Continental A-75 hub torque

It is important to use a torque wrench so you don't exceed the torque and
crack the hub. Remember it is tapered and will fail if over torqued.
Although the article used a modified socket inside, I believe a socket that
fits over the outside would also work. Might cost a bit more as you drill a
hole in the socket side wall for a 5/8" thru bolt. Using a large socket on
the outside might eliminate the need for the welded re-inforcement shown for
the inside socket.
--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot
"pittss1c" wrote in message
...
Eaa's vintage magazine just had an article about this exactly that showed
how to modify a socket so that a bolt goes through the hub and socket, and
you can attach a torque wrench to the socket. (they gave their torque
values in the article too.
The overhaul manual does have a specific procedure listed though...
I should say something like insert a long bar into the hub nut and use a
brisk strike against it with a brass hammer. this leads me to believe that
it isn't a precision activity.
(if no one answers, I can look it up when I get home)

Mike

SteveR wrote:
Can anyone tell me what I should torque the hub to on my A-75 (the
retaining piece that threads onto the engine crank)? I've searched the
continental engine manual and can't find this value.

Also, since there is no nut or bolt on this piece, is there an easy way
to make an adapter that will allow me to use my torque wrench on the
hub? How is the hub typically torqued onto the engine? I don't have
access to a welder to make an adapter.

Thanks!

Steve Ruse

I installed the hub last night, although my torque wrench doesn't go all the
way to 200ft/lbs, so I only torqued it to about 150-160ft/lbs.
Interestingly enough, that is where the holes in the hub and crank lined up.
I am planning on going to a prop shop today to have them torque it to
200ft/lbs, but I am nearly positive that will just make the holes NOT line
up. I should have marked the hole the safety bolt was in before I took it apart. I bet that is the hole that lined up at 150ft/lbs, as there are only two holes in the crank that this bolt will fit in, and it was in one of them before I took it apart. I don't think adding another 50ft/lbs is going to turn the hub exactly 90 degrees, which is what it would take to line up the other holes.

Hope that makes sense without reading it eight times...

I did coat the threads and tapered surface with anti-seize compound. That
was used last time it was assembled, and I saw that in a service manual
somewhere too. There were no cracks that I could see with the naked eye, I
did check it closely. Next time I'll probably magnaflux it.

Thanks for the tips, I'm not sure what to do at this point, leave it at 150ft/lbs, or go to 220ft/lbs or so to see if it will line up with another hole for the safety bolt. Hopefully the prop shop or someone here will shed some light on it.

Steve Ruse
N6383J - KFTW

Originally Posted by Cy Galley

It is important to use a torque wrench so you don't exceed the torque and
crack the hub. Remember it is tapered and will fail if over torqued.
Although the article used a modified socket inside, I believe a socket that
fits over the outside would also work. Might cost a bit more as you drill a
hole in the socket side wall for a 5/8" thru bolt. Using a large socket on
the outside might eliminate the need for the welded re-inforcement shown for
the inside socket.
--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot
"pittss1c" wrote in message
...
Eaa's vintage magazine just had an article about this exactly that showed
how to modify a socket so that a bolt goes through the hub and socket, and
you can attach a torque wrench to the socket. (they gave their torque
values in the article too.
The overhaul manual does have a specific procedure listed though...
I should say something like insert a long bar into the hub nut and use a
brisk strike against it with a brass hammer. this leads me to believe that
it isn't a precision activity.
(if no one answers, I can look it up when I get home)

Mike

SteveR wrote:
Can anyone tell me what I should torque the hub to on my A-75 (the
retaining piece that threads onto the engine crank)? I've searched the
continental engine manual and can't find this value.

Also, since there is no nut or bolt on this piece, is there an easy way
to make an adapter that will allow me to use my torque wrench on the
hub? How is the hub typically torqued onto the engine? I don't have
access to a welder to make an adapter.

Thanks!

Steve Ruse

I had one of the local prop shop guys come by today and check my hub torque. He gave it a good twist using an ~18" rod, and it didn't budge. I torqued it to approximately 150ft/lbs using my torque wrench, so that is where it is still at, AND where the safety bolt holes line up. There is no way they are going to line up if it is torqued another 50ft/lbs. The prop shop guy said it seemed plenty tight to him, and he thought it was fine.

Should I just leave it at ~150ft/lbs?

Thanks,

Steve Ruse

Originally Posted by SteveR

I installed the hub last night, although my torque wrench doesn't go all the
way to 200ft/lbs, so I only torqued it to about 150-160ft/lbs. Interestingly enough, that is where the holes in the hub and crank lined up. I am planning on going to a prop shop today to have them torque it to 200ft/lbs, but I am nearly positive that will just make the holes NOT line up. I should have marked the hole the safety bolt was in before I took it apart. I bet that is he hole that lined up at 150ft/lbs, as there are only two holes in the crank that this bolt will fit in, and it was in one of them before I took it apart. I don't think adding another 50ft/lbs is going to turn the hub exactly 90 degrees, which is what it would take to line up the other holes.

Hope that makes sense without reading it eight times...

I did coat the threads and tapered surface with anti-seize compound. That
was used last time it was assembled, and I saw that in a service manual
somewhere too. There were no cracks that I could see with the naked eye, I
did check it closely. Next time I'll probably magnaflux it.

Thanks for the tips, I'm not sure what to do at this point, leave it at 150ft/lbs, or go to 220ft/lbs or so to see if it will line up with another hole for the safety bolt. Hopefully the prop shop or someone here will shed some light on it.

Steve Ruse
N6383J - KFTW