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  #16 (permalink)  
Old 06-18-2007, 06:21 PM
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scary steering

had simler problems on my 32 the cure was to have pitmen exactly paralel with tie rod with wheels on the ground,re codinghams book on rod steering. i had used a 65comet box with crose steer, but with tie rod on tha rear side with the pitemen,like you used the split wish bones. cliff
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  #17 (permalink)  
Old 06-18-2007, 06:51 PM
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Quote:
Originally Posted by cliff tate
had simler problems on my 32 the cure was to have pitmen exactly paralel with tie rod with wheels on the ground,re codinghams book on rod steering. i had used a 65comet box with crose steer, but with tie rod on tha rear side with the pitemen,like you used the split wish bones. cliff
See if I can have an extra arm I have extended and flattened out. As it is now the steering arm is about 3 to 4 inches in front of the pitman arm. Thanks for the info.
Greg
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  #18 (permalink)  
Old 06-18-2007, 06:54 PM
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The Ackerman angle (or lack of it) may very well be at play here. As mentioned, the Ackerman angle makes the inside wheel turn sharper when going around a corner because the inside wheel needs to follow a tighter radious. The way this car is set up, the outside wheel is going to turn sharper than the inside (also previously mentioned). Even on a mild turn going down the highway the outside wheel is going to be turning at a different (sharper) angle. In other words the front wheels are going to facing in different directions at every second of driving it except while driving perfectly straight. Go out and drive, you will find you are going perfectly straight very little. So even on the slightest curve your tires are fighting against one an other trying to take a different path!!

Brian
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Old 06-18-2007, 06:55 PM
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How much caster do you have on that axle? I have built several T Buckets with a straight axle and we run about 5 deg caster, and 1/8 toe in
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  #20 (permalink)  
Old 06-19-2007, 06:10 AM
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You cant fix it by randomly moving things around.
You have to understand what is wrong, why and how what you are doing is going to fix it. Only then will it work properly.

You need to be able to tell US why you moved it to where you did. Why the geometry is the way it is. I am not capable of designing a steering system over the internet.
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  #21 (permalink)  
Old 06-19-2007, 09:26 AM
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Originally Posted by 427v8
You cant fix it by randomly moving things around.
You have to understand what is wrong, why and how what you are doing is going to fix it. Only then will it work properly.

You need to be able to tell US why you moved it to where you did. Why the geometry is the way it is. I am not capable of designing a steering system over the internet.
Sometimes when all you have is parts and a limited knowledge you work with what you have and when you reach a wall you ask for help as I have. If you know of a book source that talks in detail about this I'll be glad to read it. I have only found limited resources. And what comes off as sarcasm doesn't help at all. I have posted pictures and detailed as best I can to explain it.

Here's everything I can think of. The base starts off at the center section of the stock VW beam, then I welded an extended spring perch so as to clear the bolts that hold the beam in place. The steering box and pitman arm are stock VW. The reason for the tie-rod being in front of the axel is because of the tunnel that is the back bone of the bug is in the way. I had thought of cutting a hole through it and passing the tie rod through it. But I am not that good of a welder to re-enforce it. I tried using two tie rods like the stock vw setup uses, and may try that again if I have to, but I knew that would make bump steer even a bigger problem. The split wishbones have about a 5 degree caster in them. I found last night in looking at the extra steering arm I have, that it will not have to be bent. Looks like it will clear and bring the drag link into line with the pitman arm. Will know that tonight when I get home and take it apart and try it. I may also try to take a leaf out of the over axle spring to soften it up some and allow the suspension to work more. Seems to be too stiff.

I hope this helps, not trying to be a jerk. But I am really frustrated and with no one here with any knowledge to help I am doing all I can with what I have. Now if some one wants to come help...... I'll buy the beer! Come on down

Thanks again
Greg
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  #22 (permalink)  
Old 06-19-2007, 10:04 AM
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Tenn is too far plus I don't drink

Stiff ride in front: Bugs are so light that the original tire pressure was 17 front 24 rear with bias tires! You might want to try lowering the pressures, plus pulling leaves. Your extended bug will have even less weight on the fronts so you need to get some road feel back. I'd drop the pressure a lot to test, but too low will cause problems too.

