THE SCIENCE OF SETUP: Episode 7 - Steering Ackermann [VIDEO]
Thursday, Feb 16, 2017 07:13pm
By Aaron Waldron LiveRC.com
This bi-weekly column by RC Crew Chief founder Bob Wright delves deep into how and why particular adjustments alter the handling of your RC car or truck. You can download a trial version of RC Crew Chief for free and follow along to learn more about how to get the most out of your vehicle by tuning it the right way to suit track conditions: rccrewchief.wrightdesign.ca/RcccDownload.aspx
The term “Ackermann” refers to the geometric relationship of a vehicle’s front tires when turning, as the inside tire must trace a circle with a smaller radius than that of the outside. The concept can be traced back to British physician Erasmus Darwin in 1758. More popularly, the first linkage constructed for a horse-drawn carriage designed according to this principle was built by Georg Lankensperger in Munich, Germany in 1817 - but it was named after Lankensperger’s agent, Rudolph Ackermann, who patented the idea in England the following year.
On an RC car, Ackermann can be adjusted by moving either the inner or outer ball studs of the front steering links to a different location, or by installing washers to move the ball studs forward or rearward on some vehicles.
If you do any research on the effect of Ackermann (also called Dynamic Toe), you'll find a lot of different opinions. One of the main arguments is that most of the turning is done by the outside wheel so the inside wheel has little effect; while this certainly has some merit at mid-corner, when the inside tire has very little load, it still does have load on it - anything you can do to squeeze a little more overall grip is going to give you an edge. Also, at corner entry and exit, the inside tire has more load on it so it becomes much more effective.
So let’s have a look and see what we can learn about Ackermann Steering Geometry.