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post #1 of (permalink) Old 01-21-2004, 11:36 AM Thread Starter
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Are two Tie Rods better than one?

I have been looking at a lot of high steer, and cross over steering systems, and reading a lot of write ups lately. I am getting design Ideas for my own system. I have noticed that most of the time when a high steer system is used, or a full cross over the orig steering arms are almost always left on the knuckle, but not used.
I was wondering why it is that more people don't run 2 tie rods. The one above the axle, and one in the stock location. It would spread out the stress of turning over more of the knuckle, and the stress on the actual tie rods would be half of those on a single rod set up. Plus if you bust one... You still have another one.
I would like to hear other opinions on this matter
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post #2 of (permalink) Old 01-21-2004, 11:45 AM
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Re: Are two Tie Rods better than one?

If you look at the axle from the front and draw a vertical line through the ball joints, they are not parallel but lean towards each other at the top. I don't know if the new upper arms could have the tie rod end holes in a proper position to be able to use both. It would take some accurate machining if it is possible.
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post #3 of (permalink) Old 01-21-2004, 11:52 AM
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Re: Are two Tie Rods better than one?

Another advatage of putting the tie rod up high is that it is out of the way of rocks and other obsticales. I think most people leave the lower ears on either because they are lazy or that it offers some protection to the rotor. Maybee if you cut them they alter the structrual integrity of the cast. It realy isn't in the way of anything tucked back up in there. I have seen people cut them off howerver.

I'm just going to build my tie rod out of 1 1/2" DOM w/ 3/4 heims and forget about it.
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post #4 of (permalink) Old 01-21-2004, 11:52 AM Thread Starter
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Re: Are two Tie Rods better than one?

Hmmm will, I am not quite sure what you mean.
You are correct in one aspect. You could not run two rods that are the same length. The one on the top steering arms would probably have to be a few inches shorter than the one in the stock location.
If you are wondering if having two different length tie rods will cause binding when turning... It shouldn't, in fact I would think it would be a smoother operation, because the rotational force is not only coming from the top of the knuckle, but also from the middle.
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post #5 of (permalink) Old 01-21-2004, 12:22 PM
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Re: Are two Tie Rods better than one?

But your pivot axes aren't parallel with each other.
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post #6 of (permalink) Old 01-21-2004, 01:13 PM
 
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Re: Are two Tie Rods better than one?

I tend to agree with WILL here. It's not just a matter of the difference in the length of the rods, you have to realize that this means the attachment points at the ends of the arms swing through different circles. This is not a problem as long as you have one tie rod, but my wager is that a second tie rod would have to be able to change length as the steering wheel was turned. I would expect point to point distances would change at different rates on non-concentric circles if you hold angle of rotation constant.
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post #7 of (permalink) Old 01-21-2004, 01:54 PM
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Re: Are two Tie Rods better than one?

Yeah, probably would want to bind.

But -- on the lighter side - you could turn both ways at once!
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post #8 of (permalink) Old 01-21-2004, 02:57 PM Thread Starter
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Re: Are two Tie Rods better than one?

When I was first thinking about this issue I thought the same thing.
I figured it would not work unless the two sets of arms were exactly the same. And the two tie rods were the same length.
However, I was not sure.... So I did some research
My trusty (but dusty) Rigid body dynamics Text book proved to me that a 4 bar mecanisum having equal length shorter sides

(Ie the two steering arms connected to the same tie rod have to be the same lenght from knuckle pivit point to tie rod connection point) (they are, for both top and bottom tie rod)

with a single drive link

(the steering arm attacthed to the steering box) Is the drive link

Will keep the two oppisite (shorter sides) at the same angle.

I will admit that text books never make things totally clear. But I was pretty sure it would work, even if the steering arms were not the same length. But not totally sure. So I developed a modle.
I used a simple computer Drawing and rotated the drawing about the pivit points on the axle. The two tie rods with different length steering arms never changed lenght. Well that is all fine and good but for those that still don't believe. Here is a simple proof.
You know when you have a cardboard box and you open the top, and open the bottom it kind of flops down flat. Think of the part on the ground as the axle shaft, and the part oppisit it the tie rod. The two parts left are the steering arms. Now say you have another unfolded box. This one is not a rectangle but a box that has 3 different length sides. The to sides that are the tie rods are the same length (but not the same as the first box) the side on the ground that is the axle is the same lengh as box one. Put those two boxes together so that the pivits are the same. the boxes would be stacked on the ground top to bottom. Kind of making a long cardboard tunnel. Set the angle of box one and two differnt in ref to the axle tube box. Stick them together some how to make the whole system ridgid, and rotate the whole system about the pivit points. (knuckle pivit points) It will swing through an arc smoothly.


I am pretty sure two tie rods will work. This post has turned into a brain teaser.
I was just wondering what everyone thought of the idea of having two tie rods. I am not saying I am going to set my jeep up like this, I wsa just wondering what people thought.
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post #9 of (permalink) Old 01-21-2004, 03:05 PM
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Re: Are two Tie Rods better than one?

</font><blockquote><font class="small">In reply to:</font><hr />
Stick them together some how to make the whole system ridgid, and rotate the whole system about the pivit points. (knuckle pivit points) It

[/ QUOTE ]

It still sounds like you are trying to model the pivot axes parallel though.
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post #10 of (permalink) Old 01-21-2004, 04:57 PM
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Re: Are two Tie Rods better than one?

In addition the ends of the arms are inboard from the ball joints. From above, the axel and linkage form a trapezoid, not a parallelogram. Both sets of arms would have to have the same angle built into them.
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