Steering shaft holes and ackermann

(Eric Riggs) #1

I get that the holes closest to the steering shaft will result in slower steering and opposite for holes furthest from the shaft but I’ve heard conflicting theories on which results in more ackermann. Has anyone actually tested this or know for certain?

(TJ Koyen) #2

Holes furthest from the shaft = more Ackermann

I also appreciate your correct spelling of Ackermann :beers:

(Jamie Gonzalez) #3

Further question:

Is moving to outer hole on steering shaft same effect as moving to inner hole on steering spindle?

(Jim Maier) #4

I always understood that the holes on the steering shaft are for rate and the holes on the spindle are for ackermann. The heim location on the spindle relative to the kingpin is what adds or reduces ackermann. The more inboard the heim is relative to the kingpin, the more Ackermann. Of course rate can be adjusted on the spindle too by have the heim closer or further from the kingpin. Further away would be less turning rate.

(Eric Gunderson) #5

Ackerman increases the further you move from your pivot point location, be it steering shaft or the spindle king pin.

So full Ackerman would be furthest away from shaft on the steering shaft “leaves,” and furthest away from king pin on spindle.

Ackerman is a great adjustment with drivers that are uncomfortable or to “force” young drivers to slow their hands down a bit. For more experienced drivers it seems to be less impactful aside from personal preference as often these drivers will simply ‘drive around’ steering discomfort.

(Jim Maier) #6

This is steering rate Eric. Ackermann is basically the rate the inside tire is turned vs the outside tire.

Imagine if your heim was directly behind the kingpin bolt on your spindle. No matter if that heim position was one inch back from the kingpin or 3 feet back from the kingpin those tires will always be Exactly parallel when the steering wheel is turned. Zero ackermann.

Taking this to extremes as you can see.

Now if your inner tie rod heim was a millimeter away from the steering shaft your wheels would not turn much. If the inner heim was a foot away from the shaft they would go lock to lock with minimal input on the wheel. This is steering rate. The same can be done on the spindle.

Ackermann is increased or decreased with the position of the outer heim relative to the kingpin. If it is straight back from the kingpin (not possible on karts) you would have parallel steering with no Ackermann. As the relative position changes you get Ackermann. The further inboard the heim position gets relative to the kingpin, the more Ackermann you get.

Of course on karts there are only a few positions, and like camber/caster pills one usually affects the other. So these holes generally adjust rate and Ackermann.

(John Leah) #7

Older karts had both inner track rod ends/ heims on one bolt and all the Ackermann effect came from the stub axles/ spindles.
Then karts came out with the ’ new’ Ackermann steering where part of the effect came from the two bolt attachment of the two heims
at the steering column.The further apart laterally the two bolts are, the greater the effect.
Not sure on the original question, tend to the view that using the holes nearer the column will give slightly more effect.
Next question .What effect does more or less Ackermann have on the way the kart performs / handles?