Meursault74
Well-known member
SI system is clearer.
Newton-meter when implying torque
Joule (which is a N-m) when implying work/energy
Let's not talk about the imperial slug and horsepower.
[rant] What the Hell is Pound-feet?
- Thread starter Beerhippie
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Newton-meter when implying torque
Joule (which is a N-m) when implying work/energy
Let's not talk about the imperial slug and horsepower.
minke
Well-known member
The only reason to use newton meters is to measure your newtons.
minke
Well-known member
Meursault74
Well-known member
Old Man Roger
Well-known member
What's so confusing?I knew it.lol
See my first post.
Wait, what?
If you weigh 300 pounds you can stand on a 1 foot lever (lbs-foot) and get 300.
If you have a 300 foot breaker bar, you can set a 1lb object on the end and get 300.
No one would ever think you can weigh 300 feet. Is that what this nerdfest is really all about?
@Beerhippie I support the cause based off your passion alone.
I intend to borrow your “pounds feet?? Sounds like what I do when her husband comes home from work early” joke but I will act like I made it up myself.
I intend to borrow your “pounds feet?? Sounds like what I do when her husband comes home from work early” joke but I will act like I made it up myself.
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Old Man Roger
Well-known member
Ahh, I read your other post wrong.What's so confusing?
If you weigh 300 pounds you can stand on a 1 foot lever (lbs-foot) and get 300.
If you have a 300 foot breaker bar, you can set a 1lb object on the end and get 300.
No one would ever think you can weigh 300 feet. Is that what this nerdfest is really all about?
dnschmidt
Well-known member
Cam, stop living in the stone age. I know you like the old stuff but time marches on.Ya know what Denny, you’re welcome to take all those 25.4mms and shove it straight up your….
alfadan
Well-known member
I have to convert everything to footballfields per fortnight.
Maybe my dimwittedness comes in handy; if I see lb-ft or ft-lbs, I automatically know what they're talking about and use my fancy clicky-stick.
Maybe my dimwittedness comes in handy; if I see lb-ft or ft-lbs, I automatically know what they're talking about and use my fancy clicky-stick.
Wamsutta
Well-known member
pound feet = more **** 
rancherbill
Well-known member
The point is CHANGE.
With today's emphasis on STEM the old lazy thinking has to go. Asia is beating North America on standardized math and science tests.
We have to do better. And that means we have to do better on everything.
pizza
Well-known member
well... if you want to be pedantic about what's in (advanced, calculus-driven) books used in mech eng undergrad, the torque cross product expression actually usually appears like this with the position vector first to yield the correct sign:
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Dave455
Well-known member
In British standard units (pre S.I.) Foot Pounds (ft lbs) are a unit of force.
Pounds Feet (lbs ft) are a unit of torque (turning force).
These terms are not interchangeable.
I would be very surprised if the U.S, is vastly different.
Pounds Feet (lbs ft) are a unit of torque (turning force).
These terms are not interchangeable.
I would be very surprised if the U.S, is vastly different.
NORTON'S SHOP
Well-known member
It's GET OFF MY LAWN FEET! Sheesh! Didn't you read the memo?
finn
Well-known member
Yup. Life gets a lot easier once you realize multiplication is commutative.
You don’t even need your BSME to know that. I think it was fifth grade math for me.
PelicanPines
ALLIANCE MEMBER
I would like to hear more about this "TOE" aspect of this story. Where there is a foot... there are at least 5 toes... Unless you have diabetes in your life... in which case... you may be toe limited.
bwringer
Well-known member
It's grammar.
Not the one who made you cookies, the one that makes you talk more gooderer.
It's a curious, but nearly inviolable quirk of English that adjectives don't "sound right" or "feel right" unless they are in a very specific order. This rule is almost completely unconscious, but it's one of those things that every native English speaker "knows". Sometimes it's called the "Royal Order".
In this case, it's a lot simpler than that; "foot" functions as the adjective that modifies the noun "pounds"; adjectives always go before the noun, and you pluralize the noun if needed. "Foot" is a special kind of "pound", in other words.
"Foot-pounds" sounds right, "pound-feet" or "pounds-feet" are backwards, grammatically speaking, at least in English.
www.grammarly.com
And of course, there's a hyphen in there:
www.grammarly.com
Not the one who made you cookies, the one that makes you talk more gooderer.
It's a curious, but nearly inviolable quirk of English that adjectives don't "sound right" or "feel right" unless they are in a very specific order. This rule is almost completely unconscious, but it's one of those things that every native English speaker "knows". Sometimes it's called the "Royal Order".
In this case, it's a lot simpler than that; "foot" functions as the adjective that modifies the noun "pounds"; adjectives always go before the noun, and you pluralize the noun if needed. "Foot" is a special kind of "pound", in other words.
