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Steering question

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mikegeo

Mechanical
Jun 27, 2005
3
Someone recently told me this:

"Want to see how bad your suspension really is? Go to an empty, flat, level parking lot, turn the wheel lock to lock in one direction. Proceed forward for a few feet, open your door, place a quarter on the ground. Close the door and proceed in a circle around to where you began. Open the door to retrieve your quarter … you’ll see how terrible of a circle your suspension is really capable of – the quarter won’t be anywhere near where you first opened your door to place it."

This orginated from a discussion about body roll and weight transfer (body roll does not cause weight transfer other then a very small amount from a lateral shift in the location of the center of gravity). Anyways, I don't see how any of that has to do with the suspension. My first thought when reading this is that of course it wont go in a pefect circle. The radius of the turn you make is dependant upon speed. You are starting out at 0 mph and accelerating to some speed. That alone will cause you to not end up in the same location.

So, my question is, if you are driving at a constant speed with the steering wheel at full lock, will you go around in a pefect circle? This is assuming a level surface with no bumps or changes in surface to cause bump/roll steer. It is also assuming a relativly low speed where are you arnt sliding around.
 
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"if you are driving at a constant speed with the steering wheel at full lock, will you go around in a pefect circle?" Yes, it goes round in a circle. What other shape could it make?

"Want to see how bad your suspension really is? Go to an empty, flat, level parking lot, turn the wheel lock to lock in one direction. Proceed forward for a few feet, open your door, place a quarter on the ground. Close the door and proceed in a circle around to where you began. Open the door to retrieve your quarter … you’ll see how terrible of a circle your suspension is really capable of – the quarter won’t be anywhere near where you first opened your door to place it."

That is a very odd test all in all, I don't think it really proves anything.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
 
Given the amount of rubber in a typical vehicle's suspension, and the resulting compliance of the linkage, and of course of the tires, even small variations in engine torque will cause the path of the vehicle to wander.

But, as Greg says, so what?



Mike Halloran
Pembroke Pines, FL, USA
 
"That is a very odd test all in all, I don't think it really proves anything."

Thats exactly what I thought.

MikeHalloran, assume ideal (unrealistic) conditions of constant vehicle speed (and thus torque, since this is also on an ideal surface).
 
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