physics question

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  • b*saint
    No R3VLimiter
    • May 2006
    • 3794

    #1

    physics question

    Its probably pretty basic but for some reason I cannot remember this - On a rotating axis, if the axle is a constant speed, what is the speed relation, in rpm, 3" from the center as to 6" from the center? Twice as slow / twice as fast / or the same speed? I think its slower the further away from the center you go. If I remember right, this is the old way machine tools controlled their speed.
    Ma che cazzo state dicendo? :|
  • Wh33lhop
    R3V OG
    • Feb 2009
    • 11705

    #2
    Linear speed is doubled, rotational speed is the same.
    paint sucks

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    • snitzer
      Advanced Member
      • Jul 2008
      • 137

      #3
      Engineers Edge - Engineering tools, Engineering Reference for the engineering world.

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      • decay
        R3V Elite
        • Oct 2003
        • 5637

        #4
        the plane won't take off.
        past:
        1989 325is (learner shitbox)
        1986 325e (turbo dorito)
        1991 318ic (5-lug ITB)
        1985 323i baur
        current:
        1995 M3 (suspension, 17x9/255-40, borla)

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        • Bimmerman325i
          R3V OG
          • Dec 2007
          • 6854

          #5
          w=v/r => v=rw

          if r1=3, and r2=2*r1=6, v1=3*w, v2=6*w

          v2=2*v1, w is constant.

          In words, the farther you go from the center of the axis with a constant rotational speed, the higher your linear speed will be.
          2017 Chevrolet SS, 6MT
          95 M3/2/5 (S54 and Mk60 DSC, CARB legal, Build Thread)
          98 M3/4/5 (stock)

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          • briansjacobs
            E30 Fanatic
            • May 2010
            • 1278

            #6
            C
            Brian Jacobs

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            • reelizmpro
              R3V OG
              • Dec 2003
              • 9445

              #7
              It's been a while but a big diameter wheel will have less revolutions than a smaller wheel. We see this on our cars when we run wheels with smaller overall diameter than what came stock so our speedos read higher than we are actually traveling. However, if you're talking about 1 wheel, it will have the same RPM 6" from center that it does 3" from center since it's a solid wheel.
              "I'd probably take the E30 M3 in this case just because I love that little car, and how tanky that inline 6 is." - thecj

              85 323i M TECH 1 S52 - ALPINEWEISS/SCHWARZE
              88 M3 - LACHSSILBER/SCHWARZE
              89 M3 - ALPINEWEISS II/M TECH CLOTH-ALCANTARA
              91 M TECHNIC CABRIO TURBO - MACAOBLAU/M TECH CLOTH-LEATHER

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              • b*saint
                No R3VLimiter
                • May 2006
                • 3794

                #8
                ok so no matter what size pulley I use, it will always be spinning at the driving rpm anywhere on the pulley. Its the linear speed that varies. Thus a 6" pulley is spinning slower than the 3" driving pulley because its coupled with a belt moving literally linearly.
                Ma che cazzo state dicendo? :|

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                • mrsleeve
                  I waste 90% of my day here and all I got was this stupid title
                  • Mar 2005
                  • 16385

                  #9
                  Originally posted by Wh33lhop
                  Linear speed is doubled, rotational speed is the same.
                  this
                  Originally posted by Fusion
                  If a car is the epitome of freedom, than an electric car is house arrest with your wife titty fucking your next door neighbor.
                  The American Republic will endure until the day Congress discovers that it can bribe the public with the public's money. -Alexis de Tocqueville


                  The Desire to Save Humanity is Always a False Front for the Urge to Rule it- H. L. Mencken

                  Necessity is the plea for every infringement of human freedom. It is the argument of tyrants.
                  William Pitt-

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                  • SpoolnDaapex
                    Advanced Member
                    • Jan 2010
                    • 150

                    #10
                    This probably doesn't help much but the only thing i know is that people change the pulley sizes on supercharged cars to make more boost.
                    M42: Because 110 feels like 140 :finger:

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                    • mrsleeve
                      I waste 90% of my day here and all I got was this stupid title
                      • Mar 2005
                      • 16385

                      #11
                      Originally posted by SpoolnDaapex
                      This probably doesn't help much but the only thing i know is that people change the pulley sizes on supercharged cars to make more boost.
                      similar principal, smaller pulley = faster rotor speeds (rotational speed) = more boost this is more to do with gear ratios than axle speeds

                      But when you have something that is attached to the same axle the further away you get from the center of the axle the faster the liner speed needs to be to make 1 Revolution at the same rate as the center of the axle.
                      Originally posted by Fusion
                      If a car is the epitome of freedom, than an electric car is house arrest with your wife titty fucking your next door neighbor.
                      The American Republic will endure until the day Congress discovers that it can bribe the public with the public's money. -Alexis de Tocqueville


                      The Desire to Save Humanity is Always a False Front for the Urge to Rule it- H. L. Mencken

                      Necessity is the plea for every infringement of human freedom. It is the argument of tyrants.
                      William Pitt-

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                      • Erik
                        R3V Elite
                        • Oct 2005
                        • 5370

                        #12
                        Originally posted by dk
                        the plane won't take off.
                        Hahahaha YES!
                        -Erik
                        '16 Focus 2.0L - '99 Protegé DX 1.6L POS (Sold) - '87 4runner 22R-E (Sold) - '86 Schwarz S50 (Sold) - '02 WRX Wagon (sold) - '07 Impreza 2.5i (sold) - '91 Alpine M52 (Sold) - '89 Alpine 325is (Sold)


                        Originally posted by 87e30
                        I just want to dance with some beezies

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                        • Jand3rson
                          Banned
                          • Oct 2003
                          • 37587

                          #13

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                          • Wh33lhop
                            R3V OG
                            • Feb 2009
                            • 11705

                            #14
                            Originally posted by b*saint
                            ok so no matter what size pulley I use, it will always be spinning at the driving rpm anywhere on the pulley. Its the linear speed that varies. Thus a 6" pulley is spinning slower than the 3" driving pulley because its coupled with a belt moving literally linearly.
                            Yes. The belt will be moving at the same linear speed with either pulley, and a 6" pulley would turn over at half the speed of a 3" pulley for any given linear belt speed.
                            paint sucks

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                            • fryerfighter94
                              Mod Crazy
                              • Jan 2010
                              • 794

                              #15
                              Originally posted by teamdynasty43
                              Aye listen here ph fucking dick cheese mother fucker ...go back to touching your self or your fucking boyfriend because you're just some dumb mother fucker that has no fucking life than other to ridicule others because you have no fuckin life and low self esteem so you try to make your self feel better so you act all big!!!! Sooooo get the fuck out of here and shut your stupid little Whore mouth the fuck up and just leave!

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