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Torque Steer Demonstration

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  • Torque Steer Demonstration

    The first video demonstrates the effects of free revving a slot car with over 12 volts, using an on/off switch.

    http://s164.photobucket.com/albums/u20/davejr-photos/?action=view&current=TORQUESTEER1.flv

    The second video demonstrates the amount of force, in grams, created by free revving a slot car at over 12 volts.

    http://s164.photobucket.com/albums/u20/davejr-photos/?action=view&current=TORQUESTEER2.flv

    In the third, fourth, and fifth video, the effects of this force on steering are demonstrated by accelerating a slot car from a dead stop, with no guide, using over 12 volts.

    http://s164.photobucket.com/albums/u20/davejr-photos/?action=view&current=TORQUESTEER3.flv

    http://s164.photobucket.com/albums/u20/davejr-photos/?action=view&current=TORQUESTEER4.flv

    http://s164.photobucket.com/albums/u20/davejr-photos/?action=view&current=TORQUESTEER5.flv



    The first photo below demonstrates how the car was suspended by a string, on the axle and motor center lines, for the free rev demonstrations.

    The second photo demonstrates how the torque steer was performed.

    The third photo shows the bottom of the chassis.

    The chassis weighs 78 grams, 42 rear, 36 front. The Red motor makes 240 g/cm Ts @ 12volts.

    Dave

  • #2
    Good lord, no wonder my cars handle like crap. What would a sidewinder do under identical conditions! This is very interesting.

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    • #3
      VERY interesting demonstration. We will really need to see what happens if we reverse the motor leads, and flip the crown gear around. Will the car veer off to its right?

      We'd need to see this to verify that the effect isn't from something in the car's setup that makes it turn left. This is the 'control experiment'.

      Now, since torque is really only applied during motor acceleration, this effect is almost entirely experienced on the straights.

      Comment


      • #4
        And an Anglewinder would be interesting too.

        I wonder if a test, like this,could be devised using a skid pad and no guide. But you would need some way off measuring the centrifical force generated on a tether.

        Comment


        • #5
          A good approach would be to:

          1) Limit the degrees of freedom, so you can look at the effect of torque separately on the vertical axis, as well as on the longitudinal axis.
          2) Find the center of mass, and with the degrees of freedom restricted, suspend the car using a torsional spring with a known spring constant.

          Comment


          • #6
            When the three acceleration videos are viewed frame by frame, you will see that in the second frame of each composite the car veers to the right the instant the voltage is applied.

            In the first and second video, in the third, forth, and fifth frames, the car is going straight and then turns to the left.

            In the third video the car veers to the right in the second frame then continues straight until it hits the retaining wall.

            Comment


            • #7
              Dave, do the power leads short against each other during the test? It looks like bare wire was used. I can't see it clearly.

              Comment


              • #8
                Originally posted by davejr View Post
                When the three acceleration videos are viewed frame by frame, you will see that in the second frame of each composite the car veers to the right the instant the voltage is applied.

                In the first and second video, in the third, forth, and fifth frames, the car is going straight and then turns to the left.

                In the third video the car veers to the right in the second frame then continues straight until it hits the retaining wall.
                Point is, without a control experiment, we don't know if the car would do that anyway.

                I'd recommend a control experiment before people jump up and down on conclusions.

                Comment


                • #9
                  The power leads to the chassis are 30 gauge insulated magnet wire.

                  Dave

                  Comment


                  • #10
                    The crown gear was installed on the left side of the test chassis and the demonstration was repeated.

                    In the first composite, second frame, the car veers to the left the instant the power is applied, then continues to go straight.

                    In the second composite the car is placed facing to the right. In the second and third frame the car veers to the left as the power is applied, then continues to go straight.

                    In the third composite a Ferrari 312 sidewinder is run. In the first three frames the car accelerates straight, then drifts to the left.

                    After many runs, most of the time both cars had a tendency to drift to the left after the first two feet, it must be a traction difference in the track surface.

                    Dave

                    Comment


                    • #11
                      Thanks, Dave. I think this pretty much confirms what high school physics would lead you to expect. Because the torque and the resistance to it are greatest at startup, it's not surprising that the effect all but disappears after the first few feet. I think that also explains why the effect isn't more noticeable while driving - it's not that pronounced once the car gets rolling.

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                      • #12
                        I'm intrigued by the fact the sidewinder car seems to demonstrate similar behaviour, if to a lesser degree. Seems probable that the weight of the motor being offset to the right side of the chassis would be a cause of this - or is it because the torque is being applied through the left end of the axle?

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                        • #13
                          If you apply torque to the left or right side of the axle, the effect would be the same. It is the tires on the road that apply the torque, which is all that matters in the case of the sidewinder. Inequalities in traction on right and left side would be the cause of steering off the line; whether that is caused by the car being heavier on one side, the track being more sticky, or one tire being more sticky, we cannot tell. Yet.

                          Comment


                          • #14
                            I love these discussions ...

                            If you apply torque to the left or right side of the axle, the effect would be the same.
                            Theoretically, this seems to make sense.

                            But then, theoretically horsepower should be the same whether measured at the crank or the rear wheels. Only t'aint so eh?
                            Hah! I just defeated you, with logic.

                            Comment


                            • #15
                              OK, I give up. You win. I quit. I'm done. I've had it. I am outta here.

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