the maximum output of a horse can be up to 15 horsepower,
That's the problem. The unit was not developed on the maximum power a horse could put out. It was intended to be what a typical horse could continuously sustain throughout the work day.
Also why switching horses was a thing: a fully rested horse could run at a higher hp, then change horses and the new one could keep outputting thevhigher up whilecthe previous one rested.
Like switching rechargeable batteries, only the battery was the horse.
That's the problem. The unit was not developed on the maximum power a horse could put out. It was intended to be what a typical horse could continuously sustain throughout the work day.
Also why switching horses was a thing: a fully rested horse could run at a higher hp, then change horses and the new one could keep outputting thevhigher up whilecthe previous one rested.
Like switching rechargeable batteries, only the battery was the horse.