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JAE 09-12-2014 11:15 PM

Engine Mount Bolts
I made a locking device to prevent the bolts coming out.
1/Purchase qty 4, 5mm bolts approx. 20mm long, Bolt heads should be same size as the hex in the socket headed engine mount bolts.
2/ Fabricate from alloy bar, 4 pieces to the internal diameter of the steel engine mount tube that the engine mount bolts are recessed into and approx. 1/8 in longer than the distance from the head of the bolt to the outside edge of the steel engine mount tube. Thread the centre of the alloy bar plugs with a 5mm tap. Screw the 5mm bolts into the plugs using Locktite.
Ensure the engine mount bolts are Locktited and torqued into the engine.
Install the alloy plug into the engine mount tube ensuring that the 5mm bolt head is engaged into the hex of the engine mount cap bolt.
Using a 1/16in drill, drill a hole through the steel enine mount tube and the alloy plug approx. 1/8in from the outer end of the steel engine mount tube. Install a 1/16 S.S cotter pin through the hole and fold over the tails.
This should prevent the problems of the engine mount bolts coming out.

Dave12 09-13-2014 07:11 AM

Pictures man, pictures!

Buzz J 09-15-2014 04:34 PM

Applause and gratitude for a job well done & request for pics
What a terrific, creative solution to ensure a redundancy factor to this concern for all 12 builders/owners! You put your aircraft engineer experience to work! I'm impressed and very grateful! Possible to get some pics either via this thread or by email? Thank you so very much!

Buzz Jensen

Slane 01-05-2016 11:42 PM

Mounting bolts still holding...
I did the 100 hour ROTAX maintenance check and am happy to report that each of 4 bolts had maintained the 30# torque.

Chopkins 02-24-2016 04:53 PM

That's a very clever solution. Nice one!


LUKLA 12-23-2017 09:14 PM

Rotax torque/chart
Where can I find Torque Chart/Table for 912 ULS?
I could not find any where. If you guys could give me the specific manual and page #. It would save my **** load of time.

Piper J3 12-30-2017 12:18 PM

I searched this thread... trying to find metric allen wrench size to fit the engine mounting cap screws so I can have correct tool at hand when I next remove cowling.

Does anyone know metric allen wrench size?

I'm thinking 3/8" socket extension will allow me to torque bolts once I cut access hole in fiberglass cooling shroud. Am I making correct assumption here?

Thanks in advance...

John-G 12-30-2017 01:51 PM


I purchased a set of inexpensive metric 3/8" drive hex sockets from Harbor Freight. The set had the correct size for the engine mounting hardware ... which, if memory serves me correctly, was 6 mm (but don't hold me to that).

I also purchased the extended ball tip version when they were on sale for around $9.

Happy flying .... after spring thaw LOL

DaleB 12-30-2017 03:47 PM

I seem to recall they were 8mm... but I wouldn't swear to it in court. I used a 3/8 drive like the Harbor Freight link above, with an extension and torque wrench.

John-G 12-31-2017 07:30 AM


Thinking about it Dale is probably right about 8mm being the size for the hex socket needed and it is in the HF hex set.

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