Marine air filled roller haul out force calcualtions

Discussion in 'Boat Design' started by Annode, Sep 22, 2019.

  1. Joakim
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    Joakim Senior Member

    Sounds like a friction coefficient, not rolling resistance. That would be valid for dragging a rubber ship on wet asphalt, not for any kind of rolling.
     
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  2. Joakim
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    Joakim Senior Member

    Seems rather outdated at least for asphalt and concrete. In EU passenger car tires get the worst energy rating, if they have more than 0.0121. For the best rating RR needs to be below 0.0065. For bus and truck tires the limits are 0.0081 and 0.004. http://www.etrma.org/uploads/Module...ustry-guideline-on-tyre-labelling-(vers4).pdf
    Most tires seem to be in the top categories (A-C, below 0.009).
     
  3. DCockey
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    DCockey Senior Member

    I agree that the over 25 year old data for tire rolling resistance on asphalt and concrete from the 1993 edition of the "Automotive Handbook" is outdated, and may have been outdated at the time of publication. My recollection from when I left the auto industry a decade ago is the rolling resistance coefficients for passenger cars and light trucks on hard, solid surfaces such as asphalt and concrete were typically 0.005 to 0.011 with most being toward the lower end of the range.

    However the rolling resistance on softer surfaces is probably dominated by the surface conditions and contact pressure. Improvement in the materials and construction of tires to decrease internal energy losses probably have very little effect on soft surface rolling resistance as internal tire losses would be only a small part of the total energy losses.
     
  4. Annode
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    Annode Junior Member

    What a fantastic discussion. Thank you all so much. I got to think about this in a new way.
     
  5. philSweet
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    philSweet Senior Member

    For what it's worth, drawbar pull rating of a Cat D8t is 140,000 pounds, dropping to 80,000 pounds at 1 mph. Winch attachments are available with similar ratings.
     
  6. Joakim
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    Joakim Senior Member

    "In general, tractors can only exert as much drawbar force as the machine itself weighs. This is typically limited by the amount of traction the machine is able to produce, depending on terrain and underfoot conditions. However, in certain cases, tractors can produce more drawbar force than their machine weight."
    Source https://s7d2.scene7.com/is/content/Caterpillar/C840571
    140,000 lbf is much more than it weighs thus can only happen with some extra grip.
     

  7. Squidly-Diddly
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    Squidly-Diddly Senior Member

    Tall Industrial Wheel Chock - 21.9 https://www.discountramps.com/traffic-control/wheel-chocks/p/MC3012/

    850,000lbs capacity, only 24lbs per unit. scoot them along up against the rollers as you go. I guess you'd want a whole row of chocks behind a roller, but I wouldn't want to be the guy in the middle, so attach the chocks to long flat beam.
     
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