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Thread: Beam Suffering

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Posts: 91-100 of 117
2012-08-16 21:16:11
#91
Originally Posted by Disney
Scott Russell


Watch that. When EBC is parrallel to AB the arm is at full extention. At any point other than that, it'sa shorter distance from A-C. This is the over center, or binding that we're referring to. It's just built in to this type of linkage.


i guess when i read binding i'm thinking something completely different to you, as with the compliant bush centred at a given ride height it's not going to move far enough either direction to bind. have a look at the pictures here to see the amount of travel thats happening, and how out setup differs from the animation you linked too by having extra linkage points >> QT Adjustable link( rear alingment link))
2012-08-16 22:04:18
#92
With the shocks/springs disconnected from my beam, as I move the rear end through it's motion it gets more difficult to raise as I approach the "center" point where the linkage is straight and then gets easier the very second I get past that point. This is the binding i'm trying to describe.
2012-08-17 13:03:39
#93
Isn't the conclusion that you actually have to keep the B15/P11 at stock ride height but do change the springs and dampers to stiffen it up? (plus swaybars, bushings, strutbraces sticky tires, alignment etc etc) to get the best performance?
2012-08-17 19:53:22
#94
Originally Posted by Disney
With the shocks/springs disconnected from my beam, as I move the rear end through it's motion it gets more difficult to raise as I approach the "center" point where the linkage is straight and then gets easier the very second I get past that point. This is the binding i'm trying to describe.


when which linkage is straight? the srl or the panhard? as the only resistance you should feel in that situation (bar the weight of the beam and connected parts) is the pressure to move the compliant bush either side of its natural centre point, is this what your talking about?

....phone....
2012-08-18 12:06:18
#95
Originally Posted by damasterpnut
Isn't the conclusion that you actually have to keep the B15/P11 at stock ride height but do change the springs and dampers to stiffen it up? (plus swaybars, bushings, strutbraces sticky tires, alignment etc etc) to get the best performance?


This guy says yes to all. I'll also add the B14 on your list.
2012-08-18 14:25:39
#96
That's what I'm thinking too, but that still leaves the roll center way up. This is why I kept the Tein's in the back, since they have the most conservative drop, but it didn't seem to help all that much so will try 1.5" B&G's in the back.
2012-08-18 15:07:36
#97
A dozen things impact roll center. Adamant try Vadim.
Last edited by Kyle on 2012-08-18 at 15-08-18.
2012-08-19 03:55:12
#98
Originally Posted by Kyle
A dozen things impact roll center. Adamant try Vadim.


Sure, Mike K wasted time converting to panhard then
2012-08-19 04:02:35
#99
I did not say he wasted time. He did the best he could with what he has. He also bent the rear beam correctly to aid in his success.
@Vadim try giving this a read Handling and Brakes
2012-08-21 17:27:30
#100
Just an update, Kyle and I were talking and came to a conclusion, when most of us say roll center, we really mean center of gravity. Roll center is a whole different animal, that is covered very well in this article.

On another note, I noticed the Maxima guys are replacing the Russel link bushings with delrin. I thought that was a no no, but someone pointed out that Mike K was actually talking about the bushing that connects to the link body of the car itself. The Delrin bushing should not bind at all.

How To: Install Delrin Rear Beam Bushings + Review!





ES bushing for Axle beam ? - Maxima Forums



Originally Posted by speedymax99
Originally Posted by jac121479
don't you want big soft rubber bushings in a Scott Russell. i thought the reason for the squishy stuff was to keep the beam from binding causing an infinite spring rate???

You want a bearing that allows the parts to rotate/swing smoothly, that's what this is. There's no binding, which is why I mentioned I could swing it up and down smoothly by hand when installed on the car.
You don't want a big squishy bushing that allows the parts to move side-to-side unwantedly and that doesn't rotate smoothly, but rather twists, adding an unknown spring rate into the equation.


Originally Posted by speedymax99
Originally Posted by jac121479
here's a quote from Mr Kojima, whom i trust when it come's to suspension.
Originally Posted by Mike
To keep the stock rear suspension from flexing sideways under load, Nissan uses a device called a Scott-Russell linkage. The linkage does reduce flex but the big soft rubber bushings needed to keep it from binding up hinders it. The linkage causes binding and uneven wheel rates from side to side.

I don't think you're understanding or looking at the pictures right. There are 4 bushings back there. Only 1 is made to flex sideways, and that's left alone. 2 are in the link, and these make that link operate much smoother. The remaining bushing is almost too small to replace with delrin/alu and would require a spherical bearing because it moves in more than 1 axis.

Originally Posted by speedymax99

Originally Posted by ajm8127
Point b is where the bushing goes that allows side-to-side flex. Although this diagram is a simplified version of the linkage on the 4th gen. Notice how it is lacking the extra link at c. I suspect that the addition of this smaller link, the one that is getting the delrin bushings, better approximates vertical motion of the rear beam without inducing as much side to side motion of the beam, or flex in the bushing at b. Less flex = less bind. Point b is on the very right side of this picture:

http://upload.wikimedia.org/wikipedia/commons/thumb/2/20/Scott_Russell_Linkage.jpg/800px-Scott_Russell_Linkage.jpg

Speedymax, are these delrin/aluminum bushings for sale, or are you just trying to generate some interest?

That diagram is actually exactly like our rear beam setup, as view from front to back. It does show the 2 links we have. Imagine points "A" and "C" not being able to rotate freely, but depending instead on a hard rubber to twist. The whole assembly will not move up and down smoothly, but will still move side-to-side because it's rubber. Not what we want.
Last edited by Vadim on 2012-08-21 at 17-28-45.
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