Micro Drive is based on the focusing adjustment of an astronomical telescope. The "course" adjustment is the floor to floor run and the "fine" is the final stop even with the floor.
Simple science really. To get extremely accurate floor levels it helps to be running the machine on a very low gear ratio. This machine runs most of the way driving through the usual worm gear, then for levelling into the floor, a second worm gear is coupled to the back. The second little motor is driving through two worm gears I can’t remember the exact ratio, but it’s certainly extreme. That big round thing under a guard is the clutch that connects the two together for the final level. In 42 years as a lift engineer I’ve only ever seen a couple of them and they’re probably gone now.
What an amazing machine room with the large motor and the smaller motor to do the lift movements. This equipment is from the early 1900's. 1908-1915 period. Absolutely incredible equipment over one century old.
She's a little younger than that. She looks like 1920s machinery to my eye, 1930s at the absolute youngest - no younger than that though. Slate panels for the switchgear, with small(ish) contact assemblies- suggests 1920s to me. But I agree with you - the really smooth and curvaceous profiles on the castings, the svelteness of some of the cast sections and webs, screams "Great War" vintage or earlier. I'd bet she was designed around the 19-teens and was just continued in production much unchanged through the 20s. Probably Otis was running the same patterns in the foundry unchanged for a while.
On the machine tag, the latest legible patent date is 1922. So she's gotta be at least that young. I guess I'm going to have to go patent diving to see what the mechanics behind the large spinning clutch between the two motors is. I guess that's for the automatic floor-leveling system (I think that's what the "micro drive" moniker meant). Haven't seen that before.
There were two of these Otis Micro Drive machines in the building where my elevator company was located in down town Los Angeles. They were originally powered by 600 VDC fro the street car line that came into the basement of the building. In the 1950's they were powered by an AC/DC motor generator in the machine room. Where does the elevator in this video get it's power from?
While these motors are DC and having spotted a DC rectifier in one of the controllers likely a 3 phase circuit either fused or circuit breaker in the electrical panel room (primary disconnect) powers the rectifier board.
One big geared traction machine, 2 DC motors if this machine room was from one of the two earlier videos of the cabs with the 2:1 roping I noted the dead hitch plate and ropes. I noticed it has a DC rectifier on one of the controllers.
