A question: most cars have the "king pins" or steering knuckles close to or on the centre line of the hub. Gokarts and your race mower have the whole steering mechanism on the insed of the wheels - even some distance away from the wheels. I don't understand why. That would increase the forces on those pivots enormously and make the Ackerman steering geometry seriously ineffective, as the wheels go around an arc, rather than pivot around their centre line as Ackerman would have anticipated. Is it a fabrication issue or a racing geometry reason?
Cheers,
Joe
Having the king pin closer to the center of the wheel, is always better, but how much? In this case, there is no way to fit the kingpin inside the rim. The next best solution, is to have the line drawn through the kingpin, to meet the road in the center of the tire contact.
So what happens if the line is not in the center? A blowout, can cause the steering to pull dramatically to that side. An issue with the braking, can cause the steering to pull, as can bumps. In this case, with the small tires, and no brakes on the front, None of those are going to show much, except maybe the bumps. A big bonus of having that line meet to the inside of the wheel center, is while moving, the forces are trying to pull both wheels outward, Essentially taking any play (what we call backlash) out of the steering system.
In the end, it is all trial and error. Just look how race car teams spend the week prior to a race getting the car dialed in to that track.
You can not just angle the kingpin more, as the steeper the angle then you are causing the front end to lift when the wheels are turned. But that does add a benefit of the weight helping to keep the steering centered.