SonexBuilders.net

As a relative new comer to Imperial measurements and even more incomprehensible AN nuts & bolts.

I am wondering what torque I should apply to the four AN 4 bolts secured by castellated nuts on my Sonex / Rotax engine adapter.

I have already done them up firmly, to the elbow click but am now worried I may have over tensioned them - what could be the ramifications?

Castellated don't get torqued. They are for shear loads where parts need to rotate.

Scott Todd wrote:Castellated don't get torqued. They are for shear loads where parts need to rotate.

Not always true and I don't think that is true in this case. Not every location that a castellated nut is used is subject to rotation. There are places where heat or vibration or a number of other issues can warrant the use of a castellated nut. For those types of conditions where the nut/bolt is not subject to rotation (likely in the motor-mount example being asked above) the nut should be torqued to the same torque as a locking nut (50-70 inch/pounds for AN4). For areas that a nut is used that are subject to rotation (think aileron bell cranks on the Sonex) that nut should be tightened snug but not to exceed the standard torque requirement (50 to 70 inch/pounds for AN4).

If you don't have a copy I suggest buying or downloading a copy of AC 43.13. There is a wealth of information in there that will help you answer questions like this when building.

Keith
#554

Delete. Posted too quickly and didn't finish my thought. Carry on!

Scott Todd wrote:Castellated don't get torqued. They are for shear loads where parts need to rotate.

A castellated nut can be used in any location on an aircraft. They were invented long before self-locking nuts. There are lots of places where standard torque would be applied to a castellated nut. See Keith's post above. I second the recommendation to get a copy of AC 43.13. Downloaded free from the FAA website, or purchase the printed version from EAA or other aviation suppliers. A wealth of info and pretty much required for aircraft construction or maintenance.

Thanks Guys,

FYI I elected to go with castellated nuts because this is a critical part of the engine/airframe, in my mind is demanding of additional security ie split pin or safety wire, above that given by a lock nut. I have used safety wire on the crankcase to bracket bolts and will also drill & safety wire the bolts securing the rubber "Barry mounts"

Torque Max 8 Nm (from your inch pounds).

If I have already over torqued - what action should I take? - discard existing & replace all bolts?

I'll pass this on to the DAR that used nearly those exact words during my recent inspection.

Could not wait, for your DAR, any longer Scott - have ordered new bolts & hopefully gone up in strength from AN4 to NAS6604