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  1. #131
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    Default Re: Does HP matter?

    Quote Originally Posted by EE_Bota View Post
    Yes, I remember that a radian is unitless, and they told us in school, but I was just pleased to have a method to make the factor/label math work perfectly.
    As a former engineer/physican/mathematican, as well as a former illiterate farmer, I understand people, their scares/fears away when they see math symbols. But, actually, they are nothing else than very short usage way of literature way of social communications. All seem-to-be-complicated symbols of maths are not different than using just P instead of Power in math communications, equations, equivalences, etc. Problem with mathematics is not about common people, it is about mathematicans, especially pure mathematicans who like to hide their communication symbol systems against common people. However, they found themselves in a big pond of symbols, even mathematicans in different branches aren't understanding each others anymore. For example, give (to a group theory mathematican who is used to tensoral way like indices) a group of equation with vectorial math application symbols such as cross products which engineers often use, he won't like. However, like I did in "Power ~ Torque / Time", different symbols such as this "~" can be useful to understand physical meanings for comparisons without calculating exact values. In market, people usually do comparisons rather than calculating exact values which are left to engineers/accountants/etc anyway. So, perhaps, a new mathematics should be introduced to common people.

  2. #132
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    Default Re: Does HP matter?

    I use a lot of "thought" experiments since in many cases I don't actually need a number. But if I need a number, my factor / label approach must work, or I know I am out of luck.
    Which is bigger?: a) $100 per month since the Big Bang or b) the US National Debt.

  3. #133
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    Default Re: Does HP matter?

    My advice to people who don't like math and its symbols is to use "units" only.
    For example, you don't need to know famous F = mxa. But, you know their units, kg or lb and m/sec^2 or m/sec/sec or ft/sec/sec. Just multiply these units, you'll see lb x ft/sec/sec which is the unit of force, and you'll be obtaining famous F=mxa. Similarly, you can derive any other relations without knowing formulas, but, by just knowing units of quantities and I guess most of people know, say, speed unit is ft per second. Unless you need to calculate exact values, you'll have enough knowledge on relationships between power, torque, pressure, etc etc without knowing their formulas so that you can make comparisons. Just play with units to see the relations between quantities, that's it. Leave calculating exact values to engineers who make their incomes in calculating such things. and, today, calculating exact values too is very hard and engineers gave up calculations and they are having computers to do calculation works.

  4. #134
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    I'm going to lay down now, lol. My brief foray into trig and calculus 15 yrs ago when I considered a career in mechanical engineering is enough to understand the concepts, but mathematical computation of them is beyond my skill set.

  5. #135
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    Default Re: Does HP matter?

    When I was taking calculus first time in engineering, it was hard really (though at the end of year, my grade was A+.)
    Then, when I went into math further (at master), my confusions and troubles during engineering were gone a little. Not that I learnt more, but, I was more clear about the calculus while I was learning at engineering.
    Later, during doctorate (math in as well), again, I hadn't learnt much actually except a new ways and methods, but, I was more and more clear about what I was doing at calculus at engineering, from physical points of view too. I done works in computational math too such as engineering calculations of flows, but, it is very boring after a while. In pure math I put my nose a little, it was fun to do symbolic computations without calculating numbers. These were 10-15 years ago, when I was writing my own source codes of symbolic calculations. Now, they too are visualised a lot like this Windows OS after mapple, matlab, etc are developed more. Today, unless you become a scientist, engineering calculations or even symbolic calculations, all are very easy, visual, like Windows OS. Without knowing whats happening in background, you can calculate all numbers (forces, torques, etc) of an attachment you are driving on friendly visual softwares.

  6. #136
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    Default Re: Does HP matter?

    Quote Originally Posted by brain55 View Post
    I'm going to lay down now, lol. My brief foray into trig and calculus 15 yrs ago when I considered a career in mechanical engineering is enough to understand the concepts, but mathematical computation of them is beyond my skill set.
    And you absolutely dont need to go there. All you need to know is what Force, Work[Energy], and Power is and have the discrimination to deal with each of them correctly. If you want to hide the actual Physics of these terms start using dynamic torque and radians. While including the right stuf they camouflage the simple rigorous Physics that can be expressed so obviously that intuitive understanding is likely. Dont get distracted by the math terms. All you really need is to understand this:
    Quote Originally Posted by SPYDERLK View Post
    YOU are right John. HP will make any torque you want -- just run it thru an appropriate gearbox. It is very difficult to soundbyte this issue because the terms become inseparable as soon as you start talking HP transmitted by rotation. Torque is a static - a force at the end of a leverage arm trying to twist around a pivot. There is no work done until there is motion. As soon as there is motion you have the Force times a Distance that the force at the end of the lever moves. Work is being done. Also, inherent in any motion is its speed - so that D component is truly D per unit time. So with motion attributed you have (F X D)/Time. Thats Foot Pounds per second. Thats HORSEPOWER. The fact that the distance is in a circle doesnt matter.
    ---- Just imagine that circle is a drum on an engine shaft reeling in a rope with a weight on it. For convenient example make the drum 1' in radius. Its circumference is then 2 Pi feet ~ 6.28 ft. Note that the lever is 1foot so engine torque in ft lbs arrives out at the end of the lever as a force in pounds ... 30 ft-lbs gives you 30lb on the drum rim. If that drum rotates once lifting a 30# weight your engine does 6.28 x 30 ~ 189ftlb of work. What HP? ... Well, how fast did the engine do the work? ... Suppose it was running at 1200rpm - thats 20 rps - therefore it produced 189 x 20 ~ 3800 ftlb/sec. I think the conversion is about 550. Looks like about 7HP.
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  7. #137
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    Default Re: Does HP matter?

