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http://www.youtube.com/watch?v=RA7G5w4Zreg&mode=related&search=
In this video we see the mechanic turning the wheels back and forth. It seems like one wheel is turning more than the other, like what would be the inside wheel for a turn has more steering lock on it than the outside wheel. Is this just an optical illusion or is it the case, and if so why?
Front wheel movement?
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http://www.youtube.com/watch?v=RA7G5w4Zreg&mode=related&search=
In this video we see the mechanic turning the wheels back and forth. It seems like one wheel is turning more than the other, like what would be the inside wheel for a turn has more steering lock on it than the outside wheel. Is this just an optical illusion or is it the case, and if so why?
In this video we see the mechanic turning the wheels back and forth. It seems like one wheel is turning more than the other, like what would be the inside wheel for a turn has more steering lock on it than the outside wheel. Is this just an optical illusion or is it the case, and if so why?
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Think about the radius of the circle each wheel must scribe when turning. The inside wheel must turn more because the radius of the arc it scribes is smaller by the distance between the two front wheels than the outside wheel's scribed radius in any given turn.
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This is called "ackerman" steering. Simply put because the inside wheel in a corner is on a tighter radius than the outside tire, the steering geometry is designed so that one wheel progressively turns at different angle than the other. The tighter the corner, the more steering input, the more angle difference there is.
No it's not an illusion
No it's not an illusion
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Just curious, but does it do that to the point of completely negating the toe-in, or even going into toe-out?
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[quote:6cc0cdf05d="mlamagra"]Just curious, but does it do that to the point of completely negating the toe-in, or even going into toe-out?[/quote:6cc0cdf05d]
Yes; as speedsense noted, this is called 'ackerman'; as the wheels are turned they toe out to achieve this effect.
Yes; as speedsense noted, this is called 'ackerman'; as the wheels are turned they toe out to achieve this effect.
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The Ackerman effect is variable toe, based on unequal upper and lower arms. It allows for managable scrub (difference of intended and actual direction) when turning. What you saw was no illusion.
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The location of the steering tie rod at the upright, it's relationship to the "kingpin" (this is the turning pin that allows the front upright to swivel) determines the ackerman.
There are unequal length a arm suspensions that have zero ackerman.
There are unequal length a arm suspensions that have zero ackerman.
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Correct you are. I re-read what I wrote and I'm not sure what I was trying to say, but I clearly missed it. Thanks for the catch.
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[quote:e3915730c2="mlamagra"]Just curious, but does it do that to the point of completely negating the toe-in, or even going into toe-out?[/quote:e3915730c2]
With our shifter karts we use the static toe setting to modify the ackerman angles built into the steering. Our local track has several tight turns, so we set the static toe to about 1.5 degrees toe OUT to increase the ackerman. The resulting "splayed out" appearance looks strange as heck to someone used to road cars.
With our shifter karts we use the static toe setting to modify the ackerman angles built into the steering. Our local track has several tight turns, so we set the static toe to about 1.5 degrees toe OUT to increase the ackerman. The resulting "splayed out" appearance looks strange as heck to someone used to road cars.
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he heee....
