Hi all,
In my Avon I shift lower wishbone brakets to use sierra uprights.
Today I find I have anti Ackermann angle!
I do not know how to do to have right Ackermann angle. I try to shift sterring rack a little up and down and a little front an back but with no
benefit. Can anybody learn me how to do to variate this angle?
Thank you very much!
First of all forget anything you may in text books about ackerman geometry -- The book theory works with wehicles with a proper centre track rod it
dosen't hold fully true with rack and pinnion steering.
You have anti-ackerman because as I recall the Avon has the centre line of the steering rack in front of an imaginary line joining the centres of the
trackrod end ball joints. To get some ackerman you need to move the rack backwards until it is a least 50 mm behind the track rod ends. -- might
entail substantial chassis mods.
How much Ackerman do you want? Reason I ask is, depending upon the purpose of the car, some designers feel anti-Ackerman is a good thing.
(I don't, but that's just me)
Hi Rudy,
I'm not 100% sure why you would have moved the wishbone brackets in the first place?
Cheers,
James
For front steer racks, you will need to move your rack back about an inch. I have made an adjustable rack bracket.. As acherman interacts witih other adjustments like toe, bump, and general wear, I think the final adjustment and ultimate test will be done doing circles in the local underground parkade, adjusting until the tyres no longer squeel in the corners. That sqealing in factory cars has always driven me nuts.....
The amount of Ackerman required goes in and out of fashion over the years.
What is it about the handling of the car you don't like? It's potentially going to be a lot of work to change.
Rudy, if you can find a copy the current edition of Practical Performance Car has an interesting article on bump steer which may help. If you
can't find one send me a U2U and I'll forward it. Cheers, Pewe
The problem with Sierra (and Cortina) uprights is that the angle of the steering arm to c/l is nowhere near enough.
Try putting the rack just in front of the axle line.(40~50mm) You'll get Ackerman steering enough. Then the balljoints at the rack need to be
centred on a line through the top and bottom inner pivots. Move rack up and down to dial out bump steer.
Cheers,
Syd. 
I try to do as britishtrident teach me....
IT WORKS!
Thankyou very much.
Gunner1 , may you post a foto of your adjustable rack braket?
Syd Bridge, tomorrow I will try to do as you seid and we will see wath appens
Iank, my car only moves with my body power and not with zetec power
I hope to finish the car within end of year.
There where too and too much anti Ackerman.
James, I shift the bracket to have right camber. If I fix bottom wishbone in original place I only have too much positive camber.
Now I can chose to have positive, zero or negative camber.
You all are always very helpful!
Thank you
Will do Rudy.
Will be in a later post, perhaps on the weekend as I have to make take some pictures. I will use Ackerman as the subject line.
quote:
Originally posted by Rudy
I try to do as britishtrident teach me....
IT WORKS!
Thankyou very much.
Gunner1 , may you post a foto of your adjustable rack braket?
Syd Bridge, tomorrow I will try to do as you seid and we will see wath appens
Iank, my car only moves with my body power and not with zetec power
There where too and too much anti Ackerman.
James, I shift the bracket to have right camber. If I fix bottom wishbone in original place I only have too much positive camber.
Now I can chose to have positive, zero or negative camber.
You all are always very helpful!
Thank you
what syd and BT say is slightly different as far as i can see, similar when pointing forwards but the arms will be rising or falling rate depending on
if the rack is forward or back.
With the rack set back, the outside wheel will have rising rate, meaning it will turn more into a corner. This seems like anti ackerman to me?
the difference is very slight though, id love to model it and see but really cant be arsed. Im pretty sure that at speed the slip angles will complete
cover up any change.
This is plus or minus as sayd Brithis
trident.
I have Ackerman
Rescued attachment IMAG0082.JPG
... and this is as Syd Bridge sayd.
But in this case I have ANTI Ackermann.
Sorry for the foto dimensions
Rescued attachment IMAG0084.JPG
I think you'll find Syd said 40~50mm in front of the AXLE LINE.
You should see where the Locost race setup puts the rack! But you'll have to get near our racecars with a tape for that.
Cheers,
Syd
[Edited on 5/10/06 by Syd Bridge]
sorry,
as you see, I have some difficult to understand english.Does Axel line means centre to centre of the well? If Yes put the steering 50 mm back of
"an imaginary line joining the centres of the trackrod end ball joints. " or put the steering front of 50mm from axle line is plus or minus
the same.
It would be a great pleasure to see your racing 7. I hope to go to UK in the future .
P.s: what means " near our racecars with a tape?"
Regards
Rudy
he means a measuring tape. (a ruler)
sorry syd, read yours a little fast, so in fact you and BT are broadly in agreeance. Which is good, cos my rack is vaguely where you suggest. Just a
shame the rest of the car is so wonky!
quote:
Originally posted by Rudy
Does Axel line means centre to centre of the well (wheel)?
quote:
If Yes put the steering 50 mm back of "an imaginary line joining the centres of the trackrod end ball joints. " or put the steering front of 50mm from axle line is plus or minus the same.
....................as I said, BT and Syd said basically the same..........................both quite right!!!
cheers rudy.