"Foot-pounds" sounds right, "pound-feet" or "pounds-feet" are backwards, grammatically speaking, at least in English.
Adjective Order in English
“Every Sunday, my grandma makes an Italian big meal,” said no one ever. Why? It’s technically correct—it’s a big meal, it’s…
www.grammarly.com
And of course, there's a hyphen in there:
How to Use a Hyphen Correctly
What is a hyphen? A hyphen (-) is a punctuation mark that’s used to join words or parts of words. It’s not interchangeable with the…
www.grammarly.com
I'm going to call ******** on that one. The issue isn't the subject, it's the teachers...
sz0k30
Well-known member
I'll bet you're the guy that still thinks that the "#" symbol is a pound or number sign (like it has been forever) and not a "Hashtag"!
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The only newtons I can stomach are the ones with figs in them.
Exactly! You install the breaker bar, and pound on it with your foot!
If you're right-footed, it's pound feet.
If you're left-footed, it's foot pounds.
dnschmidt
Well-known member
Partially, mostly it's parents that let the little bastards do whatever they like. I HAD to do my homework. I HAD to go to school and if I got anything under an A my mom gave me the stink-eye. Discipline the kids (they actually NEED IT). Get their asses off of their phones and video games and show them how to live in the real world, not the virtual world which doesn't exist.
alfadan
Well-known member
Very true. Bullet impact force is given in ft/lb. Would be weird to see it as lb/ft.
Tahoe
Member
Are They Interchangeable?I own some torque wrenches--not as many as y'all, but as many as I need. They're calibrated in Foot-Pounds:
I don't see no Pound-Feet there, and that's about eighty years of tools.
Pound-Feet sounds like what I do when caught with another man's wife--and he's armed.
Seems I just started hearing and seeing it in the last decade or so. Did I miss the memo? Is Foot-Pounds somehow offensive to feet?
[/rant]
The short answer is no. They are each separate, distinct units of measure. However, as it turns out foot-pound and pound-foot can be converted between one another via complicated math, even though they measure two different things. First, we need to define what each unit is, and what it measures.
The “pound-foot” (lb-ft) is a unit of torque and a vector measurement that is created by one pound of force acting on a one foot lever. The formula for torque in the instance of tightening a fastener would be: Torque equals force times radius, or T=FR. When tightening a bolt, “R” would be the length of your wrench.
The “foot-pound” (or more accurately, “foot-pound-force”), on the other hand, is a measurement of work. Work is the measurement of force over a given distance. So one foot-pound-force (ft-lbf or just ft-lb) is the energy required to move a one pound object one foot of linear distance.
So while both measurements have a force component (pounds) and what is called a displacement component (feet), one is a scalar and one is a vector – which is a fancy way of saying they measure different things.
Interesting. I see the semantics are not interchangeable.
Can you show an example where lb-ft and ft-lb show a different value? Or the conversion formula?
strutaeng
Well-known member
A unit of force is what I would say is the definition. I'm not sure if OP was asking about the units?
Interesting on the ft-lb vs lb-ft being different by the Brits... wasn't aware of that.
In my engineering field (structural), they are used interchangeably. I prefer to use ft-lb and see it this way most of the times in articles and pronounced this way. But again, interchangeable as far as I know.
It gets more challenging when using inches and kips, however. And converting between then. So you can use or see: lb-ft, k-in, lb-in or k-ft in calculations or equations...
1 kip = 1,000 lbs.
Interesting on the ft-lb vs lb-ft being different by the Brits... wasn't aware of that.
In my engineering field (structural), they are used interchangeably. I prefer to use ft-lb and see it this way most of the times in articles and pronounced this way. But again, interchangeable as far as I know.
It gets more challenging when using inches and kips, however. And converting between then. So you can use or see: lb-ft, k-in, lb-in or k-ft in calculations or equations...
1 kip = 1,000 lbs.
Tahoe
Member
I wish I were a brainiac that could explain it simply, but I'm not so the best I can do is give you link to the explanation.
https://study.com/skill/learn/how-t...ue-using-the-torque-equation-explanation.html
https://study.com/skill/learn/how-t...ue-using-the-torque-equation-explanation.html
VolvoRyan
Well-known member
Forget the fact that lots of furrin' car makers round their n-m's to convenient numbers.... then we 0.74 them to Freedom units which turns them into wacky random numbers.... and if you work on the same sorts of cars long enough you wind up with a load of these random numbers stuck in your brain.
Of course, why are we even talking about this? Aren't we macho-macho-men, so skilled in the exquisite art of the wrench to tighten things with the biggest air gun we can find?
-Ryan
Of course, why are we even talking about this? Aren't we macho-macho-men, so skilled in the exquisite art of the wrench to tighten things with the biggest air gun we can find?
