Gear leg mounting

[Mike Betti]

Does anyone know the correct torque for the 5/16 and 3/8 gear leg saddle bolts? The manual doesn't specify and I don't want to rely on my chart.
Thanks,
Mike Betti
771E



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[Wayne G. O'Shea]

From charts 100 to 140 inch lbs (8.33 ft-lbs to 11.6 ft-lbs) for the 5/16
and 160 to 190 inch lbs (13.33 to 16 ft-lbs) for the 3/8. Mind you 18 to 21
ft-lbs is an acceptable # for 3/8" prop bolts! Remember to see how much
torque it takes to turn the nytrol nut on the open thread and add this to
the # your are trying to acheive for a total torque reading.

Wayne

----- Original Message -----
From: "Mike Betti" <mbetti@up.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 21, 2005 10:37 PM
Subject: Gear leg mounting

Does anyone know the correct torque for the 5/16 and 3/8 gear leg saddle

bolts? The manual doesn't specify and I don't want to rely on my chart.

Thanks,
Mike Betti
771E



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[mbetti]

Thanks Wayne,
I have a hard time with airplane torques. I'm a mechanic and a 3/8 bolt in our engines we build take anywhere from 30-45ft#.
Mike

On Mon, 21 Nov 2005 22:47:22 -0500, rebel-builders@dcsol.com said:

From charts 100 to 140 inch lbs (8.33 ft-lbs to 11.6 ft-lbs) for the 5/16

and 160 to 190 inch lbs (13.33 to 16 ft-lbs) for the 3/8. Mind you 18 to 21
ft-lbs is an acceptable # for 3/8" prop bolts! Remember to see how much
torque it takes to turn the nytrol nut on the open thread and add this to
the # your are trying to acheive for a total torque reading.

Wayne

----- Original Message -----
From: "Mike Betti" <mbetti@up.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 21, 2005 10:37 PM
Subject: Gear leg mounting

Does anyone know the correct torque for the 5/16 and 3/8 gear leg saddle

bolts? The manual doesn't specify and I don't want to rely on my chart.

Thanks,
Mike Betti
771E



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[bransom]

Remember to see how much
torque it takes to turn the nytrol nut on the open thread and add this to
the # your are trying to acheive for a total torque reading.
Wayne

I'm not sure I get the above...
Is this to make sure that the nut/bolt are torqued with the nut still in the
thread area, as opposed to the nut inadvertantly being bottomed and torqued
against the non-threaded portion of the bolt?? Otherwise I'm confused.
-Ben/ 496R




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[tlmcclary@juno.com]

The torque required to turn the nut on the open thread is the running torque or the resistance (torque) of the nylon locking feature in the nut. You want to add the running torque to the required torque value to get the correct bottoming torque.

If you don't add the running torque you don't achieve the required torque when the nut bottoms. Your final torque value would be required torque value minus the running torque value. Did that muddy the water even more?

Terry
R666 (in the box)

-- bransom@dcsol.com wrote:

Remember to see how much
torque it takes to turn the nytrol nut on the open thread and add this to
the # your are trying to acheive for a total torque reading.
Wayne

I'm not sure I get the above...
Is this to make sure that the nut/bolt are torqued with the nut still in the
thread area, as opposed to the nut inadvertantly being bottomed and torqued
against the non-threaded portion of the bolt?? Otherwise I'm confused.
-Ben/ 496R




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[jimsrebel]

http://www.murphyair.com/SUPPORT/Bulletins/springgr.htm
When re-attaching the bolts remember to tighten to the specified torque value
of 13 - 16 ft.*lb.

There are 3 spring gear bulletins under Rebel Tech. supports worth reading.
This is the only place I have seen any torque values listed. The torque
values listed seem to be right off the chart and I would stay to the high
side of the spread. If you use MS21042 nuts for the saddle bolts you can use
a smaller access hole for the saddle bolts. I have a one inch hole that I use
to get to the aft saddle bolt using a 1/4 inch Snap-on torque wrench (click
type). My saddle bolt are 3/8 inch as originally supplied be MAM. Not sure
why they down graded the bolt size.
Jim


On 11/21/2005 6:37 PM, mbetti@up.net wrote to rebel-builders:

-> Does anyone know the correct torque for the 5/16 and 3/8 gear leg saddle
bolts? The manual doesn't specify and I don't want to rely on my chart.
-> Thanks,
-> Mike Betti
-> 771E





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[Ken]

To keep it easy I generally just tighten up to the upper value in the
recommended range. Maybe someone knows of cases where this doesn't work
but it seems to work for me. I've read that most amateur aircraft
bolts tend to be overtightened. (that little extra tug on the wrench to
make sure...)

Mike was commenting on how low the recommended torque is compared to
engine bolts. AN bolts are really only about grade 5 strength bolts
whereas engine bolts may be grade 8 or higher. Engine bolts that are
used in tension for rapid cyclic loads are generally tightened enough
that the bolt is always under tension to resist fatiguing etc. (The life
of the bolt is longer if it is always kept in positive tension through
each load cycle). You can't always just use a larger bolt as you may
need the elastic stretch of the thinner bolt to accomplish this. On the
other hand the overtension failure of AN bolts is supposed to be
stripped threads. The nuts tend to be shorter with less threads engaged.
That way the bolt shank is never overloaded in tension and a stripped
bolt might still do its job if it is resisting a shear load. Apparently
most AN bolts are used in shear instead of tension. A highly tensioned
bolt can not resist as much shear, as tension actually generates
internal shear if my memory is correct, so it makes sense to go easy on
the torque/tension. Fine thread AN bolts are also loaded more for a
given torque than course thread bolts although many engine bolts are
also fine thread.

Ken

I'm not sure I get the above...
Is this to make sure that the nut/bolt are torqued with the nut still in the
thread area, as opposed to the nut inadvertantly being bottomed and torqued
against the non-threaded portion of the bolt?? Otherwise I'm confused.
-Ben/ 496R

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