Cambo

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Hi everyone

For the longest time I thaught that "1 horspower" was exactly what they said, the power of 1 horse. But now i am not so sure. Just recently i saw something on the Discovery Channel that the human body can reach 4 horsepower. What? I am in no way near the power of one horse and now that i think of it I don't think my st40 has the power of a real horse either.

Any thaughts?

Charley

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1 Horsepower = The force required to raise 33,000 pounds at the rate of one foot per minute.

CR

daveopam

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Are you sure about the 33,000 lbs? I though it was much lower.

David

NikolayTT

something more easy to measure:
1bhp = 750 Watts is something agreed long time ago,
maybe that time the horses were smaller

Charley

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Yup, I looked it up.

Hay mod, what's up with you?

CR

NikolayTT

Oh yes, something also easy to measure: - if you have at home or at the gym-hall
an Ergometter (home-bike which never moves) then if you set effort of 250 Watts
i.e. 1/3 of a Horse Power, then you can see how much your force is worth of.
Would be nice to have chance to try such ergometer with 750 Watts but I
have not seen them in a regular gym; maybe for Macho-Gyms there have
somehing like that.

Charley

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AIR, its 746 Watts. I often wondered how James Watt tested this between his engine and his horse(s). []

CR

NikolayTT

I think Mr. Watt might have been involved in a "Political" Debate with Sales & Marketing Dpt of How Many horses one
should sale in otder to get his Machine and there comes to coefficient from; otherwise measuring it on a real horse
might prove to be a hazard - how about if the Horse likes to kick-back [sm=spinnyeyes.gif][sm=spinnyeyes.gif][sm=spinnyeyes.gif]

Heliko

I took this exert from [link=http://en.wikipedia.org/wiki/Horsepower]Wikipedia[/link]:


Mechanical horsepower

The term "horsepower" was coined by the engineer James Watt (1736 to 1819) in 1782 while working on improving the performance of steam engines. This occurred while using a mine pony to lift coal out of a coal mine. He conceived the idea of defining the power exerted by these animals to accomplish this work. He found that, on the average, a mine horse could pull (lift by means of a pulley) 22,000 foot-pounds per minute. Rather than call this "pony" power, he increased these test results by 50 percent, and called it horsepower i.e. 33,000 foot-pounds of work per minute.

Under this system, then, one horsepower is defined as:

1 hp = 33,000 ft-lbs/min (550 ft-lbs/sec) (745.69987158227022 watts)

Hughes500E

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I don't think my engines can lift 60 to 90 000 pounds [:-]

daven

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Nelson .40 LS Q40 motor at roughly 17 oz, turning a 7.5 pitch prop at over 25,000 rpm.

Can you say 3 hp

Priceless!

jaka

Hi!
1 horse power= lifting 75kg , 1m, in one second.

Try it...
Don't think anyone will make it...

Red B.

Your definition is for the metric horsepower = 735.5 W (approx)
The traditional mechanical horsepower is 33,000 ft-lbf/min = 745.7 W (approx.)
For electrical motors the electrical horsepower = 746 W (exactly).

It is probably a modern myth that Watt himself performed experiments to determine the power output of mining ponies. Instead he probably sought the advice of experienced millwrights, men whose profession was designing and building factories. Among Watt's surviving papers are his “Blotting and Calculation Book 1782 & 1783.� In an entry made in August 1782 one can read “Mr. Wriggley, millwright, says a mill-horse walks in 24 feet diar and makes 2½ turns per minute....say at the rate of 180lb p. horse.� This is equal to 32,400 ft-lbf/min, but in the 1783 Watt himself has rounded this figure to 33,000 ft-lbf/min, probably to simplify calculations.

longdan

Some may be interested to know that a manual labourer (person) is continuously rated at 1/8 HP. This used to be a measure used in comparing machines to people, and weather it was economic to replace a person with a machne. In these politically correct times, rating people by their work output probably isn't the done thing.

donkey doctor

Hello; Perhaps a more useable measurement might be the amount of thrust an engine can maintain. I noticed that some electric brushless engines are being advertised with a thrust rating in lbs. or in kilograms. That is a more useable measurement for me as I know how heavy my planes are. I have a hard time linking "horsepower" to our model airplane engines. The mental image just isn't there.

