x1 / Hax1 needles that come with the machine (although it does require some modification).

    All in all, it works great!  I still need to create a replacement stand/tripod and rig up a foot pedal, but that should be relatively straightforward.  Going to declare this project a success!

  • Finishing and testing the patcher

    polyfractal • 03/06/2019 at 13:25 • 0 comments

    Quick video, just milling a mounting bracket for the motor shaft.  Rather than a grub screw, the d-shaft is sandwiched between two plates, and the whole thing screwed down to a 2x4 for testing.  A cheap EST and PWM servo tester later, and the patcher is moving on it's own volition!

    The ESC is under-rated and insufficient (it's just a cheapo ESC that I had laying around).  Spec'ed at only 14v (4s lipo) the motor is too slow.  Overvolting to 20v speeds it up a bit closer to realistic RPM, but the ESC grows very hot.  In reality the motor would prefer 30-48v, so I need to get a larger ESC for actual usage.

    The PWM generator is just a simple servo tester, and will eventually be embedded in a foot pedal.

    Finally, the patcher really needs a belt tensioner.  I tensioned by just applying force and screwing down to the 2x4, but as you can see in the video there is a fair amount of play in the belt (in addition to the runout *cough*).  When I make a proper stand for this, I'll include a belt tensioning mechanism.  Probably just some kind of swivel for the motor mount, allow it to be pulled tight.  Or potentially a spring-loaded pulley similar to how cars tension belts.

  • Fabricating a motor pulley adapter

    polyfractal • 02/27/2019 at 14:25 • 0 comments

    In this video I fabricate an adapter that mounts to the face of the hubmotor, and allows attaching a small cast pulley.  I had several options for attaching the belt to the motor.  I could have put the pulley on the outside diameter of the hub motor, which would have been the simplest.  But I wanted better gear reduction.  I could also have attached the pulley to the back faceplate which would have been very simple, since the plate is just bolted on.  But I was afraid placing the pulley there would have made mounting the shaft difficult (not much clearance).

    So I opted to bolt an adapter to the face of the rotor bell.  It looked like there was plenty of material to work with, after facing off the decorative details.  But as it turned out the bell was very thin (and an uneven casting).  So there were some amusing moments like my center punch going straight through the bell :)

    Got the job done, but certainly not the prettiest or most professional arrangement.  A fair amount of runout, and the adapter piece is pretty ugly.  But it should work :)

    The adapter is a piece of mild steel, not because it needed to be, but because I wanted some practice at machining steel.

  • Fabricating the v-belt pulley for crank flywheel

    polyfractal • 02/22/2019 at 13:21 • 0 comments

    In this first video, I fabricate a v-belt pulley that will mount to the cast iron flywheel.  I originally wanted to groove the flywheel itself to accept the v-belt, but there are tracks on the inside of the flywheel that control the motion of the sewing arm.  Unfortunately, this track is perilously close to the edge of the flywheel in places, and I was afraid the v-belt groove would cut into the track.

    So instead I fabricated the pulley out of some spare tooling aluminum plate I had laying around.  I don't own a lathe (yet!), so I was forced to mill out the pulley on a rotary table and various milling cutters + dovetail cutter.  The v-belt profile isn't correct/ideal, but for this application it shouldn't matter much.