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  1. #26
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    1 out of 1 members liked this post. Yes Reputation No
    the lack of material forming a direct load path between bearings significant this rod is obviously not for a high BMEP big bore engine which needs good compressive strength. i still think there is not enough shear strength to carry bending loads properly its the big rectangular hole under the pin that would concern me. i would have used a series of elliptical holes (or circular) aligned if i had to do something like this.

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    Shluld have just used an aluminum rod and be done with it.

  3. #28
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    Click here to enlarge Originally Posted by DFM Click here to enlarge
    Im willing to bet the strength reduction is negligible. It depends on if they did their HW on where to cut metal out of them. On compression (which is the biggest force on a con rod) the material will attempt to spread in a lateral direction (perpendicular to the direction of the force vector). its all a matter of having enough material (in the right places) to counter this lateral spread.

    Now I'm deviating from what I know to be true and just speculating. The very high RPM will probably put a lot more stress on a regular con rod than it will this one, due to the reduced weight. Having less stress due to high RPM's means that what strength there is in these "holey" con rods will be better optimized to deal with the compressing force applied on it from the piston. like I said, just speculation. could be just talking out of my $#@!...im no expert on this stuff.
    Your high rpm speculation is more or less accurate. The kinematics of the reciprocating rod deal with forces, masses, and accelerations(both positive and negative). So, the less weight you have throughout the rod, the less compressive force at the bottom of the stroke and the less tensile stress at the top of the stroke. Given the beam was drilled with a truss design, I would imagine it is still extremely strong for compressive and tensile stresses. Also, I would bet it is still very capable of dealing with what is likely the main mode of failuer in a rod, buckling, given the truss design.

    The thing I am really surprised about is that there is no moly type coating on the piston skirts! Upon second look, I'm also a little curious of the cross sectional area of the rod in the center vs the min cross sectional areas of the other cut out areas.

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