Who knows what BHP and lbs/ft are?
Discussion
1) Work
Is the ‘physical effort’ required to do some thing, such as pulling a Bucket of Water out of a Well. Its measure or ‘Unit’ is ‘foot-pounds’ or ‘kg-meters’. As an example, consider pulling a bucketful of water weighing 15 Kgs from a depth of, say, 10 Meters. So the ‘work’ done is 15 x 10 = 150 ‘kg-meters’.
2) Power
It’s the ‘Rate’ of doing ‘Work’, such as pulling 10 buckets as above in one hour or a part of it.
The most popular unit of Power is the ‘Horse Power’, which from ancient times was the rate of work an ‘average horse’ could do. In scientific parlance today, it translates into 4,500 kg-m/min or 33,000 ft-pounds/min. In Metric System of Measurement, therefore, one ‘horsepower’ = 746 Watts.
In post-war Germany, ‘PS’ was and is still used – which was/is a functional equivalent of the ‘British’ Horse Power. In reality, it equates as 1.0 HP = 1.07 PS.
Is the ‘physical effort’ required to do some thing, such as pulling a Bucket of Water out of a Well. Its measure or ‘Unit’ is ‘foot-pounds’ or ‘kg-meters’. As an example, consider pulling a bucketful of water weighing 15 Kgs from a depth of, say, 10 Meters. So the ‘work’ done is 15 x 10 = 150 ‘kg-meters’.
2) Power
It’s the ‘Rate’ of doing ‘Work’, such as pulling 10 buckets as above in one hour or a part of it.
The most popular unit of Power is the ‘Horse Power’, which from ancient times was the rate of work an ‘average horse’ could do. In scientific parlance today, it translates into 4,500 kg-m/min or 33,000 ft-pounds/min. In Metric System of Measurement, therefore, one ‘horsepower’ = 746 Watts.
In post-war Germany, ‘PS’ was and is still used – which was/is a functional equivalent of the ‘British’ Horse Power. In reality, it equates as 1.0 HP = 1.07 PS.
In strict engineering terms, referring to work in kg-m seems a little strange as kg are a unit of mass and one of the oh-so-important things to consider is the environment, eg on earth you need to consider gravity... hence you're not looking at mass x distance moved, you're looking at force x distance moved. Force = mass x acceleration (thanks, Newton) and hence the unit of work is the Joule (=N x m)
It's late, so I hope that's right :-)
-kenski
It's late, so I hope that's right :-)
-kenski
It is all Jan's fault! She asked me on Saturday what the two terms meant and I had to admit I couldn't remember exactly what they did mean.......
We do have mains water in deepest Gloucestershire and also cars.......although there are also a lot of horses....very good for the roses OOARGH!
We do have mains water in deepest Gloucestershire and also cars.......although there are also a lot of horses....very good for the roses OOARGH!
Sorry for a minute I thought I went to the engineering forum. As explained in this month’s EVO magazine, power and torque are different things, but directly related. Torque is a force (strictly, a force times a distance). Power is a rate of working. In an engine, power is torque times (engine) speed. Without torque, there’s no power. But because power is so easily understood, it has become most people’s yardstick.
As a first-order simplification, acceleration is determined by torque (at the driving wheels) divided by weight. Maximum speed is determined by power divided by aerodynamic drag.
But remember that torque at the wheels depends on two things: the engine torque output and the gearing. You can achieve the same acceleration with a high-torque engine running slowly in a high-geared car, or a low-torque engine running faster in a low-geared car.
You pays your money and you takes your choice. The high-torque engine will probably be bigger and heavier (the American who said “there ain’t no substitute for cubic inches” was talking about torque, not power). The low-torque engine, because it is running faster, will be noisier, but because of the power it is swallowing internally through friction, may not be as economical as its small size would lead you to expect. In the high-torque, high-geared car, you won’t have to change gear so often. The low-torque, low-geared car is more likely to appeal to the enthusiastic driver – nice noises, and the feeling that you are working, and exercising skill, to extract its performance.
There aren’t many easy ways of improving the torque of any given engine, except by adding a turbo/supercharger. Improving the power, on the other hand, is easy: you just enlarge the valves and the ports, and re-jig your value timing with more overlap, so that you can run the engine as fast as its bottom end strength will allow. The performance industry tends to emphasise power, because that’s where they achieve visible improvements.
