Bill:
I think one thing you can read between the lines in what Neil wrote is that
most of out LSR efforts stress most kinds of rods well above 60% of yield.
(Super rods-- like Carillos-- may be an exception, in all but the most
powerful engines).
In classes that allow enough power to be produced that engine parts often
approach overstress-- rod strength is typically a key limiting factor. I'm
no expert in flatties or Arduns, but I've learned enough from you to know
that the block simply won't hold tremendous horsepower-- so in that case, it
probably doesn't take very exotic rods to avoid overstressing those parts.
Russ, #1226B
p.s.: I think IT IS possible to predict the useful life of a set of rods
with useful accuracy, if one is willing to prioritize the time to collect
the data and to do the calculations. Neil has told you exactly the
methodology that Reliability Engineers use-- and they make similar
predictions routinely, for a process called "predictive maintenance".
-----Original Message-----
From: owner-land-speed@autox.team.net
[mailto:owner-land-speed@autox.team.net]On Behalf Of ardunbill@webtv.net
Sent: Thursday, June 05, 2003 7:17 PM
To: Albaugh, Neil; land-speed@autox.team.net
Subject: RE: to buy or not to buy??????
Neil, I'm glad you mentioned fatigue life, maybe we can kick this around
a little. I recently read a tech article by Kevin Cameron(probably the
best mc tech writer active today) in the journal of the Aircraft Engine
Historical Society on stress and fatigue, and he mentioned that ferrous
parts that operate somewhere in the 25-60% of their yield stress range
may have an INFINITE fatigue life. Maybe that's why, to cite a 'homely'
example, a stock Flathead conrod, which seems so skinny, may after 200K
miles of ordinary service where it's stroking along almost all the time
in the 1500-2500 rpm range, be perfectly sound and unstressed. So Joe
Rodder can come along, grab this old rod and the rest of them, mag 'em,
they pass, put in new small end bushes and re-size the big ends, and
stick them in his hot Flattie. And they may be actually just as good as
brand new unused ones. Not that that means as strong as Cunninghams or
Fergusons, mind you!
The trick here though, is to know what the stress level is for iron and
steel parts that keeps them in the 'infinite fatigue life' range.
Generally, we don't. Bill
/// unsubscribe/change address requests to majordomo@autox.team.net or try
/// http://www.team.net/mailman/listinfo
/// Archives at http://www.team.net/archive/land-speed
/// what is needed. It isn't that difficult, folks.
|