Castelated nuts and torque

[Dorfie]

I have read that castellated nut are often used where some rotation is expected or allowed. I know that we torque the engine mount hardware and secure with cotter pins
I am now unsure what should be done with the rear spar attach hardware as well as the vertical stabilizer front attach point. The plans call for castellated nuts but no mention of torque. I have torqued them per bolt size and thread.
Thanks.
Johan

 

[Mel]

I have read that castellated nut are often used where some rotation is expected or allowed. I know that we torque the engine mount hardware and secure with cotter pins
I am now unsure what should be done with the rear spar attach hardware as well as the vertical stabilizer front attach point. The plans call for castellated nuts but no mention of torque. I have torqued them per bolt size and thread.
Thanks.
Johan

Castellated nuts are used on two different situations. One is where the bolt is subject to rotation. In these cases a specified torque is not required. "Snug" is good. In other cases where the bolt is NOT subject to rotation, the nut should be torqued to standard specifications. Example would be engine mount bolts and wing spar attach.

 

[Toobuilder]

Also need to consider if it is a shear nut or a tension nut. Different torque tables between the two.

 

[Jesse]

In actual practice, torque tables usually have a range. I take it to the low end of the range then to the next hole if they don't line up at the low end.

 

[az_gila]

In actual practice, torque tables usually have a range. I take it to the low end of the range then to the next hole if they don't line up at the low end.

Per AC43.13 - try a different washer if the high end torque value doesn't work...

f. When installing a castle nut, start
alignment with the cotter pin hole at the minimum
recommended torque plus friction drag
torque.
NOTE: Do not exceed the maximum
torque plus the friction drag. If the
hole and nut castellation do not align,
change washer or nut and try again.
Exceeding the maximum recommended
torque is not recommended.

 

[Bill Boyd]

sincere question

Castellated nuts are used on two different situations. One is where the bolt is subject to rotation. In these cases a specified torque is not required. "Snug" is good. In other cases where the bolt is NOT subject to rotation, the nut should be torqued to standard specifications. Example would be engine mount bolts and wing spar attach.

Mel, given the flex in the wing under load cycles, how is the rear spar attach bolt not subject to some small bit of rotation?

 

[Mel]

Mel, given the flex in the wing under load cycles, how is the rear spar attach bolt not subject to some small bit of rotation?

Even thought this bolt "may" rotate a minute amount, it is not "designed" to rotate. This bolt should be torqued to normal specifications.
In this case the castellated nut is used just in case the bolt does rotate not because it is designed to do so.

 

[rvbuilder2002]

Even thought this bolt "may" rotate a minute amount, it is not "designed" to rotate. This bolt should be torqued to normal specifications.
In this case the castellated nut is used just in case the bolt does rotate not because it is designed to do so.

Mel is correct.

The only fasteners on RV's that should not be torqued to normal specs are those that are used as pivot points in the control system (rudder cable ends, etc.)

 

[maniago]

Good question and good answers. Havent had to think about this yet, but will file it away under "things to remember". Excellent!

 

[Walt]

And just to add my 2c..

Anywhere a rod end bearing is used, the bolt is NOT subject to rotation and the fastener should be tightened/torqued accordingly.

Here's an example of rod end bearings I often find 'loose'.

 

[az_gila]

hardware

And just to add my 2c..

Anywhere a rod end bearing is used, the bolt is NOT subject to rotation and the fastener should be tightened/torqued accordingly.

Here's an example of rod end bearings I often find 'loose'.

Walt, should the throttle arm nut even be a castle nut/cotter pin combo as shown?

If it doesn't rotate and is fully torqued down wouldn't an all-metal lock nut be more appropriate?

 

[Mel]

Walt, should the throttle arm nut even be a castle nut/cotter pin combo as shown?
If it doesn't rotate and is fully torqued down wouldn't an all-metal lock nut be more appropriate?

I'm not Walt, but I'll give my opinion. A castle-nut/cotter pin can always be used in place of a lock-nut as long as proper torque rules are applied. In places like this where there is a lot of vibration, it couldn't hurt.

I find it interesting that Walt often finds these bolts loose. I don't often find this. Guess I'll have to start looking a little closer.

 

[Bill Boyd]

Interesting pic

I'm a long way from mounting my next engine and have not had the opportunity thus far to inspect a de-cowled RV-10. I'm certain Van designed that linkage for good reason in a manner quite different from the straight cable-shot to the throttle arm on my -6. But when I look at that set-up, a little voice in my head goes, "Paging Mr. Goldberg to the courtesy phone. Mr. Rube Goldberg..."

Carry on.

 

[Toobuilder]

Good catch. The salient point is relative rotation. If the nut/bolt can rotate relative to the component it is securing (I.E, its a pin connection), then it typically gets a shear (the thin kind) castle nut and a cotter pin with minimal torque.

In the linkage shown above, I use metal lock nuts, fully torqued. Another area I've seen loose is the pivot of the bellcrank. I have seen the scenario where the pivot bushing is narrower than the bellcrank itself and therefore will not allow movement with a fully torqued fastener. A little deressing with a file will take just enough off the crank to allow the bushing to protrude, as it should, and allow full clamp up of the assembly.

 

[Dorfie]

Thanks to all for your input. It has been very educational.
Blessed Christmas to all.
Johan