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How many RPM is "high?" I have a router that can go up to 40,000 RPM, reciprocating sander that goes about 2000 RPM, et. al. But if I want to actually do good h

by throwway120385 2y ago

How many RPM is "high?" I have a router that can go up to 40,000 RPM, reciprocating sander that goes about 2000 RPM, et. al. But if I want to actually do good high-quality sanding, lower RPM with higher momentum is better. Also how big is a "large?" motor? Are we talking tens of horsepower, or single-digit horsepower? My drill press's motor is about 2 horsepower and my router is about 2.5 horsepower, for reference.

tomcam 2y ago
Unfortunately your drill press is now manually driven. When I found out it was 2 horsepower I “borrowed” it from your shop and turned it into a tiny go-kart
- throwway120385 2y ago
  Look it's a 1950's Craftsman I got from a guy who wired the hot and neutral backwards when he replaced the original motor. They did things differently back then.
SoftTalker 2y ago
> Also how big is a "large?" motor? The motors discussed in the article were described as "fractional horsepower"
- DoctorOetker 2y ago
  that question was obviously not directed to the authors of the article, but to doe_eyes: > Many large motors don't use permanent magnets, and even for the ones that do, neodymium isn't all that rare and is mined in the US. What doe_eyes is referring to are motors or generators where the magnetic fields are generated by currents through windings. Under certain conditions it is more LCO efficient to generate magnetic fields that are stronger than even Neodymium magnets can supply. Your dig about fractional horsepowers is thus misplaced.
  - SoftTalker 2y ago
    Wasn't meant to be a dig. The featured article is about electrostatic motors that provide less than one horsepower. Therefore any comparison to "large motors" is kind of off subject.
Panzer04 2y ago
Most motors connected directly to AC power are likely to be induction motors, which require no special magnets. From fans, to fridges, to AC etc. Because they don't need drive electronics they can be very cheap compared to BLDC and the like, which would need power conversion from AC. Turbine generators typically use Synchronous motors, which often use DC to generate the opposing magnetic field ("exciters"), though they can also use permanent magnets for the same effect.

tomcam 2y ago

Unfortunately your drill press is now manually driven. When I found out it was 2 horsepower I “borrowed” it from your shop and turned it into a tiny go-kart

throwway120385 2y ago
Look it's a 1950's Craftsman I got from a guy who wired the hot and neutral backwards when he replaced the original motor. They did things differently back then.

SoftTalker 2y ago

> Also how big is a "large?" motor? The motors discussed in the article were described as "fractional horsepower"

DoctorOetker 2y ago
that question was obviously not directed to the authors of the article, but to doe_eyes: > Many large motors don't use permanent magnets, and even for the ones that do, neodymium isn't all that rare and is mined in the US. What doe_eyes is referring to are motors or generators where the magnetic fields are generated by currents through windings. Under certain conditions it is more LCO efficient to generate magnetic fields that are stronger than even Neodymium magnets can supply. Your dig about fractional horsepowers is thus misplaced.
- SoftTalker 2y ago
  Wasn't meant to be a dig. The featured article is about electrostatic motors that provide less than one horsepower. Therefore any comparison to "large motors" is kind of off subject.

Panzer04 2y ago

Most motors connected directly to AC power are likely to be induction motors, which require no special magnets. From fans, to fridges, to AC etc. Because they don't need drive electronics they can be very cheap compared to BLDC and the like, which would need power conversion from AC. Turbine generators typically use Synchronous motors, which often use DC to generate the opposing magnetic field ("exciters"), though they can also use permanent magnets for the same effect.