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-   -   RV-12: Engine Mounting Cap Screws Inspection (https://vansairforce.net/community/showthread.php?t=65020)

jtdehaan 06-30-2012 03:55 PM

Upper right bolt loose
 
During my annual inspection found the upper right bolt completely loose. This is the long engine thru bolt. Could not get bolt started in the threads. Looking in the case, saw the threads messed up. What is my option now? A heli-coil repair seems to be the only way to go.

Jake - s/n 120025 with 176 hours.

MartySantic 06-30-2012 05:29 PM

Quote:

Originally Posted by jtdehaan (Post 674911)
During my annual inspection found the upper right bolt completely loose. This is the long engine thru bolt. Could not get bolt started in the threads. Looking in the case, saw the threads messed up. What is my option now? A heli-coil repair seems to be the only way to go.

Jake - s/n 120025 with 176 hours.

You may be OK. Sight down thru the engine mount frame to the engine. You may have to put a bit of pressure on the frame to get everything aligned. Then try to install the bolting.

Bill_H 07-16-2012 03:44 PM

One more data point for what its worth. Installed the bolts with loctite and 30 ft-lbs. Used torque seal paint as an indicator. Just did my 25 hour check today - no movement of the bolts. Plus everything else under the cowl looks great! Getting ready for OSH 2012.

rv3flier 04-22-2013 08:01 AM

I just arrived home in SW Washington in my new to me RV-12 which I picked up in Stonewall, OK on Friday. On the way I thought I detected an increase in the level of vibration. I attributed it to the carbs probably being out of balance, even though the EGT/CHT's were quite close. Having just stumbled across this thread and with just 100TT on the airplane, I'm sure that these bolts are the likely problem. The first thing I'll be checking today -- and will post what I find.

rv3flier 04-23-2013 06:29 PM

Both bottom bolts were tight. Still haven't checked the top ones yet and have been looking and thinking about John Peck's mod cutting away the top part of the cooling shroud. I wonder if anyone has tried drilling the fiberglass shroud slightly larger than the cap screw diameter. It would seem that you might be able to remove and replace the bolt using 3/8" drive extension with a 6" 7mm allen 3/8" drive cheaply available from Harbor Freight. The holes could then be plugged with red RTV. Has anyone already tried this?

RFSchaller 10-26-2013 08:33 PM

For what it's worth I torqued my mounting bolts to 30 ft-lbs with no Loctite almost 2 years ago and checked them today at 110 hours. All four were still torqued to 30 Ft-lbs.

yankee-flyer 10-27-2013 01:10 PM

Ditto at 199.8 hours
 
Locktite, 30 ft-lbs, torque-marks not broken

Wayne 120241/143WM

Buzz J 10-28-2013 01:02 PM

A more permanent fix in the works?
 
So glad the 30# of torque and Loctite are doing the job. Has anyone (you engineer types, perhaps) designed a more permanent fix for these so important screws, such as, perhaps, a pin or safety wire through a very carefully designed/drilled through the engine mount on top of each screw...so it can't back out?! Just an idea. The other four engine mount bolts have castle nuts with cotter pins to give the assurance that they cannot loosen! That's real assurance! Why not a like solution for these four screws that, in spite of frequent inspections could cost us both safety and money?! The current "solutions" of inpection and Loctite to ensure that our engines stay put, especially as they age, are not enough!! There needs to be a more permanent solution than frequent inspections and Loctite to ensure safety!!! Is anyone working on such a fix? I think that this is a critical issue that needs to be solved and put to rest! Really appreciate your concern an efforts, everyone!

Buzz

Mich48041 10-28-2013 02:59 PM

It is my understanding that safety wire does not prevent bolts from loosening. The bolts loosen first, then the safety wire prevents them from backing out any further. With engine bolts subject to vibration, it is not desired for the bolts to loosen even a little.
See previous posts about Nord-Lock, aka wedge-lock, washers.
Joe Gores

RFSchaller 10-28-2013 09:42 PM

Buzz,

The 3/8" bolts are in tension and the mounting bolts are in shear. The 3/8" bolts experience the forces along the axis which tends to loosen the nuts. The mounting bolts normally wouldn't be expected to loosen in shear. My guess is that's why the cotter pins are only on the 3/8" bolts.

Rich


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