bob gresko
ArboristSite Member
Hi guys, I don't want to sound stupid but here goes: What is meant by a saws torque, low end torque, etc. I understand what rpm is but how do the three relate to each other -torque, rpm, hp?
Torque, HP, Rpms
- Thread starter bob gresko
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slowtorque1
ArboristSite Member
Torque is a measure of work (force thru a distance). Horsepower is a measure of how fast work is being done (work rate). Take two saws of equal horsepower. One might be rated 4 hp at 10,000 rpm and the other may be rated 4 hp at 5000 rpm (an old Mac or something). The old Mac is producing twice the torque at half the speed (rpm) to produce the same horsepower. Hope this helps.
Let's expound on that just a bit...
How do the three (HP, torque, and RPM) relate? Mathematically.
<blockquote>HP = ( torque × RPM ) ÷ 5252
torque = ( HP × 5252 ) ÷ RPM</blockquote>
Generally speaking, with two engines of the same displacement, one having a smaller bore and longer stroke than the other, the longer stroke configuration will produce greater torque but will not rev as high while the larger bore and shorter stroke will sacrifice torque for the ability to reach a higher rev ceiling. Because HP is also a function of RPM in an engine, the higher-revving version will produce a higher HP figure. So long as it's able to work while spinning fast enough it will outwork the slower engine. If for whatever reason it's unable to maintain the RPM advantage, the longer stroke smaller bore (torquier) version will outwork it.
Think Harley compared to rice grinder.
If you had two saws the same size and one could pull the chain through the wood faster because it could maintain higher RPM, it would be quicker. But if conditions are not ideal, the "slower" saw could well be "faster" since they're typically more forgiving of operator error (technique and/or chain condition).
There really is quite a large number of variables involved and I've simplified it considerably for the "quick" answer.
Glen
How do the three (HP, torque, and RPM) relate? Mathematically.
<blockquote>HP = ( torque × RPM ) ÷ 5252
torque = ( HP × 5252 ) ÷ RPM</blockquote>
Generally speaking, with two engines of the same displacement, one having a smaller bore and longer stroke than the other, the longer stroke configuration will produce greater torque but will not rev as high while the larger bore and shorter stroke will sacrifice torque for the ability to reach a higher rev ceiling. Because HP is also a function of RPM in an engine, the higher-revving version will produce a higher HP figure. So long as it's able to work while spinning fast enough it will outwork the slower engine. If for whatever reason it's unable to maintain the RPM advantage, the longer stroke smaller bore (torquier) version will outwork it.
Think Harley compared to rice grinder.
If you had two saws the same size and one could pull the chain through the wood faster because it could maintain higher RPM, it would be quicker. But if conditions are not ideal, the "slower" saw could well be "faster" since they're typically more forgiving of operator error (technique and/or chain condition).
There really is quite a large number of variables involved and I've simplified it considerably for the "quick" answer.
Glen
Fish
Tree Freak
I would expound on this terribly, but my response would include
some tricky calculus and some really big words.....
Hope this helps...
some tricky calculus and some really big words.....
Hope this helps...
dbabcock
Hi Tech Redneck
I too would repond, but I know that I can just let Glen do the work for me. He obviously made the most of his eleventh grade education. Ben will be here soon as well.
dbabcock
Hi Tech Redneck
Hey Fish,
Remember when you taught me how to calculate piston position, speed and acceleration? I still can't quite grasp the concepts in some cases, but your math and teaching prowess is second to none as far as I'm concerned.
I wish Dagger would come back.
Remember when you taught me how to calculate piston position, speed and acceleration? I still can't quite grasp the concepts in some cases, but your math and teaching prowess is second to none as far as I'm concerned.
I wish Dagger would come back.
Doug, don't make it sound like I didn't complete my H.S. requirements at that time. It was a spur of the moment decision to leave early, or they would have printed and bound my diploma then. I did stop by and pick it up eventually.
