Thread: Low-budget/T-Bucket Pickup

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Some basics-----------the wheels set on the ground-they don't move up or down---

the frame/body moves up /down

angles relative to ground are meaningless-drive line angles are what matters-----and they are effected by chassis angles to suspension / rear end---------

Wheels certainly do move up and down relative to the frame. And when they do, the geometric relation is exactly the same as when the frame moves up and down relative to the wheels.

∆Y=∆∅

Firebird----------maybe instead of you argueing about deltas, cosigns,etc,etc----you would attempt to visualize the concept that all the wheels set on the planet earth, and everything else about a vehicle is relative to those points------the suspended vehicle is in an orbit and is effected by external forces but that the wheels remain pressed against the ground by gravity attracting its mass------

the vehicle must be seen as an object that is completely interrelated within its self ( angles are vehicular, not ground related) the lines drawn between various components aren't related to each other because of wheel travel but because of unit travel of the vehicle------

So for dealing with the angles on the rear bars we must go back to the angle of the crankshaft centerline and its relation to the pinion centerline, maintaining an acceptable relationship to each other thru out the travel distance of the suspension AS THE VEHICLE TRAVELS UP AND DOWN FROM LOADING AND ROAD TRAVEL INDUCED FORCES-------

Lighten up guys!
This stuff is supposed to be fun!
I love to see discussion on this stuff, and I love hearing new/different ideas tossed out there. That's what this fourum is for. If we keep it friendly more people will participate. Thanks

On this particular topic, I do agree that the u joint is designed to allow momentary angle misalignments. However, the very short driveshaft in a T-Bucket is going to aggravate any large misalignment issues. I am curious enough that I am going to check it when get home next. Thanks for bringing it up 36 sedan.

I'm not uptight and I sincerely hope Jerry isn't either.

I've merely been trying to apply mathematical concepts to the real life issues and situations which are presented in this forum as a means of increasing my comprehension.

I am tempted to discuss the details further as I am positively convinced of my position but I respect Jerry too much to needlessly badger him over minutiae.

I'm perfectly fine with the complete discussion-------I only try to point out the simple basic reasons for STUFF and I believe my background qualifies me for my opinion--

Since your in Florida-----go over to Ocala and ask Don if would approve or disaprove of my works???????? I think I could probably get a job working for him but am pretty busy with other dealings right now-------

And if you want to discuss commercial aviation also????????

Glad I didn't overly frustrate you Jerry. I know your qualifications exceed my own.

We agree on key points: the pinion angle relative to the transmission is key. (I recall it is down three degrees?). Ideally, the pinion angle does not change with chassy articulation.

The rest is philosophical.

I measured the pinion angle change over 3 inches of suspension compression, and one inch of rebound. The pinion angle change was less than half of a degree. While I was at it, I also swung each side of the rear end up and down independently to make sure there was no binding in the suspension. Everything moved nice and freely.




IMG_0385.jpg

But it looks like you checked pinion angle relative to the ground--thats not it--it is the angles of the drive line ---------

https://www.brightstorm.com/math/geo...lines-theorem/

Originally Posted by jerry clayton

But it looks like you checked pinion angle relative to the ground--thats not it--it is the angles of the drive line ---------

You may have gotten a little confused. I was not setting the pinion angle. I was measuring the pinion angle change in relation to suspension travel. This was in response to 36 Sedan's question.

When I do set the pinion angle, I will set it equal and opposite to the transmission output shaft angle. It is pretty simple.

So actually since the pinion angle didn't change(less than 1/2 *) your driveshaft angles will change at the u joints, however, if your drive shaft is less than 60 inches long, your angular change will be withinn an acceptable limit of 3* or less-----

OK I feel like I am entering Alzheimer's or something:

Somewhere along the line, it got drilled into my head that the pinion angle is supposed to be 3* down relative to the transmission.

Am I completely wrong, or perhaps this specification was specifically for leaf spring set ups, to compensate for spring wrap?

Originally Posted by firebird77clone

OK I feel like I am entering Alzheimer's or something:

Somewhere along the line, it got drilled into my head that the pinion angle is supposed to be 3* down relative to the transmission.

Am I completely wrong, or perhaps this specification was specifically for leaf spring set ups, to compensate for spring wrap?

That sounds about right for a leaf spring setup. On a high performance leaf spring car, you have to lower the pinion angle to allow for the spring twist under acceleration.

Ok I did some digging. It looks like the 3* is not a fixed angle. It depends on the suspension. Ladder bars being most rigid, require 1* down. Four bar 1.5*. Leaf can be as high as 7* down. This is to compensate for the tendency of the pinion to rise under hard acceleration, maintaining the overall pinion angle at zero or less.

It is nasty mojo for the pinion angle to become positive.

Relative to transmission of course.

I hope I regurgitated that correctly.