I liked that wikipedia James Watt story; They had to have something to compare it to, just like we do. We don't have horses any more, but we still ahve thrust.

Cambo

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Donkey, i also use thrust over hp. It is just a more usable measurment.

Cyclic Hardover

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So is a Clydesdale run about 2 horsepower due to is casing size?

seanychen

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I think 1 pony can lift 50 kg 1 meter high in 1 second.

I can probably make it with leg press. Does that make me a pony?

rainedave

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Not to get too OT, but the discussion of thrust reminded me to ask if there is a good freeware XLS reader out there so I can use Pe's thrust spreadsheet calculator.

Thanks,
David

Edited to add: Never mind. I remembered OPenOffice.

DarZeelon

Dave,


You can try [link=http://www.openoffice.org/]OpenOffice[/link].

It costs you nothing flat.

When you open this MS-Excel file with it, it will be in 'read-only' form.
After saving it as an OpenOffice spreadsheet (.ods), you can edit it and make all your calculation.

speedster 1919

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Keep in mind this was thru leverage and pulleys and a horse has to rest. Our engines have a false HP behind them with hardly any torque . Take your 3 HP engine and put prop into the ground and engine will usally die instantly. Now take a 3 HP electric motor and do the same with an 11" prop and if the prop doesn't break (MAS) it will dig a hole and keep going.

DarZeelon

HP and torque are interdependent.

If torque is expressed in lbs. ft., <torque> X RPM / 5.252.1 = <HP>.

At 5,252.1 RPM, HP and torque have the same numerical value.


Torque is a mere force that does not express the ability to actually move something.

Any number of horsepower can produce any torque... All you need is the correct gearing, or prop-pitch.


In fact, a 3 mm O/d electric DC motor, like the type spinning the tail rotor of those 10 gram electric helicopters, geared at 70,000,000:1, will lift an M1A1 Abrams tank...

It will not do it fast, but it will do it... It will lift it to 4" within a few days...


So, torque is nothing and HorsePower/kilowatt is king.

speedster 1919

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Dar as you know I don't own a slide rule But without some torque the HP and RPM will dwindle down fast. Case in point --in the 70's I owned a Yamaha RD 350 six speed 2 cycle. At half speed crusing and open the throttle all the way in 6th gear it would do 88 MPH max. Now from a standing start and keeping the RPM up using all 6 speeds it would get up to 135 MPH and with throtle still full open it would slow down to 88 MPH. We have modernized our HP ratings in the engine and motors to look better than were originally intended. The old antique tractors here in the US had ridiculus low HP reading like 12 HP at draw bar with huge heavy cast iron motors that peaked out at 1,200 RPM. And yet we have 12 HP RC engines that can be held in the palm of your hands. You can't tell me if I put those RC engines in the old tractors I could go and plow a field all day.[:-]

DarZeelon

Randy,


So, I guess this Yamaha reaches its maximum speed, while traveling in fifth gear.

Changing up to sixth puts the engine below its 'sweet spot'; into a 'torque pit', where the tuned pipe robs the ...

The torque the engine needs to produce, to maintain 135 mph (overcoming air resistance) in a certain gear is 2.35 times as large as the torque the engine needs to produce, to maintain 135 mph in the same gear. If at the RPM that corresponds to 135 it is making only 2.3 times as much as at 88 mph, it will begin to lose speed....


Are you trying to say this 'torque pit' isn't a 'HP pit' as well?
I am sure you are not.

This Yamaha apparently has a pipe with a very narrow effective RPM range.

BTW, the Corvette in standard shift with a 6 speed gearbox also reaches maximum speed in fifth and slows considerably after switching to 6th gear.


If you take a Nelson/Jett/ Profi F1 engine and use it to replace the Briggs & Stratton engine on your lawn mower, it will mow the lawn and will do it no more slowly than did the original engine.
They both have the same output, so there is no difference in work capacity. It will not last as long, however.

The larger gas engines that power 1/3 scale models, while spinning around 6,000 RPM, should be geared 5:1 to do the same work as do those farm tractor engines.
But you would need to add ballast... These tractors need their own weight to pull their tools.


Since HP is expressed in units of force, distance and time, torque at speed (distance/time) is HP.

Jezmo

That's good. I laughed until I had tears. 4" within a few days... Thanks, you brightened my day Dar.