How to calculate impact of a rotating steel cable (think weed eater)? 2

[rtengineer]

Hi,
I'd like to calculate the impact of a rotating steel cable on a steel surface (think weed eater contraption) and I'm not sure how to tackle this problem.

Any suggestion?

Rick

 

[JStephen]

For a rough guess, I would assume that when the cable smacked the steel, it collapsed to, say, 3/4 of its original diameter, in which case, all of the deceleration is spread over about 1/8 of the diameter. Knowing speed and that distance gives you acceleration, and F=ma gives you a force. Which, of course, will be highly approximate, but probably about as well as you'll do without any actual testing.

This assumes a cable hitting a long flat surface, not wrapping around a surface as it hits.

 

[chicopee]

See the attachment as it should be self explanatory.

 

[chicopee]

Reeaxaming, the value of Vc, it should be relabeled as Vcx whereby Vcx is the component of Vc being perpendicular to Rc which is the distance from the center of rotation to the point of tangency. From the diagram, the angle of Vcx in relation of Vc is based on the position of Rc to the vertical line. You have to make an estimate of the radius of curvature at the point of tangency and that can be done by simply bending the steel cable to its maximum without kinking it.

 

[rtengineer]

Thank you to both of you! Very helpful!

Rick

Rick