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valve monkey
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Discussion Starter #1 (Edited)
Rather than rehash everything here, this link will bring you "up to speed" to the point I'm at now... the pertinant info is on page two of this thread... (edit: skip down two posts for the info contained in the link below)

http://www.webrodder.com/forum/viewtopic.php?t=85


Thank you in advance if you bothered to read that. Now my question is this:

In order to get the upper bars to fit in the available space, I'll have to cut them from their original length of 14.5" to 10.5" (eye-to-eye). Is that too much of a change and is pinion angle delta the only concern? Is 4-5 degrees too much delta through full suspension travel? I don't mind cutting the bars and retapping them but I want to be sure it's the right thing to do. BTW, the lower bars are 18" long.

TIA,
Richard
 

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I can't read your linked post because I am not a member, but if I understand you correctly you want to take 4 inches out of the upper control arms and leave the lowers at stock length!? That's going to rotate the entire housing down and point the pinion damn near into the ground. I doubt the arms would even line up anymore with the housing mounting points (remember, this is triangulated).

Now, if you move the mounting points out from the frame four inches in line with what the original arms were, it should be okay. Range of motion up and down will not be what it used to be, though.
 

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valve monkey
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Discussion Starter #3 (Edited)
These are not stock mounting points, they are fabricated as well.
So others can read it w/o joining another forum here's the context of the thread link above...

Hello again. I need to resurrect this tread for some more advice. I got the lower bars done and all is well. However when I got ready to do the top bars I ran into a problem. The bars and brackets are designed to go in at a 45 degree angle. Therein lies the problem.

I'm using an 8.8" Ford rear from an '01 Explorer. The center section is offset 2'' to the passenger side from the factory. This shortens the available axle tube to weld the upper brackets to (can't weld to the cast iron center section). The lack of space requires one of two changes:

1) Make new brackets to fit the bars at a (in this case) 30 degree angle to the frame. I've already made 'em but haven't installed 'em.

2) Shorten the bars enough to make 'em fit in the abbreviated space at a 45 degree angle.

How critical is the 45 degree angle of the bars? I could see a little variation being OK but is going to 30 degrees too much?


Next post:

What should I do? Shorten the bars, or install them at 30 degree angles? Those are my only two options (as I see it).


Next post:

After shifting my attention to the front suspension for a while (parts came in!) I went back to the rear suspension and mocked up a set of "shortened" upper bars that would fit at a 45 degree angle. I tacked everything in place and moved the rear suspension through it's full travel.

Results? Well from "bottomed out" to "full droop" there is about 4 degrees of pinion angle change. About 1.5 degrees of change from the "ride height" position to "bottomed out" and another 2.5 degrees of change from "ride height" to "full droop".

What say you, oh street rodding gurus? Will this work? Looks to me as though it will. I like the bars mounted this way as opposed to compromising their ability to locate the axle's side-to-side movement under the car.
 

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I think you might want to look into not wanting to weld on the center section. This is from a 4x4 site but I'm sure the same thing could happen with big power and traction to put it to the ground.
http://www.4x4wire.com/jeep/tech/axle/ford8_8/

You could also look into another 4x4 way of doing things. Some guys that put triangulated 4 bar links into their trucks use a axle truss welded to the axle tubes and a "rock ring" with an extra tab on it to bolt it to the truss to tie it all together.
http://www.4x4rockshop.com/scripts/prodView.asp?idproduct=1864

Also I have been working on an excel spreadsheet that will calculate out all the perameters of a 4 bar linkage.
http://home.earthlink.net/~triaged/Files/
Note that version 2.1 is a BETA version that isn't 100% yet but it will do bump and droop travel.

I think I would rather have the upper links at 45deg and be shorter then to have them at 30deg and stock length. The reason is because of lateral stiffness...and what compliance is there will most likely be in the oversteer direction which isn't optimal.
 

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valve monkey
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Discussion Starter #5
Wow, thanks for the links! I don't know if they accomplished much welding mild steel to cast iron but maybe it'll help a little.

I REALLY like the "Rock Ring" I could modify the "ear" (tab) on the top to accept the upper bars and have them closer to the center (like a factory 4-link a la G-body cars, etc).

I looked at the spread sheet and must admit I'm lost! I'd gladly provide the info from my car if you'll tell me what it means!
 

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I thought the "rock ring" was a good way to get out of alot of welding cast iron to mild steel. I'm sure the pre-made ones would be way to heavy for your application and you don't need the ring gear protection (at least I hope you will never back into a rock that big). Maybe you could buy one and just use the top half? There are alot of places that make them and maybe you could get one made special?

If you take the measurements I will plug them into the spreadsheet and tell you what it spits out. I'd need:

Distance from each link end to the ground at ride height
Distance forward from the centerline of the axle of all the link ends
Distance from side to side from one mount to the other

For the first 2 you only have to do one side of the car.

Also need your wheelbase and total weight.

The center of gravity height is the hard one to get but often the engine camshaft height (off the ground) is used as a ballpark guess so I would need that dimension as well.
 

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Sinistr, I assume you made your own bars. I'm curious about the 18" lower arm. That seems very short to me and makes for a much tighter arc vice say a 36" arm and seems as though you are going to have some limited vertical travel. I think the optimum angle for the top arms is 45 degrees, but don't ask me why. There probably is an optimum ratio of upper to lower lengths and if you are using 18 inchers, you probably stand to shorten the uppers to the same ratio. I really like my set up by Air Ride Technology and I think I will measure the arms and figure the ratio for you.

Trees
 

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valve monkey
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Discussion Starter #8
trees said:
Sinistr, I assume you made your own bars. I'm curious about the 18" lower arm. That seems very short to me and makes for a much tighter arc vice say a 36" arm and seems as though you are going to have some limited vertical travel. I think the optimum angle for the top arms is 45 degrees, but don't ask me why. There probably is an optimum ratio of upper to lower lengths and if you are using 18 inchers, you probably stand to shorten the uppers to the same ratio. I really like my set up by Air Ride Technology and I think I will measure the arms and figure the ratio for you.

Trees
I didn't make 'em but they were fabbed up by someone (bought 'em 2nd hand). I'd appreciate the measurements on the ART bars!
 

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Sinister, my lower bars are 28 1/2 inches long, set in the middle of the adjustment. the upper bars are 17 1/4 inches set in the middle of the adjustment. I can see where the one upper bar would reach the cast part of the Ford 9 inch, but using a good Chevy 10 bolt, you can weld any where on the housing, One thing you could do to gain about an inch is to mount the upper bar on the inside wall of the frame channel instead of on a boxing plate. You would still need to box, but just leave enough void to clearance the arms.

Trees
 

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valve monkey
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Discussion Starter #10
You're bars are considerably longer. Thanks for the info.

I think you got the Ford 9" and Chevy 10 bolt backwards in your post (you can weld anywhere on a 9" but not on the cast iron center section of a 10 bolt or the 8.8" Ford that I'm using)

My frame's a "top hat" style not "C-channel" so that won't work to help me gain room.

As long as the pinion angle changes less than 5 degrees throughout the suspension travel, shouldn't it be OK?
 
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