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Old April 1st, 2017, 05:52 PM   #63
bjvircks
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Join Date: Aug 2010
Location: Iowa
Posts: 1,406
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Hi NDS !

"Efficiency"

(background) In June of 2017 I will have been a practicing mechanical engineer for 37 years. In that time I've done some (but not much) design work with bearings of various types.

In my experience in general (and applying here to bearings) there is Data, Craft, and Art.

"Data" is hard fact that is demonstrateable, reproduceable, quantifiable. The concept of efficiency in its purest sense is hard data. Power out divided by power in is "efficiency". Pure science and just numbers. No opinions! In my business, multi-million dollar decisions are preceded by "Show me the data."

"Craft" is a combination of hard data and anecdotal evidence used in combination to arrive at informed but perhaps not absolutely proveable conclusions. Here there may be less data and more anecdotal evidence, which means care must be taken to not compare things that are not really comparable. (here in USA we use expression "comparing apples to oranges" to describe a comparison that is not appropriate). Applying "Craft" well requires a lot of technical depth and insight.

"Art" in my opinion is nothing more than a beauty pagent. Purely subjective opinion and personal bias are used to assign completly arbitrary relative value to characteristics which may or may not have any importance to product perfomance. Reading a product material specification off of a manufacturer's datasheet and and using it to affect an "efficiency assignment" is nothing more than a beauty contest.

So... with respect... I (and I think matguy and others... I cannot speak for them, but suspect I'm on target) feel you are bringing a lot of Art, some Craft... but little DATA to your bearing efficiency discussion.
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