craig1410
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| posted on 18/1/04 at 11:45 AM |
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quote:
Originally posted by blueshift
having the rack inline with the track rod end balljoints is more critical for bump steer than having the rack end balljoints in line with the
suspension brackets..
Blueshift,
Glad it was useful. I'm intrigued by the quote above as this flies in the face of my understanding and I'd be interested in your analysis.
When you say "inline", do you mean this in terms of height or in terms of longitudinal position (or both!)?
I suppose, thinking about it, if the rack was way too high and the track rods were in droop when the lower suspension arms were level then as the
suspension is compressed, the lower suspension balljoint will move towards the centre of the car while the track rod end balljoint will move away from
the centre. This will produce toe-out bump steer so I suppose height is indeed important.
As for longitudinal position, I don't see what effect this would have on bump steer although it would affect ackerman angles I think. My theory
goes like this:
If the angle formed between the track rod and the steering arm on the hub is exactly 90 degrees when steering is straight ahead then no ackerman
effect will result but if the angle is greater than 90 degrees as would happen when the steering rack is moved farther forward then more ackerman
effect will be felt.
Someone please check my logic here, especially on the ackerman bit as I am less than 100% confident in the correctness.
In any event, the escort rack is almost a perfect fit on a +4" chassis when fitted level with the steering arms and at the theoretically optimum
height. Besides, a little bit of toe-out bump steer is good for making a chasses less twitchy over bumps. You certainly don't want toe-in bump
steer!
Cheers,
Craig.
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dblissett
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| posted on 18/1/04 at 04:16 PM |
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escort rack
hello blueshift
i forgot to tell you that my rack mounting are the same as craigs as in i went for a slot in each mounting for future adjustment
i have also read some where that the rack needs its final adjustment with the full weight of the car placed on it
this seems to me to be when the car is almost finished and thats why i went for the slots
cheers dave
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blueshift
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| posted on 19/1/04 at 03:49 PM |
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Thanks chaps. Will be a little while before we get to steering rack stage, plenty to get our teeth into first. I might have a tinker about making a
model of the steering gubbins in solidworks to see if I can look at the bump steer effect in CAD.
This reminds me, anyone know of a CAD model or diagrams for a 'tina front upright?
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