ACKERMANN EXPANATION FROM X-RAY MANUAL
Originally Posted by Baedarlboo
On my NTC3, i've changed out my wimpy steering ball joints for some larger RPM bll/cup. But this has changed my ackermann. How will this effect handling?
I guess it has "less ackermann" (inside wheel has more toe out during turning)?
Ackermann controls the difference in steering arcs between the front inside and outside wheels. The inside wheel always has a tighter arc in any corner. The amount of grip provided by the tires, in relation to the steering arc and speed of the car, create an amount of measurement called a “slip angle” for each wheel. For some tires you need a greater difference in slip angles between the inner and outer wheel and for some you need less.
The size and geometry of the servo saver on cars forces the inside wheel to increase its turning angle at a greater rate than the outside wheel, as the servo turns either way from center.
The rate of the increase, called Ackerman effect, can be changed by the angle of the steering rods connecting the servo saver to the steering blocks. The straighter the rods are in relation to each other, the more Ackerman effect will be applied to the inside wheel.
Slip angles work differently on each wheel when the car is slowing down & pitching forward, than when the throttle is applied & the tires are pulling the car forward. The goal in tuning ackerman is to get the car to keep a consistent steering arc after going from off-power to on-power, while not allowing the front inside wheel to be turned too much and drag through the corners instead of rolling through them. If the car steers well off-power
but pushes on-power, then use more Ackermann effect and decrease your transmitter EPA/dual rate. If the car steers well on-power and pushes off-power, or if you can hear the front inside wheel chattering at mid-corner, then use less Ackermann effect and increase your transmitter EPA/dual rate.
The angle of the steering rods can be changed by moving the steering rods inner mount position on the servo saver, or outer mount position on the steering blocks.
1. Inner Ackermann Position (servo saver) – Changing the forward/rearward position of the servo saver has the greatest Ackermann effect
Position #1 (forward) – less Ackermann effect (steering rods more angled)
Position #2 (rearward) – the greatest Ackermann effect (steering rods straighter)
2. Outer Ackermann Position (steering blocks) – Changing positions on the steering blocks is used to fine tune the Ackermann effect
Position #1 (forward) – more Ackermann effect (steering rods straighter)
Position #2 (rearward) – less Ackermann effect (steering rods more angled)
NOTE: It is recommended to use more Ackermann effect in low-to-medium grip conditions and less Ackermann effect in medium-to-high grip conditions.