Ah, the power of . . . horse?

[Psi Baba]

Why do we still use "horsepower" as a unit of measurement for power? How many people can mentally conceive of how much power "x horsepower" really is? What does it convert to? If a motor is rated at one horsepower, what does that tell me? How likely is it that I would know what one horse is capable of achieving? It would make more sense to me if H.P. stood for Hewlett-Packard. Thus: "This engine can produce the same amount of work as 250 Hewlett-Packard printers." Now that's something I can relate to. Isn't it time to update this unit of measurment?

[ceptimus]

The unit's not used so much anymore. Most engineers, (except maybe in backwards America) use kilowatts these days.

Actually a horse cannot continuously produce one horse power. The early steam engine manufacturers deliberately inflated the measured performance of horses, as they did not want to make extravagant claims about their engines. Can you imagine manufacturers today being as honest?

1 horsepower = 745.699872 Watts (According to google, so it must be right).

[uneasy]

This is very amusing. While you were posting this, I was posting something that mentioned my 6.5 horsepower lawnmower. I thought about finding the watts for my overseas friends, but didn't bother. I use it, but I find it embarrassing, like all non-metric units.

On a purely non-scientific basis, though, I've been ingrained to think of watts as units of consumption for light bulbs and such. I admit I find it hard to think of an roaring engine as producing watts. Makes no sense, but it's a language thing I think.

[Rocky]

It is used a lot like scientific notation. My racing motor puts out 154359.9 watts. I guess I could say it makes almost 155KW but 207 Hp sounds cooler. If you go for the big motors; how impressive is 745KW from 2000cc?



1000Hp is much cooler. :cool:

[ceptimus]

Originally posted by Rocky
1000Hp is much cooler. :cool: Pah! If you want real power from a piston engine, take a look at this (http://www.bath.ac.uk/~ccsshb/12cyl/).

[roger]

It never occured to me that HP was restricted to America. So car engine specs in the rest of the world are given in kilowatts?

[roger]

Originally posted by roger
It never occured to me that HP was restricted to America. So car engine specs in the rest of the world are given in kilowatts?
Wow! That's a big freakin engine! Over 100,000hp.

Now, since this is intended for container ships, is the hp rating based on how much power a horse can exert while swimming?

[ceptimus]

Originally posted by roger
It never occured to me that HP was restricted to America. So car engine specs in the rest of the world are given in kilowatts? It's gradually becoming more common in the UK. A few years ago, car engines were quoted in BHP, but there were different flavours depending on how it was measured, and the Japanese used a unit called 'PS' that was close to a horespower, but not quite the same. Now the trend is to quote in KW. My small french car makes a measly 59 kilowatts, but my motorbike makes over twice as much. :)

[Rolfe]

The good old US is also the only place left, just about, that knows so little of moles or Avogadro that it still reports clinical chemistry data in mg/100ml. You tell anyone anywhere else that your blood glucose is 80, and they'll drag you in for treatment for a diabetic coma. And those silly cholesterol numbers! It's incredibly backward, but there you go.

Wasn't there some space probe that crashed straight into Mars or somewhere because the US engineers were working in bongo-bongo units while the rest of the team in civilised countries were standardised on SI?

Come on guys, it's a bit late for a new millennium resolution, but go for it anyway!

Rolfe.
(who really means that sig. line this post!)

[Rocky]

Originally posted by ceptimus
Pah! If you want real power from a piston engine, take a look at this (http://www.bath.ac.uk/~ccsshb/12cyl/).

108920hp / 25480L = 4.27hp/L ..... Thats awful. I've seen more than 500Hp/L .

Still, 109KHP is good. "Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine " I want to see the Turbo! :D

[jj]

A horsepower is just one of those joules of American units these days (can't even say English Units any more, can I?). Well, that's going to be watt ever it will be.

Ever since somebody in RayGun's government called the metric system a commie plot and had the "we will metrify" law nullified, we've been on a headlong course into unit-based obsolescence.

Don't ask me why, I loathe the English system.

For extra credit, what's 1/2688th of a mile per hour?

[Rocky]

Originally posted by jj
A horsepower is just one of those joules of American units

For extra credit, what's 1/2688th of a mile per hour?

Other than HP I prefer metric.

And everyone knows that a 1/2688Mph = 1 furlong/fortnight.

