ADI  steering

Also this time the thing that has made me to waste more time has been the steering.
It's the geometry that caused problems.
Rear steering is known to be not working because the three forces  involved:  trail, gravity and centrifugal can't act together.
Only after three rebuilding I got a final solution that I consider valid.



Even if I had no problems till now, I do not assume responsibility about copy.

l.delorenzi@libero.it


Is an absurdity but the configuration that gives me the best results has 2,7 cm “trail” the same value of “rake”, than  “caster” is  90°, and a 20° “kingpin”,  with 90° “camber” and 1 cm °positive distance of kingpin axis and wheel point of contact .
The “kingpin” angle, normally considered not important for stability, in effect is the most important in this configuration because is gravity that determine wheel realignment.
Trail contribute to stability but being only 2,7 cm  the negative action of centrifugal force, over-steering action, remain under control.
The only problem is excessive sensitivity of the joystick control when going straight but using a cam it's possible keep the central position. This will avoid  oscillations or windings. After you  will find the realization.

To determine angles I have used a 3D model simulating wheel rotation around kingpin in relation to a virtual plane.   Because the virtual plane was fixed the under-vision shoved how much the wheel enters the plane itself.  
This give an idea of how high must be the movement of the wheel to maintain the same image on the ground,  real plane, "gravity effect" and how will change the “trail”.




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The steering linkage use ball bearing  SKF SIKB 6F

Rear steering needs habitude, is not possible run near a wall because it's not possible to turn far, the turn bring you against the wall itself.
This generates also a strange sensation because if you turn right you go left before and right after.

Rear wheels have bearing inside the kingpin supports.   I have removed balls from wheel bearing than I have increased the hole to 12 mm .
A 12 mm nut will pass thru the wheel than a ring will keep it centered, than thru ball bearings inside support. 
The support has two ball bearing used for the wheel and two used on the kingpin axle.

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This is the cam used to increase stability because the "trail" must be kept small to avoid oversteering and this cause an excessive sensibility arround central position ( driving stright ). The solution is a cam that  force strigth direction but allows steering.

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                                                                                                                                        Luciano De Lorenzi
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