I am building a roadster pickup with a Desoto Hemi and I was told I can't use a rack and pinion with a Model A axle unless it is mounted directly to the axle (butt ugly in my opinion). Any body have any info on if I can do it without the front wheels doing crazy shit every time I hit a bump? Could I add a panhard bar and eliminate side to side movement of the axle to make it work? I have the rack hidden under the chassis now but can still change it back to a steering box and drag link if I have to. Any input is greatly appreciated.
It's not the side to side movement as much as its the up and down movement that causes the wheels to toe in and out. I had the same situation with my Willys with a dropped tube axle. I mounted the Saab R&P behind the axle and inline with it and it wasn't so noticeable then used a PTO slip shaft with universals on each end to connect the rack to steering column. It worked fine and steered great for over 20000 mi until I sold the car.
Ok, if the problem is with up and down, how does it work with modern vehicles without the wheels toeing in and out?
I did this about 10 years ago. Everyone said it wouldnt work, and it would have terrible bump steer. But it did not. Not one little bit. And it also had a real light steering, almost like power steering. Was good for the 6 years my father owned the car. And he drove it a lot too. The only thing I can think that I did different than most was that I used a torsion bar front suspension from S&W race cars, instead of the usual transverse spring. I think with the transverse spring, the rack pushing on one side and pulling on the other side causes the spring shackles to deflect (possibly the spring to flex also), and shift the whole axle over. If I am correct on that, then a panhard would solve the problem. But I havent tried it. I just know I have used a R&P on a 4" drop axle and didnt have any bump steer or other negative effects.
With an A arm car, the rack and the control arms would pivot at the same point and all work together. With a beam axle, the axle moves up and down, while the ends of the rack move in an arc. And it is that, that is supposed to give the bump steer. But this gets really complex. First of all, the beam axle doesnt really move up and down during use. It will if both front tires hit the same size bump at the same time. But in reality, they dont. You are more likely to have one wheel hit a bump or dip. And that make the axle rise or fall in an arc also. So many people say it cant work, so if you choose to try it, go into it carefully. I never liked the slip joint on the steering shaft idea. It just seems to me that to make it slide easily, it would have to have some play in it. And play in the steering never works out good.
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