I am working a steel frame supporting a hammer mill. I have used Staad to find the natural frequency of the frame without imposiing the hammer mill loads.
I am not sure how to convert the vendors load info to loads I need to impose on the frame. This would be dynamic loading. Here is the info given me.
U=normal rotating vector = 3033 pound feet
P=abnormal rotating vector = 11,176 poud feet
W=static weight = 12,750 pounds
Rotor Assembly moment of inertia = WR, where R is squared = 2,500 pound feet-feet squared
they say to multiply P by 1.5 and apply resulting vector independently in horizontal and vertical direction.
next they instruct the primary forcing frequencys are
(1) speed of the rotor @ 720 RPM and
(2) rotor speed multiplied by the number of hamme rows (3)
Next they say that the above loading should include rotationg vector "U", as a dynamic steady state harmonic load.
Finally, after all that:
"The worst load condition is the sum of "U" and "P"--as modified by the above.
I hope someone can help me figure out what the loads to the frame will be and help me with the dynamic loads imposed.
thanks
Jeff
Very poor instructions.
What does the prime mover look like?
Go back to the vendor and find out:
1) what is the meaning of
U=normal rotating vector = 3033 pound feet
P=abnormal rotating vector = 11,176 pound feet
2) is U the normal uniform torque load on the unit with or without loading?
is P an oscillatory torque (dynamic at frequency)developed under loading?
Come to think about it, maybe the vendor should do the calculations for you since you are buying or bought a very expensive piece of equipment and you ( and I) don't have a clue.
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