#CC machining plans for a #mechanical micrometer popularly (but probably falsely) believed to have been made by James Watt
#video about #mechanical #gears sliding; #math says that if you take a parametric curve γ(s) and add a parameter t for its motion over time γ(s,t) the Jacobian of that function will have determinant zero at its envelope (where movement through time is the same as a movement along the surface), and from that this video derives a closed-form parametric representation of that envelope curve, which is the mating gear.
#Harrison-Low #video about a #mechanical linear actuator design for a juggling robot, capable of a full 263mm stroke in 100ms. He’s mostly using carbon-fiber reinforced plastic tubes, with six 6001RS cartridge bearings for rollers (one too many for #exact-constraint), held in place by a piece made by #3D-printing, with interchangeable spacers to adjust the fit in 100μm units to the imprecisely-sized tubes. He’s doing the actual actuation with a kevlar-kite-string cable drive, with the cables actually run through teflon Bowden tubes so the motors don’t have to add mass to the actuator joints; the motor pulley has two V grooves for the two ends of the cable. This seems like a good way to do robotic #mechanisms in general. This replaces his first hydraulic design made out of syringes and a second iteration using a ballscrew which was too slow and (I assume) also super expensive. He has an AS5048 magnetic encoder for positional measurement, coupled to the actual moving parts with a constant-force spring, whose rotation is what it measures, but so far he’s just using encoders on the motors themselves (which I guess are brushless since he’s using #ODrive; in fact, the motors are ODrive-branded, model D6374-150KV). He says ODrive's current sensing “completely removes” the need for limit switches. His attempts to clamp the three frame tubes with a flexure from the inside failed, but I don’t know why he doesn’t clamp them with a flexure on the outside, instead relying on hammering them in. He uses a thin wire with a hook bent on the end as fish tape to pull the kevlar string through the teflon Bowden tubes, but doesn’t always need it because of how stiff the kevlar string is. On one occasion the kevlar string was able to friction on the 3-D printed plastic and just cut right through it, presumably from heat (a big advantage for kevlar over UHMWPE, except when you want to cut it; presumably kevlar will creep less for the same reason). #robotics
#video about improved high-speed linear actuator #mechanisms design using carbon fiber for #Harrison-Low's juggling robot. Now his motor is in the linear actuator itself, and its shaft has two reels on it, one to let out string (kevlar kite string?) and one to take it up, or vice versa when moving the other direction. He’s also added TPU sleeves to the six bearings he was using as rollers to constrain the shaft’s motion to one degree of freedom. I think it's about 500mm of stroke. He’s able to get 3.4m/s and >50k cycles endurance. The theoretical precision is 8.4μm, which is more precise than his ±20μm Mitutoyo calipers, but with a pulley mechanism he got a standard deviation of 57μm, which is pretty good. The string breaks at about 70 or 80 newtons. #robotics
#video about improved #mechanical servomotors for hobby robotics. He’s using an SPI magnetic encoder with on-chip sensors to read the motor position, controlled with an #STM32 G0 interfaced via I²C, programmed in Rust, which controls an LV8548 H-bridge driver chip, which can handle 12V 2A output. #microcontrollers #electronics #hardware
#video #toread about #mechanical motors in hobby robotics
#video #toread about #mechanical threaded inserts for #3D-printing
#video about “putting salt on your electronics soldering iron” is actually using a tin/lead solder electrode for #electrolysis with tuz (NaCl) to tin(?)-plate an oxidized copper wire and then his carbon-coated kind of ruined soldering-iron tip
#Advanced-Tinkering #video about a homemade magnetron. Explains #vacuum considerations like vent holes for screw threads to prevent virtual leaks and face seals rather than radial seals (due to, he says, his inexperience). He used #3D-printing to make drill guides to transfer the precision of his 3-D printer to his drill and thence into stainless. He’s doing water cooling inside a copper plate in hard vacuum! But his water-cooling hoses aren’t exposed to vacuum. He’s powering it with the guts of a microwave and a half (one MOT and two oil caps) plugged into a variac. He got his metal parts machined by his video’s sponsor PCBWay. One of them cost him US$227, US$1170 for the entire magnetron assembly.
#video by #Breaking-Taps about a homemade #vacuum box, made from a used eBay Laco Technologies box, so not really very homemade at all. Explains roughing rotary vane pumps vs. his 50krpm turbomolecular pump that gets down to 2.4 nanobar, oil mist eliminators, coaxial foreline traps to eliminate backstreaming of oil, ISO 100 flanges, KF16 and KF40 and KF50 flanges, conflat (CF) flanges with copper gaskets, KF/NW centering rings with green Viton O-rings, etc. This is the first time I remember seeing a detailed explanation of the KF/NW flanges, and I really like the design.