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GT40 Tech - Chassis,Brakes,Tires,&Wheels Chassis and Handling.

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Old 11th February 2018, 05:07 PM   #1
Pat
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Steering intermediate shaft phasing

In putting my steering rack together I decided to check on the ideal placement of the u-joints on the intermediate steering shaft. On end goes to the rack the other to the steering column. What I found are two contradictory schools of thought.

The one says:

STEERING U-JOINT INSTALLATION
The yokes at opposite ends of any shaft segment should be aligned with their bores parallel, at least within reason. Phasing or “clocking” of the universal joints is especially
important when welding u-joints directly to the shaft, since it will be impossible to re position them once you’ve done it. Any back-to-back pair should be aligned like the ends
of a driveshaft, as in the picture at the right. Please study it closely; the difference is not obvious unless you are looking for it. The more acute the operating angle, the
more critical the phasing. At around 45 degrees out of phase, the shaft will react to
applied torque with a wobble, with the condition being most pronounced at 90 degrees. A badly out-of-phase setup makes excessive u joint angles act even worse, and cannot
be improved by re timing the steering wheel. For reference, most stock car steering layouts will tolerate joints 20 degrees out of phase, and will not likely cause noticeable problems in steering, but 45 degrees out will be noticeable, and 90° will almost certainly cause problems.

And the other:

Contrary to common belief, and information supplied by some of the larger manufacturers of aftermarket steering components, steering universals should never be phased (or ‘timed’) in-line with each other like a vehicle drive-shaft. This should
be avoided at all costs, for the following two reasons:
1.Universal joints are not constant velocity joints, and will rotate with a fast and then slow rotation on the output side, with a constant speed rotation on the input side.
2.Universal joints do not rotate without the shaft lengths changing.
Correct installation of more than one cross-bores when timing universals is done by advancing either the top or bottom unit by 15° to 45° clockwise or anti-clockwise, depending if it’s a left or right-hand-drive application, or a steering rack or steering box, to prevent the fast/slow velocity, and the shafts from changing length while rotating.

Any thoughts here???
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Old 12th February 2018, 06:57 AM   #2
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Re: Steering intermediate shaft phasing

Hi Pat
I've been through this a few years ago.
I think its a combination of both depending of your setup.
If both Uni's have the same angle as each other, then the "in phase" would work the best.
If the angles differ, then its a trial and error of moving them out of phase a spline at a time to see if it helps.
By help, I mean if the steering is hard one way and easy the other just off centre. It can help with the initial turn either side.
My setup had two different angles and the only way I could fix it was by extending the column shaft so the angles were the same.
Made a huge improvement to the steering.
This is a picture of my original setup and its obvious now that it wasn't quite right...
You live and learn.
Hope that makes sense.

Clayton
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Steering intermediate shaft phasing-dcp_0003-jpg   Steering intermediate shaft phasing-dcp_0001-jpg  
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Old 12th February 2018, 09:02 AM   #3
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Smile Re: Steering intermediate shaft phasing

Thanks so much for the insight Clayton and especially the helpful pics.
It's interesting that there are such contradictory views on phasing but your approach of "in phase" but "spline at a time until smooth" makes good sense. The splines on my intermediate shaft are not exactly aligned so the closest I get to "in-phase" is about 15degrees offset. It seems smooth but I haven't torqued everything down as yet. I found it interesting that one of the articles recommended +15o for left hand drive and -15o for right hand. One would think there wouldn't be a difference.

It certainly was a lot clearer than the response I had from another forum in which i participate:

"Well, I'm remembering a sine wave, indicating the output speed, that rose slightly above and below the input shaft speed (a horizontal line, of rotation velocity). The variation in speed would be affected by how severe the angle was between the shafts. Not likely to harm things with small "steering" inputs. Being in phase would make the issue moot."

"Huh???"

Again thanks.
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Old 13th February 2018, 12:29 AM   #4
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Re: Steering intermediate shaft phasing

No probs Pat
Just to clarify the above statement.
The intermediate shaft speed will oscillate from fast, slow, fast slow etc in one rotation of the input shaft (steering column) with its speed constant.
The way to gain a constant output speed is to add another uni "in phase" so that it converts it back.
-Input yoke (steering column) at constant velocity
-Intermediate shaft at varying velocity (fast, slow, fast, slow)
-Output yoke (Rack pinion) at constant velocity.

This all depends on the two uni's having the same angle.
In my case I had 10 degs and 42 degs = hard, easy, hard, easy turning the steering wheel. The steering wasn't binding or anything. Its just that at points in the turn the input of say 1x would produce a output of say 2x (hard) and at others it would have an input of 1x and the output would be say 1/2x (easy)
Very hard to put into words.

I added a spline adapter to increase the length of the column, so that both uni's were at 26 degs (see drawings below).
This made a massive improvement to the feel.

Clayton
Attached Files
File Type: pdf GT40 Steering adapter.pdf (577.3 KB, 22 views)
File Type: pdf GT40 steering shaft.pdf (606.5 KB, 21 views)
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