dj park

Discussion in 'Downhill & Freeride' started by jerseydirt, Jan 10, 2008.

  1. jerseydirt

    jerseydirt Turbo Monkey

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    i really dont feel like going all the way to highbridge. i wanna smooth out upper dominion a little so i can ride it on my hardtail. it was so bumpy last time. Maybe there should be a dirt jumps park in that space by phantom drop so when your done dirt jumping you can do the drop.
     

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  2. Timekiller

    Timekiller Monkey

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    heh.. did you see uppers on diabloween? that was crazy
     
  3. downhillbkr247

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    upper was a S#1THOLE...or should i say MUDhole lol during diabloween...for once i wished i had tear-offs!
     
  4. NJMX835

    NJMX835 Monkey

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    The good news is Diablo will be installing tampon & pad dispensers at the top of every trail this year.

    No more leakage! :thumb:
     
  5. runnin12s

    runnin12s Monkey

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    are there gonna be bathrooms to go with those feminine products?:clapping:
     
  6. Timekiller

    Timekiller Monkey

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    dude, this is crymonkey.com.... er i mean ride.
     
  7. demo 9

    demo 9 Turbo Monkey

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    how many seconds will u spend in the air in a season at the diablo jump park...lol
     
  8. Timekiller

    Timekiller Monkey

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    haha.... ill bite

    Lets say average of 3 seconds / drop
    15 drops in a day
    every day of the season (105)

    That would be 45sec./day
    4,725sec/season or 78.75min/season
    or just about 1-1/2 hours of flight
    :imstupid::banana::ban:
     
  9. jcook90

    jcook90 Turbo Monkey

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    3 seconds a drop is very very off. Clearly your understanding of gravity is off, but all of your other math/physics is right. Gravity is 32 ft/second/second, so in 1 second you fall 16 feet, resulting in typical airtime off the normal drop (say 8 feet) to be roughly .75ish seconds (speed increases the more you drop so you cover more in the last increment of time). Jumps can be interpreted slightly different, you get double the time for the same height achieved as drops. Say you get 16 feet up on a domination drop, then your airtime would be 2 seconds because of the above mentioned constants. Close though, the other stuff about rotation on wheels, moments of intertia, centripietal force, etc was all pretty cool.

    Oh, and yes, pvssys
     
  10. The303Kid

    The303Kid Monkey

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    there not that much room above deck for jumps but it would still be sick
     
  11. demo 9

    demo 9 Turbo Monkey

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    eye kan skip werds too
     
  12. Timekiller

    Timekiller Monkey

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    Thank you for the correction. I just pulled the 3 seconds out of my @$$. I was being lazy as usual and didn't look it up. I also didn't realize we were talking about jumps instead of drops.

    Drops:
    Lets say average of .75 seconds / drop
    15 drops in a day
    every day of the season (105)

    That would be 11.25sec./day
    1,181.25sec/season or 19.67min/season
    or just about 1/2 hour of flight

    Jumps:
    Lets say average of 2 seconds / jump
    30 jumps in a day
    every day of the season (105)

    That would be 60sec./day
    6,300sec/season or 105min/season
    or just about 1-3/4 hours of flight
     
  13. jcook90

    jcook90 Turbo Monkey

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    Bueno.

    How about now total volume of brake fluid moved per year, saying 2mL of fluid are moved in the average braking (that's just one way, 4mL all together). Say you brake uhh 15(?) times a run.
     
  14. Timekiller

    Timekiller Monkey

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    30ml/run (1 way) 60ml/run (2 ways)
    20 runs / day...
    600ml/day(1 way) 1200ml/day (2 ways)

    about 20 oz/day one way... 40oz 2 ways.

    So you move about this much fluid in one day:



    and if you rode the whole season (105 days) you would move 105 old E's in the season.
     
  15. jcook90

    jcook90 Turbo Monkey

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    I'm starting to run out of ideas here...

    Heres one:
    The rotational kinetic energy of a 1.3kg .66m diameter wheel with a 20t chainring and a 38t front chainring rotating at 2(pi) rad/second (the cranks, that is)

    Also, the perpendicular force required on a 175mm front crank with 38t chainring attached to the same rear wheel to get it to accelerate at 3 rad/sec/sec.

    GO!

    Also, how bored are you? And i'm guessing you paid attention in physics class if you can solve those two
     
  16. Timekiller

    Timekiller Monkey

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    Hmm... so the crank is rotating at 2(pi) rad/second and with a 1:1.9 ratio the wheel is spinning at (1.9*2(pi)rad/sec)
    155.12"/sec or 8.913MPH
    Angular velocity is 684º/sec
    Moment of inertia is .429kg*M

    ERotational= 1/2Iw(2)
    Erot= 1/2(.429)(467856)
    Erot= 2.007

    Therefore the RKE should be 1.00355112kg*m
    or
    9.8414746 joules

    well the force required to spin the static wheel at that acceleration is:
    1.287kg-m or 9.3088888ft-lbs.
    so
    the static force required at the crank is:
    2.4453kg-m or 17.687ft-lbs.
    which means
    if the front chainring has a radius of 79mm the leverage ratio is 2.215 (mechanical adv.)
    then
    you would need to apply 1.1046571kg-m or 7.99 ft/lbs. to the pedals. Unfortunately I have to leave work right now so Im not going to figure out the force in the arc (perp. force) Ill do it tomorrow.