    Quote Originally Posted by SPYDERLK View Post
    YOU are right John. HP will make any torque you want -- just run it thru an appropriate gearbox. It is very difficult to soundbyte this issue because the terms become inseparable as soon as you start talking HP transmitted by rotation. <b>Torque is a static - a force at the end of a leverage arm trying to twist around a pivot.</b> There is no work done until there is motion. As soon as there is motion you have the Force times a Distance that the force at the end of the lever moves. Work is being done. Also, inherent in any motion is its speed - so that D component is truly D per unit time. So with motion attributed you have (F X D)/Time. Thats Foot Pounds per second. Thats HORSEPOWER. The fact that the distance is in a circle doesnt matter.

    ---- Just imagine that circle is a drum on an engine shaft reeling in a rope with a weight on it. For convenient example make the drum 1' in radius. Its circumference is then 2 Pi feet ~ 6.28 ft. Note that the lever is 1foot so engine torque in ft lbs arrives out at the end of the lever as a force in pounds ... 30 ft-lbs gives you 30lb on the drum rim. If that drum rotates once lifting a 30# weight your engine does 6.28 x 30 ~ 189ftlb of work. What HP? ... Well, how fast did the engine do the work? ... Suppose it was running at 1200rpm - thats 20 rps - therefore it produced 189 x 20 ~ 3800 ftlb/sec. I think the conversion is about 550. Looks like about 7HP.

    larry
    This is another good explanation using another language of technique (perhaps, some can understand this language better.)

    But, calling torque as force (as you did above in bold sentence) may make some people get confused. Because the unit of Torque is Foot Pound (ftxlb) while the unit of force is only Pound, lb. Maybe, most people confuse because of this unit confusion. True, torque can be called a static quantity. (you can try to rotate a drum by applying a force, drum won't rotate around its pivot and there won't be any motion or rotation until torque level reaches at certain level. That's, there won't be any displacement of a point of the drum in the space. So, there is Force, there is Torque, but, there is no displacement or rotation or motion, there is no work done, hence, no power done by drum.

    So, "Torque" is equal to multiplication of "Force" you apply (it is called tangential force) and "Radius of Drum".

    While "Work" is the multiplication of "Force" and "Displacement" of a point on drum when moves/rotates.

    Since rotational motions are periodic, we prefer to express Displacement of points on drum in terms of velocity of drum. And, in rotational or circular motions, we prefer polar or angular coordinate systems, hence, radyans, etc. At more than 1 revolutions or many more revolutions, we prefer not radyans but Revolutions per Seconds or Revolutions per Minutes, RPM, not to be busy with decimals after commas.
    So, while we use "Power = Torque x RPM x Some constants" in rotational motions (where RPM comes from Displacement of points), we use "Power = Force x Length / Time" expression way in cartesian or straight motions in which Length is really Dpslacement while Displacement Lenght is hidden in Torque Power expression.

  8. #138
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    Default Re: Does HP matter?

    Quote Originally Posted by SPYDERLK View Post
    YOU are right John. HP will make any torque you want -- just run it thru an appropriate gearbox. It is very difficult to soundbyte this issue because the terms become inseparable as soon as you start talking HP transmitted by rotation. Torque is a static - a force at the end of a leverage arm trying to twist around a pivot. There is no work done until there is motion. As soon as there is motion you have the Force times a Distance that the force at the end of the lever moves. Work is being done. Also, inherent in any motion is its speed - so that D component is truly D per unit time. So with motion attributed you have (F X D)/Time. Thats Foot Pounds per second. Thats HORSEPOWER. The fact that the distance is in a circle doesnt matter.
    ---- Just imagine that circle is a drum on an engine shaft reeling in a rope with a weight on it. For convenient example make the drum 1' in radius. Its circumference is then 2 Pi feet ~ 6.28 ft. Note that the lever is 1foot so engine torque in ft lbs arrives out at the end of the lever as a force in pounds ... 30 ft-lbs gives you 30lb on the drum rim. If that drum rotates once lifting a 30# weight your engine does 6.28 x 30 ~ 189ftlb of work. What HP? ... Well, how fast did the engine do the work? ... Suppose it was running at 1200rpm - thats 20 rps - therefore it produced 189 x 20 ~ 3800 ftlb/sec. I think the conversion is about 550. Looks like about 7HP.
    larry
    Quote Originally Posted by nomad View Post
    This is another good explanation using another language of technique (perhaps, some can understand this language better.)

