RPM - a weird measurement

Lately I’ve been working with formulas to calculate various things, and I realized that RPM is truly a strange measurement. Definitely not as weird as Horse Power, but oddball none the less. Measuring something over a minute - 60 seconds, when calculations are always based on seconds is inconvenient. It’s not “English” and it’s not Metric, it’s time based (dang time lords).

Honestly, who really cares how may times something turns in a minute? How many times in a second seem much more reasonable. Maybe it’s because 15000 RPM sounds impressive? More impressive than 250 RPS for marketing? But then you can easily get your head around how long a second is as you can quickly count it out (one thousand one). 250 rotations in that span of time actually sounds impressive - at least to me. But then I think different, being an engineer…

I think machinery turned at very low RPMs (low 100s of RPM) when the unit was popularized maybe early in the Machine Age (1880-1945). image


RPM was started when machines were a lot slower. 60 rpm vs 65 rpm is easy to see, but 1 RPS vs 1.08 RPS not so much

Edit: @OldFartKarter already said this

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3600 RPM is 60 Hz! Yes, RPS is a lot easier to calculate with.


Stupid rotating objects. I blame Pi. Why do cars give you Revolutions per Minute and Miles per Hour, while Acceleration is often reported as Feet per Second per Second? Its all over the map!!

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