-Ryan
VolvoRyan
Well-known member
Do not do the GJ brethren such an injustice as proclaiming we’re complete heathens.
Most of us have highly calibrated torque arms.
LopezBart
Well-known member
Impact energy is given in ft-lbs. Note that 1 horsepower is 550 ft-lbs/sec - the power (energy/unit time) needed to lift 550 lbs one foot. A
A .30-06 bullet has typically around 3000 ft-lbs of energy - or a 6 hp engine running for about 1 second. Note that the resulting force on the target depends on both the target and the bullet. A piece of paper will have very little force applied; a piece of AR500 steel will experience a lot more.
Aaron_W
Well-known member
I'm right there with you on the change from pled to pleaded. It makes my skin crawl every time I read an article and see someone pleaded guilty. For the first 40 or so years of my life it was pled. When I see pleaded I imagine Al Capone in front of the judge Oh please your honor, please throw me in jail.
Let me help clarify:
Torque = Radius <cross> Force
= |Radius|*|Force|*sin(theta)
where Torque, Radius, and Force are vector quantities. |..| denotes magnitude. Theta is the angle between the Radius and Force vectors and <cross> denotes a vector cross product. This definition holds regardless of units.
Radius has units of length. Force has units of mass*length/time^2. In English (SAE) units (wonky) length can measured in feet and force can be measured in mass * gravity units with gravity the earths surface gravitational constant (roughly constant = 9.8 meters/sec^2 in better units). We take |Force| = m*g and measure the force equivalent by the mass in lbs that would produce the same force in the gravitational field at the surface of the earth. Then torque has units of foot-lbs.
Now since we work in magnitudes and force and mass are classical observables, we have foot*lbs = lbs*foot so we can take our torque unit to be foot-lbs or lbs-foot with no difference whatsoever. If one were working with elemental quantized action, some care would need to be taken. But Garage Journal people are ususally torquing macroscopic fastners etc.
All clear now? Glad to do my duty as a theoretical physicist (who is also a DIY guy) to help clarify! But seriously, English (SAE) units need to be retired. It encourages use of gravitational lbs as a force unit. I am a modern guy and do not mind what people do in the privacy of their own homes. But use of SAE torque units should not meet any reasonable standard of decency in public.
Torque = Radius <cross> Force
= |Radius|*|Force|*sin(theta)
where Torque, Radius, and Force are vector quantities. |..| denotes magnitude. Theta is the angle between the Radius and Force vectors and <cross> denotes a vector cross product. This definition holds regardless of units.
Radius has units of length. Force has units of mass*length/time^2. In English (SAE) units (wonky) length can measured in feet and force can be measured in mass * gravity units with gravity the earths surface gravitational constant (roughly constant = 9.8 meters/sec^2 in better units). We take |Force| = m*g and measure the force equivalent by the mass in lbs that would produce the same force in the gravitational field at the surface of the earth. Then torque has units of foot-lbs.
Now since we work in magnitudes and force and mass are classical observables, we have foot*lbs = lbs*foot so we can take our torque unit to be foot-lbs or lbs-foot with no difference whatsoever. If one were working with elemental quantized action, some care would need to be taken. But Garage Journal people are ususally torquing macroscopic fastners etc.
All clear now? Glad to do my duty as a theoretical physicist (who is also a DIY guy) to help clarify! But seriously, English (SAE) units need to be retired. It encourages use of gravitational lbs as a force unit. I am a modern guy and do not mind what people do in the privacy of their own homes. But use of SAE torque units should not meet any reasonable standard of decency in public.
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Torque doesn't care whether the distance is horizontal or vertical. It's still a distance.
It's also all work.
RedneckWelder
Well-known member
whateg01
Well-known member
"/" =/= "*"
Junkdrawer Dog
Well-known member
This is a huge talking point. Until I was 18, I HAD to obey my parents or there were definite consequences. This included homework, chores, obeying social expectations, etc.. Their presence in my life and their advice and expectations continued in my life long after age 18, and almost universally for my benefit. Parenting seems to be a lost art these days and the quality of public education suffers because of it.
LopezBart
Well-known member
In all fairness, I've seen kids flame out in college when the parental constraints were lifted. Raising humans successfully is hard; there's no correct answer for all parents and all kids. And raising kids so they will be successful parents is harder yet.
Junkdrawer Dog
Well-known member
Yes. I almost did this myself. I was never a great student despite the fact that my mother was a teacher. She started teaching on a temporary certificate during WW2 and later got her Masters in education. Her sister obtained a Doctorate in education as well. Education was a big deal in our house. When I moved away to college, my grades plummeted due to lack of those parental constraints. Eventually, due to "heat" from home, in the form of phone calls, letters, and the threat of being financially cut off, I finally got my act together sufficiently to graduate with my Bachelor's degree. Trust me, my life was better for it.
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