This is the biggest problem with susp. tuning as far as changing thru susp. movement. This suspension is tuned around this, and there is almost no bump steer. Although small, the tires "toe out" at the bottom of the susp. cycle. This effect is much more pronounced on a sled's suspension.
This is ackerman. Notice how the right side tire does not steer as far as the left tire. This is the effect that I washighlighting in the discussion on the REV. All IFS will have this effect, but add in allot of travel, and the toe out can be moved easily if one a arm moves up or down, such an is chassis roll thru a corner. This will make the center of the toe out change easily, and make one hunt with the handle bars to keep the sled pointed the way you want it. I think this is the problem AmSnow was talking about.
With Ackerman principle, the steering arms are placed at an of 100 to 105* instead of 90* to the centerline of the wheel spindle. as a result of this arrangement, the inner wheel (ski) turns out at a greater angle than the outer wheel when the vehicle makes a turn.
</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (800MXZ @ Aug. 09, 2002, 10:37am)</td></tr><tr><td id="QUOTE">This will make the center of the toe out change easily, and make one hunt with the handle bars to keep the sled pointed the way you want it.[/b][/quote]
You lost me on the "the center of the toe out". What's that mean?
"Center of Toe" with the wheels strait would be in the center of the chassis. Now turn full lock to the left such as that in the lower ackerman picture would be like 20 deg. to the left. Move one wheel up and down as in the pic below. The wheel on the left stays pointed the way it was, while the right one turns towards the left some. In a roght hand turn that this emulates, since the outer tire turns in more, it moves the "center of toe" towards the left more. Like 22 deg.
This will take an inmput from the driver to turn away from the curve to maintain a consistant arc around the turn.
Everyone has felt this effect driving a car on a off ramp on the highway. Ever notice that you have to constantly "hunt" with the wheel to maintain a consistant arc around the turn. As the chassis stops rolling side to side, the less you have to change the wheel poistion.
Another thing to notice on these pics, look at the position of the titanium tie rods (blue). Notice how drastic the angles change with the wheel posiions.
Reverend - Ackerman is a the change of the relationship of one wheel to another, not a specific location of the components. On this suspension we can change the length of the steering linkage, and the length of the "rack" of the rack steering and it will change how fast the ackerman changes. Kind of like a rising rate susp. it changes how quickly the ackerman moves.
Porsionaly, I think that the dual runner skis will make this worse. I would like to see a test using the Dual skis vs. a flex of a C+A.
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