#PDF slides on #pericyclic #gears for NASA. Uses straight-faced gear tooth profiles like a rack (I mean, a rack designed for interfacing with involute spur gears), which seems like it would be better than Retsetman’s toothform; they used #3D-printing in 17-4 PH stainless for the prototype. “Competitive with harmonic gears for Mars 2020 application investigated.”
on 02024-06-24#PDF #introduction to #pericyclic #gears
on 02024-06-24#video by #Retsetman about "pericyclic" #mechanical transmission, which looks like a strain-wave gear without the strain, instead nutating because the barrel-shaped gear can spin freely on a part of the shaft that’s ground (well, 3-D printed in this case) with its axis at a 4° angle to the shaft’s own axis of rotation. Four moving parts to get 409.5:1 reduction, or six to correct for vibration. It’s apparently too inefficient to be backdrivable at least in its plastic incarnation. The 409.5:1 version is differential: each rotation, the nutating gear rotates the output shaft one 8.37° step forward, while rotating backwards one 9.23° step with respect to the fixed gear, which I guess means they’re 43 and 39 teeth respectively. It seems to have a lot of backlash or something though. The video contains erroneous statements about spur #gears. With the gear profile he’s chosen (some kind of involute-like tooth profile, which may be responsible for the backlash), he gets a slip-clutch effect which he considers a defect but which is a great advantage in some situations.
on 02024-06-24