Bryan:
seriously (this time)--
I can't definitively confirm that these are not myths, but there is some
basis in science for each idea.
Any old metal that has been in service-- especially thermodynamic service--
will be "seasoned", more or less. Some will be seasoned "to death"!
An old, high milage engine will have a few advantages:
#1. It will likely have revealed any hidden flaws in its major parts-- they
will have fatigued and broken, making it obvious that "this is not a
keeper".
#2. The metal "solution" typically does not have perfectly homogeneous
distribution in most factory parts (due to insufficient heat treating).
That means that the physical properties of the metal (strength, hardness,
etc.) vary some throughout the part. Time alone will allow the solution to
become more homogeneous, in some alloys. Add low heat-cycles (as in a
water-cooled engine), and this process works even better.
#3. The manufacturing processes typically induce internal stresses that are
not fully relieved (again, due to insufficient heat-treating). And again,
time and the engine's heat cycles will gradually help to dissipate these
internal stresses. Note that this will also tend to induce slight geometric
deformation of the parts-- however, those deformities can be corrected when
the parts are "blueprinted". And then they won't come back! (unless you
"cook" the engine)
Never heard of a shaker table used for stress relief. A couple of things it
could do:
a. Begin to open microscopic cracks (via fatigue), so that flawed parts can
be more easily culled
b. Increase the overall strength of (good) parts through the process of
"strain hardening"
Not sure about using this for relief of manufacture-induced internal
stresses. But heat treatment works for that (when done right)-- why use
something more exotic?
Note that good heat treatment and careful NDT can also make a brand-new
block or head a better bet than the "seasoned" one. But it will cost more.
Russ, #1226B
-----Original Message-----
From: owner-land-speed@autox.team.net
[mailto:owner-land-speed@autox.team.net]On Behalf Of Bryan Savage
Sent: Saturday, December 14, 2002 5:08 PM
To: Bob Jepson
Cc: Land Speed
Subject: Re: Stress relief
I have read that a rebuildable engine out of an old school bus or truck
is good for racing use because it is "Seasoned".
I also read about vibrating parts with a high power "Shake Table"
will relieve stress.
Are these Racing Myths?
Bryan ( wondering & wet )
/// 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.
|