Rotax ring mount to engine M10 bolts

[Blueadventures]

There’s no trouble drilling the bolts. The Allen head bolts that hold the ring mount to the engine are seated deep in those sockets shown in the picture. 

 

Yep agree / understand.  Sometimes there is enough tolerance to allow thin lock wire. past allen wrench in the cap head and then between the tube.  Case by case matter.  Cheers and thanks for comment.

 

 

[ruffasguts]

Why not just do it as the manufacturer says

 

 

[skippydiesel]

Yep agree / understand.  Sometimes there is enough tolerance to allow thin lock wire. past allen wrench in the cap head and then between the tube.  Case by case matter.  Cheers and thanks for comment.

 

 I am pleased you think my suggestion may be a solution, however dont quit understand how the lock wire  needs to go "past  allen wrench"  - You would be torquing down the bolts first, then applying the lock wire (after removing the allen key)

 

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[M61A1]

One more point - use the aircraft manufacturer recommended or if not available, bolt approved torque settings.

 

The way it shows in the previously posted image is the manufacturers approved procedure and given that none of the other crankcase bolts fall out, it should be fine.

 

The only mounts I know of that have ever come loose are ones done similarly to your description ( on a different style mount) with longer bolts  but with a rubber mount and a bush. While it may have actually been the fault (poor installation) of the original installer, I can see how the stackup of spacers could transfer the load further out on the bolt, introducing a bending load instead of shear.

 

 

[skippydiesel]

The way it shows in the previously posted image is the manufacturers approved procedure and given that none of the other crankcase bolts fall out, it should be fine.

 

The only mounts I know of that have ever come loose are ones done similarly to your description ( on a different style mount) with longer bolts  but with a rubber mount and a bush. While it may have actually been the fault (poor installation) of the original installer, I can see how the stackup of spacers could transfer the load further out on the bolt, introducing a bending load instead of shear.

 

We might be indulging in topic drift here, however I very much doubt that snug fitting  (bolt shaft & recess) custom made spacers, correctly torqued, will have any significant "transfer of  loads further out" and the piece of mind that being able to safety wire the bolts will bring, would be worth it in my book.

 

 

[M61A1]

Who cares about thread drift......

 

Just out of interest, how much torque do you reckon it would take to break a standard 0.032" lockwire on a 10mm allen head bolt?

 

According to the Loctite TDS the breakout for a 10mm bolt with a nut, pre-torqued to 5 NM (not one screwed into a deep thread) is 24 NM.

 

 I reckon 24 NM would snap a lockwire like it wasn't there.

 

Not saying a lockwire isn't good, but don't underestimate the chemical locking methods. They also seal out corrosion if done properly, 

 

 

[Blueadventures]

 I am pleased you think my suggestion may be a solution, however dont quit understand how the lock wire  needs to go "past  allen wrench"  - You would be torquing down the bolts first, then applying the lock wire (after removing the allen key)

 

"

 

That's right.  some times on the larger allen heads you can loop the thin lock wire through in a long loop.  insert the allen key and torque up. Then do the twists and safety onto the frame, etc. The lock wire is secured after torquing the cap screw / bolt up.  Cheers