912 ULS Crankshaft Nut Torque Question

Todd,

We initially received incorrect information, but after verifying with Rotax, we can confirm that the correct torque value is found in the HMM: 300 Nm (221 ft-lbs.)

This means you torqued the hex nut correctly, and no further action is required. We have also updated the previous post to refect this.

VERY sorry for the confusion!

No problem.  I have about 65 hours on my engine since reinstalling the gearbox and had not noticed anything unusual so, obviously, it was not something that would cause an immediate failure.  The weather here has been absolutely miserable since mid-December so I haven't got any flying in.  If the bolt torque I used was incorrect I was going to make sure I corrected that before I started flying again. 

Thanks for checking!

Rotax Owner,

Why did they increase the torque from 147 to 221 ft/lbs. That's a fairly big change. I've never seen or heard of one coming loose when it was torqued to 147 and had Loctite 648 on it.

I have not installed mine yet, but it worries me about such a large increase in torque (1/3). Hope all the other connnecting parts and assemblies can stand the increase ( locking pin, crankshaft threads and nut, crankshaft bearing). If torquing the nut to 147 can cause crankshaft alignment issues, what will 221 cause. How much force will it now take to remove the nut in the future and what will that have on other assemblies? I assume the 147 has been used since 912’s became available? I guess I just worry to much about such a large change without much information.

Hi Steve,

For what it's worth, I torqued mine to 219 ft/lb last year and have not experienced any issues.  The locking pin, threads and nut were all fine and alignment was still good.  So far, it has held up for 65 hours.  I used a digital torque adapter along with the biggest breaker bar I could find so that I could control the torque more precisely as I wold not have to strain to get to the value I wanted.  I bought good tools, studied all available documentation, planned everything out and took my time checking each step.  Everything went fine.

I, too, was concerned about the large variation in the torque values presented in the different manuals - which is why I asked for help here.  It seems that Rotax has confirmed the 221 ft/lb value so I am comfortable with it. 

Hope this helps ease your mind a bit.