Back to front end;


-Oversensitive feel or twitchy: Different cars run different ratios on steering. What you really need to do is make sure your ratio on the arms is good. Since you are using the VW pitman arm, measure the old VW steering arms on the old spindles. Measure from the centerline of the king pin(or a line drawn through each ball joint if 66 or newer), to the center of the tierod hole. Now compare that to your aftermarket arms. You wouldn't want the aftermarket measurements to be shorter than the VW arm measurement. If they are shorter, try drilling a new hole in the VW pitman to "make" a "shorter" pitman arm.

-I just remembered that all the solid axle 4x4 american trucks use a front mounted tierod. I'll have to look at one to see what happens to the turning radii on each wheel when turning.
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  #23 (permalink)  
Old 06-19-2007, 10:55 AM
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Quote:
Originally Posted by PureC4
Sometimes when all you have is parts and a limited knowledge you work with what you have and when you reach a wall you ask for help as I have. If you know of a book source that talks in detail about this I'll be glad to read it. I have only found limited resources. And what comes off as sarcasm doesn't help at all. I have posted pictures and detailed as best I can to explain it.
snip---


I hope this helps, not trying to be a jerk. But I am really frustrated and with no one here with any knowledge to help I am doing all I can with what I have. Now if some one wants to come help...... I'll buy the beer! Come on down

Thanks again
Greg

I understand your fustration, really. I put a rack and pinion in my Vette and spent a LOT of time figuring out the geometry. I know I sounded harsh, but you are asking a lot and don't seem to be doing much yourself. Yes you may be working hard, spending lots of time, but this is a design issue, not a work harder issue...

Also, if you were putting an R&P on an old Vette I could give you lots of detailed advice. but I know nothing about cross steered solid axles.

Still you might want to take a look at the Corvette Forum, do a search for "bump steer" We discussed it a LOT! ( make sure to search the archives )
http://forums.corvetteforum.com/forumdisplay.php?f=3

You have to stop trying to find a quick fix. there isn't one. You are designing a new steering system, not rebuilding an existing one.

you have pull the spring out completely so you can move the suspension through it's full travel.
Then you need to build or buy a bump steer gauge and determine your bump steer. Untill you can quote me a number your shooting in the dark.

Bump steer is a HUGE issue, it has to be designed in. You MAY find you have really good BS, then you now know to tackle something else...

Then pull the steering box off the car and put it out of the way.

Then you need to do a suspension analisys, find the instant center, the roll center everything. Lot's of math, geometry and thinkin.

Then you use that information to determine where the steering rod must go.
This is the place where when you move the suspension through it's travel the toe changes how you want it to. Like I said before you want slight understeer.
There is one and only one right location for your setup. It is a pretty decent engineering challenge to design a steering system. Don't expect any pat answers. No one else has built what you are building. Maybe something close, but not close enough.

Once you have the steering perfect, THEN you can set your spring rates, tire pressures etc

bring it to Minnesota with a LOT of beer and we can do it

Last edited by 427v8; 06-19-2007 at 11:20 AM.
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  #24 (permalink)  
Old 09-12-2007, 02:45 PM
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straight axel steering help

