# Plate thickness

1. Feb 23, 2014

### Mauriza

Hello guys, i have a problem in determining a thickness of a plate. i have a motor (m = 17 kg) attached to a plate. the design can be seen in the attachment. i need to know the dimension of "t".

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2. Feb 24, 2014

### RocketSci5KN

Use a caliper if it already exists. Or, is this a homework type problem to calculate the minimum t to hold the 17kg? If you just want to make something, use 1/4" alum.

3. Feb 24, 2014

### PhanthomJay

One way to do it is to calculate the force in each of the 4 bolts that fasten the plate to the wall. Then calculate the bending moment in the plate equal to the bolt tensile force times its perpendicular distance to the inner set of the bolt circle which holds the motor to the plate. Then check the plate stresses from that moment.
If I convert to customary USA units, the motor ways say 50 pounds lets use 100 pounds to account for vibration impacts and throw
a safety factor of 4 on it. That's 400 pounds. Assume a 12 inch diameter motor 12 inches long. Moment at plate = 2400 inch pounds. Load to one bolt is 2400 divided by 12 on 2 bolts, or bolt tension = 100 pounds. Moment to inner bolts is say 1000 in pounds. Using 30000 psi steel or aluminum, the required section modulus is 1/30 inches cubed and that is 10t^2/6 solve t = about 1/8 inch. Use 1/4 inch aluminum as suggested, or use 1/4 in steel for better plate rigidity. Based on a lot of assumptions here. Disclaimer: proceed at your own risk, the author absolves himself of all responsibility.