>> 60 DIN PS ~= 59.2 SAE HP. (1 PS ~= 735.5 W, 1 HP ~= 745.7 W)
>
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> nowadays. But where does HP come from? A horse of course, but no metric
> weight in there?
>>> 60 DIN PS ~= 59.2 SAE HP. (1 PS ~= 735.5 W, 1 HP ~= 745.7 W)
>>
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> first used in the UK in (IIRC) the 18th Century (invented by James Watt,
> for whom the watt is named!),
Uhm - didn't want to relocade Mr. Watt's steam machine to germany. But
AFAIK the horse was used as an "excuse" for itroducing the unit "PS"
over here too.
> and defined as 550 lb-ft/s.
Ok, so it's at least kind of a round lot in imperial units.
Maybe as the transfer to kilogramm and meters would have given a really
crude number, so someone decided to go for 75kgm/s.
> (Why 550
> pounds? I have no idea, but that's what it is. ;-)
AFAIK this was supposed to be the workload that a horse was supposed to
deliver continously when working 12hours per day. Easy calculation for
the factory owner how many horses could be replaced by a steam engine.
> The PS
> ("pferdestarke") came along later, and was defined to be close to the
> HP, but using MKS units, thus 75.0 kgf-m/s, which was calculated out to
> 735.5W based on a "g" of about 9.807 N/kg.
kgf stands for "KiloGrammForce"? At least over here the abbreviation
"kp" was used for the force equally to a mass of 1kg - before kp was
completely disposed in favour of Newton.
Ingo