Nice work sheet. They are important, even when using one of these:
Nice work sheet. They are important, even when using one of these:
dbabcock
Hi Tech Redneck
Glen,
Obviously the mention of eleventh grade thing is just horsing aroiund and therefore meaningless. I like HP gonkulators as well, having been an RPN convert since I got my first HP 35 back in 1973 (for $400!). I've kept almost all of them over the years. If memory serves, I still have the 35 as well as: 45, 65, 67, 11, 15, 41CV, 41CX, 28S, and the 48.
Nowadays, I find it troubling to see my 15 year old son, who's in 10th grade, using one for math class. Today, kids don't have to use printed log or trig tables. They are encouraged to use their calculators. In math class, they also get in the habit of using the thing for everything else as well, hence a general lack of "feel" for both estimation, application and rudimentary excercising of the brain in general. Ask many junior high school kids how much 137 minus 43 is and watch the fingers come out. An estimate of how much 50 times 40 is is equally dismaying, as answers like 20,000 or 200,000 are common.
Obviously the mention of eleventh grade thing is just horsing aroiund and therefore meaningless. I like HP gonkulators as well, having been an RPN convert since I got my first HP 35 back in 1973 (for $400!). I've kept almost all of them over the years. If memory serves, I still have the 35 as well as: 45, 65, 67, 11, 15, 41CV, 41CX, 28S, and the 48.
Nowadays, I find it troubling to see my 15 year old son, who's in 10th grade, using one for math class. Today, kids don't have to use printed log or trig tables. They are encouraged to use their calculators. In math class, they also get in the habit of using the thing for everything else as well, hence a general lack of "feel" for both estimation, application and rudimentary excercising of the brain in general. Ask many junior high school kids how much 137 minus 43 is and watch the fingers come out. An estimate of how much 50 times 40 is is equally dismaying, as answers like 20,000 or 200,000 are common.
Tony Snyder
Addicted to ArboristSite
Slowtorque, you have aired slightly. as we all some times pass some air. (with all do respect)
Torque is technically not a measure of force thru distance, it is mearly force thru an arc. It can be static torque as when you hang a one pound weight from a lever at 3:00 o'clock one foot from the center line of a shaft (you must balance at 9 o'clock to offset the weight of the arm) Then you would have 1 (one) foot pound of static torgue, no movement distance required. Again torque is just force applied through and arc. No motion is implicite in its definition. If it helps you to think of torque in association with distance, that is o.k., but just understand that there needs to be no movement for torque to exist.
RPM should be self explanatory.
Horesepower is a force appled over a distance in a given time. (the key words here being distance and time) Horsepower has three elements; force or torque if it is thru an arc , distance , and time.
Horsepower is a measure of work done in a defined time. You could pull on the end of an 18 " breaker bar on a stuck rusted 1 inch bolt for 5 minutes and have done no work in scientific terms. Until you apply the torque thru a distance all you have done is apply force, no work, no horsepower.
James Watt defined horsepower by experimentally determining that mine ponys could do 22,000 foot- pounds of work in a minute. He mutiplied that times 1.5 to get 33,000 which he estimated a horse cound do. The figure stayed with us.
Horsepower is also commonly expressed in KW (metric) There is .746 kilowatts in one horsepower. I'll stay away from the minor difference between Dutch (DIN) and English horsepower.
Glens give a good practical answer.
Someone will surely dive into the math on this, some student of Sir Isaac.
Gearing (or mechanical advantage) mutiplies torque or speed.
Now lets get into the chansaw world; you may decrease your sprocket tooth count and get more torque (luggung power) and loose speed. Or, you may increase the tooth count and gain speed and loose lugging power (torgue).
Energy remains in equalibrium; The energy of a running chainsaw can be changed to heat, light, sound, or creat combustion by products that themselves contain energy. You lift a log with your loader, you have expended horsepower, but much of the energy still exist as potential energy in the lifted log. (I guess I have digressed. I will quit.)
