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4link related, upper link chassis mounts

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Gravity Fed
Alex Staidle
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4link related, upper link chassis mounts
November 19, 2014 01:04PM
For the four link upper links, mounting to the chassis....

How tall should the brackets be. Meaning, if i have the lowest hole of the mount at say 0 degrees for the sake of visualixztion, how far should the upper most hole be for maximum angle adjustment? Afco sells ready made brackets with 5 holes that are 7" tall. Thry also have 6 hole at 9". Would these work well for the upper link mounts and thus determining upper link angle or should i make something?



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Gravity Fed
Alex Staidle
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Re: 4link related, upper link chassis mounts
November 19, 2014 04:33PM
The power of math suggests a 0 to 20 degree range of adjustability. Thoughts?



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Jon Rood
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Re: 4link related, upper link chassis mounts
November 21, 2014 09:32AM
Most people will likely disagree, but when I built my 4 link on the Celica, I went with the 70% length up arms to the lower arms, then 80% height on chassis pivot to axle pivot points. I then made it adjustable, 1" down, 1" up to dial in the anti squat for getting the best traction. I've never moved the upper links from the middle position, the car has amazing bite off the line, so why mess with it. Most rally car builders, OLD SCHOOL RWD, will tell you parallel equal length links. It works, but could it be better..?

-Jon
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Pete
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Re: 4link related, upper link chassis mounts
November 22, 2014 11:52AM
I tried equal length/parallel on the 3 link and suffered righteous wheelhop.

I'm curious by what you mean with the 70%/80% business, though.



Pete Remner
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john vanlandingham
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Re: 4link related, upper link chassis mounts
November 22, 2014 12:11PM
Quote
Pete
I tried equal length/parallel on the 3 link and suffered righteous wheelhop.

I'm curious by what you mean with the 70%/80% business, though.

I think he means upper link 70% length of the lower .
That way it will end up tracing a different arc than the lower..
Same thing is accomplished moving the upper front link down..
I guess.



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Pete
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Re: 4link related, upper link chassis mounts
November 22, 2014 02:10PM
I wouldn't have thought that would work very well as a 4 link, since it would bind up once you tried to articulate the axle. And if the axle isn't articulating, then you're driving too slowly to care about what the suspension can or can't do.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 11/22/2014 02:10PM by Pete.
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Re: 4link related, upper link chassis mounts
November 22, 2014 02:37PM
this may help


http://www.how-to-build-hotrods.com/parallel-4-link.html

http://www.how-to-build-hotrods.com/triangulated-4-link.html



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Edited 1 time(s). Last edit at 11/22/2014 02:41PM by tdrrally.
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Re: 4link related, upper link chassis mounts
November 22, 2014 02:55PM




As long as both wheels are moving up and down the same (i.e. no body roll or bumpy/uneven surface) it doesn't really matter.
So you are likely to see it on drag racing cars, where that doesn't matter a lot, and often due to regulations stating that the floor pan must be stock => not giving room for longer upper arms.

Since gravel rallying is all about articulation, roll and uneven surfaces, equal length should be the thing.



Brgrds
Brian

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Pete
Pete Remner
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Re: 4link related, upper link chassis mounts
November 22, 2014 04:13PM
Drag cars often/usually have ladder bars here. Two A-frames between the rearend and chassis. The axle can only move up and down. It is simple, proven, and tends to be stable.

What is more fun, every setup I have seen used clevises as the pivot instead of a rod end. Rod ends are not as strong as a clevis, so a clevis is used and you just use a Nyloc style nut on the bolt so you don't have to tighten it. The suspension rotates around the bolt.

Drag racing is often an amazing example of what you can get away with.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 11/22/2014 04:16PM by Pete.
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jrally
Jon Rood
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Re: 4link related, upper link chassis mounts
November 25, 2014 04:34PM
I'm pretty sure with all heim joints, my rear axle articulates just fine. John is correct, I was refering to top arm length to lower arm length, then axle pivot points vs chassis. (15/20 and 7.5/6.0)



That's 10" of travel with minimal pinion change. I would have gone with longer lower arms, but stuck with stock when I built it. The factory top arms where something like 9 or 9.5 inches long, to accommodate having the back seat in a sporty car.

-Jon



Edited 1 time(s). Last edit at 11/25/2014 04:35PM by jrally.
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Pete
Pete Remner
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Re: 4link related, upper link chassis mounts
November 25, 2014 08:04PM
Yah, I'm not suggesting that it doesn't work, just that I didn't think that it would, and therefore there's knowledge to be gained.

My 3-link has lower links 19.5" long and the upper is 14" and I don't know what the height difference is, I just kept making it lower and lower and grip kept going up and up, and I can't go any lower for space reasons. Pinion angle definitely changes over the course of suspension travel.

Stock RX-7 4-links have the upper links pretty short and the axle and body flex in order to allow it to work, and if you unbolt one link and articulate the axle, you'll see a 2"+ discrepancy between the body and the link. No wonder the upper mounts tear off of the car, or the rearends twist and flex and take a permanent set.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 11/25/2014 08:06PM by Pete.
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