Adjusting torque value
So, there are a number of factors that suggest that you should adjust your torque setting to compensate for various factors here.
First, even if you are torquing the nuts, you have the friction associated with the locking feature that is above and beyond the thread friction that is included in conventional torque specs.
Second, if you are torquing the bolt heads rather than the nuts, you have the friction of the bolt head seating area, plus the bolt shank area turning in its hole.
So here is what I do: Loosen the bolt just a bit, not enough to make it actually loose, just take some of the preload off. Then, measure the torque required to turn the bolt at all. With a beam type torque wrench, this is easy. With a clicking type torque wrench, you will have to iterate, working up to the point where the bolt just starts turning before the wrench clicks.
Either way, note the torque value that gets the bolt turning.
Now, add that to the specified torque setting, and torque the bolts to that value, unless one notable exception below.
This technique compensates for all of the turning friction, including the nut thread friction. On the other hand, it is only including the head contact friction when the bolt is not fully tight. So I figure these two effects cancel. But you could also find an alternative torque setting that assumes lubricated threads rather than dry threads and use that as the base, plus the measured friction torque.
The purpose here is to establish a proper tension pre-load in the bolt. My bet is that virtually everyone is a bit under-torqued because of the friction torque being higher than normal. Add to that the conservatism that NAS close-tolerance bolt recommended torque levels are WAY below normal engineering practices that call for pre-loads of 60--80% of bolt yield stress.
So I have no concerns about getting the torque a little high because of the procedure described above.
Now the one caveat, as mentioned above: Assuming the U-803 brackets have been fitted properly, there should be a small gap between the U-803 bracket and the U-805 wear plate. As you approach the target torque, you must be sure that gap does not close up. If you see it close up at or before you get to the normal specified torque, I would grind some material off the U-803. If you get somewhere in between the normal specified torque and the target torque based on the above, then I would just stop there.
It is frustrating that the U-803 are as flexible as they are, limiting the amount of bolt pre-load that can be acheived without bending them. I have made some alternative U-803 brackets that have a thicker strap over the gear leg, and a counterbore to allow a NAS hex head to fit so the same length bolts can be used, and no additional fairing over bolt heads is needed.
I haven't installed those yet. Anyone that would like the drawing of that modified U-803 should PM me. I made them from 4340 steel.