Torque is technically not a measure of force thru distance, it is mearly force thru an arc. It can be static torque as when you hang a one pound weight from a lever at 3:00 o'clock one foot from the center line of a shaft (you must balance at 9 o'clock to offset the weight of the arm) Then you would have 1 (one) foot pound of static torgue, no movement distance required. Again torque is just force applied through and arc. No motion is implicite in its definition. If it helps you to think of torque in association with distance, that is o.k., but just understand that there needs to be no movement for torque to exist.
RPM should be self explanatory.
Horesepower is a force appled over a distance in a given time. (the key words here being distance and time) Horsepower has three elements; force or torque if it is thru an arc , distance , and time.
Horsepower is a measure of work done in a defined time. You could pull on the end of an 18 " breaker bar on a stuck rusted 1 inch bolt for 5 minutes and have done no work in scientific terms. Until you apply the torque thru a distance all you have done is apply force, no work, no horsepower.
James Watt defined horsepower by experimentally determining that mine ponys could do 22,000 foot- pounds of work in a minute. He mutiplied that times 1.5 to get 33,000 which he estimated a horse cound do. The figure stayed with us.
Horsepower is also commonly expressed in KW (metric) There is .746 kilowatts in one horsepower. I'll stay away from the minor difference between Dutch (DIN) and English horsepower.
Glens give a good practical answer.
Someone will surely dive into the math on this, some student of Sir Isaac.
Gearing (or mechanical advantage) mutiplies torque or speed.
Now lets get into the chansaw world; you may decrease your sprocket tooth count and get more torque (luggung power) and loose speed. Or, you may increase the tooth count and gain speed and loose lugging power (torgue).
Energy remains in equalibrium; The energy of a running chainsaw can be changed to heat, light, sound, or creat combustion by products that themselves contain energy. You lift a log with your loader, you have expended horsepower, but much of the energy still exist as potential energy in the lifted log. (I guess I have digressed. I will quit.)
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When most people refer to torque what they are really describing is a nice flat low rpm hp curve.
Glens, your short/long rod example is quite true when it comes to 4 strokes, but the watters become muddy when the same is applied to two strokes. Look at the bore abd strokes for any 250cc two stroke dirtbike. Not torquey engines, but they have under square engines. With a two cycle the port timing is the best indicator of HP and where it falls on a rpm graph.
Glens, your short/long rod example is quite true when it comes to 4 strokes, but the watters become muddy when the same is applied to two strokes. Look at the bore abd strokes for any 250cc two stroke dirtbike. Not torquey engines, but they have under square engines. With a two cycle the port timing is the best indicator of HP and where it falls on a rpm graph.
Tzed250
Addicted to ArboristSite
Rice huh?
Glens, when you said Harley vs. rice grinder, I am sure you meant Harley(barely qualifies as a water pump engine) vs. Honda, Kawasaki, Suzuki, Yamaha(precision engineered, oil tight, long lasting, high output).
Glens, when you said Harley vs. rice grinder, I am sure you meant Harley(barely qualifies as a water pump engine) vs. Honda, Kawasaki, Suzuki, Yamaha(precision engineered, oil tight, long lasting, high output).
tony marks
Addicted to ArboristSite
so all our figures depend on mr. watt being correct. and no way he was.besides a big draft horse could pull 3-4 ponies with little trouble.so assuming im rite [and i will]. all the figures regarding
hp and the rest are incorrect. making me smart as any of u.
hp and the rest are incorrect. making me smart as any of u.
That was a typo, TZ. I meant <i>Hardly</i>, as in Hardly Ableson.
It's really hard to try to condense everything on a topic like this. There's so much that can be said. I think between all of us, it's a pretty good set of Cliff's notes.
Doug, are you familiar with http://www.hpmuseum.org/?
