Driver Steering Force

[amyjenks]

hi there, im looking to find out the average force that a driver applies to the steering wheel.

i have a figure of 100Nm, does anyone know if this is a reasonable figure or know of a specific test that we can carry out to find this value.

Many thanks
amy

[murpia]

Originally posted by amyjenks:
...know of a specific test that we can carry out to find this value.
Come on, a rope and a bucket of water is all you need...

Regards, Ian

[Drew Price]

I remember a thread about almost exactly this topic not that long ago, please go find it and read that first.

Also, you are referencing an input torque, not force. Referring to it as a torque eliminates the dependency on steering wheel diameter.

To elaborate on Ian's comment (which is completely valid in it's aggressiveness, in my oppinion), are you looking for the maximum that the driver should have to put in to help the driver from becoming fatigued during the race, because that will be driver conditioning dependent.

If you are looking for the input torque necessary to steer the car, it is entirely geometry dependent in the steering and is dependent on: steering wheel diameter, steering box ratio, steering arm length, scrub radius, trail, tire geometry and compound, and self-aligning torque, so there really is no value available, like nearly every system on a racing car.

That said, probably anywhere from 30-80 NM would be reasonable for someone who is not a body builder.

You also need to look into control system theory, as making the steering too 'light' will make it harder to feel when the front wheels are about to break away. Get your hands on Carroll Smith's 'Drive to Win' and read the section about tires, and self-aligning torque versus slip angle, and lateral acceleration versus slip angle.

Best,
Drew

[BillCobb]

Let me try to help you with this one. For 'normal' vehicle maneuverabilty in your series, a PEAK steering torque of even 30 NM would almost be undrivable (Its too high). From Human Factors work, you will find that there is an optimum ratio of the torque buildup rate per g and the lateral acceleration by steer gain per g, no matter what the vehicle is: racing, cruising, autocross, flying and submarines. From a car racing perspective, the problem you will generally have on a flat track is that your tierod loads per g are low. Therefore, air pressure, kingpin inclination, caster, steer ratio, steering wheel diameter and tire aligning moment stiffness and corresponding wheel rim width need to be factored into a simulation and then appropriate settings made.

For the steering and maneuvering part of the autocross/endurance event, the time in band for the speed and g levels you are faced with, should set this 'Steering Work Sensitivity' ratio value. High efforts should not be equated to 'road feel' and/or corresponding ease of maneuvering. A driver worn out 1/2 way thru an event is not having any fun nor are their lap times any good. Some simple measurements with instrumented tierods and a steer angle and glevel sensor will deliver the 'best' handling car and greatly impress the judge(s) by your consideration of the human factors elements of the chassis and tire setup.

[exFSAE]

Bill Cobb?? No way. Didn't know you were involved with FSAE at all.

For those of you that don't know, Bill Cobb = really smart dude. Listen up on what he says.

[BillCobb]

http://s272.photobucket.com/albums/jj165/zzvyb6/?action=view&current=20517050.jpg

UNC Charlotte Buds. Then there was http://s272.photobucket.com/albums/jj165/zzvyb6/?action=view&current=00312129.jpg