Torque conversion.
Discussion
Can't do maths on a Sunday afternoon, so need some help on this one.
Yamaha say to tighten the head bearing on my bike to 52NM using a torque wrench set at right angles to a C spanner
Part of me thinks the angle of the wrench to the C-spanner shouldn't matter, as you're applying a torque at that point, but if you used a meter long wrench and applied 52N to the end of it, the torque at the nut would vary with the angle as the 52N is constant but the lenght is 1 meter +- the length of the C-spanner
Basically what I'm wondering is if I were to get a socket made up that sits on the castelated nut, thus applying the torque directly to the centreline of the nut, would it still be 52NM?
Yamaha say to tighten the head bearing on my bike to 52NM using a torque wrench set at right angles to a C spanner
Part of me thinks the angle of the wrench to the C-spanner shouldn't matter, as you're applying a torque at that point, but if you used a meter long wrench and applied 52N to the end of it, the torque at the nut would vary with the angle as the 52N is constant but the lenght is 1 meter +- the length of the C-spanner
Basically what I'm wondering is if I were to get a socket made up that sits on the castelated nut, thus applying the torque directly to the centreline of the nut, would it still be 52NM?
The torque wrench has to be at right angles to the C-spanner main axis (i.e. the line through the C-spanner 'handle' - I hope the socket/hole on the C-spanner is aligned to it!!), if not, you'll have a force now acting not at 90 degrees to the C-spanner main axis, so you'll have to figure out what your resolved Torque at 90 degrees is, and adjust your torque wrench setting accordingly.
You could make up a socket to fit over the nut and torque it to 52NM and that would achieve exactly the same effect as using the torque wrench attached to a C-spanner in the suggested manner. I suspect it's easier to obtain the C-spanner, which is why it's in the manual.
Of course, it doesn't matter to the nut how long your Torque wrench is, as long as you can set the lock to 52NM, and it clicks at that setting, the torque wrench can be 30cm long or 300cm long - it just affects ease of use by you.
Edit for the above paragraph - it doesn't matter how long your torque wrench is, on the handle side of the torque setting device
You could make up a socket to fit over the nut and torque it to 52NM and that would achieve exactly the same effect as using the torque wrench attached to a C-spanner in the suggested manner. I suspect it's easier to obtain the C-spanner, which is why it's in the manual.
Of course, it doesn't matter to the nut how long your Torque wrench is, as long as you can set the lock to 52NM, and it clicks at that setting, the torque wrench can be 30cm long or 300cm long - it just affects ease of use by you.
Edit for the above paragraph - it doesn't matter how long your torque wrench is, on the handle side of the torque setting device
Edited by coanda on Sunday 23 September 12:55
Edited by coanda on Sunday 23 September 12:56
Edited by coanda on Sunday 23 September 16:52
coanda said:
The torque wrench has to be at right angles to the C-spanner main axis (i.e. the line through the C-spanner 'handle' - I hope the socket/hole on the C-spanner is aligned to it!!), if not, you'll have a force now acting not at 90 degrees to the C-spanner main axis, so you'll have to figure out what your resolved Torque at 90 degrees is, and adjust your torque wrench setting accordingly.
You could make up a socket to fit over the nut and torque it to 52NM and that would achieve exactly the same effect as using the torque wrench attached to a C-spanner in the suggested manner.
So it's the same torque at 90 degrees and 0 degrees (ie on top), but less in-between?You could make up a socket to fit over the nut and torque it to 52NM and that would achieve exactly the same effect as using the torque wrench attached to a C-spanner in the suggested manner.
Simpo - I think you have the wrong end of the stick/torque wrench there!
What matters here is the orientation of the Torque wrench and the C-spanner only.
Quick thought experiment (because I can't be arsed to do it in GIMPShop.....)
If the C-spanner is attached to the torque wrench at an angle of 90 degrees to the wrench handle, there is no further offset in the direction of the handle - so long as a line running down the C-spanner handle passing through the middle of the socket on the handle should also pass through the centre of the C section.
If we re-arrange the C-spanner in such a way as it's at an angle of 45 to the wrench handle, we now have extra distance in the direction of the wrench handle. The C-spanner has now added to the wrench handle length on the other side of the torque setting mechanism. This will now alter the applied Torque by a given amount (ratio of lengths) over and above the torque setting mechanism value.
Really, it's all tied in to making sure 52NM is actually applied to the nut. You can either do that by:
1. putting the torque measuring device directly over the centre of the nut you are tightening and tightening it that way, or,
2. you can translate the torque measuring device to one side, keeping the centre of the torque measuring device and the centre of the nut in line. At the same time, making sure the torque wrench handle is perpendicular to a line joining the centre of the torque measuring device and the centre of the nut.
Its the same thing, as there is no extra offset in the direction of the moment arm.
I hope that make some sense?
What matters here is the orientation of the Torque wrench and the C-spanner only.
Quick thought experiment (because I can't be arsed to do it in GIMPShop.....)
If the C-spanner is attached to the torque wrench at an angle of 90 degrees to the wrench handle, there is no further offset in the direction of the handle - so long as a line running down the C-spanner handle passing through the middle of the socket on the handle should also pass through the centre of the C section.
If we re-arrange the C-spanner in such a way as it's at an angle of 45 to the wrench handle, we now have extra distance in the direction of the wrench handle. The C-spanner has now added to the wrench handle length on the other side of the torque setting mechanism. This will now alter the applied Torque by a given amount (ratio of lengths) over and above the torque setting mechanism value.
Really, it's all tied in to making sure 52NM is actually applied to the nut. You can either do that by:
1. putting the torque measuring device directly over the centre of the nut you are tightening and tightening it that way, or,
2. you can translate the torque measuring device to one side, keeping the centre of the torque measuring device and the centre of the nut in line. At the same time, making sure the torque wrench handle is perpendicular to a line joining the centre of the torque measuring device and the centre of the nut.
Its the same thing, as there is no extra offset in the direction of the moment arm.
I hope that make some sense?
Edited by coanda on Sunday 23 September 16:50
That's what I was trying to say with the 1 meter +- C-spanner length example, which makes perfect sense to me. but what I can't get my head around is how that relates to just a torque at the offset point. Imagine you had a flywheel and you braked it to give the torque, there's no directional component to it so how do you translate the torque at the flywheel to the torque at the offset position?
ker up and move on 
This has just cropped up again on another forum, and I realised I didn't get my head around it the first time.
Someone found this calculator http://www.cncexpo.com/TorqueAdapter.aspx
My immediate thought is why the hell is L relevant? The torque wrench should be set to trip when a given torque is applied at the hinge point (+), so why would it matter if the wrench was 300mm long or 3m long?
Can anyone explain spikeyhead's comment as to how it's increasing the effective length?
Someone found this calculator http://www.cncexpo.com/TorqueAdapter.aspx
My immediate thought is why the hell is L relevant? The torque wrench should be set to trip when a given torque is applied at the hinge point (+), so why would it matter if the wrench was 300mm long or 3m long?
Can anyone explain spikeyhead's comment as to how it's increasing the effective length?
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