He he. Ye got me wi that one, ya wee rascal.Merecat wrote:To quote Captain Montgomery Christopher Jorgensen Scott, Jr.
"Ye canne change the laws "o" physics"
Had to look him up.
Torque
Moderators: slparry, Gromit, Paul
Not forgetting the steam engine.Herb wrote:I am going to go back to the original post.
'Can you have torque without movement'
Yes, of course.
An electric motor produces maximum torque at zero rpm. Imagine a small motor, spinning a small disc which you grip tighter and tighter until the motor stops rotating.
It is still producing force at the contact point with your fingers, hence it is producing torque, because the force is exerted at a distance from the centre of rotation.
I think I was just bored because no one is playing out on the dyno mystery thread.
The welded bolt head.
By loading a spanner on it, is that classed as a torque or not?
It doesn't seem to be a torque about the bolt centre because the force is not trying to rotate the bolt, is it?
I'm talking about as if we'd mig welded the bolt head to the main structure.
I can see how the centre of rotation would shift from the bolt centre to elsewhere on the main structure. What I'm driving at is asking if every case where we apply a force at a distance is classed as a torque?
In other words, every time we apply a force at a distance, is there always, somewhere on the structure, a centre of rotation? I'm quite keen on the welded bolt head scenario because I think maybe it creates an illusion?
By loading a spanner on it, is that classed as a torque or not?
It doesn't seem to be a torque about the bolt centre because the force is not trying to rotate the bolt, is it?
I'm talking about as if we'd mig welded the bolt head to the main structure.
I can see how the centre of rotation would shift from the bolt centre to elsewhere on the main structure. What I'm driving at is asking if every case where we apply a force at a distance is classed as a torque?
In other words, every time we apply a force at a distance, is there always, somewhere on the structure, a centre of rotation? I'm quite keen on the welded bolt head scenario because I think maybe it creates an illusion?
I Think you're thinking yourself round in circles!
In every bolt/nut/ spanner scenario the force is a force X a radius which is Torque.
The force applied to the end of the spanner by arms/legs big FO hammer is linear.
However big or small the nut/bolt, when said torque is applied it will want to rotate around its centre. This point can not move.
It the bolt is welded then the applied torque will have to exceed the shear stress of the weld to rotate the bolt.
In every bolt/nut/ spanner scenario the force is a force X a radius which is Torque.
The force applied to the end of the spanner by arms/legs big FO hammer is linear.
However big or small the nut/bolt, when said torque is applied it will want to rotate around its centre. This point can not move.
It the bolt is welded then the applied torque will have to exceed the shear stress of the weld to rotate the bolt.
Mick
2001 R1100s Frost Blue
Its not going the fastest,
Its stopping the quickest
2001 R1100s Frost Blue
Its not going the fastest,
Its stopping the quickest
Won't welding the head to the surrounding structure cancel out the threaded portion? Suppose we weld just a bolt head, with the threaded portion and shank lopped off. Then load it with a spanner. What kind of force is that?Merecat wrote:?............
In every bolt/nut/ spanner scenario the force is a force X a radius which is Torque.
The force applied to the end of the spanner by arms/legs big FO hammer is linear.
However big or small the nut/bolt, when said torque is applied it will want to rotate around its centre. This point can not move.
It the bolt is welded then the applied torque will have to exceed the shear stress of the weld to rotate the bolt.
In practise each scenario is assessed individually. It depends what you want to do to the object and then the practical way of doing it is then calculated. The welded bolt is a poor example. Applying a force that want to rotate an object about its centre is called torque, doesn't matter where that force is applied to the object. Torque is what you can call an unbalanced force because it only has to overcome the friction in this case, welded or not.
To calculate strength in a structure or the bending of a beam we use as a simple example; clockwise moments = counter clockwise moments. The forces acting on a beam will be either upwards or downwards hence when looking at the beam side on it will want to bend the beam clockwise or counter clockwise. Where the moment is calculated almost the same as torque but here you have to distinguish between spread loads, point loads, shock loads etc.... and the gravitational acceleration, you get the point. You will use this method to calculate the bending in the spanner as you apply the force to rotate the bolt. If the bolt is welded to a piece of metal then you'll want to know if the spanner is sufficient to do the job and you'll compare your calculation to Young's modulus to determine if the tensile strength of the material is up to the job.
