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Date: Mon, 27 Jun 2005 11:25:44 -0400
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From: Alain Gauthier <alphagolf@videotron.ca>
Subject: On Boosting Engines, Stressing Crankshaft and TBO
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Hello friendly listers !
Why build Lancairs if not in pursuit of speed ?
Here is a copy of an e-mail I just sent to Stuart Featherstone.

Hello Stuart,
First, congratulations on your achievement : completing and flying a 
modified L2K is no small feat !

Don Barnes in his post on the Lancair Mail List reporting on N54NE's 
first flight, mentions :
“... Lycoming IO-580 (Angle Valve) by Performance Engines 400+ hp”.
This brings the following questions (from a potential client who is 
quite interested in Performance Engines’ products) :

1. When boosting engines beyond their design output, does Performance 
Engines take into account the significant stresses imposed on the 
crankshaft (and other stressed parts, for that matter)?
As you will no doubt know, Lycoming recently lost a court case on the 
basis of experts’ report claiming that their large-bore crankshafts were 
significantly undersized. I understand that the claim was that the 
crankshafts were originally sized for smaller engines and supposedly now 
being used on larger-bore engines beyond their capacity to sustain a 
2000-hour TBO.
(Disclaimer here: although I graduated in Engineering Physics, I’m in no 
way qualified to review and qualify crankshaft design. In addition, the 
fact that Lyc. lost its case, does not imply that the jury was in the 
least bit qualified to understand the tech subject matter. Finally, this 
may not apply to the 580 series, but the general question would hold.)
That being acknowledged, I wonder what consideration is given to vital 
parts stressing when Performance Engines pushes engine parts beyond 
their design limits, thus possibly reducing significantly the engine 
safety margins and service life expectancy,

2. What is the expected TBO on your engine ?

Regards
Alain
L2K Wannabe


Not that I would like to drag you, experts on our List, into another 
heated debate, but would you please kindly provide your views on what 
appears to me as a serious push on the aircraft envelope and risk 
factors. Not that I condemn this exploration attitude, but it would 
rather seem to me that in this case, some serious hard-nosed tech 
consideration and serious in-lab engine beating are in order...
If Stuart is intent on racing and expecting and mentally ready for 
possible difficulties, this is not for me to judge. But our community 
might benefit from a bit of reflection on pushing engines or engine 
parts beyond their intended performance envelope...

Regards, Alain
L2K Wannabe

PS. I love to read old works from great scientific minds of the past, 
and found this which could guide some of our debates...

Writing about Chymists and Aristotelicians :

"... But I blush not to acknowledge that I much less scruple to confess 
that I Doubt, when I do so, than to profess that I Know what I do not : 
And I should have much stronger Expectations than I dare yet entertain, 
to see Philosophy solidly establish't,if men would more carefully 
distinguish those things that they know, from those that they ignore or 
do but think, and then explicate clearly the things they conceive they 
understand,acknowledge ingeniously what it is they ignore, and profess 
so candidly their Doubts , that the industry of intelligent persons 
might be set on work to make further enquiries, & the easiness of less 
discerning Men might not be impos'd on."

Robert Boyle, The Sceptical Chymist, Part of First Dialogue, , as 
printed in year 1680.
( I just replaced the old "f" for "s" wherever aplicable... Sorry, no 
typos introduced here ! :-) )