Ask MO Anything: Transverse or Longitudinal V-Twin?
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Thread: Ask MO Anything: Transverse or Longitudinal V-Twin?

  1. #1
    Junior Member
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    Nov 2016

    Ask MO Anything: Transverse or Longitudinal V-Twin?

    Dear MOby,

    Excuse the noob question, but what’s the difference between a transverse V-Twin and a longitudinal one, and what are the advantages of each?

    Navigational Ade

    Dear Ade,

    It has to do with the orientation of the crankshaft. Any engine, be it a V-Twin, V-Four, or inline-Four, is considered to be “transverse” if its crankshaft lies perpendicular to the motorcycle’s wheels, i.e. across the frame, parallel to the axles. Most motorcycles have transversely mounted cranks, including all Harley-Davidson V-Twins, nearly all four-cylinder sportbikes like the Yamaha R1, Kawasaki ZX-10R, Aprilia RSV4, all Ducati V-Twins and V-Fours… including the Monster 797 pictured on the left, above.

    Chain or belt drive to the bike’s rear wheel is simplest and lightest with this layout, and having the crankshaft spinning in the same plane as the rear wheel means power can be transferred through the gearbox and straight on into the drive chain and rear sprocket without making any power-sucking changes of direction.
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  2. #2
    Senior Member GuzziHero's Avatar
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    May 2015
    Guzzi is better. End of

    Its actually more complex than that. The Guzzi layout has its issue - shaft 'jack' where the torque rotation turns the bike over to the left (a little like how helicopters require an anti-torque tail rotor / notar or counter-rotating propellers), you are restricted to a large single plate clutch, changing that clutch requires removal of the back of the engine and all of the UJs required in the drivetrain along with all their associated lubricants.

    The shaft jack is controlled by a Cardan countershaft - this holds the drive shaft, allowing the suspension to move independantly and stops the torque rotation. The single plate clutch can't really be bypassed but they don't wear out particularly quickly so that maintenance job isn't too much of an issue. The final problem is what it is. You have engine oil, gearbox hypoid oil, and final drive hypoid oil.

    There is a misconception that the chain drive is more efficient than a shaft. Actually, it is not. A well tensioned chain loses around 10-15% power from the front sprocket to the wheel depending on its weight / design, a shaft loses around 12% with a cardan shaft and 16-18% without, and a belt drive is usually between 15% and 20% if the figures I've seen are to be believed. In fact even that chain number is a bit misleading - when under power, the chain effectively acts as a (slightly cushed) solid pull-shaft. Most of the power is actually lost through rotational weight of the rear wheel and attached items, I believe. A friend of mine also showed that when he disconnected the rear brake of a bike he ran on a dyno, the power loss dropped several %.

    I feel the main reasons why no sportsbikes use shaft drive is down to the unsprung weight on the rear (not inconsiderable), final drive universal joint seals and leakages therefrom, and the difficulty in cushing the final drive. Anyone who has ridden a shaft drive with badly tensioned throttle cables can attest that the drive 'lash' is offputting, if not downright vicious. The other problem of course is that with a chain you can quickly and easily change sprocket sizes and weights, which is impossible with a shaft final drive.

  3. #3
    Senior Member R Powell's Avatar
    Richard Powell
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    Join Date
    Feb 2010
    Hi There, I think we should celebrate the differences between bikes, this is what makes them fun! Unlike cars which follow similar formats bikes are all very different. Some bikes have 1 cyclinder some 6, small and large CC ,heavy light, on road off road. I don't think I have ridden a bike yet that doesn't have some redeeming feature or some character. Unlike cars this is what brings us all together as bikers ' One for all and all for One'
    enjoy your Easter ridingg
    The Benelliman
    1981 Benelli Sei 900
    1989 Benelli Sei 900
    1976 Benelli 125 Enduro
    1981 Benelli 250 2c
    1976 Benelli 250 Quattro
    1992 Ducati. 907 ie


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