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Horses vs. Horsepower

07/23/2007 12:00 PM

I just read a post by mareng in another thread. The origins of "Horsepower" was mentioned. It led me to wonder ... I've heard that James Watt coined the term; but how accurate is the literal term horsepower? I mean ... does 5HP truly equate to 5 horses? 5 horses doing what, exactly? What kind of horses? Or is the term now no longer relative to actual horses ... and only relative to itself? If this is the case, why?

Has the literal relationship ever been tested?

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#1

Re: Horses vs. Horsepower

07/23/2007 5:01 PM

The term Horsepower was indeed coined by James Watt for marketing purposes of the steam engine - what it actually implied was that a 10hp engine could replace 10 horses.

It has an indirect relationship to the mechanical power of a horse.

Watt was working with mine ponies and he establish by test that the average pony were capable of lifting a bucket of coal (weighing 22000 lb) a distance of 1 feet in 1 minute.

He then defined a mechanical horsepower as 33000 ft - pound per min.

Other definitions of horsepower followed (Metric, electrical, brake, dawbar, taxable,boiler etc)

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#7
In reply to #1

Re: Horses vs. Horsepower

07/24/2007 12:00 AM

I thought I read one time that the actual power of 1hp was derived as the equivalent to a specific measurement in a structured sort of test involving two horses, not one.

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#8
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Re: Horses vs. Horsepower

07/24/2007 12:41 AM

I stand corrected. I looked it up in my handy conversin table. 33,000 foot lbs./min or 550ft.lbs./sec.

Just as a side note, my wife's horse pulled against his cross ties and bent a 4"dia 1/4"wall steel pipe. I don't know how long it took in miliseconds, but it took me a couple of hours to fix it.

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#2

Re: Horses vs. Horsepower

07/23/2007 5:01 PM

I gave this some thought in as far as the analogic interpretations reach and came to similar questions. Don't think it is any longer relative to horses. But, if you lived 150 to 200 years ago, were used to working with horses and had never seen or worked with a machine, it gave you something to relate to in as far as what power was available.

I would guess that there must have been some means of determining the average output of a horse in order to arrive at a horsepower, but there seem to be too many variables.

Could it have been a physical test given to a steed, that if passed, would qualify it as being up to the acceptable standard of a healthy horse? 33K pounds lifted one foot in one minute seems a bit of a stretch for one horse, but on the other hand, there are an infinite number of ways to accomplish it.

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#3
In reply to #2

Re: Horses vs. Horsepower

07/23/2007 7:48 PM

Hendrick is correct as usual.

Also consider this:

"R. D. Stevenson and R. J. Wasserzug published an article in Nature 364, 195-195 (15 July 1993) calculating the upper limit to an animal's power output. The peak power over a few seconds has been measured to be as high as 14.9 hp. However, for longer periods an average horse produces less than one horsepower."

-John

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#4
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Re: Horses vs. Horsepower

07/23/2007 11:15 PM

Watt actually increased the value of the horsepower (effectively down-rating his engines) so that the public would not think he was exaggerating his product. Gotta love those marketing guys!

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#5

Re: Horses vs. Horsepower

07/23/2007 11:38 PM

I may be wrong but it has been my understanding that 1hp is the ability to lift 1000lbs at 1foot per second.

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#10
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Re: Horses vs. Horsepower

07/24/2007 3:47 AM

1 HP = 550 lbf-ft/sec

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#6

Re: Horses vs. Horsepower

07/23/2007 11:58 PM

Wikipedia says:

"Watt was working with ponies lifting coal at a coal mine, and he wanted to define the power available from one of these animals. He found that, on average, a mine pony could do 22,000 foot-pounds (lift a bucket of coal weighing 22,000 lb. a distance of 1-foot) of work in a minute. He then increased that number by 50 percent and fixed the measurement of horsepower at 33,000-foot-pounds of work in one minute.

Under this system, one horsepower is defined as:

1 hp = 33,000 ft·pound-force·min−1 = exactly 745.69987158227022 W"

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#9

Re: Horses vs. Horsepower

07/24/2007 2:35 AM

I don't think Watt actually determined the power of the ponies, it may have been an educated guess.

