Double Shear Pin Failure
Double Shear Pin Failure
(OP)
I have a shear pin on a snowblower auger that is bending before it shears. I'm currently trying to figure out the max shear force the pin can take, having the materials given for the pin. The thing is, I'm not sure if I need to account for the bending of the pin or just try to solve for shear force. Any ideas?





RE: Double Shear Pin Failure
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RE: Double Shear Pin Failure
If it were me I would just check it for shear.
RE: Double Shear Pin Failure
RE: Double Shear Pin Failure
If the shear pin is bending, that means there is excessive clearance in the joint at assembly, or some part of the joint is yielding under operating loads. Maybe check the pin and shaft holes for edge bearing stress.
RE: Double Shear Pin Failure
In reality, the shear load is distributed over some effective bearing thickness. Once you do a free body diagram for that, the eccentricity allows you to calculate the amount of bending. There are various methods that are used, but the problem is determining the effective bearing thickness (and hence moment arm). First order calculations use half the lug thickness, but those are usually too conservative. If you can show acceptance for that, then you are done. The next order solutions use the bearing strength to determine the effective moment arm. If you have a copy of Bruhn's book, Chapter D.1 has some calculations. You can also look at ESDU 91008:
https://www.esdu.com/cgi-bin/ps.pl?sess=unlicensed...
But the you don't "interact" the bending stress of the pin with the shear stress. This is because the peak bending stresses occur at a different location along the pin than the max shear stress. So in that sense, what Jboggs and tbuelna can be true. Pin bending is not usually critical for well designed connections. If there is no gap between the shear planes, it should be shear critical. In a situation where there is a gap, it can be bending critical. This can occur when a design uses a spherical bearing and allows for angular travel. A gap is required to allow the joint to rotate to some degree.
Brian
www.espcomposites.com
RE: Double Shear Pin Failure
One end has a large diameter that engages an enlarged diameter hole in the tubular auger shaft. Just below the enlarged diameter the the bolt body diameter is reduces significantly. The other end is nominal bolt size, as are the holes in the solid drive shaft, and the opposing hole in the tubular auger.
http://i5.walmartimages.com/dfw/dce07b8c-f7e7/k2-_...
By now the large and small holes in the tubular auger shaft are deformed some. After a shear pin/bolt failure, The stub captured in the solid shaft usually shows significant bending at the un-notched end. I believe that was the case on the first shear pin to fail.
RE: Double Shear Pin Failure