steering, went in a new direction, thoughts...

i went from the cowl steering to this setup, thoughts about it wanted,

 

Clean

 

Should work a lot better.

 

does the pitman arm look ok, i lost anout 1 1/2 or so in length to miss my header, didnt want to remake them unless i needed to....

 

A shorter pitman arm will slow down the steering. Slower helps at high speed just makes it harder at slow speed. The FOGGER

 

thanks

 

what is the ideal geometry. whats it look like<!-- / message -->

 

Ideally you would want the drag link and radius rod close to the same length with the radius rod, Pitman arm and steering arm all in line, but your setup doesn't seem to allow for it. You've probably got it licked anyways or at least a hundred times better.

http://books.google.com/books?id=b_...esult&ct=result&resnum=8#v=onepage&q=&f=false

 

Also, in case you might consider lowering your box to get closer to factory alignment, keep in mind that it may be better where it is with the short drag link, as it may tend to keep the steering arm end in a more neutral arc through travel with upward movement of the axle. Since it would be half way through it's swing in the middle of travel, opposed to swinging back right from the start. I hope this makes as much sense to you as I think it does to me. The best plan is just to make a scale drawing of the three points and run their arcs with a compass, trying to get the least amount of conflict between them with what parameters you have to work within.

 

What you're looking for is your drag link and radius rod/wishbone to be as close to equal lengths as possible and also as close to parallel as possible. You'll probably have some bumpsteer with the setup you have now, but not as bad as I'm sure you had with the cowl steering.

 

Nice work, but I think you just traded one case of bad bump steer for another. Like landsea said make a scale drawing plotting your arcs. I think you'll find that your short drag link will have a very radical arc compared to that of the radius rod. I do think that it's an improvement over the previous geometry. I drove a vintage modified for a guy a few years ago. The steering geometry is, as far as I can see, identical to what you have now. The car drove great as long as you had it hung out sideways. When the body would roll back to level coming off of the corner the bump steer created would turn the car hard right (a very puckering experience the first few laps). Once you'd hit the straight away it was nothing but sawing at the wheel as hard and fast as you could just to run a straight line. I think you'll find that as the left front goes up or down in travel it will want to turn the front tires to the right due to the shorter more severe arc of the drag link. From what I can see from the pics the best set up would be to lengthen the pitman arm on the original cowl steering set up dropping the drag link to parallel with the radius rod. There would be some bump steer but minimized and your steering would be quicker. There is only one way to COMPLETELY eliminate bump steer and that is to mount a rack and pinion directly to a beam axle. With this set up all of the links travel with the axle, so there are no arcs created by suspension travel. With every other suspension you can only minimize bump steer.

 

Parallel is great for a four bar, but not necessarily a radius rod or hairpin setup.

 

That cowl steering arm would be 2 foot long at least and rack and pinion, bite your tongue. Also, most of these cars have minimal suspension travel and his main complaint with the old setup was a low speed wobble that may have come from the combination of the original, less than subtle steering geometry quirks and the extended steering arm you cant see in the picture that may also have had some deflection in it.

 

I'd disagree. With a hairpin set up you're just replacing two radius rods with one. If you make a scale drawing of the set up I think you'll see that any time that you have a shorter link and a longer link the shorter links arc will pull away from the larger links arc at a greater rate for every scale inch of travel. When both links are level they are both at their longest point. With the drag link angle down I think what you'll find is that when the left front goes up in travel the hairpin will be slightly shortening the wheelbase on that side, while the drag link will be arcing towards level, essentially getting longer, turning the wheels slightly to the left. When the left front goes down in travel the hairpin will once again, because it was level to begin with, will be shortening the wheelbase on that side. The drag link though, will be in essence getting shorter, because of it's more radical arc at a faster rate than the hairpin, causing the car to steer to the right.

 

In my post I originally had (not very traditional) after rack and pinion. You are right about the steering arm being too long also, but I do think the geometry wise it would be better.