If you want to move the object from point A to B then you are most probably going to use acceleration formula for the simple reason that you start at zero velocity and end at zero velocity but somewhere in between you have accelerated to a steady or peak velocity and then decelerated. Note that velocity has got direction and speed vector. Moving the object can be accomplished by applying the force directly, or by using pulleys, capstans, levers (a lever is not a lever unless there is a support or pivot point ie fulcrum), gears to multiply the force, Remember that pulleys and gears are effectively levers and the efficiency is expressed as as a ratio example 2:1.
From all the examples above you can then calculate the energy needed to perform work. In the case of torque you'll use angular acceleration. Or if you know what energy is available to do the job then you can calculate it backwards to determine the size tool needed for the force that needs to be applied.
So draw yourself a picture and visualise the scenario.
To calculate strength in a structure or the bending of a beam we use as a simple example; clockwise moments = counter clockwise moments. The forces acting on a beam will be either upwards or downwards hence when looking at the beam side on it will want to bend the beam clockwise or counter clockwise. Where the moment is calculated almost the same as torque but here you have to distinguish between spread loads, point loads, shock loads etc.... and the gravitational acceleration, you get the point. You will use this method to calculate the bending in the spanner as you apply the force to rotate the bolt. If the bolt is welded to a piece of metal then you'll want to know if the spanner is sufficient to do the job and you'll compare your calculation to Young's modulus to determine if the tensile strength of the material is up to the job.
If you want to move the object from point A to B then you are most probably going to use acceleration formula for the simple reason that you start at zero velocity and end at zero velocity but somewhere in between you have accelerated to a steady or peak velocity and then decelerated. Note that velocity has got direction and speed vector. Moving the object can be accomplished by applying the force directly, or by using pulleys, capstans, levers (a lever is not a lever unless there is a support or pivot point ie fulcrum), gears to multiply the force, Remember that pulleys and gears are effectively levers and the efficiency is expressed as as a ratio example 2:1.
From all the examples above you can then calculate the energy needed to perform work. In the case of torque you'll use angular acceleration. Or if you know what energy is available to do the job then you can calculate it backwards to determine the size tool needed for the force that needs to be applied.
So draw yourself a picture and visualise the scenario.
'Let me check my concernometer.'
noCorvus wrote:Isn't an open ended spanner on a hexagon an example of a fulcrum? Isn't a pipe wrench a fulcrum?Merecat wrote:?.......
I don't see how you can have torque using a fulcrum. A fulcrum is a pivot point.
........
Mick
2001 R1100s Frost Blue
Its not going the fastest,
Its stopping the quickest
2001 R1100s Frost Blue
Its not going the fastest,
Its stopping the quickest
Firstly, thanks for the detailed reply. I'll have to get my head around the beef of it later. For the moment (no pun intended) I'm not understanding the bit above.tanneman wrote:
..........Remember that pulleys and gears are effectively levers and the efficiency is expressed as as a ratio example 2:1.
...........
I consider the efficiency of pulleys or gears as a measure of the mechanical losses. ie: nothing is 100% efficient. If you're putting in 100hp you won't get 100hp out the other end.
Cheers.
He meant "Mechanical advantage"Corvus wrote:Firstly, thanks for the detailed reply. I'll have to get my head around the beef of it later. For the moment (no pun intended) I'm not understanding the bit above.tanneman wrote:
..........Remember that pulleys and gears are effectively levers and the efficiency is expressed as as a ratio example 2:1.
...........
I consider the efficiency of pulleys or gears as a measure of the mechanical losses. ie: nothing is 100% efficient. If you're putting in 100hp you won't get 100hp out the other end.
Cheers.
Al
If I am ever on life support - Unplug me......
Then plug me back in..........
See if that works .....
Then plug me back in..........
See if that works .....
http://en.wikipedia.org/wiki/Torque
The Wikipedia link is interesting. The section on terminology.
Also, further down, they link the use of the term "fulcrum" with torque. Obviously, with regards to shafts or spindles etc, the torque value is calculated from the centreline. This means, by the Wikipedia definition, the fulcrum point is at centreline.
The Wikipedia link is interesting. The section on terminology.
Also, further down, they link the use of the term "fulcrum" with torque. Obviously, with regards to shafts or spindles etc, the torque value is calculated from the centreline. This means, by the Wikipedia definition, the fulcrum point is at centreline.