(Torque x RPM) ÷ 5,250 = Horsepower
#11
01-18-2016 | 07:35 PM
Seasoned HDF Member
Joined: Jan 2006
Posts: 11,369
Likes: 2,867
From: Charleston, SC
The rpm where the peak is achieved doesn't matter because the lines don't have to be flat, they can be convex or concave. I have had this same conversation before. It's just not cut an dried as a simple math equation. If it was then every bike that made peak tq @ 3000 rpm and had x tq at that peak would have the exact same hp at the exact same rpm as the other bike.
It's math, a specific value times another specific value should always return the same given value.
Change any of the two values and you get a different result.
2x5=10 on one calculator should be the same on another calculator right?
I'm probably just not getting what you're saying.
Last edited by lp; 01-18-2016 at 07:38 PM.
#12
01-18-2016 | 09:56 PM
Ultimate HDF Member
Joined: Mar 2012
Posts: 6,129
Likes: 141
From: Santa Cruz
Torque has nothing to do with speed. It is a measurement of rotational force, no matter engine speed. It may be different at different engine speeds but speed has nothing to do with the measurement. A steam engine has maximum torque at zero rpm. HP (a unit of power equal to 550 foot-pounds per second) is a mathematical calculation: (Torque x RPM) ÷ 5,250. Because 5250 is the constant in the calculation, TQ and HP will always be the same at 5250 RPM (if the engine/motor will turn that fast). Torque is measured at each rpm to "plot" a torque graph/line. Then Horsepower is calculated at each rpm to "plot" the HP graph/line. Torque is a measurement of force. Horse power is a calculation of the rate at which work is done. I won't start the which is most important, HP or TQ thing...
Last edited by 0ldhippie; 01-18-2016 at 10:17 PM.
#14
01-19-2016 | 05:15 AM
Seasoned HDF Member
Joined: Nov 2006
Posts: 5,499
Likes: 1,669
From: East Coast, USA
The 5252 comes from a unit conversion due to converting a rotational force (torque) to a power measurement (force * time)
James Watt determined that a horse could turn a mill wheel 144 times in a hour (or 2.4 times a minute).
The mill wheel was 12 feet in radius.
Remember Circumference = pi * diameter
So the horse traveled = pi * 2 * radius or
distance: 2.4 * pi * 2 * 12 in a minute
Watt also estimated that the horses pushed the shafts with a force of 180 pounds. It's unclear how he measured this.
P = W/t --> Power = work / time
W = F * d ----> Work = force * distance
P = W/t = (F * d)/t = (180 lbf * 2.4 * pi * 2 * 12ft) / 1 min = (32572 lbf ft) per min
So what we have is that Watt deduced that a mill horse could push 32,572 pounds one foot in one minute!
Watt rounded this number up to an even 33,000 foot pounds per minute
So 1 HP = 33,000 ft-lb/min
Torque = r x F
so
P = (F * d)/t = [(Torque/r) * d]/t
distance = radius × angular distance (for a rotating object)
distance = speed × time = radius × angular speed × time
back to our power definition, and substituting for rotating distance
P = (F * d)/t = [(Torque/r) * d]/t = [(Torque/r) x (r * angular speed * t)]/t
The radius r and time t have dropped out of the equation.
P = torque * angular speed
The circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. If the rotational speed is measured in
revolutions per unit of time, the linear speed and distance are increased proportionately by 2 * pi
P = torque * 2 * Pi * rotational speed
The above equation gives power in foot pounds-force per minute. The horsepower form of the equation is then derived by applying the
conversion factor 33,000 ft-lbf/min per horsepower:
P = torque * 2 * Pi * rotational speed [(ft-lbf)/min] x horsepower / [33,000 (ft-lbf/min)]
5252 approx 33,000 / (2 * pi)
See the link below for a better explanation
https://en.wikipedia.org/wiki/Torque
James Watt determined that a horse could turn a mill wheel 144 times in a hour (or 2.4 times a minute).
The mill wheel was 12 feet in radius.
