lml@lancaironline.net Mailing List Archive

<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> To Jim Cameron (and everyone else) -- I never really considered replacing the little steel washers (AN960) with aluminum, though I suppose I could in certain places. I'm really interested in replacing the larger area washers (AN970) with aluminum ones where possible. You're right -- you don't save much weight replacing the washer on a #10 bolt! However, I have two AN970-7 area washers under each engine mount pad. These take the place of the fiberfrax I removed from under each engine mount pad so that I have a non-crushable material between the engine mount and the firewall. (Since Jim's building an ES this may not make any sense. I don't know, since I have no knowledge of the ES engine mounting configuration.) The bottom line is that there are 6*2=12 area washers used as spacers between my engine mount and the firewall. On top of this, two of the pads need an additional spacer as they are not coplanar with the other four. That brings the total to 14 AN970-7 area washers between the engine mount and the firewall. Fourteen AN970-7's weigh 443 grams, or basically a pound. (453.6 grams is one pound so it's real close.) With aluminum about 1/3 the density of steel, I can save 2/3 of a pound with no labor, cost, or risk by using aluminum washers under the engine mount pads. On the other side of the firewall there are six more area washers, one under each engine mount bolt head. These are used to spread the load over a greater area of plywood, thus the washer is carrying a bending load. I will NOT replace these with aluminum as they would bend. (Hell, the STEEL ones bend visibly when the bolts are fully torqued!) Other guys have made other suggestions for reducing weight by substituting lighter parts of equal strength. The MS21042 in place of an elastic stop nut is one example. These are the easy ways to save weight and we should all do it. Shear nuts where appropriate, for example. Someday I'll save a whole pound and buy a pair of Tim Ong's shocks. But I need to buy a propeller first.... and another radio.... of, and flight instruments.... and.... Happy building! - Rob Wolf >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML website: http://www.olsusa.com/Users/Mkaye/maillist.html LML Builders' Bookstore: http://www.buildersbooks.com/lancair Please send your photos and drawings to marvkaye@olsusa.com. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>