Done with Blue Ox - a cautionary tale

[davidbrady]

Have you noticed that Blue Ox changed their design. They no longer let that clevis rotate. Here's one of their new bars: http://www.blueox.com/tow-bars/bx4370bx4...t-tow-bar/. Notice that the rotation about the x-axis (the direction the vehicle is traveling) now occurs at the middle joint. The first joint now has fixed ears welded to the receiver tube. I guess we now know the problem with the old design: one of the ears of the clevis fails, most likely the one that failed at the bolt hole, then the clevis rotates and the other ear breaks in bending. Probably doesn't matter if the clevis is made of steel or T6 aluminum, In this scenario both materials would break. The new design eliminates this. More better!

A quick back of the envelop calculation shows that a 5000 lb vertical force applied 12" away from the bus's receiver would bend that bar. If the bar was solid steel, like the Roadmaster extension, than 7500 lb. So, pretty much the full weight of the toad plus some came down onto that receiver!