Remember Circumference = pi * diameter
So the horse traveled = pi * 2 * radius or
distance: 2.4 * pi * 2 * 12 in a minute
Watt also estimated that the horses pushed the shafts with a force of 180 pounds. It's unclear how he measured this.
P = W/t --> Power = work / time
W = F * d ----> Work = force * distance
P = W/t = (F * d)/t = (180 lbf * 2.4 * pi * 2 * 12ft) / 1 min = (32572 lbf ft) per min
So what we have is that Watt deduced that a mill horse could push 32,572 pounds one foot in one minute!
Watt rounded this number up to an even 33,000 foot pounds per minute
So 1 HP = 33,000 ft-lb/min
Torque = r x F
so
P = (F * d)/t = [(Torque/r) * d]/t
distance = radius × angular distance (for a rotating object)
distance = speed × time = radius × angular speed × time
back to our power definition, and substituting for rotating distance
P = (F * d)/t = [(Torque/r) * d]/t = [(Torque/r) x (r * angular speed * t)]/t
The radius r and time t have dropped out of the equation.
P = torque * angular speed
The circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. If the rotational speed is measured in
revolutions per unit of time, the linear speed and distance are increased proportionately by 2 * pi
P = torque * 2 * Pi * rotational speed
The above equation gives power in foot pounds-force per minute. The horsepower form of the equation is then derived by applying the
conversion factor 33,000 ft-lbf/min per horsepower:
P = torque * 2 * Pi * rotational speed [(ft-lbf)/min] x horsepower / [33,000 (ft-lbf/min)]
5252 approx 33,000 / (2 * pi)
See the link below for a better explanation
https://en.wikipedia.org/wiki/Torque
Last edited by LQQK_OUT; 01-19-2016 at 06:19 AM.
#17
01-19-2016 | 09:33 AM
Road Warrior
Joined: Apr 2013
Posts: 1,295
Likes: 481
From: St Louis
I always wondered why torque and horsepower cross at 5,250 RPM's so today I googled it.
http://www.motorcyclepowersportsnews...s-talk-torque/
The typical chassis dyno measures how quickly the test bike can accelerate a heavy steel drum – so it’s actually measuring torque (acceleration)
http://www.motorcyclepowersportsnews...s-talk-torque/
The typical chassis dyno measures how quickly the test bike can accelerate a heavy steel drum – so it’s actually measuring torque (acceleration)
umm not exactly. I am going to go all physics on you here.
Torque is twisting force. It is a measure of the force available to turn a shaft or an axle under resistance.
#18
01-19-2016 | 09:37 AM
Road Warrior
Joined: Apr 2013
Posts: 1,295
Likes: 481
From: St Louis
The 5252 comes from a unit conversion due to converting a rotational force (torque) to a power measurement (force * time)
James Watt determined that a horse could turn a mill wheel 144 times in a hour (or 2.4 times a minute).
The mill wheel was 12 feet in radius.
Remember Circumference = pi * diameter
So the horse traveled = pi * 2 * radius or
distance: 2.4 * pi * 2 * 12 in a minute
Watt also estimated that the horses pushed the shafts with a force of 180 pounds. It's unclear how he measured this.
P = W/t --> Power = work / time
W = F * d ----> Work = force * distance
P = W/t = (F * d)/t = (180 lbf * 2.4 * pi * 2 * 12ft) / 1 min = (32572 lbf ft) per min
So what we have is that Watt deduced that a mill horse could push 32,572 pounds one foot in one minute!
Watt rounded this number up to an even 33,000 foot pounds per minute
So 1 HP = 33,000 ft-lb/min
Torque = r x F
so
P = (F * d)/t = [(Torque/r) * d]/t
distance = radius × angular distance (for a rotating object)
distance = speed × time = radius × angular speed × time
back to our power definition, and substituting for rotating distance
P = (F * d)/t = [(Torque/r) * d]/t = [(Torque/r) x (r * angular speed * t)]/t
The radius r and time t have dropped out of the equation.
