Zachary Tong (AKA Polyfractal) got himself a Chinese sewing machine. These machines, nicknamed “patchers,” are used to sew leather goods like boots, gloves, jackets, etc. By all appearances, these machines are knock-offs of an old model Singer brand sewing machine. They were originally designed to be powered by manually turning a hand-crank, and if Polyfractal was a street peddler, fixing the shoes or the purse of the occasional passerby, then he might have left it as it came. However, not content to crank away, he decided to motorize his knock-off Singer.
Also, besides the fact that mechanization is convenient and generally awesome, having both hands free to manipulate the work, is probably a bit safer than cranking and sewing simultaneously. A machine that can stitch leather without effort will probably have no problem sewing the operator’s hand to an old shoe.
What he needed to make his vision reality was a pulley attached to the cam wheel that originally cranked by hand. With a pulley attached, a motor could now spin the pulley/cam-disk unit via a drive belt.
Machining a pulley is no problem on a lathe. Any appropriately sized slug of metal is just a few operations away from being transformed into a pulley. The thing is, Polyfractal did not have a lathe. So he did what makers do, he used what he had, and what he did have, was a milling machine. With his rotary table, a pretty thick slitting saw and a dovetail cutter, he machined a serviceable v-belt pulley. Polyfractal admitted to some concern about his chosen methods and he did have a few setbacks but the final result was impressive, all things considered.
Side note, with care, a lathe can be a mill and sometimes, a mill can be a lathe… kind of. That’s a lesson makers and professional machinists alike always end up learning, and that is we work with what we have.
To motorize the machine, Polyfractal modified a brushless hoverboard hub motor purchased from EBay. To start with, he removed the tire, and then he decked the side of the hub in his milling machine.
When attempting to mount a drive pulley to the hub, Polyfractal’s automatic center punch hilariously blasted through the thinned out metal like the Cool-aid guy busting through drywall. While frustrating it really didn’t matter because he ultimately got it working.
Next, he fabricated a mount to hold the motor in place and laced a drive belt between the pulleys. Then, to get everything moving, he wired the motor to a barely up-to-the job ESC (Electronic Speed Control) and a servo motor tester. The servo motor tester supplies an adjustable square wave to the ESC, which then throttles the motor’s speed. Power was provided by a benchtop power supply.
Like so many machines that hale from China, the fit and finish are generally very rough.
Razor sharp edges, un-removed casting flash and lousy fitment between components are the rule rather than the exception. They are the definition of crude. This author has a fair amount of experience with machines like the patcher. My maker spirit literally vibrated in sympathy as I watched Polyfractal crank the machine by hand.
Despite not having the best raw materials to work or the most ideal tools, Polyfractal pulled it off. You can see the whole project progression here or you can follow these links to Polyfractal’s videos of the build.