KB wrote on Sat, 08 November 2014 13:37

JohnL455 wrote on Sat, 08 November 2014 06:49

My assumption was always that the shaft was an addaptatiin of an off the shelf Spicer truck part and still available. My concern is that in the video the upper joint appears to be a U joint and not a CV. That would provide non linear speed transmission from the wheel to the box. That could provide a wierd non linear driving experience.

Interesting point. My current theory is that they used a CV joint at the top because it can handle bigger angles than most u-joints, so could apply to more vehicles. I think the non-linear u-joint response you mention helps explain why it's so critical to get the steering shaft aligned correctly to the center of the steering box.

Two u-joints, phased correctly, mostly counteract each other and act more like a CV joint.
I wonder if having a u-joint at the top, phased with the lower joint, would help counteract the non-linearity of the lower u-joint?

If we added a third u-joint (a double at the top, a single at the bottom), we'd have to add an intermediate support,
which adds more complexity than I'd want to deal with.

just thinking out loud...

Karen
1975 26'

2 u joints only cancel if their angles are the same.
And the top steering angle is way different than the lower angle. They wont cancel.
Now in a slow speed device like a steering wheel, I'm betting you won't notice it much.

I think the CV joint is a better solution.
I do wonder about the stiffness of the DD shaft in a heavy application like the GMC.
I'm betting there is a little twist during turning...