Continental A-75 hub torque

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

Good question. Make sure it's tight and then safetied with a small
bolt and castellated nut when you put it on. No beating,whacking, or
hammering. Don't wallow out the rod holes in the hub nut. Use a
snug-fitting long rod. The crankshaft is tapered. So is the female
hub.

Those crankshafts and hubs should also be magnafluxed before being put
back into service. The keyway for the woodruff key is susceptible to
cracks. Have you checked for cracks?

Also make sure you have a lockring which secures the nut to the hub, or
when you remove the hub down the road, you'll have the devil getting it
off. I don't know how many of those hubs I've seen without lockrings.
Check the hub for runout.

I did visually inspect it for cracks, but did not magnaflux it. I will likely be changing props again in 6-8 weeks, and will add that to the list of things then. I could see no evidence of cracks around the keyway with the naked eye.

It does have a lockring.

200ft-lbs is what the local prop shop suggested as well. I'm going to try to rig up some type of adapter for my torque wrench this evening. Maybe I'll go my a cheap socket, drill a hole through it, and insert the correct size rod.

Thanks for all of the information!

Steve Ruse
DFW, TX

Originally Posted by

Good question. Make sure it's tight and then safetied with a small
bolt and castellated nut when you put it on. No beating,whacking, or
hammering. Don't wallow out the rod holes in the hub nut. Use a
snug-fitting long rod. The crankshaft is tapered. So is the female
hub.

Those crankshafts and hubs should also be magnafluxed before being put
back into service. The keyway for the woodruff key is susceptible to
cracks. Have you checked for cracks?

Also make sure you have a lockring which secures the nut to the hub, or
when you remove the hub down the road, you'll have the devil getting it
off. I don't know how many of those hubs I've seen without lockrings.
Check the hub for runout.

225 FOOT-Pounds. It is in the C-series manual. Look at the March 2005
Vintage magazine, I believe for making an adapter. If not send your email
address and I think I can send an adapter picture to you.


--
Cy Galley - Aeronca Aviators Club
Newsletter Editor & EAA TC
www.aeronca.org
Actively supporting Aeroncas every day

"SteveR" wrote in message
...

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


--
SteveR

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

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

Hello, Pitts1c. (Nice airplane) If you can publish those numbers and
specific procedure from that vintage magazine, it would be very helpful
for those of us who work on those engines.

Thanks.

Cy's information has been very helpful too, but 225 foot lbs. on that
A-75 hub nut is a lot of torque, sorta like chinning yourself on an
iron bar.