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Al W wrote:>
> Here's an excellent example. I've seen people describe their > reasoning
> for going rotary. Often I would hear: "It only has three moving > parts,
> therefore it's safer". I suspect that 80% of you believed that. That > is a
> gross error in perspective. No maybe, it's a huge distortion. It's > a
> wonderful theory, it has a component of truth in it, but totally > fails
> the tests for significance.
I can't agree with you on this one, Al. Partly, it's not the whole story. In fact, your characterization of the premise is, itself, a distortion. Low parts count DOES, indeed, mean fewer things to fail, but the simplicity means little if the parts are fragile.
Most renditions mention not only how *few* moving parts there are, but also how _robust_ they are. Compare the eccentric shaft with a typical crankshaft: it is massive; there are no rod journals to flex. The rotors are heavier than a whole set of pistons, but there are no true reversing loads, just a continuous gentle change of vector. It's the *combination* of low parts count AND robust parts that made the sale.
Dale R.
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