[hammegk]

Originally posted by roger

Wow! That's a big freakin engine! Over 100,000hp.



Er, a big freakin engine is a RollsRoyce gas turbine @ 250,000 hp =+- 200,000 kwatts[edit: KW, not W]. Guess they don't like gas turbines in ships?

Unless I screwed the math:

the big diesel is getting 4 hp/liter displacement;

pah!

A stinking Ford Cobra makes 70 hp/l for 320 hp;
the new Mercedes 90 /l for 470 hp.

Nascar is getting 110 hp/l for 1100 hp, indy cars 270/l for 800 hp,

AA Fuelers 600 hp/l for 6000 hp (for about 5 seconds anyway).


A 747 uses 60,000 hp at cruise speed; the space shuttle main engine has 90,000 hp of fuel pumps, and Boeing's site says 12,000,000 hp in vacuum (10,000,000 at sea level).

[jj]

Originally posted by Rocky


Other than HP I prefer metric.

And everyone knows that a 1/2688Mph = 1 furlong/fortnight.

Rocky wins the prize. And it is:

CONGRATULATIONS!

:D :D :D :D

[_Q_]

Originally posted by ceptimus
It's gradually becoming more common in the UK. A few years ago, car engines were quoted in BHP, but there were different flavours depending on how it was measured, and the Japanese used a unit called 'PS' that was close to a horespower, but not quite the same. Now the trend is to quote in KW.
I think we get the "PS" from the Germans - "Pferdestaerke".

(Please don't beat me, Umlaut Police.)


_Q_

[xouper]

Rocky: 108920hp / 25480L = 4.27hp/L ..... Thats awful. I've seen more than 500Hp/L .Yeah, but was that 500hp/L at 102 RPM and a fuel consumption of only 0.260 lbs/hp/hour (50% thermal efficiency)? Remember these aren't optimized for racing boats where you can overhaul the engine every few hours.

[xouper]

Rolfe: ... the US engineers were working in bongo-bongo units while the rest of the team in civilised countries were standardised on SI?And let's not forget the "Gimli Glider", an Air Canada Boeing 767 which ran out of fuel halfway across Canada at 41,000 feet.

[BTox]

Originally posted by hammegk

A stinking Ford Cobra makes 70 hp/l for 320 hp;
the new Mercedes 90 /l for 470 hp.

Nascar is getting 110 hp/l for 1100 hp, indy cars 270/l for 800 hp,

AA Fuelers 600 hp/l for 6000 hp (for about 5 seconds anyway).


A 747 uses 60,000 hp at cruise speed; the space shuttle main engine has 90,000 hp of fuel pumps, and Boeing's site says 12,000,000 hp in vacuum (10,000,000 at sea level).

Subaru STi makes 120/L for 300, not bad for ~$30K.

[fishbob]

108920hp / 25480L = 4.27hp/L ..... Thats awful. I've seen more than 500Hp/L . Another big plus for using low Hp/L is that this engine will last forever. The higher the power/displacement, the faster the motor will wear out.

[Walter Wayne]

Originally posted by Rocky


108920hp / 25480L = 4.27hp/L ..... Thats awful. I've seen more than 500Hp/L .

Still, 109KHP is good. "Wartsila-Sulzer RTA96-C turbocharged two-stroke diesel engine " I want to see the Turbo! :D But did you look at the torque on that baby!

Walt

[ceo_esq]

Originally posted by roger
It never occured to me that HP was restricted to America. So car engine specs in the rest of the world are given in kilowatts? They seem to still use horsepower (chevaux) in France.

[roger]

Originally posted by hammegk
[B]

Er, a big freakin engine is a RollsRoyce gas turbine @ 250,000 hp = 200,000 watts. Guess they don't like gas turbines in ships?
All right, that's a big freakin reciprocating gas engine! :)

If we're allowed to change the type of engine, how about the Space Shuttle Main Engine (SSME) which outputs, oh, 37 million hp. :eek:

[Jon_in_london]

Originally posted by hammegk


Er, a big freakin engine is a RollsRoyce gas turbine @ 250,000 hp = 200,000 watts. Guess they don't like gas turbines in ships?


Actually they do....
I was quite suprised to see that they are still using piston engines in large ships these days.