I were not present in 1887 but I don't think they could have used a single pony for lifting 10000 kg. (22000 lb). (They would have wasted a number of ponies a day or maybe that was part of the recycling for food policy)

Their watches may have been accurate enough but I don't recall seeing a seconds arm on the watches at a museum at the Kimberley diamond mine of that era. They however had a digital watch (mechanical disks with numbers).

I think Watt knew that his estimate was bad and he corrected for that by increasing the figure by 50%. The decision may have been glamorized later.

The 1933 source I used (About the same as Wikipedia) may however not be that reliable (they are wrong in other instances).

From a film I saw I believe the Americans compared the strength of working horses by letting them pull weights . Other definitions may have started there.

Does anybody have some other documented definitions?

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#12
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Re: Horses vs. Horsepower

07/24/2007 11:32 AM

I think it was a typing error, because the date shuold be 1787, ´cause by 1887 Watt was already dead. Fortunately, someone else has put the conversion factor between HP and watts, that is, 1 HP is more or less 746 Watt. You know, the watt unit, and its multiples, like KW and MW are broadly used in electric energy generation and distribution, while HP is a mechanical wok of unit, mostly used in motors. There is, still, another unit known as CV (for cheval de vapeur), used mainly in the Continental Europe, which is a little bit less, i.e. 1 CV=736 watts

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#13
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Re: Horses vs. Horsepower

07/24/2007 2:19 PM

So your saying Watt used a Fudge Factor!?!?!?

Inconceivable!!!!

What kind of engineer uses a fudge factor? Its not possible...

Tell me its not true!!!

help me mommy..........

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#14
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Re: Horses vs. Horsepower

07/24/2007 3:57 PM

Thanks is must be 1787 my dating of the watch is then also wrong.

Watt increased the value by 50% for some reason.

1 Brilliant salesman.

2 Bad tester

3 to convert from a pony to a horse.

4 For no reason at all.

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#11

Re: Horses vs. Horsepower

07/24/2007 10:08 AM

50 odd years ago my high school physics teacher had us conduct an experiment to find how much horsepower a person could exert. A student ran up a flight of stairs while we timed him. Using his body weight, the time, and the height gained we calculated his strength at a little less than 1/4 horsepower.

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#15
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Re: Horses vs. Horsepower

07/24/2007 5:53 PM

That was before steroids. I'll bet today he could probably top 10 hp.

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#16

Re: Horses vs. Horsepower

07/24/2007 6:06 PM

Hi OofBE,

If I recall correctly, Watt did a measurement using 100 lb being moved fairly rapidly by ponies. For some unknown reason, he multiplied that result by 1.5 to get our present-day definition. My belief is that a hp is about what you get from a horse or mule but it varies greatly by breed and conditions, perhaps from 0.5 up to 1.5.

Iowa State University did studies back in the 1920s to see what horses could actually do. For brief periods (maybe 10 seconds or so) a big Belgian, e.g., can do over 10 hp. But they found the need to specify loads like plowing, pulling a wagon etc. in order to make any useful comparisons. And that's not so different from how some folks rate tractors today, i.e., drawbar hp.

I think its just one of those arcane measurement things that could never actually be used in everyday life. Sort of like the acre being the area a team of Oxen could plow in a day. But none of the surveyors I know ever use that method now.

I know of at least one instance where Shires were replaced with mules for pulling because mules had more power than Shires (at least in the old days before modern breeding and vet care). The problem turned out to be that mules won't work a 15 hour day unless you beat them and then they remember and later, when you drop your guard, bite or kick you. So horsepower and ability to do work can be very different for living critters.

I do digress.

Tom

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#17

Re: Horses vs. Horsepower

07/24/2007 6:38 PM

It's funny nobody noticed the dates being quoted for Watt's work, till well into the thread. We are supposed to know that kind of stuff at the drop of an apple! Sadly I missed it too.

Speaking of mules ... I wonder how close we came to boasting about the massive Mule Power (MP) in our '72 Chargers or '67 Mustangs.

It's also good Newton wasn't sitting under a coconut tree.

Remember ... if you ever go back in time to prehistory as a tourist ... don't step off the path ... you might crush a butterfly in the mud.

