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Hi All, There have been three requests for subject information in recent days on this list. The variety of response and apparent genuine confusion was such that I went back and reexamined the subject "from the beginning" to get it straighter in my own mind. I now think some of my earlier posts on this subject were less accurate than they should have been. For this I apologize, and hope the following is a more useful reference. The range of torque on Page 81 of the CMC C85 Overhaul Manual (Form No. X-30010) applicable to the 3/8 - 24 Bolt(s) is 275 to 325 inch pounds, or 22.9 - 27.1 foot pounds. It further states "Torque loads are listed for use with oil on threads, except for studs. Teledyne Continental Aircraft Engine Service Bulletin SB76-7B further elaborates on the "oil on threads", describing same as "clean 50 weight aviation engine oil..., unless otherwise specified." McCauley (per current Univair catalog), and Aircoupe Service Manual, Model F-1 and F-1A, p. 31 lists 300-360 inch pounds (with threads DRY) for installation of their props. I personally prefer the more uniform "pinch" available with the "wet-torque" method. Seeking the "common ground" between the Continental and McCauley specifications, I would personally want a prop bolt/nut torque between 300 and 325 inch pounds "wet". It is easy to misread and misapply the Continental manual's specified torque for the "Bolt, Propeller hub" of 200 - 220 In. Lbs. on p. 80 You have to look to the right to understand the thread size of 3/8-24 describes the propeller flange bolt(s) on a flange shaft engine (and the nut size used on a taper shaft installation) and NOT the propeller hub nut. It would also be my guess (they don't say) the indicated range was to avoid crushing a wooden prop's hub, considering the increased torque range allowable for this size/thread on the following page. Continental's nomenclature would be accurate for torquing the (6) propeller hub bolt(s) into the threaded rear flange of a flanged crankshaft. There is no indication (other than common sense) that it also applies to the PROPELLER FLANGE NUTS that are torqued onto (6) propeller shaft bolts (installed from the rear with threads forward per the Ercoupe Parts Catalog, p. 22, Fig. 17, Item No. 50) of a tapered crankshaft installation. The Ercoupe Service Manual specifies 125 to 175 in. lbs. torque for such bolts/nuts (presumably from Sensenich for Erco's (then) standard wood prop). As for the taper shaft "prop hub" nut, the Ercoupe Service Manual, p. 44, says 1200 inch pounds (100 foot pounds-WRB). I find no value listed by Continental in their manual for this nut. Comments anyone? Regards, William R. Bayne <____|-(o)-|____> ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers-tech/
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