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News: Honda's New GP Transmission

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  • News: Honda's New GP Transmission

    Shaving .06 seconds from .06 second shifts or they don't call 'em rice rockets for nothin'.

    http://www.cycleworld.com/motorcycle...ssion_-_racing

  • #2
    When I designed it for Honda last year I incorporated a different engagement method but it looks like they read the drawings wrong

    Seriously It uses gears that spin freely on the output shaft when they’re not engaged, with internal ratchet mechanisms in each gear. There are four pawls on each ratchet – two take drive loads when the ratchet is engaged and the other two are used to limit backlash. During engine braking, the backlash-limiting pawls take the load. These pawls are normally held in the “neutral” position, so the gear isn’t engaged, by sliding rods inside the output shaft. These rods have indentations in them, so when they’re slid into a particular position, they allow the pawls for one gear to engage (the pawls are sprung, so they will pop out and try to engage the ratchets on the inner circumference of each gear as soon as the selector shaft allows them to). Honda’s DCT twin-clutch system (banned by MotoGP rules) uses hollow output shaft technology to run one shaft within another to drive both clutch baskets.
    On changing up to the next gear, first the backlash pawls in the first gear are disengaged (but not the drive ones) and the drive pawls in the second ratio are engaged. As the 2nd gear pawls connect with the ratchet inside 2nd gear, they take the load and accelerate the output shaft. Because the ones in 1st gear act as a ratchet, they can remain engaged right up to that moment – when the output shaft starts spinning faster than the 1st gear output ratio, the pawls will get pushed out of the way. Then, in the second stage of engagement, the backlash pawls in 2nd gear will be released and slot into place while the drive pawls in 1st gear are locked out of the way.

    .

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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    • #3
      Interesting. Makes for a very compact gearbox I must say. As the article suggests, you can't just add all of the 60ms changes for a total gain because not all changes are made at full power.

      In picture 2 there seems to be a two pairs of opposing rockers locking the gear to the shaft. I can't see how that can allow a gear to freewheel on the up-shift when the next higher ratio is selected.

      EDIT: John has it covered
      Last edited by Peter.; 04-13-2011, 09:18 AM.
      Peter - novice home machinist, modern motorcycle enthusiast.

      Denford Viceroy 280 Synchro (11 x 24)
      Herbert 0V adapted to R8 by 'Sir John'.
      Monarch 10EE 1942

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      • #4
        The Japanese can copy and improve ideas well.

        Seems to me that an automobile manufacturer was doing something very similar on their top end racing cars just a few years back. They were doing it with a double clutch but the basic idea of having a gear staying engaged with clutch number one while the next gear is synced up but disengaged with clutch number two. Mclaren maybe?

        Getting all of that in a motorcycle tranny is a heck of a challenge and I will give them..... I mean John, credit for that.

        rock~
        Civil engineers build targets, Mechanical engineers build weapons.

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        • #5
          Won't be very long before the dragracers copy that. They already have 'auto' conventional boxes that have the dogs ground as a ramp so that selecting a gear pushes the previously held gear out of engagement.
          Peter - novice home machinist, modern motorcycle enthusiast.

          Denford Viceroy 280 Synchro (11 x 24)
          Herbert 0V adapted to R8 by 'Sir John'.
          Monarch 10EE 1942

          Comment


          • #6
            Amazing at what lengths they will go too to create more of an edge, I wonder how it will be dependability wise as that's not only allot of load but lots of extra parts to run it through,

            I don't know about GP because those engines are rapping out so high to begin with and are so responsive that they may not practice this method due to potential engine damage or just plain breaking the rear tire loose at every shift but I would like to see the specs of the amount of time/power wasted in a typical crotch rocket POWER shift,
            even though it's .06 seconds it's not .06 seconds worth of power loss, powershifts allow for the engine to climb to even higher RPM's working against just the engines flywheel and crank mass and when the clutch is re-engaged you reap "most" of these energies back in acceleration ( minus the clutch disc heat )
            so realistically I would think a typical .06 second shift would be under .03 seconds of loss, but that's going by GP time shifting standards and that could be an entirely different ballpark to begin with...

            I probably had more powershifts than normal shifting on my old CBR F1 hound dawg that's why I sold it before I killed myself.

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            • #7
              A K Boomer,
              The article covered dependability issues. Frequent transmission changes.

              Article says it is .06 sec power loss because a kill switch is engaged.

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              • #8
                Speaking of double clutch transmissions with continuously engaged gears and hollow shafts, they are said to be the automatic transmission of the near future, if not already available. The advantage is that they have the efficiency of a manual transmission , but are shifted automatically. The only thing I'm unclear on is how they handle a stop and idle mode, with no clutch pedal or converter. There must be signals fed to the electronics that can tell you're going to brake and stop.

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                • #9
                  BMW has had a Double Clutch Transmission for a couple years now. Blazing fast shift.
                  BMW Blog
                  Wiki DCT

                  DJ

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                  • #10
                    Our Jeep Patriot that we bought a year ago has a continuously variable transmission along with manual joystick shifting. In auto mode it is constantly varying the ratio to keep the engine in the most efficient power band. It works amazingly well too. Power is always engaged and the engine rpms are kept within a fairly narrow band as long as power is applied.

                    The best is the manual shift mode. Drop the stick down to the bottom of the gate and then you shift by bumping it left and right. It has six ratios and they are very crisp and well defined. It stays in the gear you select, period. Shifting is immediate with no disengagement of power. It is the nicest transmission I have ever driven and I have driven a lot of different vehicles from two wheels to 18 wheels to no wheels (hovercraft ).

                    It also has excellent engine braking, every bit as good as a standard transmission.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Not to point out the obvious, but.....

                      Time saved in shifting does not equal a corresponding reduction in laptime.

                      Here is an interesting analysis after the first race of the season: http://www.motomatters.com/analysis/...re.html?page=1

                      PM

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