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Ackerman or Anti Ackerman's geometry? Which is best?

Question asked by Vinay Mishra in #Mechanical #Automobiles on Feb 2, 2020
Vinay Mishra
Vinay Mishra · Feb 2, 2020
Rank B2 - LEADER

Actually I am designing the steering for efficycle(tricycle). I have previously used parallel steering geometry for the same but it was not much effective. Actual problem was, the vehicle was not able to take sharp turns and also the effort on steering was more. Some seniors suggested me to use Ackerman or Anti Ackerman's geometry to reduce the effort on steering.

Can anyone help me choosing one of these geometries? Which is better in terms of effort/turnings and How?

Posted in: #Mechanical #Automobiles
bill yorke
bill yorke · Feb 2, 2020
Rank C2 - EXPERT

The optimum slip angle for the tyre at reduced vertical load (inner wheel) is considered in Anti Ackerman. Since your inner wheel remains at midrange torque on the ground so you have Pro ackerman the inner wheel must have more angle of steering = more angle of slip and has much fewer vertical load. So you wouldn't properly use the inner wheel you're abussing it a bit.

For Anti ackermann, the inner wheel has less steering angle than the outer wheel but has more grip. The overall outer tyre lock in the corner could of consequence be increased as the inner wheel doesn't really move more than the outer wheel.Clearance wise its much safer and for certain aerodynamically as the inner wheel will not block / tweak the airflow as much if there is not much lock on the inside open.

Vinay Mishra
Vinay Mishra · Feb 2, 2020
Rank B2 - LEADER

@bill Thanks for details. I got it. If i want clearance, I should go with Anti Ackerman's. But what if I want to decrease the effort of steering as well?

Noothan Kumar
Noothan Kumar · Feb 22, 2020
Rank C1 - EXPERT

Anti ackerman takes into consideration the optimum slip angle for the tyre at reduced vertical load(inner wheel ).

If your inner wheel stays on the ground at cornering speeds and you have Pro ackerman the inner wheel has to have more steering angle=more slip angle but has much less vertical load. So you're not using the inner wheel properly you are abusing it a bit .

As we have learned tyres do not like to be punished at low vertical loads.

With Anti ackermann the inner wheel has less steering angle than the outer wheel but has more grip(unless your tyre would like more slip angle at lower vertical load).

The maximum lock of the outward tyre in the corner can be increased of course, as the inner wheel does not steer more than the outer wheel. Clearance wise its much better and aerodynamically for sure as the inner wheel does not block/modify the airflow as much when there is not much lock available un the inside.

Definitely not good for pushing the car around in the pits, but at racing speeds more than worth a thought to have anti .

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