Quoting power in hp, not kw

[Sonic]

Continuing on from Waz's idea, what about

Wheel size (some Euros used metric wheel sizes but they were scrapped in the late 1980s) when tyre size is metric? and what about Subwoofer/Speaker sizes?

[Lozza150]

cool, i have two 25.5 cm Sub's in my Commodore with

two 15 x 23 (cm) 's in the parcal shelf.....

Fullllllllyyyy SikKKKKKKKK

[Duncan]

yep, and I've got the stock 6.34cm exhaust and 43.18cm wheels for the track and 45.72 for the street

OK, it does sound a bit wierd....

[WazR32GTSt]

yeah but if we were going properly down the metric path then by now items that we use would be in round figure centimetre values rather than just the inch value converted to centimetres...

it annoys me really. why can't we just be individual???

[Warpspeed]

A lot of things still originate from America, like text books, software, dynos, turbos, and so on.

So you buy a book like Corky Bells Maximum Boost, he is certainly not anti turbo ! But his book has inches, horsepower, and temperatures in degrees Fahrenheit.

Just about all of the engine dyno simulation packages come from America as well, you can specify things in millimeters, but the readout is always in horsepower and foot pounds.

Garrett turbos are imperial as well.

Try and buy metric tyres to fit metric diameter wheel rims though ..........

You find something like 255/60/15, where the 255 is tyre section in millimeters, 60 % profile, but the 15 IS IN INCHES. So you get a bastard mix of metric and imperial measurements on the same item. And this is now the world wide standard as well !

[Roy]

So Duncan what does your car do over the 0-400m?

[pentae]

When I was holidaying in America a dude asked me after talking about how shit the imperial system was, "So in Australia, do you guys have like.. 24 hour time?"

:bahaha:

[Duncan]

Originally posted by pentae

When I was holidaying in America a dude asked me after talking about how shit the imperial system was, "So in Australia, do you guys have like.. 24 hour time?"

:bahaha:

Just as good, I was doing a training course for time capture system and the US instructor asked if we have leap years down here....."hell no, the bottom half of the earth goes around the sun faster :D"

And good q re 400m, is eastern creek 1.4 mile (402.325m) or 400m?

[two40]

when i owned the skyline everything, to me, was in kw

now that i own the datto, everything is in hp. i've always associated turbos with kw and cubes with hp for some reason.

oh, and the yanks love their turbos. don't let anyone fool you. they are into everything and anything over there. car scene is fantastic.

[Duncan]

of course, the datto only has hp, kw weren't invented back then

[two40]

[eddy murphy laugh] :bahaha: [/eddy murphy laugh]

[Ronin 09]

my question is this - who the hell invented the imperial system of weights and measures anyway??? who thought 12inches to a foot would be easier to count than something in base 10?!?

And dont get me started on pounds and ounces...

[Warpspeed]

Actually horsepower is the rate at which MECHANICAL work is done.

Kilowatts are the rate at which ELECTRICAL work is done.

It has nothing to do with metric or imperial measurement.]

Who ever heard of a one horsepower light bulb, or a one kilowatt petrol engine, it is just plain silly.

[Ronin 09]

Originally posted by Warpspeed

Actually horsepower is the rate at which MECHANICAL work is done.  

Kilowatts are the rate at which ELECTRICAL work is done.

It has nothing to do with metric or imperial measurement.]

Who ever heard of a one horsepower light bulb, or a one kilowatt petrol engine, it is just plain silly.

Umm BUZZ - WRONG...

A watt is a measure of energy per second - one watt is equal to one joule per second of energy. It can be applied to any form of energy use, production or transmittal.

[Warpspeed]

Ronin, if you want to be pedantic...........

One watt is equal to one volt multiplied by one amp, that is a measurement of electrical power.

And a joule is one watt per second, which is a measurement of energy flow. With total energy, the time element comes into it as well. By the way, there is no such thing as a joule per second.

Now please explain how volts and amps are relevant to measuring mechanical power ?

While it is true that heat energy, mechanical energy, and electrical energy have equivalents, and the study of thermodynamics is based on this fact, it is usual to measure in units most suited to the task.

Light bulbs are usually rated by wattage. A really large bulb in killowattage. In the film and television industry we commonly used individual bulbs rated at up to five kilowatts each.

Please explain how the output of a rotating machine can be converted to volts and amps, with a resultant power in watts (or kilowatts). Please tell me, I would dearly love to know.

I would also be really interested in how many foot pounds of torque, and at what RPM my Eveready lantern puts out ?

I still say it is a silly concept.

