Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Drivetorque reaction

  1. Dec 26, 2009 #1
    Hi Pfians and friends

    When propeller shaft rotates , due to action reaction transmission and also engine rotate in opposition direction to that of propeller shaft and so the whole chassis will and this would cause lateral load transfer. Correct me if I am wrong upto here.
    My question is: Will the reaction of drive torque rotate the rear axle also?If yes ,why?
    Well, I thought it won't rotate because since engine or transmission block is unsprung mass , then only the unsprung mass would rotate with it in a direction opposite to driveshaft rotation, which doesn't include rear axle.
    But on searching net i found axle will also rotate! Can you expalin why?
    Thanx
     
  2. jcsd
  3. Dec 26, 2009 #2
    Can you relate the Principal Axis Theorem for moments of inertia to torque? What would happen if the differential (on a solid axle) were at one of the two drive wheels rather than at the center? Do you believe that if the propeller shaft torque were high enough, one of the two drive wheels could rise off the ground?
    Bob S
     
  4. Dec 27, 2009 #3
    I don't beleive that either of the wheels would rise off the ground, whether the differential is at center or at end.
    Only the suspended chassis would roll side ways compressing and extending springs.
    Because everywhere this phenomenon is explained as a drill machine. Rotor rotates in one direction and then the casing tend to rotate in opposite direction that's why proper hold links are made.
    In case of a car engine or transmission is like the drill machine, so propeller shaft rotates in one direction and the casing along with the chassis rotates the other way.
    Why would axle rotate?
     
  5. Dec 27, 2009 #4

    Ranger Mike

    User Avatar
    Science Advisor

    see post on mech forum -Weight transfer due to drive torque! Nov10-09, 09:08 PM
     
  6. Dec 27, 2009 #5
    that thread was started by me in fact!
    I am sorry for starting a similar new thread ,

    but in that everyone gave me same answer of action and reaction, screw driver, drill machine, helicopter and i understand action and reaction but it should be betweem engine(or transmission) and it's casing and chassis. Engine crankshaft is like electric screw drivers motor and propeller shaft like the driver shaft. So shaft spins one way and screw driver's casing spins the other way. Similarly the engine crankshaft and prop shaft spins one way and the casing along with chassis spins other way , then why will axle rotate??????????????????????????/
    Please help me!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!:confused:
     
  7. Dec 27, 2009 #6

    Ranger Mike

    User Avatar
    Science Advisor

    imagine a rear wheel drive automobile that is on ice. totally slippery condition. if you engage the clutch, the drive shat rotates as doe the axle and wheel. but we have no movement because the tires lack traction. we have no chassis movement. now if we move the automobile to dry pavement and again engage the clutch , we have movement. the engine rotates the drive shaft and axle. the wheel and tire rotate and because we now have friction we have force transferred from the rotating tire to the pavement. since there is no tire spin force is applied to the pavement in varying amounts as controlled by the accelerator pedal. the more we press the pedal the more fuel air mixture is admitted and the engine makes more power. the more power applied to the pavement will cause more movement in the form of vehicle speed or wheel spin ( because more torque is a applied than the tire tread can transmit to the pavement) and the more chassis roll as a reaction to the tire adhesion to the pavement. In all cases the axle will rotate. it is a matter of how fast the axle will rotate but it will always rotate. are you following this?
     
  8. Dec 27, 2009 #7
    I am talking about axle rotating about the logitudnal axis of vehicle i.e about the axis prependicular to the axle and thus tranfering load laterally.
     
  9. Dec 27, 2009 #8

    Ranger Mike

    User Avatar
    Science Advisor

    when we have a lot of traction ( tire plants torque on the pavement with out breaking traction..spinning) the reaction to this torque is to compress the right rear spring AND try to lift the entire chassis. in extreme cases this is the classic wheel stand. both the lateral and longitudinal twisting forces are the direct reaction of torque meeting pavement. in most cases we have wheel spin and the above two twisting forces displayed.
     
  10. Dec 27, 2009 #9
    This photo shows the torque reaction in the attitude of a car under heavy acceleration:

    http://www.buyagift.co.uk/Images/product/large/2095_drag.jpg [Broken]

    but I'm not sure I understand the basic question so if it helps to clarify anything let me know.
     
    Last edited by a moderator: May 4, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Drivetorque reaction
  1. Beam reaction question (Replies: 2)

  2. Reaction wheels (Replies: 7)

Loading...