What did you do to your KJ today?

[blek]

6mm 316S/S backing plate with high tensile bolts/washers torqued to 100Nm. Between the Tred's and snatching from the rear, these will be a last resort recovery option and Id never dream of using them without an equalizer strap considering the KJ has a monocoque chassis.

[Stressball]

Originally Posted by camper

6mm 316S/S backing plate with high tensile bolts/washers torqued to 100Nm. Between the Tred's and snatching from the rear, these will be a last resort recovery option and Id never dream of using them without an equalizer strap considering the KJ has a monocoque chassis.

Might I suggest that you fit some kind of locking nut & washer arrangement. It appears that they are not locking nuts that are fitted. I would suggest nylock nuts and even with something like a nordlock washer (otherwise a spring washer). I couldn't make out if there was a spring washer under the bolt head on the earlier photo. Without either of these I'd be surprised if you maintain your tension for long at all. Also a dribble of anti-sieze would be a good idea for future sanity when you refit the new hardware.

[glend]

Yeah that looks ok, sorry for suggesting otherwise but that view was missing. Not sure about nylocks, I've had them back out on my camper trailer axle clamp when pounded by corrugations. But then again you won't have any load on them normally. I honestly can't remember what I used to secure my bar mount in the chassis rails, but It's still rock solid after eight years.
It did have a four hole backing plate on each chassis rail section, if I get some time I will stick the inspection camera in there to have a look.

[blek]

Originally Posted by glend

Yeah that looks ok, sorry for suggesting otherwise but that view was missing. Not sure about nylocks, I've had them back out on my camper trailer axle clamp when pounded by corrugations. But then again you won't have any load on them normally. I honestly can't remember what I used to secure my bar mount in the chassis rails, but It's still rock solid after eight years.
It did have a four hole backing plate on each chassis rail section, if I get some time I will stick the inspection camera in there to have a look.

No need to apologize i appreciate the extra advice incase i missed anything. I dont think nylocks are suitable for high torqued applications? There is a spring washer under the bolt head to maintain tension. If you could have a peak that would be good

[Stressball]

Tightening of bolted joints is a far more complex than one might suspect. There are so many variables and factors to consider. As far as being so set on having 100Nm of torque, I would question things like what diameter bolt are you referring to and what grade fasteners are you using 4.6, 8.8 or 10.9... In questioning the suitability of nylock nuts for high torque application I would say that when comparing nyloc to metic hexagon nuts the proof load stress is pretty much equal at around 800 - 850 Mpa (in a P type nylock anyhow).The nylon insert of a nyloc is only in an extended portion of the nut and just increases the friction required to turn the nut. Reccommended assembly torques ( Bolt tension corresponding to 65% of yield load ) is dependent on both diameter and grade.The amount of tension aimed for in general engineering practice is 65-75% of the minimum elastic capacity (proof load) of the bolt. eg. 109 Nm is recommended for a dia 12mm class 10.9 fastener. The same diameter in an 8.8 is 77Nm and if you are using shitty cheap 4.6 fasteners which I would definitely not recommend, the recommended assembly torque is 30Nm for the same diameter fastener. All these figures are based on 65% of proof load. Remembering that the accuracy of the preloaded measuring method is also a big factor on throwing numbers out there. For example, a torque wrench (which I'm sure is the method you have relied upon) has an accuracy of around +/- 25%. Surface coating/lubrication, thread interference and speed of tightening affect the torque tension relationship in preload. Basically, the best approach is overkill in terms of recovery. It may be the difference of life and death in some instances. Be careful not to over tension fasteners that will only increase their likelyhood of failure. Use locking hardware and my best experience (inc work related requirements) is that locking washers and nuts used together with torque wrenches and torque tables give the best results.

[glend]

What about 'torque to yield' bolts? I hear about them, usually in discussions about KJ CRD cylinder heads, and the need to put new ones in if you remove the old ones. Are they only used in high torque applications like cylinder heads or elsewhere also?

[Stressball]

Glend, in short TTY fasteners were introduced primarily for head applications to target thermal expansion and compression of differing materials ( aluminum heads and cast iron blocks). There is the issue of gasket relaxation that basically means that the change in height results in a loss of tension. Exactly what the TTY concept is designed to target. They have since been implemented into applications beyond this use. Basically, as for deformation of fasteners there is two types - elastic and plastic. Elastic deformation is non permanent and means the fastener will return to its original form and length but plastic deformation occurs and refers to the permanent change of length and form of the fastener upon removal. The TTY is referring to fasteners that reach the plastic deformation state and is why they are single use only. Again, the topic of bolted joints is a complicated one and is why we just do as we are told. The interesting thing is that smaller diameter fasteners with more stretch are better than larger dia fasteners with less stretch. This is why we see head bolts being slender and long.. I hope this helps