Hi John,
I always endeavor to deserve such kind words. Many thanks. And may I
say I have learned much from your posts!
On those occasions that you and I have a different "take" on an issue I
have learned over the years to revisit it with an open mind because
inadvertent omission of something important can be just as much of a
problem as a fact misstated. Accordingly, I went back to the
Continental Overhaul Manual (my reference copy is Form X-30010 dated
1/67 revised 11/68). I'm very glad I did.
It is the A-65-8, C-75-12, C-85-12 and 12F and C-90-12F used in Forneys
that have the rubber bushings I described replacing. On page 24 in
Section VI 6–1, par. c. I find I neglected to mention that the engine
mount bolts are pushed through the mounting assembly from the rear. In
par. g. it describes the nuts required are of the slotted (castellated)
type that are to be torqued to 60-80 inch pounds, adding that
"insufficient tightness will increase vibration". In par. i cotter
pins are installed (to secure the nuts). Always use new ones.
That said, I answered a question dtaylor did not ask. dtaylor has an
A-2A Alon, serial no. B-274.
In i. the C-90-16F installed (per the Alon Service Manual) (as well as
any C-90-14 and O-200 installations) is said to use Lord Mounts. While
I have no experience with these, the difference between the two
mounting methods appears similar to that between the original rubber
donuts on the main landing gear and Belleville Springs. I would
describe the donuts as pieces of rubber that squeeze and distort
relative to the hardness and age of the rubber...and so tail height and
shock absorption differs considerably over time between "new" and
"old". With Belleville Spring assemblies, tail height and shock
absorptive characteristics remain relatively constant indefinitely.
Anyway, Lord Mount installations are torqued to 180-190 inch pounds.
On p. 33 in Section VIII (trouble shooting) under "Rough running" it
lists "Engine mounts loose", and referring to Section XVIII for
tigntening.
In that section, on p. 80, is the "Nut, Engine Mount Bolt (-8, -12 and
-16 models)" and, again, the recommendation of 60-80 inch pounds of
torque.
Just below is the recommendation of 180-190 inch pounds for -14 and
O-200 models. But WAIT A MINUTE! We know (from p. 25) that the -16
model has the Lord Mounts that require the higher torque range (or do
we?)! I would think that the engine crankcase and engine mount are
entirely different on Lord Mount installations, and therefore physical
inspection should reveal what should be there (even if the wrong stuff
is presently installed). Perhaps one or more of our mechanics can
chime in and clarify this better than I.
In this same p. 80 table of Tightening Torques are the range of engine
assembly threads to which a note on p. 81 applies: "Torque loads are
listed for use with oil on threads, except for studs." I would take
that as extremely specific, considering that an exception is listed;
but it isn't the nuts on engine mount bolts.
Perhaps there is some other authoritative reference?
Best regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
--
On Mar 24, 2010, at 19:50, John Cooper wrote:
On 3/24/2010 7:26 PM, William R. Bayne wrote:
Understand that I'm NOT an A&P or IA but only offer personal
(supervised) owner experience
Bill's advise is all good...
There is one issue I think is misunderstood, though. Continental's
statement "Torque loads are listed for use with oil on threads," is
applicable to engine assembly, but I do not believe it is intended to
apply to the engine mount bolts.
--
John
Skyport East
www.skyportservices.net
