How does this work? If you take the way a car turns it’s basically (though not exactly) that one set of wheels does the turning and the other set pivots. Well it always seemed to me that if there are more then two rows of wheels, then all the other ones must be dragging/skidding along. Especially in those dump trucks with wheels from front to back. So are they basically just skidding sideways through the turn, or am I missing something obvious?
There’s a certain amount of skidding. Some vehicles, like big multi-axle cranes, have fairly flexible sidewalls on the tires to allow for some movement; otherwise, yeah, they get a lot of tire wear. The sharper the turn, of course, the more the skidding, at highway speeds making highway-radius turns, it’s not much of an issue.
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On vehicles with lots of tandem axles like a semi with one or two trailers, all of the wheels, except the drive wheels are just attached to the axle with a bearing. That allows them to turn independently of all the others because they have no connection with any other wheel.
The drive wheels are all connected to the drive shaft via differential gears so that they can turn at different speeds without skidding or slipping.
That I understand. But imagine a bike (or in this case a trike) with 3 inline wheels. Would the center (or rear) wheel skid/skip when you turn.
Ah yes, I now see what you are asking. If I draw an arc it looks to me like the front wheel is always tangent to the arc because it is mounted on a vertical pivot. However, the other wheels will have the front inside the arc and the back outside the arc. That is the wheel will be canted slightly across the arc so it will be dragged slightly sideways. This is because a straight line from the center of the front wheel to the back wheel is a chord of the arc and cuts across the arc at an angle to it.
At least that’s what it looks like to me.
IAATD (truck driver), on a tandem set of wheels one set is definatly dragged sideways. When making a sharp turn or a U turn it looks pretty ugly with some serious flex to the sidewall, but the tires seem to hold up to the abuse. On a hot day a tractor trailer making a tight turn can tear up cheap asphalt. On trucks with many axles the driver can usually lift some of them when making a tight turn to minimize dragging.
If you look at a truck that has stopped or parked in the middle of a turn you can see the distortion in the sidewall of the tires.