Why won’t my Custom wagon and/or stroller steer where I want it to? ie. What is Steering Ackerman?

This is a question I have had many times. It usually comes in the form of a question about a problem with a custom Radio Flyer Wagon someone has built. and it goes like this…. “My wheels turn to far and seem to push when  turning, what can I do”.

Most of the time it will need a complete rebuild of the front pitman/steering knuckles.

Exploded view.

Exploded view of them main steering of a go kart.

 

Below exert taken from Wikipedia.

Ackermann steering geometry is a geometric arrangement of linkages in the steering of a car or other vehicle designed to solve the problem of wheels on the inside and outside of a turn needing to trace out circles of different radius. It was invented by the German carriage builder Georg Lankensperger in Munich in 1817, then patented by his agent in England, Rudolph Ackermann (1764–1834) in 1818 for horse drawn carriages.”

 

So the outside wheels turn a larger radius than the inside wheels. The angle of the pitman arms shown below takes this into account. When turning the pitman arm angle pushes out the right side wheel less than the left side (when turning left in the example below). Note that all wheels point to the center of the turning angle.

Note both pitman arms are pointed to the center of the rear axle.

Note both pitman arms are pointed to the center of the rear axle.

As shown above the Pitman arms must(when wheels are pointed straight) be pointed at the center of the rear axle. When lining up your steering use a piece of string or dowel of wood to simulate the angles the pitman arms will be welded at.

This professionally made kart has the angles of the pitman arms perfect. They are angled toward the center of the rear axle.

This professionally made kart has the angles of the pitman arms perfect. They are angled toward the center of the rear axle.

It can get allot more complicated than what I have gone over here. A brief video about Ackerman steering can be found here.

Thanks, Chad

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