912 ULS Crankshaft Nut Torque Question

Hello Todd

The protocol is to use the newest manual for updated data.  The latest release shows 300 NM and Loctite.

Cheers

Thank you Wizard.

Using the latest value was my inclination but I just wanted to be sure that I wasn't missing something as the difference in the values was so large.   The site might want to add a note to the gearbox removal - installation video that the torque value has changed.

Thanks again for the quick reply.

Hi RW,

A couple of questions.

What was wrong with the 150 ft/lbs? Did Rotax have some nuts come loose? I haven't heard of any coming loose using 150 ft/lbs and Loctite 648 green sleeve retainer. Rotax used this torque setting for many years. What made them change?  Most people don't have the ability to get to 221 ft/lbs. 

Is there any chance of bending the crankcase locking pin?

Since I'm one of these science based analytical types I'm just curious about the inner workings here.

"What was wrong with the 150 ft/lbs? Did Rotax have some nuts come loose?"

Roger, the answer is yes.  i actually think some were never installed correctly in the first place.  That said the value for the size and thread is at the top end for that part and personally have not had an issue installing one to the new torque.  The locking pin works fine.  

Cheers

If the 300nm / 221 ft lbs is beyond the limits of ones torque wrench, how about using a torque extension and the math to calculate it out?

Two purposes, A) it is going to be like using a cheater pipe and B) a calibrated torque wrench (ratchet) is most accurate in its mid range so if a 'technician' is using a 200 ft lb 1/2" torque ratchet at max range and then just going a 'little more' it really is just a guess.

At very least I suppose they know they likely got at least 190+

I would only use the Rotax P/N locking pin for this and not an improvised grade 8 bolt imitation... A good many of us are builders and therefore 'makers'. My first locking pin for testing the gearbox clutch was just that. 

[My kids never realized that shampoo and toothpaste came in HUGE size containers until they went off to college...]