They are used in many (all?) of our major warships:

http://www.hazegray.org/navhist/rn/destroyers/type42/

Type 42s use RR Tynes as cruise engines and RR Olympus as boost engines. The latter is also used in the Concorde...

[ceptimus]

There were some tankers and big freighter ships that used gas turbines. But they were not fuel efficient enough - many of the tankers have been retro fitted with dig diesels to make them more economical.

I guess the military don't have to bother, as the fuel is payed for out of our taxes...

[Crossbow]

Originally posted by Psi Baba
Why do we still use "horsepower" as a unit of measurement for power? How many people can mentally conceive of how much power "x horsepower" really is? What does it convert to? If a motor is rated at one horsepower, what does that tell me? How likely is it that I would know what one horse is capable of achieving? It would make more sense to me if H.P. stood for Hewlett-Packard. Thus: "This engine can produce the same amount of work as 250 Hewlett-Packard printers." Now that's something I can relate to. Isn't it time to update this unit of measurment?

A horsepower is a unit of work that was defined by one of the early steam engineers, James Watt. He was working with horses in coal mines in the 1700's and he determined the average amount of work that a pony could do, so he bumped the figure up by 50% to reckon the amount of work that the average horse should be able to.

One horsepower = 33,000 foot-pounds/minute

Due to the archaic nature of the unit, it is probably why most countries now base work on 'Watts' as opposed to 'Horsepower'.

Source: How Horsepower Works
http://auto.howstuffworks.com/horsepower.htm

[tracer]

Originally posted by Rolfe
The good old US is also the only place left, just about, that knows so little of moles or Avogadro that it still reports clinical chemistry data in mg/100ml.
Well, at least mg and ml are metric units.

Back in the Good Old Days, we measured your blood glucose level in stones per hogshead! And lemme tell you, getting a hogshead of blood out of a patient was a mighty daunting task!

[exarch]

Originally posted by roger
It never occured to me that HP was restricted to America. So car engine specs in the rest of the world are given in kilowatts?(Finally able to give the answer I've been itching to post all day but wasn't able to).

What makes you think the US is the only country using horsepower as a unit of measurement?

Citroën, a French automanufacturer, has a model of car that has been known as the "deux-cheveau" for ages (literally translated, two-horse).

We use it In Belgium too, HP I mean, except we use the Dutch abbreviation. Only the insurance companies use kilowatts to calculate your monthly payments.

[roger]

Originally posted by exarch
[BWhat makes you think the US is the only country using horsepower as a unit of measurement?[/B]
The second post in this thread.

[exarch]

Originally posted by roger
The second post in this thread.I think most non-engineers still use HP, it's been around a long time.

[davefoc]

I hadn't thought about getting rid of horsepower as a measurement of engine power before. I supose excessive American centricity was at work there.

One thing though, is that in America we tend to use hp for output power and watts for input power when talking about electric motors.

A strange trend is to measure motor power in amps (kind of). Exactly why or how this misleading idea got started I don't know but it seems to be fairly common. It seems strange to tout the idea that your product uses more current than your competitiors, but that's what manufacturers of electric motor powered devices do.

[Iamme]

Uneasy---Per your first post above. A 6.5 HP lawnmower, eh? Well, mine is 4.5 and cut through didly-squat without bogging down. 4.5.! Bah! If I had 4.5 horses attached to a sharp cutter blade, I would not only be able to cut the grass...but if I lowered the blade they could cut furrows for me! MY lawmower practically comes to a stop if I hit a dandelion!:D

And then there is torque. What a person REALLY wants for initial power is lots of torque. If you have a vehicle with lots of torque,k you could, from a dead stop do jack rabbit starts while pulling a heavy load.

[NWilner]

Well, sure, but you can multiply torque all you want at the expense of rpm. Power can't be multiplied (but it can be subtracted from).

[Psi Baba]

Originally posted by Iamme
If I had 4.5 horses attached to a sharp cutter blade, I would not only be able to cut the grass...but if I lowered the blade they could cut furrows for me! MY lawmower practically comes to a stop if I hit a dandelion!:D

But surely you'd lose efficiency by having the 4 horses dragging that half a horse around!

[exarch]

Originally posted by Psi Baba
But surely you'd lose efficiency by having the 4 horses dragging that half a horse around!Not to mention over 16 hooves churning up your yard ...