# Calculating the force on a shaft

I would like to attach bearings on a shaft, see: https://www.physicsforums.com/showthread.php?p=3856547#post3856547

Therefore I would like to calculate the axial and radial force on the shaft, so I can select the right bearings.

The picture looks a as following: http://i39.tinypic.com/kd1naq.jpg

So I have a shaft, with a plate attached on it with a weight of 10kg. A load will be putted on the plate wit a weight of 37,5kg. Now I would like to calculate the axial and radial force on the shaft.

Sketch:
http://i41.tinypic.com/kd1iqx.jpg

Sum Fx to A = o

Fxa = o

Sum Fy to A = o

(-375N x 0,625 x 0,3125) – (100 x (0,725/2)) + Fya x 0,725 = 0
-73,2 - 37,6 + Fya x 0,725 = 0
-110,8 + Fya x 0,725 = 0
Fya = 110,8 / 0.725
Fya = 153N

Som M t.o.v. A = o
M in a = 375 x (0,725 – 0,3125) + 100 x 0,3625
M in a = (375 x 0,4125) + 36,25
M in a = 191Nm

The shaft would have an axial force of F = 153 N and radial momentus of M = 191 Nm according to this calcuation.

Does this look ok, or should I calculate it completely differently?
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OldEngr63
Gold Member
You need to go back and shows the bearings in your FBD, and include their forces in your force and moment sums.

Also, it is not entirely clear where some of your dimensions came from; can you identify them, please?

What dimensions are not identified? Do you see the picture?

OldEngr63
Gold Member
Yes, I saw the picture. One of the difficulties is that you have worked entirely with numerical values, rather than giving symbolic names to each of your dimensions. If you gave each of them a symbol, before plugging in the number, then it would be much easier to see where each item came from.

Also, in the FBD, I do not see any reaction forces on the upright arm; why?