Crank bolt 200Nm plus 180 degrees, how does this work?

[Jonas_R]

Hi,

Running into so small problems.

I can seem to find a torque wrench that goes up to more than 400Nm.

I know that you can thighten it to 200 Nm + 180 degress. Does this mean that you set the torque wrench to 200Nm thigthen it and then give it 180 degress more?

If yes is it then possible to thighten it to say 300Nm and then + 90 degress that would give 425Nm.

Assuming that 180 degress = 250 Nm then that it is 0,72 Nm/degree and when thighten it to 300 Nm

0,72 Nm/degree x 150Nm = 108 degress.

So that would be 300Nm + 108 degress or 400Nm + 36 degress? Or I'm wrong in this assumptions?

[Smiley]

With the special vag tool torque extender vag2079 you can use 'only' 350nm.

[Rusty]

When I did my crank bolt we used a 0.5m piece of scaffold bar and a 60kg woman

[Jonas_R]

@Andy: Yeah I know that I could use a 45 kilo something and a 1 meter bar But that has to be horizontal then,right?

@Smiley: Yeah but that takes time to get as well, going on holiday tomorrow and wanted to have the bolt done today.

[Rusty]

Yup, horizonal is correct based on the direction of gravity.

[Jonas_R]

So you just place the bar horizontal and the add the 45 kilo?

[Rusty]

Yup, thus exerting a force of 45*9.81= 441Nm, thankfully you should be able to very easily judge by eye within 10 degrees so as cos(10deg) = 0.98 you'll get 0.98*441 = 432Nm ish minimum. Remeber that there is sticktion to overcome so best to try and do it in one go or rock gently to help it on its way.

[Jonas_R]

Yeah think I will use the torque wrench upto the the 400 Nm and then do that last 50Nm with the weight.

Do you know if the 200Nm +180 degress method is just as good? Seems fairly easy to do.

[Rusty]

Normally you use angle measurements on stretch bolts to make the bolt plastically deform and then the tightening force is dictated by the Fx curve of the bolt, not the torque. You use an angular measurement (rather than a torque) becuase at the point of plastic deformation the force required to stretch the bolt (and thus torque) either plateau or drop off a touch and so you'd be turning until the bolt snapped!

I suggest that you use the weight method, worked well for me, I'm sure you can use roatation but I don't know the calcs.

[S2central.net]

200Nm plus 180 degrees is easy and reliable... Its what Audi recommend in the factory manual - I didn't make it up.

FOrget the 2079 torque multiplier unless you have one - its a red herring.

[Jonas_R]

Yeah the 200 Nm + 180 degrees seems easy, but is it correct that I just torque it up 200 Nm and then turn the bar 180 degrees?

[S2central.net]

YES - and you can do the 180 in more than one go if you like... 2 x 90 or 3 x 60 - whatever you have clearance for...

Make sure with paint marks on the angle you need and do the tightening smoothly - not with jerky action... and make sure the crank is nicely locked up each time.

[Jonas_R]

This is good news
Now I can get that bolt torque and get on with my holiday in London tomorrow..
Thanks

[EspenW]

200nm + 180 deg is interesting news.

You can get a torque angle meter (vinkelmåleskive Dkr 109 at Biltema) that takes the guesswork out of getting the right angle.

[4WheelDrifter]

When I did my crank bolt we used a 0.5m piece of scaffold bar and a 60kg woman

Interesting... I use a 46kg woman and a 1m scaffold tube.
Unless you're trying to offend my lady friend?

200Nm + 180º will be a good way to double check. Although it will require more effort on my part.