Horsepower: One horsepower isn't equivalent to a horse.

[Milkyway]

James Watt invented a novelty scientific equation to impress his future clients of the power of his steam engine.

300yrs later...
A drey horse's output was measured on a dyno, via a rope & drum setup replacing the cars engine... the Dyno recorded 5hp.
(The measurements were taken with the horse led at a normal walking pace).

Edited by Milkyway on Tuesday 13th January 18:31

[RizzoTheRat]

I think it was originally based on smaller pit ponies rather than big shire horses, but it was also supposed to be an average over a long period. A horse can manage a lot more power in a short burst but over several hours work it's average output will be way smaller.

[Lotobear]

...its a bit like one apple is not 1 Newton

[Milkyway]

RizzoTheRat said:

I think it was originally based on smaller pit ponies rather than big shire horses, but it was also supposed to be an average over a long period. A horse can manage a lot more power in a short burst but over several hours work it's average output will be way smaller.

I think that a horse can pump out about fifteen horses for a short period.
(Watts equation involved raising water over a set distance & period).

NB: The original 2CV (deax chevaux) @ 9hp... makes sense now.
Later ones...should have been called 6CV's.
(30hp = 150hp... in new money).

Edited by Milkyway on Tuesday 13th January 17:04

[Teppic]

RizzoTheRat said:

I think it was originally based on smaller pit ponies rather than big shire horses, but it was also supposed to be an average over a long period. A horse can manage a lot more power in a short burst but over several hours work it's average output will be way smaller.

Ponypower didn't have quite the same ring to it.

[Milkyway]

Teppic said:

Ponypower didn't have quite the same ring to it.

Acceptable for Mustangs.

[spitfire-ian]

When you look at it this way it makes more sense.

It's the force needed to lift 550 lbs, 1 ft in 1 second.

[Monkeylegend]

Horses, like people, come in all shapes and sizes.

[fooman]

Well if horsepower doesn't mean the power of a horse perhaps we should start using a unit of power measurement we can relate to, like a Schwarzenegger.

[Milkyway]

fooman said:

Well if horsepower doesn't mean the power of a horse perhaps we should start using a unit of power measurement we can relate to, like a Schwarzenegger.

1hp = a shetland.
In reality, about 0.5hp... but this keeps it simple.
(Sorted).

Edited by Milkyway on Tuesday 13th January 17:57

[Rusty Old-Banger]

fooman said:

Well if horsepower doesn't mean the power of a horse perhaps we should start using a unit of power measurement we can relate to, like a Schwarzenegger.

10,000,000 Schwarzeneggers = 1 Norris.

[Milkyway]

Rusty Old-Banger said:

10,000,000 Schwarzeneggers = 1 Norris.

Chuck or Lando...just for clarity.

[Warhavernet]

If you want a sore brain figure out the strange relationship
between the Foot-Pound [ft-pd] and the Pound-Foot [pd-ft].

[Evanivitch]

spitfire-ian said:

When you look at it this way it makes more sense.

It's the force needed to lift 550 lbs, 1 ft in 1 second.

People also forget this was the sustained effort of a horse working ploughing a field. It wasn't a quick, fast effort on a Dyno.

The ability of static engines to provide continuous power was their biggest attraction. If you wanted short bursts of power there were plenty of gravity solutions.

[Milkyway]

I have just read another way of looking at it.

1hp: A horse turning a 24ft mill wheel 2.5 times in a minute
(That seems a bit more logical).

In comparison: HumanPower
Average: 1.2hp
Athlete: 2.5hp

Edited by Milkyway on Wednesday 14th January 19:20

[Simpo Two]

Milkyway said:

I have just read another way of looking at it.

1hp: A horse turning a 24ft mill wheel 2.5 times in a minute
(That seems a bit more logical).

But that doesn't include load/friction...

[Milkyway]

Simpo Two said:

Milkyway said:

I have just read another way of looking at it.

1hp: A horse turning a 24ft mill wheel 2.5 times in a minute
(That seems a bit more logical).

But that doesn't include load/friction...

That must be the 'at the wheel' figure.

[poppopbangbang]

BHP/HP is just a useful way of putting a value on work done over time.

Hence why BHP = Torque X RPM / 5252

As noted above the original calculation was based on the force required to lift 550lbs 1ft in 1 second. Note force, as in torque. BHP is not a force, it's a measure of this work being done with the work consisting of moving a mass, a distance in a period of time.

When we talk about engines what we're really talking about is the work done where the mass is force on the piston crown, the distance the stroke and the period of time a crank shaft revolution. More crank shaft revolutions in a fixed period of time = more work done = more BHP in the above equation. Hence why making the same torque (force on the piston crown) at twice the RPM = a lot more BHP.

An over simplication of most of the functions but hopefully a half decent explanation of what BHP actually is and why 1 horse can have more than 1 horse power