Functional Beauty In Motion

This is the kind of thing that I love about antique equipment. Someone came up with this concept long before the age of electronics, probably using a slide rule.

Totally functional by design with an inherent beauty of motion.

Cycloidal Drive or Cycloidal Speed Reducer. A mechanism to reduce the speed of an input shaft by a certain ratio. They are capable of relatively high ratios in compact sizes. The input shaft drives an eccentric bearing that on turn drives the cycloidal disk in an eccentric, cycloidal motion.

functional beauty

14 thoughts on “Functional Beauty In Motion

  1. I was watching Jay Leno’s garage one night and he had a great observation. He was talking about all the hand fitting on a Duesenberg from the ’20s and said, “back then labor was cheap and technology was expensive, today technology is cheap and labor is expensive”.

    Are you old enough to have been around when everyone had one electric drill (usually 1/4″ chick) and a bunch of attachments for it? Today, the motors are cheap enough to have a separate motor for every task. When this was made, it was cheaper to have a speed reducer than another drive train.

    Liked by 2 people

  2. Look up low-speed high-torque gerotor and gerollor hydraulic motors for a current industry use of something quite similar to this. If you want to see something extra special, look into the Parker NIchols double gerotor units. They run 2 of these concentric to one another and are pretty cool.

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  3. We have a machine at the Mill that uses, what is called a harmonic drive. Which is almost the same concept. The main difference being extreme precision in positional accuracy and zero backlash.

    Whitehall, NY

    Liked by 1 person

      • That is precisely what it is for. Our Rollomatic 620/628/628 CNC grinders use it on the B rotary axis for swinging the workhead back and forth. The load carrying capacity and rigidity allow us to maintain incredibly tight tolerances . The last harmonic I ordered, to replace a failing unit, was right around 3800 bucks. Pocket change on a machine that costs 400k.
        Typically though, servo motors and ball-screws are more than adequate enough for typical linear drive applications. As long as there is no wear in the screw assembly, and the rails are good, we maintain a TIR under .0003″ .
        Our other machines use a worm drive for rotary axis movement coupled with a servo motor. The gear is bronze though, and very susceptible to operator induced errors(crashes). Usually costs us about 18k to send those out to be rebuilt.

        Whitehall, NY


  4. I guess this could be called a speed reducing coupling. I once had to deal with a
    torque limiting coupling at a paper mill. Picture a fractional HP motor driving
    a small gearbox, with an ACME screw output that opened and closed the plates
    on a paper refiner. Call it a paper mill version of a corn or wheat mill. The
    fucking Croatian mill geezer decided that the input coupling needed to replaced
    after the gearbox exploded. He put a Woods coupling on the machine along with
    a new gearbox.

    The first time the production guy adjusted the plates in, it blew the gearbox again.
    My turn at-bat: I dug the old coupling out of the scrap barrel and disassembled
    it. Inner hub to outer hub was a slip fit. There was a cylindrical spring-loaded
    roller with semi-circular cutouts on the inner and outer hubs. Once the coupling
    stalls, the spring-loaded roller rides inward and the input side continued to
    turn with a distinctive click with each revolution of the motor.

    OK, one problem solved. I put a wire tie on the motor shaft and the moment
    it stopped turning, I took my booger-hook of the close button. Some dumb
    fuck of an electrician did not properly adjust the limit switch. The dumbass
    Croatian mill geezer learned how to do precision shaft alignments with a
    straight edge from other mill geezers before dial indicators were invented.

    PS This mill geezer married into royalty. His father-in-law was the interior
    minister in Croatia during WWII. He made the travel plans for about 800
    thousand Jews, Gypsies, and Serbians. Andreja Artkovich was extricated
    back to Yogoslavia, where Tito showed more compassion than his father-
    in-law ever had for his victims. I pranked the old fucker by telling him I
    was a devout Jew. The Croatian Ustasi copied the German Nazi’s
    down to the helmets, uniforms, and the salute. If you see a Nazi ear-
    lap helmet with a red and white checkboard symbol, that is a Ustasi
    helmet. I still have my Harvey Magilla dancing Rabbi doll but I never
    got around to buying a Yarlmaka. Stupid people are easy to fool!


  5. my plant has a few cycloidal roller speed reducers made by a japanese company called sumitomo. actually good product. torque monsters and no backlash. smoothe output no harmonic vibrations. lube lasts a long time as it is not in shear. I have gearboxes that the OEM required #220 lube comes out as piss water after two months of usage in a shear app what with the helical cut gearing.
    did I say I just love being retired now?


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