Chapter 7193x(mm)θ(rad)F.E. ModelFull F.E. Model0−0.001 4260−0.001 4270−0.001 4160140−0.000 1466−0.000 1467−0.000 16463150.001 31200.001 32800.001 3150The main discrepancy between the results is at the gear location (x=140 mm) . The largervalue in the full model is caused by the stiffer 55 mm diameter step. As was stated earlier,this step is not as stiff as modeling implicates, so the exact answer is somewhere between thefull model and the simpliﬁed model which in any event is a small value. As expected, mod-eling the 30 mm dia. as 35 mm does not affect the results much.It can be seen that the allowable slopes at the bearings are exceeded. Thus, either the loadhas to be reduced or the shaft “beefed” up. If the allowable slope is 0.001 rad, then the max-imum load should be Fmax=(0.001/0.001 46)7=4.79 kN. With a design factor this wouldbe reduced further.To increase the stiffness of the shaft, increase the diameters by (0.001 46/0.001)1/4=1.097, from Eq. (7-18). Form a table:Old d, mm20.0030.0035.0040.0045.0055.00New ideal d, mm21.9532.9238.4143.8949.3860.35Rounded up d, mm22.0034.0040.0044.0050.0062.00
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