A borehole drilling machine with a vertical shaft of 60 mm diameter is 500 mm long and is supported in long bearings at its top end. The shaft has Youngs modulus of E = 110 GN/m2.  A disc of mass 40 kg is attached to the center of the shaft. The center of the disc is 0.25 mm from the geometric axis of the shaft. Neglecting any increase in stiffness due to the attachment of the disc to the shaft, calculate: 1.1. The critical speed of rotation.  1.2. The maximum bending stress when the shaft is rotating at 80% of the criticals peed.

Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
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A borehole drilling machine with a vertical shaft of 60 mm diameter is 500 mm long and is supported in long bearings at its top end. The shaft has Youngs modulus of E = 110 GN/m2.  A disc of mass 40 kg is attached to the center of the shaft. The center of the disc is 0.25 mm from the geometric axis of the shaft. Neglecting any increase in stiffness due to the attachment of the disc to the shaft, calculate:

1.1. The critical speed of rotation. 

1.2. The maximum bending stress when the shaft is rotating at 80% of the criticals peed.

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