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Old 01-08-2011, 11:21 PM
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Front Steer Conversion

In case it might help someone else, I offer this description of the steering changes made in my conversion of a PT Cruiser to RWD, but the same principles would apply in any change from rear steer (steering arms behind spindle axis) to front steer (steering arms forward of spindle) -- In my case I decided to swap the spindles Left to Right and Right to Left, a process that created two serious problems:
1) the revised locations create the opposite of proper Ackerman
2) the stock rack & pinnion will steer backwards (You would have to turn the steering wheel clockwise to go LEFT)

Ackerman is achieved when the innermost front wheel turns to a sharper angle than the outermost wheel in an accute turn. In the case of short wheel base cars (like the PT) 6 to 8 degrees of Ackerman is typical at a the maximum steering (tightest turn) position. In the stock case this is accomplished by having the point where the tie rod end attaches to the steering arm fall inward (toward CL of car) of the so-called "kingpin axis" -- In the case of a McPherson strut car the king pin axis is a line extending from the center of the ball joint ball to the center of the swivel joint aty the top of the strut. In the PT the tie rod end attaches to the steering arm 1.08" inward of the kingpin axis.
The goal of the front steer conversion is to achieve similar geometry and in this case it was possible to get an acceptable Ackerman by modifing the steering arms an move the tie rod attachment point inward by 2.06" and upward by 0.88", which allowed it to fall outside the kingpin axis by 1.135".
The attached photo shows how this was done, the countersunk hole is the location of the original tie rod end attachment and was drilled and reamed reamed out to 5/8'' for a flat head Allen grade 8 cap screw. Note that the welding to the original steering arm is confined to the outer "dead metal" areas that do not affect any heat treat conditions that may have been given to the original arm. Best practice is probably to weld with a Nickel rod (the parent metal of the steering arm apperas to be nodular or spherical cast), but I used Stainless 308 mig wire. Note that the bolting and welding give a very high degree of redundency and hence a high factor of safety.
Any rack from a front steer vehicle would work and Dodge Dakota units are often suggested. However, I am planning to try using a Dodge Intrepid unit which has the tie rods attach at the center. This leads to very long tie rods and reduces bump steer and rod angularity problems.
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Old 01-08-2011, 11:30 PM
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Brian Martin,Freelance adviser
 
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I am going to go out into the flaming roadway with this one.

You may feel you are qualified to relocate tie rod ends on steering arms by welding an extension on them. And you may be qualified to do so, I don't know you. But I don't think it is a good thing to post such a thing on a do it yourself car site. I would NEVER, EVER suggest for ANYONE I don't know to do such a thing. It is DEADLY, we are not talking about fabbing up some radiator support that if it fails you need to weld them again or making up a power window conversion that will leave you with rain coming in if it fails. We are talking about DYING and KILLING people.

I think if you are going to post something like that make it damn clear how serious it is and to take it to a qualified welder.

Brian
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Old 01-09-2011, 08:43 AM
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reverse akerman

A better idea might be to use the old go-cart triangle tie rod connector to get akerman. . that way you aren't doing questionable heating- welding on the steering arms. or swap in the dakota suspension-crosmember.
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Old 01-09-2011, 08:48 AM
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Ahhhhhhh swap in a whole DESIGNED suspension and steering, now that's an Idea!

Brian
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Old 01-09-2011, 12:09 PM
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The 5/8" bolt is always there making the only failure mode a COMBINATION of both SHEARING THE BOLT (which would take 27,590 lbs force ) and BREAKING THE WELDS! As I stated, the welding was confined to totally unstressed areas of the stock arm which could not affect any fractory heat treatment (in my opinion as a degreed metallurgical engineer) -- However, I will accept your suggestion and refrain from posting any further details on steering mods as this is your place and your rules.
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Old 01-09-2011, 03:30 PM
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Brian Martin,Freelance adviser
 
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You obviously have done your home work, MOST DON'T. This is why you do this neat little trick then keep it to your self unless you are telling someone in a PM or something. I just think tossing around the idea of welding on steering components is dangerous.

I am not an engineer or a metallurgy specialist but a general knowledge in welding around cars and when that steering arm is heated while welding how in the living hell can it not be affected?

Again, suggesting for people to do this is dangerous. I will stick by my opinion on this. Been hanging around forums for too long, it is not a good thing to suggest. At least not on this general forum. Now, you want big warning flags all over and comment over and over this is not something to take lightly, maybe. But just a blank "here is how you modify steering knuckles". I don't like it.

Brian
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