P = torque * angular speed
The circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. If the rotational speed is measured in
revolutions per unit of time, the linear speed and distance are increased proportionately by 2 * pi
P = torque * 2 * Pi * rotational speed
The above equation gives power in foot pounds-force per minute. The horsepower form of the equation is then derived by applying the
conversion factor 33,000 ft-lbf/min per horsepower:
P = torque * 2 * Pi * rotational speed [(ft-lbf)/min] x horsepower / [33,000 (ft-lbf/min)]
5252 approx 33,000 / (2 * pi)
See the link below for a better explanation
https://en.wikipedia.org/wiki/Torque
James Watt determined that a horse could turn a mill wheel 144 times in a hour (or 2.4 times a minute).
The mill wheel was 12 feet in radius.
Remember Circumference = pi * diameter
So the horse traveled = pi * 2 * radius or
distance: 2.4 * pi * 2 * 12 in a minute
Watt also estimated that the horses pushed the shafts with a force of 180 pounds. It's unclear how he measured this.
P = W/t --> Power = work / time
W = F * d ----> Work = force * distance
P = W/t = (F * d)/t = (180 lbf * 2.4 * pi * 2 * 12ft) / 1 min = (32572 lbf ft) per min
So what we have is that Watt deduced that a mill horse could push 32,572 pounds one foot in one minute!
Watt rounded this number up to an even 33,000 foot pounds per minute
So 1 HP = 33,000 ft-lb/min
Torque = r x F
so
P = (F * d)/t = [(Torque/r) * d]/t
distance = radius × angular distance (for a rotating object)
distance = speed × time = radius × angular speed × time
back to our power definition, and substituting for rotating distance
P = (F * d)/t = [(Torque/r) * d]/t = [(Torque/r) x (r * angular speed * t)]/t
The radius r and time t have dropped out of the equation.
P = torque * angular speed
The circumference of a circle is (2 x pi x radius), there are 2-pi radians in a revolution. If the rotational speed is measured in
revolutions per unit of time, the linear speed and distance are increased proportionately by 2 * pi
P = torque * 2 * Pi * rotational speed
The above equation gives power in foot pounds-force per minute. The horsepower form of the equation is then derived by applying the
conversion factor 33,000 ft-lbf/min per horsepower:
P = torque * 2 * Pi * rotational speed [(ft-lbf)/min] x horsepower / [33,000 (ft-lbf/min)]
5252 approx 33,000 / (2 * pi)
See the link below for a better explanation
https://en.wikipedia.org/wiki/Torque
dear god, I never realized how close the University of Missouri - Rolla came to completely making me lose my mind with this shiznit.
#19
01-19-2016 | 10:55 AM
HDF Community Team
Joined: Nov 2012
Posts: 5,370
Likes: 1,704
From: USA
Horsepower is work, torque is force.
Horsepower was originated by observing that a horse could move ~550 pounds 1 foot in 1 second. Or 33,000 pounds 1 foot in 1 minute (60 seconds).
Torque is a rotational force. To convert torque into work, we need to figure in the rotation.
Geometry and the circumference of a circle. 2*pi*R. Pi = 3.14, so 2*pi=~6.28.
Set R to 1 foot for convenience. You can measure with different units, but it becomes awkward.
So for 1 rotational horsepower, the equation is 33,000 pounds across a 1 foot wrench in 1 rotation.
And what is 33,000 divided by one rotation? 33,000/6.28 = ~5252.
And that's where that number comes from.
Horsepower was originated by observing that a horse could move ~550 pounds 1 foot in 1 second. Or 33,000 pounds 1 foot in 1 minute (60 seconds).
Torque is a rotational force. To convert torque into work, we need to figure in the rotation.
Geometry and the circumference of a circle. 2*pi*R. Pi = 3.14, so 2*pi=~6.28.
Set R to 1 foot for convenience. You can measure with different units, but it becomes awkward.
So for 1 rotational horsepower, the equation is 33,000 pounds across a 1 foot wrench in 1 rotation.
And what is 33,000 divided by one rotation? 33,000/6.28 = ~5252.
And that's where that number comes from.