Wow .. did I get off track or what?

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#18
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Re: Horses vs. Horsepower

07/24/2007 8:43 PM

"Speaking of mules..."

In its common modern meaning, a mule is the offspring of a male donkey and a female horse, which is classified as a kind of F1 hybrid. The reverse, the offspring of a male horse and a female donkey, is called a hinny

And I always thought F1 meant Formula 1!

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#19
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Re: Horses vs. Horsepower

07/25/2007 9:30 AM

Either way the offspring is sterile.

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#20
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Re: Horses vs. Horsepower

07/25/2007 12:13 PM

Hi double j b,

Apparently not all female mules are sterile, but I believe the few that have reproduced have always been covered by a horse. And, the offspring are also horses. They do have maternal instincts; we had one which "adopted" a calf and refused to allow my father to get near it, actually kicking him through a fence when he tried.

Tom

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#21
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Re: Horses vs. Horsepower

07/25/2007 12:21 PM

I did not know that. I had always been told that they always came up sterile.

I stand corrected therefore I will now sit.

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#22
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Re: Horses vs. Horsepower

07/25/2007 4:59 PM

Hi double j b,

The sterility is attributed to the differing number of chromosomes of the two species: donkeys have 62 chromosomes, whereas horses have 64. Their offspring thus have 63 chromosomes which cannot evenly divide.

Several female mules have produced offspring when mated with a purebred horse or ass. Since 1527 there have been more than 60 documented cases of foals born to female mules around the world. Mules and hinnies have 63 chromosomes that are a mixture of one from each parent. The different structure and number usually prevents the chromosomes from pairing up properly and creating successful embryos (Wiki).

Cheers,

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#23
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Re: Horses vs. Horsepower

08/25/2007 6:05 PM

If anyone is still logged in here..

I attended a draft horse pulling contest today. They used a specially made competition sled (don't quite know how it works and couldn't get down to see it) that applied a constant load. The horses were supposed to pull for a distance of 27.5 feet (don't know why that number). I timed the teams as best I could. The winner was a team of Percherons from western Maryland. The team weighed 3620 pounds. They pulled 3600 pounds a distance of 27.5 feet in approximately 6 seconds. Thus, the combined horsepower of the two horses was 30hp!

The next best team was a set of Belgians (about 2900 pounds) from SW Pennsylvania that pulled 3600 pounds 27.5 feet in 7 seconds.

It should be noted that, at 3800 pounds, none of the teams could pull nearly the whole distance. At about 10 seconds of pulling the teams simply quit.

These are specially trained team that literally "explode" at the start and dig into the dirt on specially shaped horseshoes that have two large cleats. I don't think anyone could ever use one of these teams for anything else.

At much lesser loads (like 3000 pounds) their speed was not much greater; so, their power was less.

A number of Amish farmers showed up to help handle the horses but none had horses entered. That might have been because of religious scruples against a contest for money or possibly because their work animals are not at all suitable for this kind of pulling.

Tom

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#24

Re: Horses vs. Horsepower

03/02/2008 5:06 PM

The trouble with the horsepower/horse comparison is time. If I asked whether you can pick up a pint of beer without a problem, you would probably feel insulted and spend the evening proving you could. But if you had to pick up a pint every three seconds for 8 hours, you might see it rather differently.

My 1/5th horsepower vehicle can do 20 maybe 25mph on level ground, will accelerate 200+ lbs of me up a 30 degree slope, pulls a spring tine harrow through grass for 20 minutes which has me groaning after 10 seconds. But a horse, or in my case small pony, is only suited to certain jobs, but those he can do brilliantly. Basically they make a superb organic ATV.

You don't judge Formula 1 Ferrari horsepower for its load hauling capacity on motorways. A horse, given the right job can deliver a lot more than one horsepower, but over 8 hours, one horsepower is probably about right.

Simon

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Abdel Halim Galala (1); Anonymous Poster (2); DavidaRheault (1); double_j_b (3); garyceng (2); Hendrik (3); Johnjohn (4); mareng (1); Out of Box Experience (1); saddlechariot (1); Stirling Stan (1); Trickey Engineer (1); TVP45 (3)

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