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Comment by codeflo | Hacker News Reader

I know this is off-topic, but I'm curious. I always had the impression that even in the US, standard units are used for engineering. Reading about "ft-lb" makes me think I was wrong (and my head hurt, tbh). Do you really compute stuff like torque in imperial units? Don't you need weird factors in every formula to make that work?

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There are lots of weird factors in engineering anyway. We have different factors, but there are still factors. Besides, nobody is calculating this, they are measuring and that is just a matter of what label you put on the dial.

Most engineering in the US is done in metric units. Then marketing applies a metric to imperial conversion.

I suspect China does more engineering in imperial than the US, both in total an per capita: most things I buy made in America are all metric (cars are all metric except for parts designed in the 1960s and the adapter bracket to make them fit on a modern metric car). Most things I buy made in China are imperial. I don't really know for sure, but that is my impression of industry.

> Besides, nobody is calculating this, they are measuring and that is just a matter of what label you put on the dial.

That's why I asked about engineering, not driving. Nobody converts torque to power etc.?

The engineers who do that are using metric. Marketing might do this conversion, but they just plug it into a converter and have no reason to know anything more than bigger is better.

Torque to power is just (torque * RPM) / (some constant depending on the units inolved). With ft-lbs and horsepower, that constant is 5252; with N-m and kW, it's 9549. The only thing that changes is the constant.

You make it sound like you'd have to remember a 4-digit constant in either case. That's stupid, it's simply (torque * RPS * 2 * PI).

No, power is just torque times angular velocity. No constants involved.

If you ignore units, sure.

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