Van's Air Force
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Engine Mount Bolts
- Thread starter Grandy
- Start date
az_gila
Well Known Member
Stop nut vs. cotter pin
Mahlon... I've noticed several certified planes use an all metal stop nut on the engine mount bolts instead of the castle nut and cotter pin Van specifies.
Is there any advantage to the cotter pin method? ....or is Van just being thrifty at this location....
It would seem that inserting the cotter pin may be a real pain in the %^&*.
To clarify, I'm talking about the bolts that go through the dynafocal mounts and the engine case "ears".
gil A
Mahlon... I've noticed several certified planes use an all metal stop nut on the engine mount bolts instead of the castle nut and cotter pin Van specifies.
Is there any advantage to the cotter pin method? ....or is Van just being thrifty at this location....
It would seem that inserting the cotter pin may be a real pain in the %^&*.
To clarify, I'm talking about the bolts that go through the dynafocal mounts and the engine case "ears".
gil A
I've been told by an AP/IA that using a metal stop nut is acceptable for the negine mount bolts, but I had already put on the castle nuts so I didn't change them. I didn't find putting the cotter pins in to be too bad.
If I were to do it again, I would use stop nuts. If you do so, however, you should change the bolt to one with out a hole in it.
If I were to do it again, I would use stop nuts. If you do so, however, you should change the bolt to one with out a hole in it.
FrankK90989
Well Known Member
Mine are all metal = easy
az_gila
Well Known Member
None that I can find....
IIRC, it was specified that way in the old version of AC 43.13
However, the current version has no restrictions on the hole (self locking nut use with or without a hole) that I can find. The bolt cotter pin holes should be clean and deburred as manufactured.
gil A
IIRC, it was specified that way in the old version of AC 43.13
However, the current version has no restrictions on the hole (self locking nut use with or without a hole) that I can find. The bolt cotter pin holes should be clean and deburred as manufactured.
gil A
As long as there is a solid spacer in the mount making the whole assembly rigid then using a lock nut will work. But if you don't have solid contact of all mount components, a castle nut and cotter pin is necessary. Most lock nuts need tension on the threads to lock and if the mount assembly doesn't have rigidity then the lock nut could come loose.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
az_gila
Well Known Member
Lord mounts
Hi Mahlon.... just to confirm... the Lord mounts with the "jelly bag" center piece count as a solid contact, right?
I think the bag has a solid spacer in it, but don't have one to look at...
gil A
Hi Mahlon.... just to confirm... the Lord mounts with the "jelly bag" center piece count as a solid contact, right?
I think the bag has a solid spacer in it, but don't have one to look at...
gil A
edneff
Well Known Member
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
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
az_gila
Well Known Member
Probably the MS21042 style nuts...
As opposed to the "usual" MS20145 all-metal stop nuts...
edneff
Well Known Member
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
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
Well Known Member
Difficulty inserting engine mount bolts
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.
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
Well Known Member
Use these, they really do work...
http://www.cleavelandtool.com/ENGINE-MOUNT-INST-ALIGNMENT-PINS/productinfo/282/#.WGlLioWcGUk
Kyle Boatright
Well Known Member
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.
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
Well Known Member
THANK YOU!
Thank you, THANK YOU, THANK YOU!. (It's kind of embarrassing that I've never heard of those.)
snopercod
Well Known Member
Kyle Boatright
Well Known Member
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
Well Known Member
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 ;-(
Although these cotter pins are not fun, they are not all that difficult either.
After all, you built an airplane didn't you?
edneff
Well Known Member
You have a point there-- but full disclosure, I didn't build it. Anyway it seems I am spending as much time finding an alternative to the cotter pins as I would spend just wrestling with them. Access is difficult, even after removing all my probes and the intake pipes. And as I mentioned in another post, I'm having a hard time finding a wrench that will fit on the -7 castle nuts, thus the quest for an easier way.
I think I will go with the MS21045 and just torque mark them and monitor them.
edneff
Well Known Member
rvisnext
Active Member
long reach needle nose
Maybe you already have this tool , I didn't know this existed until recently. They made the cotter pins a non-event for me. I didn't have to disassemble much to get at them with the bent long reach one.
https://www.amazon.com/Crescent-PSX204C-Reach-Plier-2-Piece/dp/B00N9ULHO6
Maybe you already have this tool , I didn't know this existed until recently. They made the cotter pins a non-event for me. I didn't have to disassemble much to get at them with the bent long reach one.
https://www.amazon.com/Crescent-PSX204C-Reach-Plier-2-Piece/dp/B00N9ULHO6
edneff
Well Known Member
I ended up going with the MS21042 all metal stop nuts, found them on the Pegasus Racing website (automotive stuff) about$3.50 ea., that was the only place I could find them in 7/16 diameter, most of the aviation sources only had them up to AN6... The flats are 1/2" so that made the install a little easier also.
