If a double joint, which they offer, were used up top, the two joints of the double are 90 degrees out of phase. That should all but cancel any non-linear effect if it really is a problem. Also the double should allow a bend up there of greater than 30 or 35 degrees.

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...

Here is the double joint I was talking about. Not two separate u-joints.

http://www.borgeson.com/xcart/catalog/Stainless_Steel_Double_Universal_Joints-orderby_0-p-1-c-12.html

Ken Burton wrote on Sun, 09 November 2014 05:47

Here is the double joint I was talking about. Not two separate u-joints.

http://www.borgeson.com/xcart/catalog/Stainless_Steel_Double_Universal_Joints-orderby_0-p-1-c-12.html

With a double at the top, unless we can get rid of the single u-joint at the bottom (on top of the steering box) then we'd end up with a total of three u-joints,
which would require something to anchor the shaft in the middle to keep it from "looping" as the manufacturers say.

Yes, I realized that but I just wanted to throw that option into the mix.

Also I thought someone said that stainless DD shafts were not available from Borgeson. Is this what we are looking for?

http://www.borgeson.com/xcart/catalog/Stainless_Steel_Steering_Shafts-orderby_0-p-1-c-20.html

http://www.borgeson.com/xcart/catalog/Polished_Stainless_Steel_Steering_Shafts-orderby_0-p-1-c-21.html

Ken Burton wrote on Sun, 09 November 2014 09:34

Yes, I realized that but I just wanted to throw that option into the mix.

Also I thought someone said that stainless DD shafts were not available from Borgeson. Is this what we are looking for?

http://www.borgeson.com/xcart/catalog/Stainless_Steel_Steering_Shafts-orderby_0-p-1-c-20.html

http://www.borgeson.com/xcart/catalog/Polished_Stainless_Steel_Steering_Shafts-orderby_0-p-1-c-21.html

the 3/4" inner DD shaft is available in stainless, but the outer sleeve of the telescoping shaft is only available in steel, as far as I can tell.
Personally, I'd just get the regular DD shaft and coat it with anti-sieze as you suggested earlier. But, I'm still concerned about the angles involved, so
not 100% sure this is a prime time solution. It obviously works in Jim F's coach though, so who knows.

Karen
1975 26'

just an update:

Borgeson u-joints are good to 35 degrees, and we already know they work here.

The pinch-bolt type u-joints do require notching the shaft for the shoulder bolt to clear (a good thing), so probably a good fit for our lower u-joint.

So, my current shopping list:
upper u-joint: Borgeson 1"-48x1"DD (stainless: #114352)
DD slip shaft (Borgeson 450024 or others)
lower u-joint: Flaming River 13/16"-36 x 3/4DD pinch-bolt u-joint (stainless: FR2719DD)

I think there are a lot of possible solutions. Thanks to Jim Fawcett for heading down this path and figuring out the sizes.

Karen
1975 26'

Karen,

Point of clarification, could you please advise some more details regarding; "Unfortunately these can only go on the DD telescoping
shaft one way, and that way is NOT correctly phased?"

Are you saying you can not perform Alex's steering box alignment procedure?

http://www.gmcmhphotos.com/photos/g6588-steering-box.html

Regards,
Rob M.
Sydney, Australia
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426

I'm not an engineer but I'm thinking it really wouldn't make any difference. It's not a driveshaft with a lot of weight and RPM. Our rpm on the steering shaft will be a single digit number...probably a very low single digit. The only time you'll turn more than a few degrees is when slow speed turning.

We know it works...right...Jim Fawcet has been running it for a year.

Perhaps one of the professional engineer types can explain why it would make a noticeable difference. I'd appreciate the education.

I'm not the least bit sure that my roadster is in or out of phase. I'll go look later.