Not trying to beat a dead horse, or be a jerk. But this is a problem only you, or someone on site can fix. It's not rocket science, but it can be tricky. Your problem is different than with independent front suspensions, but the priciples are the same. Try reading this article on rack and pinion swaps. I found it helpful in understanding why problems crop up. http://www.crankshaftcoalition.com/w...inion_steering
At the risk of insulting your intelligence, Here is what helped me.
Draw a line on a piece of paper. Now with a compass, or a pencil tied to a string, make some arcs on the paper. start each arc in the same place on the line, but vary the length of string. As you get above or below the line the arcs change. This is what happens when pitman arm and idler arm are different lengths. Now draw a line, say 10 inches long. on the left, move down an inch and draw a second line that meets the right end of the first line.
using your compass, or string, draw an arc on the end of the first line, using the left end as the anchor point. Now repeat the process on the second line using the left end of it as an anchor point. The arcs will meet only at the original point. This is what happens when one steering component is on the first line and another is on the second line. The arcs represent up and down movement of the suspension, and the differences in the arcs represent how your wheels are toed in, or out, as the suspension travels (bump steer). Based on the pictures, and descriptions, it is being assumed you have one of these conditions. If so, you have to find it and fix it. Maybe more pics, and/or detailed measurements of components, would help someone here identify it for you. For a simple test, check your toe with the vehicle on the ground. Then jack up the front end and check it again. If the toe is different by more than 1/4 inch, you must have a bump steer problem. If the toe doesn't change, then there are other things that can cause your problem. But with your confessed lack of knowledge, it is probably a design issue.
Hope this helps.
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  #25 (permalink)  
Old 09-13-2007, 12:30 AM
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Ok, I haven't seen any updates lately and I know first hand about getting out of sorts when something doesn't work right.

Questions=
1. Have you had it to a good front end shop to have it checked out?
Not necessarily one of these guys connected to a tire shop with the big computerized alignment machine but a shop that has been around a long time with experienced mechanics, This is one place a racing background or possibly guys into 4x4s might help a bit. You need someone who can think out of the box and not just hand you the readout and say "well the computer says".

2. Now having said that, what are the specs that the front end is set at now?

a. What is the caster?
b. What is the toe in?
c. What is the camber on the left wheel?
d. what is the camber on the right wheel?

3. I don't believe that the ackerman effect is bothered too much by having the steering arms in front of the axle as long as the theoretic intersecting lines of the steering arms meet at the same distance from the axle as the wheel base of the car. There was a lot written on this years ago when the Fad Ts were being built like crazy.

4. From looking at the photos I would think the Front axle has somewhere between 10 and 15 degrees of caster. I may be wrong but that is what my eyes see.

5. are the steering arm and the pitman arm the same length or real close to it? a big difference here will cause issues related to what Oldguy wrote about.

Ok after all the theories and questions WHY do you have steering rods= drag links going to both wheels? This is acting like a second tie rod. if you haven't already take off the link to the drivers side wheel so that the passenger side link acts like a proper drag/steering link instead of half a tie rod. I think that is causing about half of your bump steer. now I have a feeling that the other half is caused by BOLTS going through tapered holes where you should have the tapered end of a tie rod end. Have someone move the steering wheel back and forth a bit and watch that heim end and bolt. I would believe that the bolts are moving in the tapered holes.



You just flat don't need or want a steering link to the left wheel if you are going to run the tie rod.

It does appear that you may have the steering arms bent out too far.
Again, is there any movement between the bolt and the rear steering arm?

Here I don't like the looks of the bolt going through the stock vw pitman arm at all. If you didn't drill the hole out to fit tightly on the shank of the bolt and have a bolt long enough so that the shank of it goes through both pieces instead of having threads in contact with the hole in the pitman arm you will have a lot of movement in this area and movement = bump steer.

Last edited by Chopt 48; 09-13-2007 at 01:11 AM.
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  #26 (permalink)  
Old 02-04-2012, 10:46 PM
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bump steer

I was reading this to find some information about roll steer. Anyway, the setup you have here has two main problems. One, you dont need both of the steering arms, only use the longer one, and put in a tie rod (which the second photo shows). The other thing is that you do not have a panhard bar. with the hinges like this on the end of the cross spring, when you put pressure on the steering, you will move the entire axle from one side to the other. This is not a problem, but when the road moves the tires/axle, and the steering wheel does not move, what will move is the steering, it will wander all over the road with every sideways bump. Install a panhard from one side of the axle to the far side of the frame, and have it as horizontal as possible. This should cure your main problems.
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  #27 (permalink)  
Old 02-05-2012, 10:35 AM
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These guys may no longer be interested in the "fix" after 4 1/2 years have gone by...

Russ
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