Understand that I'm NOT an A&P or IA but only offer personal
(supervised) owner experience. (Been there, done that, results may
vary ;<)
Verify the track of your prop within 1/8" per Continental Overhaul
Manual Form No. X-30010 1/67 Rev. 11/68, p. 36 (9-3.c.)
Old (hard) engine mounts (530740) will transmit excess vibration, and
so will improperly torqued ones.
Continental has this to say: "... bolts are used with cone type rubber
washers which prevent any direct metal-to-metal contact between engine
and mounting frame. The washers make the tension of the mounting bolts
of prime importance, and these bolts must be adjusted from time to time
in service to compensate for compression which takes place during
useage. A torque of 60 to 80 inch pounds should be applied in
tightening mounting bolts."
Per Continental Overhaul Manual Form No. X-30010 1/67 Rev. 11/68:
"Torque loads are listed for use with oil on threads, except for
studs."
In service, the weight of the engine tends to unload tension on the
upper rubber mounts and tends to compress the lower ones. Consider
replacing the upper ones with new ones every 2-3 years, using those
removed to replace the (weight-and age compressed) lower ones.
Replacement is not difficult, but absolute control over the weight of
the engine must be established and maintained at all times. Any
distraction from the task at hand or lack of common sense can put one
or more fingers, etc. at risk of injury. Removing the side and top
cowling (as a unit). Remove all fasteners securing the front cowl to
the cowl ring (you want it to be able to move, but do not have to
remove it or the prop). Securely block all wheels, set brakes, and use
a properly aligned overhead hoist to (just) assume the weight of the
engine at the prop end.
Loosen the lower bolts, leaving nuts fully on threads. Remove upper
bolts/washers. Lower the hoist so as to tilt the engine forward enough
to remove and replace the upper mount rubbers. Replace upper
bolts/washers and install nuts fully on threads (but otherwise leave
loose). Remove lower bolts/washers and raise the hoist so as to tilt
the engine backward enough to remove and replace the lower mount
rubbers.
I first torque the upper assemblies to about 75 in. lbs. This is
secure, but allows further tightening to combat vibration harmonics, if
necessary. I then torque the lower ones to the minumum of 60 in. lbs.
Then secure upper and lower nuts appropriately.
If flight test reveals excessive vibration, tighten the uppers to 80
in/ lbs. and try again. If no better, tighten the lowers to 65 in.
lbs. Play around with torque values between the recommended 60 to 80
inch pounds until you achieve the "sweet spot" for minimum engine
vibration.
Hope this helps,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
--
On Mar 24, 2010, at 14:05, dtaylor9319 wrote:
What is the proceedure for replacing the Rubber Bushings isolating the
engine from the motor mount? What is the proper torque settings if any
or what is the "look" you are supposed to get when they are installed
correctly? Mine sag a little while the engine is at rest. I suspect
the engine "on" under power appearance of the bushings is much
different but I do not know for sure. I am not sure how old the
bushings are. I get a little vibration at lower RPM (18-1900) but
nothing radical.
1966 Alon\Aircoupe
N5603F