    But, calling torque as force (as you did above in bold sentence) may make some people get confused. Because the unit of Torque is Foot Pound (ftxlb) while the unit of force is only Pound, lb. Maybe, most people confuse because of this unit confusion. True, torque can be called a static quantity. (you can try to rotate a drum by applying a force, drum won't rotate around its pivot and there won't be any motion or rotation until torque level reaches at certain level. That's, there won't be any displacement of a point of the drum in the space. So, there is Force, there is Torque, but, there is no displacement or rotation or motion, there is no work done, hence, no power done by drum.

    So, "Torque" is equal to multiplication of "Force" you apply (it is called tangential force) and "Radius of Drum".

    While "Work" is the multiplication of "Force" and "Displacement" of a point on drum when moves/rotates.

    Since rotational motions are periodic, we prefer to express Displacement of points on drum in terms of velocity of drum. And, in rotational or circular motions, we prefer polar or angular coordinate systems, hence, radyans, etc. At more than 1 revolutions or many more revolutions, we prefer not radyans but Revolutions per Seconds or Revolutions per Minutes, RPM, not to be busy with decimals after commas.
    So, while we use "Power = Torque x RPM x Some constants" in rotational motions (where RPM comes from Displacement of points), we use "Power = Force x Length / Time" expression way in cartesian or straight motions in which Length is really Dpslacement while Displacement Lenght is hidden in Torque Power expression.
    Actually I didnt. I described Torque in a sentence ... in composite, hopefully, a complete thot. The development I provided was devised to avoid chance confusion between units of T and Work[Energy]. I think that as long as torque is described and dealt with as a Force to cause pivoting, that its relationship to actual energy and power will not be muddled. That way the root concept of Power being a force thru a distance divided by the time it takes [FtLb/sec or NewtonMeters/sec] remains intuitively linked only to the distance moved, no matter whether in a straight or circular path.
    larry
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  9. #139
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    Default Re: Does HP matter?

    Quote Originally Posted by nomad View Post
    As a former engineer/physican/mathematican, as well as a former illiterate farmer, I understand people, their scares/fears away when they see math symbols. But, actually, they are nothing else than very short usage way of literature way of social communications. All seem-to-be-complicated symbols of maths are not different than using just P instead of Power in math communications, equations, equivalences, etc. Problem with mathematics is not about common people, it is about mathematicans, especially pure mathematicans who like to hide their communication symbol systems against common people. However, they found themselves in a big pond of symbols, even mathematicans in different branches aren't understanding each others anymore. For example, give (to a group theory mathematican who is used to tensoral way like indices) a group of equation with vectorial math application symbols such as cross products which engineers often use, he won't like. However, like I did in "Power ~ Torque / Time", different symbols such as this "~" can be useful to understand physical meanings for comparisons without calculating exact values. In market, people usually do comparisons rather than calculating exact values which are left to engineers/accountants/etc anyway. So, perhaps, a new mathematics should be introduced to common people.
    I agree with most of what you state here. I am jaded however to any new mathematics. I saw what happened to a whole generation of school kids when some "educrat" thought it best to help kids understand "what numbers mean" That went over like a lead balloon and did not help kids worth a wit. Sort of what happened to this thread. The math,numbers, what "words" mean such as torque and power really do not add to an understanding beyond an engineers or mathematicians mind set of what actually happens in the field. Why is 6 more hp helpful or is it? When is it helpful when working a tractor? Simple enough of a question. People have all kinds of varied interests and brain wiring. Of course people are going to gravitate to their wiring and love of certain mind pondering. They want to share this with the world as everyone else would like to share. A practical sense (or I should say a practical sense of the majority) of things however can sometimes get lost in these myriads of thought processes so I do hope any new math improves upon 2+2 is 4 and the like.

  10. #140
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    Default Re: Does HP matter?