Because of the direct relationship between power and torque, if you have an engine’s torque curve, you can draw its power curve, so long as you use consistent units. An engine with a completely flat torque curve would have a power curve that was an upwards-sloping straight line.
As a first-order simplification, acceleration is determined by torque (at the driving wheels) divided by weight. Maximum speed is determined by power divided by aerodynamic drag.
But remember that torque at the wheels depends on two things: the engine torque output and the gearing. You can achieve the same acceleration with a high-torque engine running slowly in a high-geared car, or a low-torque engine running faster in a low-geared car.
You pays your money and you takes your choice. The high-torque engine will probably be bigger and heavier (the American who said “there ain’t no substitute for cubic inches” was talking about torque, not power). The low-torque engine, because it is running faster, will be noisier, but because of the power it is swallowing internally through friction, may not be as economical as its small size would lead you to expect. In the high-torque, high-geared car, you won’t have to change gear so often. The low-torque, low-geared car is more likely to appeal to the enthusiastic driver – nice noises, and the feeling that you are working, and exercising skill, to extract its performance.
There aren’t many easy ways of improving the torque of any given engine, except by adding a turbo/supercharger. Improving the power, on the other hand, is easy: you just enlarge the valves and the ports, and re-jig your value timing with more overlap, so that you can run the engine as fast as its bottom end strength will allow. The performance industry tends to emphasise power, because that’s where they achieve visible improvements.
Because of the direct relationship between power and torque, if you have an engine’s torque curve, you can draw its power curve, so long as you use consistent units. An engine with a completely flat torque curve would have a power curve that was an upwards-sloping straight line.
The easiest way to describe torque is as the amount of turning force measured as a force applied at a distance, in this case lbs & feet. Maybe I should put it in kitchen terms to make it easier to understand (I'm a dead man!!)? :lol: Luckily we're still talking in imperial measurements (who knows what a Newton feels like?). Hand her a stick & get her to hold one end while resting her hand on the edge of the kitchen table, so that the stick sticks out from the table horizontally (stick sticks?). Tell her to hold it horizontally at all times (& then clear off down the pub!). Mark some lines on it at 6", 12" & 24" from her hand. Then hang a bag of Tate & Lyle sugar from the stick directly below the 6" mark. A bag of sugar is 2.2lb so the torque she'd be feeling is 2.2 x 0.5 = 1.1lbft. She might just think that all she can feel is the weight pulling her arm down but if she ignores that she'll feel the torque trying to twist her hand. Move the bag to below the 12" line & she'll be feeling 2.2 x 1 = 2.2lbft of torque on her hand. Move it to the 24" mark and she'll be feeling 2.2 x 2 = 4.4lbft of torque. If she can still hold the stick horizontally then I've got some real problems for mentioning kitchens 
Now divide the peak torque of her Viper by 2.2 & that'll be the number of bags of sugar you'd have to hang from a stick at a distance of 12" from her hand to give the equivalent torque. We could go on about Watts, Joules, ergs, calories (& Calories), work, power, mass, weight, force, acceleration, vectors & all that stuff for ages & get nowhere. Stick to bags of sugar & sticks & it's a lot easier to explain (rather like describing electricity as smoke - cut a wire in the car & all the smoke comes out, so things stop working!).
Torque is what wins drag races as it's torque that gives acceleration.
Now divide the peak torque of her Viper by 2.2 & that'll be the number of bags of sugar you'd have to hang from a stick at a distance of 12" from her hand to give the equivalent torque. We could go on about Watts, Joules, ergs, calories (& Calories), work, power, mass, weight, force, acceleration, vectors & all that stuff for ages & get nowhere. Stick to bags of sugar & sticks & it's a lot easier to explain (rather like describing electricity as smoke - cut a wire in the car & all the smoke comes out, so things stop working!). Torque is what wins drag races as it's torque that gives acceleration.
It'd probably be easier to explain the strong & weak nuclear forces by using a Malt Loaf, a ping pong ball & a Squirrel.Gassing Station | Corvettes | Top of Page | What's New | My Stuff