Bigfoot Turns Classic Sewing Machine Into A Leather-Eating Monster

If you try to sew leather on a standard consumer-grade machine, more often than not you’ll quickly learn its limits. Most machines are built for speed, and trying to get them to punch through heavy material at the low motor speeds often needed for leather work is a lesson in frustration.

How frustrating? Enough so that [Joseph Eoff] expended considerable effort to create this sewing machine speed controller for his nearly century-old Adler sewing machine. The machine was once powered by a foot treadle, which is probably why the project is dubbed “Bigfoot,” but now uses a 230 V universal motor. Such motors don’t deliver much torque when run at low speeds with the standard foot-pedal rheostat control, so [Joseph] worked up an Arduino-based controller with a tachometer for feedback and a high-power PWM driver for the motor.

There are a ton of details in [Joseph]’s post and even more in the original blog article, which is well worth a read, but a couple really stand out. The first is with the tachometer, which uses an off-the-shelf photointerrupter and slotted disc. [Joseph] was displeased with the sensor’s asymmetrical and unreliable output, so he made some modifications to the onboard comparator to square up the signal. Also interesting is the PID loop auto-tuning function he programmed into Bigfoot; press a button and the controller automatically ramps the motor speed up and down and stores the coefficients in memory. Nice!

The short video below shows Bigfoot in action with varying thicknesses of faux leather; there are also some clips in the original article that show the machine dealing with a triple thickness of leather at slow speed and not even breaking a sweat. Hats off to [Joseph] on a solid build that keeps a classic machine in the game. And if you want to get into the textile arts but don’t know where to start, we’ve got you covered.

11 thoughts on “Bigfoot Turns Classic Sewing Machine Into A Leather-Eating Monster

    1. Yep. And if your sewing machine is mounted on a sewing table you can easily use them. Just mount the 600 watt motor with its controller and the linkage for a mechanical foot pedal under the table and you’re golden.

      My Adler doesn’t have a table. If it had its original table with treadle, I wouldn’t have needed a motor at all.

      Bigfoot gets away with a typical 100 watt sewing machine motor. That’s plenty of power for the thickness of leather that will fit under the presser foot of a normal sewing machine.

      Machines that are intended for leather workers can raise the presser foot higher to accept thicker stacks of leather and they have a true “walking foot” that can grab and accurately move heavy stacks of leather. They need a more powerful motor – though I’d doubt how much power they truly need since there were treadle powered leather sewing machines (patchers) back in the day that got all their power from the operator’s feet or a hand crank, which puts a limit on how much power they really got. What it takes it torque, and a low power motor can deliver that.

      The torque available from a 100 watt motor is sufficient for anything you can reasonably put through a normal vintage sewing machine – if you have a controller that can deliver it at need.

      Bigfoot fills its niche, small though that niche is.

  1. And here I was hoping to find an abandoned industrial sewing machine for sewing leather and thick denim. But I’d really like an open armed machine for patching sleeves and pant legs.
    For some reason SWMBO won’t let me use her $9k “sewing computer”.

  2. Back in the 1980’s I scored a regular consumer grade Pfaff straight-stitch machine that was probably made in the early 1950’s. It was all metal and with its original motor and speed control could easily punch through three or even four thicknesses of unsplit pig hide, a fact which made it possible for me to create a pair of fly front leather slacks by “duplicating” a cloth pair I had that fit well but was made of hideous plaid material my new girlfriend refused to let me wear.

    1. The video is not the content. The video is only a demonstration of the operation.

      There’s a small novels worth of written text and photos describing how big foot got to be the way it is.

      At no point did I discuss using a different ratio on the pulleys.

      The pulley on the motor is about as small as is physically possible. The other pulley is given by the original handwheel. To improve the pulley ratio, you have to make the little one smaller or the big one bigger. Neither is practical.

      You’d have to use some two (or more) stage system of pulleys and drive belts to slow things down.

      Such a setup is inflexible. When you have it manageable for one task, it is to slow for others.

  3. This seems like a reasonable and well-done modern solution to make the machine do more than it was really expected to do. The older one might be a variac; they handle slow speeds on universal motors better than choppers do.

    The bit about 300VDC being the same as 230VAC sounds questionable although it obviously seems to have worked out so far. Universal motors are normally expected to be used at the same voltage of DC as their RMS rating, and even then they will be a bit more powerful on DC. Generally, there’s at least the advantage of less iron loss on true DC, but I suppose the PWM will bring back the iron loss depending on its frequency. And anything causing more average current (DC has lower impedance, more torque available, if you use the extra torque that’s more current) or peak current (PWM, to the extent that it’s not smoothed out by the same inductance that can exhibit iron loss, makes the peak current higher than the average by an amount which for very low duty cycles should become significantly worse than typical AC except when a chopper is involved).

    The PWM’d DC should actually look a lot like the triac chopped AC in terms of characteristics; it’s interesting that it worked out so well. Maybe that’s more about the controller being able to ramp duty cycle as needed, and a bit about the extra voltage. But mainly the control; when you set a fixed speed manually, you’re doing it before loading the motor. Unloaded a universal motor will go as fast as possible until reaching 0 net torque, so you have to drop down in rpm a lot before you reach the speed of your actual loaded torque.

    1. How many would you like? You can buy a universal motor and controller on Amazon for around $30 US.

      Sewing machines have used universal motors since the beginning. Way back when, there were some power nets with DC and some with AC. Sewing machines were equipped with universal motors to run on any net.

      They’ve stayed with that type of motor ever since.

      Outside of that, I have two (relatively new) routers in the garage that have 230VAC universal motors. The mixer in the kitchen uses a 230VAC universal motor.

      I live in Germany so those are all for 230VAC. In the US, you’ll find the same appliances with universal motors rated for 120VAC.

      Have you got an electric (line powered) angle grinder? It’s probably got a universal motor in it.

Leave a Reply

Please be kind and respectful to help make the comments section excellent. (Comment Policy)

This site uses Akismet to reduce spam. Learn how your comment data is processed.