    Quote Originally Posted by arrow View Post
    I agree with most of what you state here. I am jaded however to any new mathematics. I saw what happened to a whole generation of school kids when some "educrat" thought it best to help kids understand "what numbers mean" That went over like a lead balloon and did not help kids worth a wit. Sort of what happened to this thread. The math,numbers, what "words" mean such as torque and power really do not add to an understanding beyond an engineers or mathematicians mind set of what actually happens in the field. Why is 6 more hp helpful or is it? When is it helpful when working a tractor? Simple enough of a question. People have all kinds of varied interests and brain wiring. Of course people are going to gravitate to their wiring and love of certain mind pondering. They want to share this with the world as everyone else would like to share. A practical sense (or I should say a practical sense of the majority) of things however can sometimes get lost in these myriads of thought processes so I do hope any new math improves upon 2+2 is 4 and the like.
    As someone who puts his nose into pure mathematics for a while, I can say that pure mathematicans live in another world. You can call that they belittle pure physicans and even applied mathematicans. Pure mathematicans are really in another worlds. just to give an example. For physicans, there is only one infinity. For a pure mathematican, there are infitine number of infinities. But, they do somethings real even though they themselves are not aware of what they do really and they communicate with physicans and applied mathematicans about what they are doing really, their means in the real life, etc. Sometimes, especially in last decades, big inventions (such as Einstein's general relativity, black holes, etc which are not proved physically yet) were made in pure mathematics first. Anyway, pure mathematicans are in another worlds and the gap between them and common people has increased a lot. But, this is a reason for a pure mathematican to be proud. Common should actually thank a little to physic and applied mathematicans who try to make common understand things in science and mathematics more. That's why we see different expressions of power, force, etc etc. due to their efforts of physic and applied math people, not pure mathematicans at all who live in a world they have built for themselves.

    Anyway, maybe, a new math teaching way is really necessary, maybe, should be started at the beginning. Till 2-3 decades ago, there were philosophy courses at high school, now, which are omitted. For example, without understanding what the force is, we are memorizing it and errors in our understanding are getting bigger in later stages like snowballs. For example, we often said here that force is a static thing. What an average Joe understands from this when it is called static? He'll probably understand that there is no motion. Right, engineers too understand same. But, no motion ideally means timeless, infinitely same state in time. Again, ok. But, then, we should not see "time" in its unit of force then if it is same in "all time". Now, lets look at the unit of force (in si unit system.) It is N, that's, Newton. Now, we don't see time here. See how we are forced to forget its background, hidden time in this unit.. Lets rewrite it explicitly. N = Kg x m / s / s. (here, m/s/s or m/s^2 as you know is unit of change of velocity, or, acceleration.) So, we use time even for a force on a body which always sits on the ground. We say this force is constant, and we call it weight. This is so because of our one assumption we make in our early schools, that's, gravitational acceleration is constant, which is not actually, changes a little depending on its coordinates in the world vertically and horizontally. This is another story, but, I am trying to come to a point.

    If you looked into our talks here, what thing an average Joe noticed? He probably noticed that whenever we divide a quantity by time, we called it power. So, in my words above about the force, now, he noticed that another quantity too is divided by time and he probably thought that force too is power. Technically and mathematically, correct according to grouping math method. Actually, now, saying force is power isn't a strange expression for his logic of any Joe who hasn't seen any school in his life. Now, let me give another example to tell him what we technicans call a power rather than telling him what the power really is.. When you see a man keeping a big rock in his hands above his shoulders and stays so, what do we say? What a powerful man! Well, this was in very old days, centuries ago, in pre-engineering life. Today, correct expression is "strong man", not powerful man. To call him hercule or powerful man, we technics look at "how fast" he lifted the rock up above his shoulders, which means there is "time" in ranking. This is why today we divide quantities by time to call the output as power. So, power in old days was like a static concept while today it requires a dynamic to have a power. But, even at Newton's times, 5 century ago, we forget there is a hidden "time" even in static force like gravitational force, weight. People at Newton's time were understandable as they didn't know gravitational acceleration isn't constant actually. But, although we learn it in early school days, we forget our early assumptions, neglecting things like change in gravitational accelerations which is indeed small. But, forgetting this assumption make us lose our base, and errors in technique accumulate in further stages of educations and communication language gap between average Joe and engineers gets bigger and miscommunications happen a lot. But, engineers should be respected more, even more than pure mathematicans who try to pull engineers toward themselves and they open the gap more. Engineers are like middle-men, who are blamed or critisized more than others, so, because they are close to average Joe. Average Joe critisizes engineers not by telling things to him clearly. On the other end side, pure mathematican critisizes engineer for his low level of science, and them pure mathematicans even belittle them engineers, even physicans and applied mathematicans. Average Joe living in a "very real" life and pure mathematican Joe living in totally another world out of totally real life should have a meeting and lets see what these two lazies can do about what engineers couldn't.
    Last edited by nomad; 12-15-2012 at 06:23 PM.

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