Engine Mount Bolts

[az_gila]

Originally Posted by edneff

I know this is an old thread, but it fits my situation...

I am adding some washers to my lower engine mounts for the engine sag. A local A&P friend helped me get the cotter pins out... what a job! He mentioned that there are alternatives available, specifically a locking aerospace fastener called a "compact nut"... He did not give me any other info.

Anyone know what he's talking about and where to find them? I searched aircraft spruce but could not find one.

Thanks

Probably the MS21042 style nuts...



As opposed to the "usual" MS20145 all-metal stop nuts...

[edneff]

Thanks Gil.

What a wealth of knowledge this website is.
That nut looks like it will do the trick plus it appears to have the added advantage of having a smaller flat size. That should make it much easier to get a wrench on it. The AN7 castle nut that is installed (and which I have I have yet to remove, although I did manage to extract the cotter pins) is almost impossible to access because it sits inside the case recess. I cannot get a regular box end wrench around the castle nut. There must be a special thin wrench that will fit onto that nut . Can anyone help with a source for such a tool, or do I need to modify an existing wrench?

It looks like it will be a real bear to extract that bolt when I get the nut off. If anyone has some hints on that aspect of the job I would be happy to hear that as well.

Thanks

[snopercod]

I had a lot of difficulty getting the holes in the engine to line up with the holes in the mounts. I tried clamps and pry bars and the engine hoist and everything else I could think of. I'll probably get flamed for this but I ended up grinding a short taper on the end of the bolts, grinding only the first two threads which were sticking out past the end of the nuts anyway. It made the bolts a lot easier to insert and the threads didn't abrade the holes in the engine as the bolts were tapped in. If anyone has a magic trick here, please let me know because I'll be changing out my Barry mounts for Lord mounts pretty soon.

[az_gila]

Originally Posted by snopercod

I had a lot of difficulty getting the holes in the engine to line up with the holes in the mounts. I tried clamps and pry bars and the engine hoist and everything else I could think of. I'll probably get flamed for this but I ended up grinding a short taper on the end of the bolts, grinding only the first two threads which were sticking out past the end of the nuts anyway. It made the bolts a lot easier to insert and the threads didn't abrade the holes in the engine as the bolts were tapped in. If anyone has a magic trick here, please let me know because I'll be changing out my Barry mounts for Lord mounts pretty soon.

Use these, they really do work...

http://www.cleavelandtool.com/ENGINE.../#.WGlLioWcGUk

[Kyle Boatright]

The first trick is to get the engine relatively accurately positioned. At that point, you can stick a small diameter Phillips screwdriver through the hole in the case, doughnut, and engine mount. Do that for all 4 mounts so you have reasonable alignment everywhere. The larger diameter screwdrivers you can get in there, the better, so swap large for small where you can.

Get straps or some other leverage device to pull the engine back towards the airframe and compress the doughnuts.

Then, make up one or two tapered pins the same diameter as your bolts. Drive one into one of the upper mount locations, displacing the screwdriver. Tap in a bolt to push out the pin. Add the washers and nuts, and you've got one in. Repeat for the second upper mount. Then release most of the lifting force from whatever is suspending the engine and the lower mounts will compress, making those bolts easier to install. Use the tapered pins there too.

I did my O-320 solo and in 30 minutes or so using this approach.

[snopercod]

Originally Posted by az_gila

Use these, they really do work...

Thank you, THANK YOU, THANK YOU!. (It's kind of embarrassing that I've never heard of those.)

[snopercod]

Originally Posted by Kyle Boatright

I did my O-320 solo and in 30 minutes or so using this approach.

I think it took me 8 hours the first time

P.S. I used the metal lock nuts.

[Kyle Boatright]

Originally Posted by snopercod

I think it took me 8 hours the first time

It was one of those occasional building evenings where everything went perfectly as planned. I remember going out to the garage assuming I'd spend hours getting the engine mounted. And I had the "beer signifying victory" about 45 minutes later.

[edneff]

Originally Posted by az_gila

Probably the MS21042 style nuts...



As opposed to the "usual" MS20145 all-metal stop nuts...

Well after searching the tables, it appears that the MS21042 only comes in sizes up to -6.... and the mount bolts are -7's...

The MS20145 is listed on Aircraft Spruce in every size but -7, go figure.

Guess I might be struggling with Cotter pins on the install after all ;-(

[Mel]

Originally Posted by edneff

Guess I might be struggling with Cotter pins on the install after all ;-(

Although these cotter pins are not fun, they are not all that difficult either.
After all, you built an airplane didn't you?