What does this mean?

[bernardofeio]

What does this mean?
(in the bmw manual)

Tightening torque:
Conrod bolts
Preload: 20Nm
Tightening angle: 40º+-5´

that you preload the bolts with 20Nm and after rotate them more 40º?

 

[Balders1450]

What does this mean?
(in the bmw manual)

Tightening torque:
Conrod bolts
Preload: 20Nm
Tightening angle: 40º+-5´

that you preload the bolts with 20Nm and after rotate them more 40º?

Ask a dealer!

 

[cookie]

What does this mean?
(in the bmw manual)

Tightening torque:
Conrod bolts
Preload: 20Nm
Tightening angle: 40º+-5´

that you preload the bolts with 20Nm and after rotate them more 40º?

yes. it's a method used for installing stretch bolts.

you can get a tool that fits between the socket and the handle that measures the rotation. not needed really for when something simple like 180 is specced, but 40 is a bit trickier.

 

[bumpmuncher]

Ask a dealer!

aww did you not realise you dont have to go to a dealer to get your bike fixed.

suppose that comes from having a plastic chicken and that canbus fluid stuff LOL

 

[brassmonkey001]

What does this mean?
(in the bmw manual)

Tightening torque:
Conrod bolts
Preload: 20Nm
Tightening angle: 40º+-5´

that you preload the bolts with 20Nm and after rotate them more 40º?

That's exactly what it means. Torque them to 20 Nm and then turn them nearly a quarter of a turn more. A blob of paint on the head of the bolt might help.

 

[(RIP) Proff]

That's exactly what it means. Torque them to 20 Nm and then turn them nearly a quarter of a turn more. A blob of paint on the head of the bolt might help.

ARGHHHHHH
45' is only an eighth of a turn.....

360' in full turn ...

so you mean slightly under an eighth, not quarter turn..

Also I never reuse the bolts, always new, same with driveshaft ones....

 

[(RIP) Kaister]

All bolts that need a specific torque are 'stretch' bolts.

When you tighten a bolt, you stretch it by a certain length - this creates the spring tension in the bolt shank between the thread and the head.

20 Nm takes all the 'slack' out of the joint with no preload, then 40 deg stretches the bolt an exact length by a function of the thread pitch.

Using the angle / stretch technique takes the friction component out of the job and gives a fairly consistent figure, better than a torque wrench

 

[brassmonkey001]

ARGHHHHHH
45' is only an eighth of a turn.....

360' in full turn ...

so you mean slightly under an eighth, not quarter turn..

Also I never reuse the bolts, always new, same with driveshaft ones....

Yes, 1/8th of a turn. Well done Proff, you passed my little test.

 

[bernardofeio]

Thanks to all

And what is the meaning of:

Tightening torque:
Conrod bolts
Preload: 20Nm
Tightening angle: 40º +5º (instead of +-5´)

 

[jimbo]

I did some tests on this sort of thing when at University. Torquing a bolt is not a very accurate way of obtaining a consistant clamping force. Anything like a drop of oil or a little rust on the threads can throw things out a mile.
An initial torque and then a postive angular displacement was far more accurate.

 

[Engineer]

I did some tests on this sort of thing when at University. Torquing a bolt is not a very accurate way of obtaining a consistant clamping force. Anything like a drop of oil or a little rust on the threads can throw things out a mile.
An initial torque and then a postive angular displacement was far more accurate.

If torquing is inaccurate then the initial 20Nm will be inaccurate, so how does the extra 45 degrees make things more accurate?????

 

[cookie]

If torquing is inaccurate then the initial 20Nm will be inaccurate, so how does the extra 45 degrees make things more accurate?????

i suspect achieving a set degree of rotation gets more inaccurate, the more torque applied.