Rear wheel steering for yaw correction

All that has to do with the power train, gearbox, clutch, fuels and lubricants, etc. Generally the mechanical side of Formula One.
Greg Locock
Greg Locock
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Joined: Fri Jun 29, 2012 11:48 pm

Re: Rear wheel steering for yaw correction

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roon - We call it crabbing. Imagine a body in plan view with two steerable axles. So long as both axles steer by the same amount you can have the body sat at any yaw angle to the direction of travel, whilst still tracking straight. On a Hunter alignment rig I think the total rear axle steer is called the thrust angle, a hangover from live rear axles.

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godlameroso
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Re: Rear wheel steering for yaw correction

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The 2002 Mazda RX-7 had "rear steer" which was really just compliance steer in the rear axle, it worked well on the stock car, but usually this is changed to full spherical bushings when you tune the car for speed.
The height of cultivation is really nothing special. It is merely simplicity; the ability to express the utmost with the minimum. Mr.Lee

Greg Locock
Greg Locock
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Joined: Fri Jun 29, 2012 11:48 pm

Re: Rear wheel steering for yaw correction

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Every car ever built has had compliance steer (once in a while somebody may have tuned it out for one particular lateral load and tire). The body is typically not a great deal stiffer than a hard rubber bush, and I can point you at a rubber bush that is as stiff radially as a tie rod spherical joint, so that's about 3 times stiffer than the body, and 7 times stiffer than a tall spindle. (Ballparky numbers 5 kN/mm, 2-8 kN/mm 14 kN/mm 14 kN/mm 2-5 kN/mm)

Bushings and SBJs and suspension arms behave like springs in series 1/k_overall=sigma 1/k(1...n). You may not be amazed to hear that the stiffness of the wheels and the wheelbearings (to a much smaller extent) is also significant.

What's funny is that all these bignum stiffnesses are being used to control a floppy rubber thing with a stiffness of 250 N/mm or thereabouts, yet their effect is quite measurable both on the K&C rig and the road and subjectively.

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godlameroso
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Re: Rear wheel steering for yaw correction

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I never thought about the wheel bearings, good call!
The height of cultivation is really nothing special. It is merely simplicity; the ability to express the utmost with the minimum. Mr.Lee