Prius power limit for climbing ramp angle?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by 2009Prius, Sep 29, 2009.

  1. 2009Prius

    2009Prius A Wimpy DIYer

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    I made a ramp out of wood and found it became a perfect wheel choke because my Prius does not have enough power to climb up the ramp: :(

    [​IMG]

    I tried to push down the accelerator further, the engine roared, the car tried to climb but always rolled back down after advancing what felt like only a fraction of an inch.

    Now I am back to square one. What is the angle limited by the max power of Prius? As you can see an angle just slightly less than 45 degrees won't work. :(
     
  2. dogfriend

    dogfriend Human - Animal Hybrid

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    That isn't a ramp, that's a wheel chock. You need to make a less extreme angle or step the front of the ramp so the tire can climb one 2x6 at a time.
     
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  3. qbee42

    qbee42 My other car is a boat

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    At that steep of an angle with wood, the traction control system is going to kick in.

    Tom
     
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  4. dogfriend

    dogfriend Human - Animal Hybrid

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    If its any consolation, my GF's motorhome has something like 450 lb ft of torque and it wouldn't climb that either. I have some RV leveling blocks made from plastic that stack and interlock. They are approx 1 inch thick and when you stack them there is an offset of approx 5 inches between the edge of the bottom and the edge of the one stacked on it.

    If you made an offset of 5 - 6 inches, you should have no trouble climbing one 2x6 at a time.
     
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  5. 2009Prius

    2009Prius A Wimpy DIYer

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    Interesting. So even when the tires are not moving and the car is standing still the traction control can still kick in and kill the power? :confused:
     
  6. dogfriend

    dogfriend Human - Animal Hybrid

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    But you did move a fraction of an inch. Enough to unweight the tires from the ground, and then you lose traction with the ground, and start applying force to the end of your wheel chock.

    I'm too lazy to do a free body diagram, but if you did, I think you would find that as you try to climb your wheel chock, the resultant force in the horizontal direction (backward) would be very high compared to the force in the vertical direction (which would lift the car). That is why it works so well as a wheel chock. :madgrin:
     
  7. qbee42

    qbee42 My other car is a boat

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    Exactly. If we were doing this with a 4WD vehicle, the back tires would exert a forward force keeping the front tires in contact with the ramp. With a front wheel drive vehicle, the contact force approaches zero as the ramp angle approaches vertical.

    Tom
     
  8. 2009Prius

    2009Prius A Wimpy DIYer

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    I can see the traction control comes in if the friction is reduced to such low value that the tires start to slip. In the case of wheel chock, even if the tire leaves the ground and climbs onto the chock, it still grabs the surface of the chock and does not slip. So it is hard for me to understand why the traction control would come in. It is much easier to understand as lack of power as the motorhome example suggested earlier.
     
  9. dogfriend

    dogfriend Human - Animal Hybrid

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    Unless the chock starts to move. Which is very possible because the horizontal force on the face of the chock will be very high.

    I used to have a set of metal ramps and when I tried to drive onto the ramps with my RWD truck, they would skid on the concrete. I finally got rid of them for that reason. I have a set of the plastic ramps now, but I'm not impressed with them either (they deform quite a bit with either the Prius or Avalon on them) so my normal method of raising the vehicle is to jack up the front using a floor jack and then use jack stands to support the car.
     
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