    ...never took physics.. :poster_oops:
     
  17. Timekiller

    Timekiller Monkey

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  18. jerseydirt

    jerseydirt Turbo Monkey

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    gravity has a force of 9.8
     
  19. Huck Banzai

    Huck Banzai Turbo Monkey

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    Ok.

    How much wood could a...could an educated beaver chuck if properly instructed by a qualified woodchuck? (Given up-to-date Union membership and medical clearance.)
     
  20. rollertoaster

    rollertoaster Monkey

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    how much wood could a woodchuck chuck, if a woodchuck could Chuck Norris?
     
  21. demo 9

    demo 9 Turbo Monkey

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    none, chuck norris would roundhouse kick it
     
  22. JerZ_r1der

    JerZ_r1der Chimp

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    After reading this post... it reminded me of everything I hated in Physics class. :]
     
  23. jcook90

    jcook90 Turbo Monkey

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    Even though I'm done with school, 9.8 m/s^2 which equals 32 feet/s^2. And 9.8 is just the acceleration due to it, the force of gravity is different.
     
  24. ICU812

    ICU812 Monkey

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    fourth day, five day marathon, were moving like a parallelogram.
     
  25. FBMX123

    FBMX123 Chimp

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    lets talk about olde enlish again! I actuall prefer the Colt 45, but when i'm feeling particularly frisky, i like to roll with the good ol' 211. And if i just got done rocking out to Ice Cube and Dre, I grab the St. Ides...**** "gets yo jimmy thicka, gets ya girl in the mood quicka." word
     
  26. chatua

    chatua Chimp

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    Come again? :brow:
    32ft/sec/sec is the acceleration of gravity. The very instant you leave a drop, your rate of decent is 0ft/sec, and the more time you spend airborne, the faster you fall.

    As you should know, the formula for distance traveled knowing only initial velocity, acceleration, and time is D=V0*t+at^2. Since initial velocity is 0 for a drop, you get D=at^2. This gives the distance fallen from an initial velocity of 0 in 1 second as 32ft...duhhh, not 16ft.

    Using the above equation, we can calculate normal airtime for a drop like Phantom. Let's use 8ft like you did:
    8ft=(32ft/sec^2)t^2
    t^2=(1/4)sec^2
    t=0.5 second

    Now, I really don't feel like calculating how many seconds Dom's Denial, Road to Nowhere, Anthem, the jumps, etc. would take. But if anyone wants to try, use the formula I used, multiply that by the number of times you hit the drop per day, add it to the other drops you hit, times it by number of times you visit a season, etc. For jumps, estimate the height you get off the jump and treat it like it was a drop. Just multiply it by 2 cuz you spend the same amount of time going up as you do going down. Unless of course...it's a step up/step down like the Salvation kicker, thats a different story. :crazy:
     
  27. DEMOmy8

    DEMOmy8 Chimp

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    anyone here wanna be my math tutor? :P
     
  28. DownCycles_Stef

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    Wow, I really don't want to bite into this one, but this is what I get for majoring in physics...gravity is -32ft/(s^2), it's a measure of acceleration. Here's the only other equation you need... Distance (ft) = ( Velocity (ft/s) * Time (s) ) + (Acceleration (in this case G, which is -32ft/s^s) * Time^2 (s^2) ).

    Have fun figuring this nonsense out and remember your initial vertical speed is typically 0 ft/s not how fast you are actually moving off the jump, in fact on kickers like Salvation your initial vertical speed is probably more than 0. And in general a negative speed or acceleration or distance means the object in question is moving towards the origin of gravity (i.e. the ground).

    Oh, yeah, and I can ride too, haha.
     
  29. tmoney727t

    tmoney727t Monkey

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    you guys are nerds.
     
  30. jerseydirt

    jerseydirt Turbo Monkey

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    funny how this is a dj park thread
     
  31. downhillbkr247

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    i love this thread! its an educational fight!
     
  32. jerseydirt

    jerseydirt Turbo Monkey

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    yeah tis why it hasnt been deleted
     
  33. fortenndu

    fortenndu Turbo Monkey

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    Jcook90 got F-d in the ass.
     
  34. downhillbkr247

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    i believe that the politically correct term is: OH SH13TTTTTT!!!! Jcook90 JUST GOT F'D IN THE A!!!!!!!!!!!
     
  35. mntbiker2

    mntbiker2 Monkey

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    j cook likes it in the a!!