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Old 04-22-2016, 09:51 AM   #141
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Join Date: May 2010
Location: Central Iowa
Posts: 491
Default Re: Gravity bends a crank?

I got side-tracked at work one day and decided to ran a quick finite element analysis on a 5.7L SBC crankshaft to determine the amount of deflection that occurs when its stored in various orientations. The CAD geometry was simplified - features that would not affect the analysis were removed - to reduce processing time, but was taken directly from a GM-supplied model.

Four conditions were modeled, with gravitational force being the only force acting on the crankshaft. Steel with the following properties was selected as the material.

Things to note about the images:
  • Deformation measured/shown is only that in the direction of the gravitational force (downward in the images).
  • The colored bands help delineate the amount of deflection that is occurring in a particular region of the part.
  • The colored representation is over-scaled to help show the deflection of the part. It is not 1:1 scale.
  • The vertical (or horizontal) lines depict the original condition, unaffected by forces.
  • Units = Inch

Conditions Modeled:
  1. Vertical; Standing on flywheel flange

  2. Vertical; Hanging from flywheel flange

  3. Horizontal; Supported by all main journals

  4. Horizontal; Supported by only the front and back main journals

As you can see, even in the worst condition (vertical storage), the maximum amount of deflection that occurs is in the hundred thousandths. This is less than the accuracy that can be measured by nearly all micrometers. It would be fair to assume that a Flathead crankshaft would exhibit similar behavior.

So, in conclusion, store the crankshaft however you feel fit. If you want to store it vertically to save space, do that. If you want to store it horizontally to prevent damage from tipping over, do that.
Attached Images
File Type: jpg standing-gravity.jpg (6.8 KB, 40 views)
File Type: jpg hanging-gravity.jpg (7.6 KB, 36 views)
File Type: jpg mains_all-gravity.jpg (19.4 KB, 37 views)
File Type: jpg mains_ends-gravity.jpg (18.0 KB, 38 views)
File Type: jpg steel_properties.jpg (18.1 KB, 36 views)

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Last edited by itslow; 04-22-2016 at 10:02 AM.
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