| Frame Restoration: [message #150819] |
Sun, 27 November 2011 21:30  |
noi
Messages: 293
Registered: October 2010
Location: South of Fremont
Karma:
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Senior Member |
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Greetings:
I noticed something about my frame rails, as I was in the final process of rust de-scaling in preparation for sealing & coating, that I found interesting.
When I placed the two rails next to each other, to check for relative straightness, I was shocked to see that they were not totally parallel to each other - As I had “squeezed” the back half together first (random selection):
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41619&title=rear-half&cat=5942
I then went to “squeeze” the front half together, to get a feel for how straight/parallel the rails were, and saw the “gap” that was there:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41616&title=front-half&cat=5942
At first, I attributed this to the rails being “bent” due to repeatedly being jacked up in the “weak” area of the frame, as it was in the “wavy” section – As it looked to be “bent” in the opposite direction to body load, and would therefore “straighten out” as load was placed on it, I figured it wasn’t too bad and the worse effect would be to have a slight decreasing factor on caster.
Attempting to asses the “damage”, I stacked the rails on top of one another, to see which one was worse:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41620&title=stacked&cat=5942
I was then very surprised to see that ALL the holes lined up, as far as I could visually see, exactly!
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41617&title=holes-front&cat=5942
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41618&title=holes-rear&cat=5942
I can only think of two, viable, reasons for this:
First, and most unlikely, the rails bent evenly from years of evenly applied forces.
Second, and what I think most likely, rails were built with a small bow in them to resist “sagging” and allow thinner/lighter material to be used – Much like the torsion bars are pre-stressed – I placed the “apex” of the bow on our driveway seam (yeah I know, not very scientific, but figure close enough) and it does appear that there is a slight bow in the rails.
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41614&title=bow-front&cat=5942
http://www.gmcmhphotos.com/photos/showphoto.php?photo=41615&title=bow-rear&cat=5942
Anyway, just something I found interesting – Look forward to any other thoughts or opinions.
Carl P.
76 Birchaven
South of Fremont
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