davew wrote:
Hooooooooooo
Now I understand!!!
I thought your suspension was similar to the picture at the start of the thread.
I agree that the spacer on top of your modified strut will at least be a good start in the right direction.
Another thing that could help this issue is to mod the tie rod end of your current steering arm by reaming a 1/2" hole more towards the spindle ".i.e. steering ratio" and mount a striper bolt and Hiem joint under the arm. This would allow further spacing the rod end lower to match the rack, as long as you do not get carried away.
It turns out that the "correct" vertical position of the -center- of the Heim is almost at the same height as the top surface of the present steering arm. Acad helped me determine that the center of the Heim is also not located on the steering arm though.
Luckily I can temporarily bolt a short piece of 1"x1" angle iron to the original steering limit pad that is located under the steering arm. By using a machined "cone spacer" under the Heim I can adjust the height of the Heim to set the angle of the steering link in relation to the A arms. Once the settings are correct I will weld the angle to the steering arm.This will help correct the steering attachment on both Up-Down and Fore-Aft planes.
One other thing to be careful of, once you change the steering arm ratio you will probably have to add stops inside the steering rack to prevent over travel.
Supposedly I won't have the condition where the steering link and steering arm get near the zero angular condition. But that is something I will definitely check out on the 1st temporary set up.Something else to think about, It might be better to look at swithing the steering arms from side to side and putting the rod end attachment point in the front, for front steer. It would require a different rack but in the long run it may be your best solution if the new rack had more travel per steering wheel rotation it would correction your slow steering at the same time.
I considered that but it didn't fit in with my minimum changes criteria.I do not think there is an easy answer, it looks like a lot of work will be needed to put the steering right. You need LOTS of luck on this one. Dave W
Yes, especially so since I want to do the minimum changes that will correct the major two problems (bump steer and camber correction). By the way, my caster is ~6° and the KPI is ~12°. Scrub is ~ 1.7".
I've been running computer simulations with suspension programs and Acad for many months now and I think/hope I have come up with the minimum changes that will work.
One thing for sure, I've learned a lot about suspension geometry etc because of this exercise. The suspension programs themselves may give quick results but they aren't always the results that are practical for the particular parts you already have on the car.
Hint to anyone getting ready to design/modify your suspension with a suspension program:
The most important step is making absolutely
SURE that you have made correct measurements of your steering components. +/- 1/8" error is NOT going to cut it. Even a 1/16" error can affect the results.
Get a nice flat floor to carefully measure the car. The floor doesn't have to perfectly level, but it does need to be FLAT. You may want to load the drivers seat with stuff that is equal to your weight. (Roll the car back and forth to let the suspension settle.)
Measure the car at least twice to make sure the numbers are the same each time. If not, measure it again till the numbers always come out the same.
I can get quite different Ackermann angle error vs: steering input plots by changing critical dimensions .050" when you go beyond the sweet spot. Holding the placement of the parts to that tolerance is going to be fun since there are so many variables.
Luckily I don't think anyone who is not driving at 10/10s is going to notice the difference though.
By using Acad to draw out Ackermann lines, front views of the A arms etc you can get a better appreciation of what the suspension parts are doing as you exercise them. You should see all the construction circles you end up with to do one simple Ackermann plot in Acad. I have used the program for many years and it does give VERY accurate results. By the way, I am NOT an AutoCad salesman.
Again, if all this works correctly I'll publish what I've learned etc on my website. With pictures yet!
Nice "talking" to you Dave. (Even though it is a monologue!)
_________________
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Completed building GSXR1000 CMC7, "Locouki"
Website:
http://projekt.com/locouki/