In a message dated 4/21/2004 11:23:00 PM Pacific Daylight Time, ask...@microlink.zm writes:
> I realize that this is not a simple topic, but the words "there is no > concise answer to that" - sounds a bit like something a politician will > say. Tough darts. The fellow wanted a quick & easy, yes-no sort of answer. Reality doesn't work that way. > > No offence please sir, but we are talking about a 40 plus year old > engineering discipline. Older. If you start with the Lenoir you're back before the American civil war. Other than thermal barrier coatings I can't think of any mechanical feature found in modern-day engines that was not expounded upon by Sir Harry Ricardo. By the time he published his tome on the design of the 'high-speed' (ie, >1000 rpm) internal combustion engine in 1920 or thereabouts he'd already spent twenty years experimenting with and refining such things as stratified charge, variable valve timing and so forth. ---------------------------------------------------------------------------------- > > I am consistently amazed and impressed by the ability of home builders > to learn, adapt and innovate - it was a home builder that evolved the > first composite /canard (commercial) aircraft (Beech Starship). The > same "home builder" recently flew supersonic and looks set to be the > first non-govt entity into space. Do not sell "us" short. ------------------------------------------------------------------------------ The particular "home builder" you are referring to designed the Varieze around an engine that did not exist (ie, a '68hp' VW). Were you there? Do you remember the hype? Inexpensive. VW powered. No conventional control surfaces (ie, canard & rudders only). Can you honestly say ANY of those goals were met? Burt has obviously learned from his mistakes and his accomplishments are something all airmen can point to with pride. But the topic is VW engines not a fleet of scrapped Starships and any attempt to compare the two would appear to justify my remarks rather than yours. --------------------------------------------------------------------------------- > > >From your comments, the crank failures that have occurred were > predictable (by you) --------------------------------------------------------------- Whoa! Ardem of England did a complete engineering study on the VW crankshaft more than 50 years ago when they sought certification of their license-built... whatever (Jodel? Druine? Can't remember which.) They pointed out the problems back then and it was widely reported in the magazines of that era. The limitations on power output (25hp for take-off) and the 200 TBO for the crank were considered acceptable trade-offs. That was then. So the engine grew from 1100cc (ie, their certified 4C32 model) to the present day 2332 (if you can afford it). The key fact is that the nose of the crankshaft has remained exactly the same... a little nubbin barely three-quarters of an inch long, less than an inch and a half in diameter and pierced with a threaded bore three-quarters of an inch in diameter. Are you aware the Woodruff keyway comes to within sixty thou of the metric thread in the nose of the crank? (Metric threads have a sharp point; make a nice stress riser.) The manner in which the crack initiates and propagates is well documented and anyone who has flown their share of hours behind a VW is aware of it. This is all OLD NEWS. Why do you think everyone keeps trying to come up with a better prop hub? Because the thing never fails? ------------------------------------------------------------------------------ ------ > for the lack of some basic understanding - you say > " though those detail items have been found in winning VW engines for > more than forty years (and may be found in all modern engines as a > matter of course)". > > It would be sad if we are unwittingly doing things that could have > unpleasant consequences - whilst the solution to a better way is in fact > known (by one of us). ----------------------------------------------------------------- The numerous modification I took the trouble to promulgate are time-proven methods of improving the engines reliability, mostly by ensuring adequate lubrication and better cooling. Tear apart any modern engine and there they are. The tricky bit was retrofitting those features to an engine designed in the 19 30's. Professional builders of high output engines have been applying these mo ds since the early 1960's -- and charging accordingly. You probably can't afford to buy a full-trick racing engine but most of the reliability mods are fairly easy to accomplish... once you know how. I was simply showing folks how. Although I included drawings showing the method I use to attach the prop, that's really a different issue; the cause of the pulley-hub fractures has been known and discussed since the mid-1950's. If you want to put the prop on the pulley-hub, that's you're God given right. -------------------------------------------------------------------------------- > > I have been in and around home built aircraft and rebuilding VW engines > since 1968. I have read and listened to everything available on these > engines - particularly since the internet came along. > > Why am I hearing about this weakness for the first time in 2004? ------------------------------------------------------------------------------ - That's a real good question, Steve :-) I guess the answer depends on who you've been listening too. Or how many engines you've built. -R.S.Hoover
