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Of the different failures and other difficulties observed with these motors, perhaps the most interesting are cracks in the cylinder flanges.

In the Opel-B.M.W. motor the corner between this flange and the cylinder wall is not rounded off sufficiently, the radius of the fillet being practically nil.

There is nothing remarkable in the fact that such a faulty form leads to fractures, but it is certainly remarkable that in a factory with the experience of the Opel Works such a source of failure can pass unobserved in a complete series of motors.

It is worth note that the fractures occur specially in the first and sixth cylinders, these being the cylinders which get most of the vibration.  The camshaft fixes the other cylinders.  The failures are pure fatigue fractures.

The pistons and gudgeon are a further source of trouble.  Incorporated in the aluminium pistons are cast iron bushes (the gudgeon pin housing being cast integral with the piston), in which the gudgeon pin rests.  At the slightest amount of play between gudgeon pin and cast iron bush, these bushes work

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