Engine Bolt Torque

I have the same set-up on my Eurostar. I don't apply anything to the threads and torque them to 40Nm. On my mounting frame the bolt heads are recessed and so a custom made plastic plug that engages with the hex in the bolt is inserted and held in place with a split pin.

Hi Sean

The important parts, like mount bolts, are called out for the Rotax ring mount.  You can also find this info in the installation manual.  Given the importance of securing the engine you must use bolts that are coated (like Cadmium plating or Dacromat) and must be at least a grade 10.9 metric hardness.  The contact length is also very important, for the main bolts as you are using then need to thread in at least 25mm into the block.  In general terms no anti-seize or lubricant is applied unless specifically called out.  None of the Rotax manuals call for that on the mount bolts.  A check online will get you lots of opinions but little facts on lubricated or unlubricated bolts.  Find the excerpt from the installation manual attached.

Cheers

Thanks Guys,

The black (uncoated) HT steel Allen key head bolts in both aircraft (my only experience) look identical except for the safety wire drillings.

I am a bit surprised that black steel HT bolts into aluminium alloy do not call for some forme of anti seize/corrosion protection/prevention.

I will use the recommended torque settings you have referred to.

Do not confuse the shipping bolts on the engine with what you should use.  Uncoated bolts are a bad idea.  The ones used for shipping on the temporary shipping plate were never intended to be used as mount bolts. (if that is what you were referring to)  If your kit supplier offered uncoated bolts for this purpose then I would be concerned if that is what they want you to be used.  I agree with you in that i personally would not use an uncoated one.  if you want to drill and safety wire them that is your call, especially if it is experimental.  Ask if you kit supplier has any advice for that mount, most just use the torque value for the M10 in the mount. 

Cheers

Rotax Wizard wrote:

Do not confuse the shipping bolts on the engine with what you should use.  Uncoated bolts are a bad idea.  The ones used for shipping on the temporary shipping plate were never intended to be used as mount bolts. (if that is what you were referring to)  If your kit supplier offered uncoated bolts for this purpose then I would be concerned if that is what they want you to be used.  I agree with you in that i personally would not use an uncoated one.  if you want to drill and safety wire them that is your call, especially if it is experimental.  Ask if you kit supplier has any advice for that mount, most just use the torque value for the M10 in the mount. 

Cheers

Shipping bolts??

The engine was already installed with these bolts, just as my last aircraft was. How would I know if they are "shipping bolts"?

Even if they are, my only concern would be using a suitable ant corrosive/ anti seize compound - care to make a recommendation?

I did 700 hrs in my last, Rotax 912 ULS powered aircraft, with exactly the same HT bolts (except for the safety wire holes) - never a problem.

My plans build supplier was not (at the time of plans purchase) supporting Rotax engine installation, so I doubt there would be much help from that quarter.