Shear pin question 2

[ken1959]

I am installing a rotating turntable for a stage. We are designing this thing on the fly and I need to know what type of shear pins I should use to protect the main sprocket and motor from being destroyed if the turntable should jam during operation. The Tables finished weight will be around 1000 pounds and nothing more than one and a half tons will be sitting on it. Thanks in advance for your suggestions.

 

[ornerynorsk]

I'd use a shear coupling right off of the motor shaft with a pin of mild steel 1/4 the diameter (or slightly less) of the motor shaft diameter. Please note that this is a very rough rule of thumb. You should really figure your loads accurately to be on the safe side.

 

[Pressed]

Most shear pins are notched or necked down for optimum concentration of load (but not all). The cheapest/easiest ones available to the public are the cast iron shear bolts for snow blowers. Made of the right material and the threads allow for a concentration point. If you don't want to calc it out, you could just test it before use to be sure of what happens. If it shears to easy, use more bolts or reduce the radius (as in, on a disc).

You could also use a slip or overload clutch, most are adjustable. Rig a torque wrench at the sprocket, have someone push on the stage and determine what load is right and buy clutch in that torque range. Or not.

This isn't super complicated but more detailed than what I have written here. Good luck.

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