In a message dated 4/21/2004 9:58:56 AM Pacific Daylight Time, lar...@socal.rr.com writes:
> Now people might realize that the reality of direct drive engines is the > >probability of breaking a crank is high. > ---------------------------------------------------------------------- I think the above needs to be qualified by the fact most props get installed on the fan pulley end of the crankshaft, on a whimsically small bit of shafting never designed for that level of output and an engine away from the thrust bearing. I went several broken crank episodes with the Type I more than fifty years ago and came to the conclusion that the typical VW 'expert' didn't know his ass from his elbow. Indeed, it took only a modest amount of research to discover that of the four accepted experts of that era NONE had actually built a flying Volkswagen and only ONE had even flown behind such a thing. It was my dad who pointed out that he'd never heard of anyone any successful conversion in which the prop was attached to the pulley-hub. (Bernard Pietenpol tried it with the Model 'T' with mixed success. He readily admitted the 'A' model conversion -- with the prop on the clutch-end of the crankshaft -- was the best way to go.) After I put the prop on the other end of the crank flying became down-right boring :-) It amazes me that folks don't seem to realize that all of these fantastic prop/hub/bearing/crank modifications are band-aid-attempts to make a bad idea work. Expensive band-aids, too. To attach a prop to the clutch-end of the crankshaft all you need is a matching spacer. The idea that the engine is more difficult to mount or that the bell housing gets in the way is blown away the first time you see such an installation. In fact, the only reason they put the fan on the pulley-hub to begin with was because the original engines were FREE (ie, the 985cc twirler out of the 2WD Kubelwagen), only put out about 20hp and weighed barely a hundred pounds. They never lasted very long -- SOP was to replace the crankshaft ($17.00, US) every 200 hours or so, but the result was a flying club hack that could give you an hours flight-time for less than $5, a critical factor in post-WWII Europe with gasoline going for $2.50 a gallon... when you could get it. (Great Britain didn't go off rationing until the 1950's). Reality has never been aviation's strong suit. Nor hard-ball engineering, when you get right down to it. (The maximum sustainable output of ANY aircooled engine is determined by its ability to cool itself. Rather than counting fallacious horsepower you'd be better off counting the number of fins on the heads.) The fabled superiority of the Corvair over the VW probably stems from the fact they put the prop where it belongs. -R.S.Hoover