[Ronin 09]

Definition of a watt:

"A unit of power or activity equal to 107 C.G.S. units of power, or the work done at the rate of one joule a second. An English horse power is approximately equal to 746 watts"

[Warpspeed]

One electrical watt is generated or dissipated when one amp of current flows with a potential difference of one volt in a resistive load.

A watt is true electrical power, it cannot be anything else. As you say it may be equivalent to other types of power such as heat energy or mechanical energy. There is also reactive power measured in volt amps (VA), but that is another story.

But a watt is not mechanical power, or heat energy. After thirty five years of using these units every day as an electronic design engineer, I can assure you that this is correct.

Another example of this, if you look at your gas bill, (in Australia anyhow) you have been charged for the number of megajoules of energy you have used. Your gas meter measures cubic metres of gas, and you are charged for the energy content.

Megajoules of energy are millions of watts per second. Take it from me, watts of electrical energy do not come out of your gas pipe. Likewise your engine dynamometer might calculate kilowatts of energy equivalent. But volts and amps do not flow out of your flywheel.

Also, a Joule is one watt second. RPM is revolutions per minute, and KMH is kilometers per hour.

You cannot have RPM per minute, or KMH per hour. Likewise joules per second do not exist. (That would be watt seconds per second).

The point I am making is that it is a common conversion to multiply Kw by 1.34 to convert to horsepower.

So ten one hundred watt light bulbs equals 1Kw, and this is equal to 1.34 horsepower. But calling a 100 watt light bulb a 0.134 horsepower light bulb is silly, because there is no mechanical power involved at all.

Equally silly is saying that a rotating engine driving a rotating mechanical load is developing so many kilowatts of (electrical) power, when it may not be doing anything of the sort.

If my electric jug is rated at 2.4Kw and requires 240 volts at ten amps, can I test it on your dyno ?

Hey Ronin, don't take it all so seriously, I am only stirring the pot.

Cheers.

[Ronin 09]

Originally posted by Warpspeed

Also, a Joule is one watt second.

So what you're saying is that (in units)

J = W.s

What happens when we divide both sides by the unit of time, in seconds?

J/s = W.s/s

J/s = W

Which looks alot to me like Watts = Joules per second...

This is a definition, pure and simple, and you agree.

Originally posted by Warpspeed

So ten one hundred watt light bulbs equals 1Kw, and this is equal to 1.34 horsepower. But calling a 100 watt light bulb a 0.134 horsepower light bulb is silly, because there is no mechanical power involved at all.

I agree that it is silly to quote a light globe in terms of hp, but the fact is that joules are a measure of energy, be them electrical, mechanical, magnetic or any other form. While it is 'silly' it is not a wrong unit to rate the light bulb in hp.

Originally posted by Warpspeed

If my electric jug is rated at 2.4Kw and requires 240 volts at ten amps, can I test it on your dyno?

Again, technically the kettle produces 2.4kW of energy which is 2400W or 2400 joules of energy a second. Again, an understanding of joules will tell you that this is the energy, which is pure and simple not related to turning, rotating, mechanical work, farting, or any other things that you assume must be electrical or mechanically related. It is a measure of energy pure and simple.

Originally posted by Warpspeed

Hey Ronin, don't take it all so seriously, I am only stirring the pot.

Yeah i know but mechanical engineer/law types like to argue.

[Warpspeed]

He he Ronin, I like you style.............

Yes if you want to call joules per second watts that is strictly true if you are a lawyer minded type of person, but as a working engineer I have never seen it used that way before.

Its a bit like asking how far it is to get to some place, and being told 30KMH per hour is the distance, when what you really mean it is 30 Km away. You can prove this is correct with a bit of algebra, as you have done, but people might still think you have a screw loose somewhere.

Why not just call watts watts, and kilometers kilometers. In either case time does not really come into it.

And I also agree with you that quoting energy units in non relevant terms is not strictly wrong, but just a bit weird.

I have no idea how mechanical power ever ended up being defined in electrical units though ? ? ? I wonder if it was some dork government bureaucrat somewhere, I just cannot imagine an engineer doing that.

Horsepower is a far more direct and useful unit if you are dealing with shafts, gears, pulleys, weights, and other mechanical engineering problems. Just as amps, volts, watts and ohms are all tied together very elegantly for solving electrical problems.

Next time someone asks me about engine power, I might express a number in calories, that should confuse plenty of people eh !

[Steve]

Originally posted by Warpspeed

I have no idea how mechanical power ever ended up being defined in electrical units though ? ? ?  

Easy, by mulitplying by 0.734(approx)

If you really wanted to freak people out you could start expessing calorific value in hp! That would keep them guessing:) or they would call the guys in the white coats.