I was late to the game. I've got a 32SII, 42S, and a couple of 48's (got the second one for 25 bucks new without manual or pocket reference, but with soft case after the warranty period for the last of the retail supply was finished). The ROM image running in my x48 was actually dumped from my calc, though they are all freely available (as well the 48G series [which x48 also runs, and with the proper face]) now, at http://www.hpcalc.org/, along with Windows versions of emulators for the less fortunate. The 32 is great for use on the construction site because of it's format and with it's feature to display results in fractions. You can set it to return them in 16ths and either leave it in those units or reduce the fraction. A little triangle points up or down to indicate if the result is actually more or less than represented. A flyer came in the box saying to not use the feature because something about it wasn't quite right, but I've never had rafters or stringers figured wrong as a result. And I love how the T register replicates itself on the fixed-stack models. Want to mark a 16 foot 2×10 every 10.38 inches? Load up the stack with 10.38 and keep hitting +.
RPN (and RPL) are definitely superior. But they make me look like an idiot every time I go to use a TI (alright, where's the enter key?, or you get the first result, then key in the next figure and hit × and nothing happens, plus you have to go and fetch the first result again). The thing I've always disliked about them (any calculators, really) is the simplistic rounding method; .375 and .625 should become .38 and .62, not .38 and .63, for obvious reasons. The algorithm isn't difficult so I don't understand the oversight, or at least the missing option (maybe the last semi-real HP model, HP49, offers it).
You do know that the new HP calculators since the merger are rebadged Taiwan-designed junk, don't you? Better hang on to those double-shot key units...
Tony, he may have been largely arbitrary, but the result is still good for comparative purposes.
It's really hard to try to condense everything on a topic like this. There's so much that can be said. I think between all of us, it's a pretty good set of Cliff's notes.
Doug, are you familiar with http://www.hpmuseum.org/?
I was late to the game. I've got a 32SII, 42S, and a couple of 48's (got the second one for 25 bucks new without manual or pocket reference, but with soft case after the warranty period for the last of the retail supply was finished). The ROM image running in my x48 was actually dumped from my calc, though they are all freely available (as well the 48G series [which x48 also runs, and with the proper face]) now, at http://www.hpcalc.org/, along with Windows versions of emulators for the less fortunate. The 32 is great for use on the construction site because of it's format and with it's feature to display results in fractions. You can set it to return them in 16ths and either leave it in those units or reduce the fraction. A little triangle points up or down to indicate if the result is actually more or less than represented. A flyer came in the box saying to not use the feature because something about it wasn't quite right, but I've never had rafters or stringers figured wrong as a result. And I love how the T register replicates itself on the fixed-stack models. Want to mark a 16 foot 2×10 every 10.38 inches? Load up the stack with 10.38 and keep hitting +.
RPN (and RPL) are definitely superior. But they make me look like an idiot every time I go to use a TI (alright, where's the enter key?, or you get the first result, then key in the next figure and hit × and nothing happens, plus you have to go and fetch the first result again). The thing I've always disliked about them (any calculators, really) is the simplistic rounding method; .375 and .625 should become .38 and .62, not .38 and .63, for obvious reasons. The algorithm isn't difficult so I don't understand the oversight, or at least the missing option (maybe the last semi-real HP model, HP49, offers it).
You do know that the new HP calculators since the merger are rebadged Taiwan-designed junk, don't you? Better hang on to those double-shot key units...
Tony, he may have been largely arbitrary, but the result is still good for comparative purposes.
Fish
Tree Freak
Wow, I am impressed! You guys really know your psychics!
The psychics I know best are the ones working for that Jamaican gal. I call them every time I'm about to make a post here and tell them what I plan to say. They go over every word with me, and it only costs $3.95 per minute!
Glen
Glen
Tony Snyder
Addicted to ArboristSite
What are psy-chics, those telephone advice gals?
dbabcock
Hi Tech Redneck
Beavergirl is the mother of all psy-chics.
ClearH20Scott
ArboristSite Operative
I know this may raise thorns, but, what the heII are RPM'S, I
was always taught that it is revolutions per minute, not revs
per minutes, this brings about the whole RBI baseball thing,
just something to piss and moan about.........Happy Easter's.
Have a happy Good Friday's.
was always taught that it is revolutions per minute, not revs
per minutes, this brings about the whole RBI baseball thing,
just something to piss and moan about.........Happy Easter's.
Have a happy Good Friday's.