 

I agree that, with different lengths between the drag link and radius rod, there is going to be some conflict. Worsening as the difference gets greater, but it's not really relative to angles.

With a non four bar suspension, if both the drag link and radius rod were the same length and had the same rear pivot point, they would travel in the same arc. Even though they would be at different angles. Put them parallel and they now go in two different arcs.

A four bar however, will have a similar arc between the drag link and either suspension link through travel with them parallel to each other. Assuming again, that they are all the same length.

 

Just so you know, I'm not trying to bust anybody's balls. I just like getting really involved in discussions at times.

 

Actually, and I would suggest you plot this out on paper sometime, if you run the same pivot point for both radius rod and drag link, but different end points they will travel in the same arc but at a different point in that arc which will still give you bumpsteer, if they are parallel the arcs will match up and you won't have the bumpsteer. I come from the offroad/Jeep world where we put a LOT of time and effort into steering/suspension geometries to make our rigs go down the road decent. The links MUST be as close as possible to the same length and as close to parallel as you can get 'em if you wanna have a "one finger ride".

 

Bear with me, as I only have a pencil and a dried out Sharpie to work with. Here's what I got, and that's assuming all links are the same length. Also, a Jeep would generally be a four link or parallel leaf which has it's own unique characteristics and isn't really comparable to a radius rod type suspension.


< This last picture is flawed, see posts 21 & 37 for explanation.

I'm going to bed now.

 

Actually, after looking at it on the screen, my brain is telling me you are probably right about the parallel links working. At least at equal lengths, but I am to tired to really be sure. So sorry, I think.

Edit.
Wait a minute. When my head hit the pillow, I saw this.

So I'm going to stick to my guns on that last part too.

 

landseaandair: it's not that the arcs overlap, but that at any point in the vertical travel of the axle, the two points are in the same relative position front to back.

And on my jeeps, we run everything; 3 links, 4 link, 4 link w/panhard, leafs, you name it. It takes a lot of time, experience, and testing to get this stuff right.

 

Fuck it. I was sure Lanseaandair was right. Now I think russellmn is right. I drew it and I think you are both right.....but that can't be right.

Mine steers OK so ...nevermind

 

does it matter how the drag link get to the steering arm, in an angle, or inline with the radius rod,

 

Flathead it does matter. With both links being equal length they will have an identical radius arc, but with the links being at different angles, they will be in a different part of that arc so when the tire/axle moves up they will move in a different direction relative to each other, thus inducing bumpsteer.


edit: sorry, I'm not good with computers so I can't draw you a picture to help illustrate my point. If you get a geometry book, it's in there.

 

iam talking like in this pic, on the drag angle to the steering arm,if this pic had radius rod in it, closer to the frame would it matter if the draglink was on the andle it is or following the angle of the rods. maybe in this pic

 

I haven't experimented with that angle, meaning the horizontal plane or as viewed from above, I'm talking about the vertical plane or as viewed from the side. I don't imagine it'd make a LOT of difference but would certainly affect it a little.

 

It may be the angle of the photo, but does the pitman arm shaft clear the wishbone when the front end bottoms out and the wishbone goes up?

Fwiw, I think your front shock mount would do better both appearance-wise and strength wise if the load was spread out a bit.

Instead of welding the mount bottom directly to the frame, make a rounded diamond shape plate from 3/16" flat with one hole for the shock mount and two holes for 3/8" bolts and flat hardened washers underneath.

Weld the shock mount to the plate and bolt it to the frame.
Buttonhead allens look good in an application like this.

One advantage would be if you decide to go with a longer shock, a new plate/mount is easily made.

 

yes as viewed from above, if it didnt make much difference,i wouldnt have had to bend the pitman arm as much, it wouldnt have taken that much to clear the header....

 

there is an 1in or so, not sure what to do about that,mayby box in alittle place in the radius rod,to allow for the travel, not sure if thats a good idea or not, how much does it travel that far back,