ICrashThings

well how? Id like to know.[sm=surprised.gif]

pocketrocketsAA

http://auto.howstuffworks.com/horsepower1.htm

I'm guessing they use some kind of mini-dyno similar to what is used on full scale cars to determine the horsepower of R/C engines.

ICrashThings

i ment HP = an actual horse? or what is it comparable to?

tjaf

1 hp (English horse power) = 745.7 W = 550 ft lb/s = 2545 Btu/h = 33.000 ft lb/m = 1.0139 metric horse power
1 metric horse power = 736 W = 75 kg m/s = 0.986 English horse power

To be able to visualise. Power is actually the (force x distance)/time. So, presumably one horse could put out a force of 736N (comparable to lifting 75Kg) and drag it 1m along in 1 second.

capita_88

Leave it to the pros.

hondapride59

My Feedback: (2)

yea...well basically some guy back in the day took an ordinary sized horse and hooked it up to a pulley and made it lift a wieght or somehting and thats how it all started...maybe i shoudl have payed more attention in science class last year

Frost_

My Feedback: (1)

To add a bit to this for topic relevancy, the dyno ONLY measures torque, not HP. It may DISPLAY HP but it does not measure it, it calculates it. Here is the equation used by the dyno for HP results:

HP = (torque * RPM) / 5252

If any of you would be interested in seeing how we get from what tjaf posted to the above equation, the background on the 5252 constant can be found here, as well as more information:
http://www.revsearch.com/dynamometer...orsepower.html

Jonnyd

[/quote]

To add a bit to this for topic relevancy, the dyno ONLY measures torque, not HP. It may DISPLAY HP but it does not measure it, it calculates it. Here is the equation used by the dyno for HP results:

HP = (torque * RPM) / 5252

If any of you would be interested in seeing how we get from what tjaf posted to the above equation, the background on the 5252 constant can be found here, as well as more information:
http://www.revsearch.com/dynamometer...orsepower.html
[/quote]




Well this means it is measuring the HP then doesnt it?! Um what measure of torque are you using for that rule? Nm's?

tjaf

If you take a look at the link, I see a lot of ft, lbs, pounds, minutes, ... So I am guessing that formula is not really using the international system of units (SI-units)

Frost_

My Feedback: (1)

No, it measures torque and in combination with RPM it calculates HP. End of story. The figure is in ft/lbs, if you want in/oz., you obviously need to convert units.

The US is stubborn as hell, people act like the metric system is hard..... the "standard" system has no standards at all....

tjaf

Well, this is actually a weird conversation, because how does one define "measure"? You see, the dyno won't measure torque either. It will probably measure some sort of force, and to be able to measure that force, it would actually measure a displacement (I assume) and "calculate" torque out of that reading

P.S. Metric all the way! And what do you mean with the "standard" system has no standards at all.... ?

potatoe_bird

My Feedback: (1)

Standard blows. Everybody over here acts like metric is so hard. I just think they are lazy.

Bush Wacker

I R AMERICAN, I LIKE STANDARD. But metric you can messure smaller stuff easier.

potatoe_bird

My Feedback: (1)

But metric is so easy. All you do is add 0's.

Bush Wacker

how do you messure engine displacement? Cubic Liters?

Frost_

My Feedback: (1)

The dyno measures torque against eddy currents or a generator, depending on setup.

No standards, 1yd=3ft=36in, then go to another unit of measure.... say, temperature ...etc. example: care to tell me the cubic inches in a gallon? or a quart?? The prefix-based metric system is superior and would make short work of that question.



Bushwacker: No need for the cubic (in inches, inches are distance (2 dimensions) so to define another (or more) plus dimensions the number is ^3 (cubed)) part when talking metric. It is just liters, liters are volume. Inches are the b*stards that need additional description to gain usefulness in this application.

Schizer! I hafta go back ta work....

Bush Wacker

*** did you just say?!?! To many metric units cm, mm, liter, gram, m, kl, km, pickle........

tjaf

Frost, you seem to know your stuff I'm european, so off course I am all metric and don't understand how anyone with a sane mind could possibly want anything else indeed

Bush wacker: Liter is a measure to express a volume. A volume is a cubic distance (length*depth*height), so cubic metres or cubic inches or an other method to express volume. As frost said, no need for cubic litres.

Well, just look at where this thread is going. Too funny.

Bush Wacker

I know what the stuff is, I just grew up knowing standard/traditional.

mxwrench

to see how HP in a small nitro engine is measured check out the cool video "got horsepower?" at

http://www.rc411.com

Very cool!!!

That thing is screamin' !!!

BK

zarc

There are several ways of getting the HP. The famous way is the inertia dyno.

In the motorcycle and car world its a chassis dynamometer. I know a freind of my friend who is in bussiness with these type of dyanmmometers.

Visit http://www.angelfire.com/linux/dyno46

Basically you have a known mass with known ratational inertia. then you need to get the

angular acceleration
angular velocity

then you would get the

Torque = angular acceleratiuon * inertia
Power = angular velocity * torque.

Easy as that!

Tucker01

To answer the original question, HP isn't measured, it's calculated. It' s a theoretical measurement using maths phyiscs and chemistry, using known factors such as coefficients of friction, calorific value of fuel etc.

BHP is measured on a dynomometer, and as has been said is a product of torque and speed.