Bending moment in an axis doesn´t match

AI Thread Summary
The discussion revolves around discrepancies in bending moment calculations compared to expected results using moment equilibrium. The user is analyzing forces applied by gears on an axle and is struggling to derive accurate values for bending moment diagrams despite having the necessary reactions from bearings. There is also confusion regarding the constancy of torque in the torsion diagram despite changes in the circular section. Participants are asked to clarify why torsional moments might remain constant and how to effectively determine moments from shear diagrams. The conversation emphasizes understanding the relationships between shear forces, bending moments, and torsion in structural analysis.
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Hey guys, first of all, this isn't a homework question, I just want to know why the results are what they are. I've been trying t obtain the same numbers using moment equilibrium but they still don't match. This is the example:

upload_2016-7-9_23-33-15.png

W are the forces applied by the gears in force-pounds. The gears are located at the sides of the thickest part of the axle which is the diameter D4. The distances in inches are located below where the letters are.
upload_2016-7-9_23-38-22.png

To obtain the graphs analysing x-y axis and z-x axis is necessary. The reactions in the bearings are Raz, Ray, Rbz and Rby. These are used to obtain the shear force diagrams and the bending moment diagrams. I'm unable to obtain the values in the bending moment diagrams. Also, if you could tell me why the torsion diagram (the first one above with the number 3240 on it) says torque is constant despite the change in the circular section I would really appreciate it.
Thank you guys!
 

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Why would you expect torsional moments to change at a change in cross section? Would you expect shears or bending moments to change?
Please explain your difficulty in determining moments from the shear diagram.
 

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