F1 Mini
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| posted on 8/5/04 at 08:47 PM |
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quote:
Originally posted by Mark Allanson
http://www.locostbuilders.co.uk/viewthread.php?tid=7012
[Edited on 7/5/04 by Mark Allanson]
Now that had me rolling around, thats my kind of Humor, keep it up mate..... Must admit took at least 60 sec's for it to sink in.
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WIMMERA
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| posted on 9/5/04 at 05:17 AM |
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Typo, should be drivers legs, same as using herd instead of heard
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Mark Allanson
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| posted on 9/5/04 at 10:30 AM |
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quote:
Originally posted by Syd Bridge
In my experience(for what that's worth to some!), the critical angle is that between the steering arm and track rod, then the angle between the
steering arm and longitudinal centreline comes into action.
Full ackerman geometry, and more, can be attained on cars with the steering arms parallel to the centreline.
Naturally, with rack and pinion setups, the angle between track rod and steering arm is dictated by the fore/aft position of the rack.
Cheers,
Syd.
Syd,
I have limited design experience, but load when it comes to repairing the designs of others. I am really confused now, probably missed something.
I thought the ackerman was determined by the angle between the stub axle and the cast in steering arm on the upright (knuckle) where they bisect the
KPI line.
I don't understand the relevance of the rack position to this (not being funny, I really want to open up my understanding of this). When
repairing, we ignore ackerman, because someone else has worked it out for us, but do use toe out on turns as a diagnostic tool.
 
Rescued attachment Ackerman.jpg
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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stephen_gusterson
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| posted on 9/5/04 at 11:51 AM |
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am I seeing that pic wrong mark, or does your car have massive ackerman the wrong direction?
atb
steve
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MikeP
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| posted on 9/5/04 at 02:59 PM |
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ackerman questions
When you all are talking about ackerman, is this for parking lot speeds, road handling or race handling?
Assuming race (from the pictures), what's the desired outcome? Better alignment of the inside tire during the turn, right? Anything else?
Turn in response?
I thought the inside, unweighted tire will want at a lower slip angle than the outside tire. This seems to argue for neutral or even anti ackerman -
what am I missing here?
It strikes me that there must be a very complex relationship to tire type, tire traction and road traction on weight transfer and slip angles. These
will affect steering angle, changing effective bump steer since the chassis has rolled (by how much?). Is it possible to come up with a rule of thumb
setting? For all cars in all conditions?
I wonder whether the toe setting has more overall effect than ackerman,- does it?
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britishtrident
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| posted on 9/5/04 at 03:20 PM |
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The rack position determines the ammount of quasi-ackerman because the effective length of the track rods change as the streering arms move through
an arc. Large ammounts Kpi and castor also have a small effect because they have effect on the height of the TRE as it swings the steering
angle.
Unlike true ackerman geometry perfect theorhetical alignment should it be desired can't be maintained through the whole arc of movement, for
that should it be desired you need a steering system with a centre track rod and idler arms.
Just to clarify on a question asked early in the thread with classical ackerman the construction lines are drawn from the outer TRE centres
through the steering axis (virtual kin pin) at track rod end centre height --- not the top or bottom ball joint.
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britishtrident
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| posted on 9/5/04 at 03:27 PM |
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Mark your car has a very small ammount of ackerman built into the Cortina uprights but quite a lot from the position of the rack, If you turn the
wheel to full lock you will see that a line drawn between both the track ends rods is in alignment with the rack --- the track rods have a longer
effective length than in the straight ahead position --- giving toe-out in turns --- adds up to a good bit of ackerman.
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britishtrident
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| posted on 9/5/04 at 03:44 PM |
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With full Ackerman the difference in angles can be quite large, leaving aside for now the effect the difference between inside and outside tyre
loading has on ideal slip angles, the effect of even equal slip angle throws full ackerman out the window. To have lateral grip must have a slip
angle.
Personally I am going for a little ackerman all gained from having the rack positioned 25mm to 40 mm behind the TRE centres in the straight ahead
position. If building a car for hillcimbs I would use more (to warn the front tires), also lots of ackerman for autotests and PCT, for circuit
racing i would use a bit less..
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Bob C
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| posted on 9/5/04 at 09:13 PM |
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Some of the formula 1 cars in the 70s had "anti ackerman" ie negative ackerman effect so that the loaded tyre had greater slip angles. On
a road car I'd go for full ackerman so that you don't sound like a prat squealing round every bend in the car park! My old talbot sunbeam
was a bugger for doing that...
Cheers
Bob C
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Bob C
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| posted on 9/5/04 at 09:24 PM |
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and I should read the rest of the thread before repeating part of it wrongly.....
spanner!
Bob C
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