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>on 11/27/02 8:21 PM, Randy Helm at [EMAIL PROTECTED] wrote:
>Does anyone know what torque is recommended for McAuley CM7148 on a 46
Ercoupe
... >C85-12?
>Thanks, Randy
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(11/28/02) 1:25pm
Yo, Randy,
The torque "listed on page 118 of the Continental C85 overhaul manual" of
200 to 220 inch pounds is not so much in conflict with the 300-360 inch
pounds specified by McCauley (per current Univair catalog #202, p. 201),
and
Aircoupe Service Manual, Model F-1 and F-1A, p. 31, as might appear.
The 300-360 inch pound figure from McCauley is with threads DRY.
Per Teledyne Continental Aircraft Engine Service Bulletin SB76-7B, "TORQUE
VALUES LISTED (presumably all such values originated by Continental,
although propeller torque is not listed in this Service Bulletin) ARE FOR
USE WITH CLEAN 50 WEIGHT AVIATION ENGINE OIL APPLIED TO THE THREADS,
UNLESS
OTHERWISE SPECIFIED".
Variations in final fastener tightness (bolt shank tension and/or hub
compression pressure achieved when both bolt and hub threads are "virgin"
new from manufacturer versus a used hub and all new bolts, used hub with
used bolts, and the almost infinite possible combinations thereof) can be
significant.
Continental apparently believes specifying thread lubrication ("wet
torque")
as their "norm" reduces above variations (compared to "dry torque"
installations). The true objective is not to see a torque value or hear a
wrench click (when was the last time you had your wrench calibrated?) but
to
achieve uniform bolt shank tension (and resulting "pinch pressure" on the
prop hub).
The addition of lubricant before torquing a fastener significantly reduces
any "dry" torque value necessary for a given "target range" of compressive
security and/or bolt shank tension (thus the 200-220 range wet versus
300-360 dry), so verify all such figures as "wet" or "dry" before
proceeding. THEY WILL NOT BE THE SAME!
Above Service Bulletin further advises "THE USE OF...LUBRICANTS OTHER THAN
THOSE SPECIFIED BY TCM...CAN CAUSE INCORRECT TORQUE APPLICATION AND
SUBSEQUENT ENGINE DAMAGE OR FAILURE."
Whether torque method/values of the manufacturer/type certificate of the
engine/flanges (Continental), the prop (McCauley) or the aircraft (Forney
was the first TC 787 airframe design produced with the McCauley prop) take
precedence I defer to the infinite wisdom of the legal departments of the
FAA, each type certificate holder and (ultimately) the courts.
Regards
--
William R. Bayne
<____|(o)|____>
(copyright 2002)
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