Lapierre DH Team 2013

Lapierre ha renovado este año su modelo de DH, y aunque a simple vista el cuadro parece el mismo, el sistema ha sufrido una evolución muy importante. Lapierre no ha dado mucha información sobre los cambios y la poca que ha dado creo que no es del todo correcta... el cuadro ha aumentado el recorrido en 20mm y eso coincide con el modelo del Linkage, pero en la presentación se hablaba de que la nueva versión era un poco mas lineal y a mi me sale una curva prácticamente idéntica. La parte del Pendbox también ha cambiado lo que pasa es que al ser un sistema tipo Semi-Unificado no se puede calcular bien con el Linkage, por eso no he realizado la Tabla de Excell y tampoco quiero que os toméis las dos primeras gráficas al pie de la letra... 


Como comentaba al principio las gráficas de Anti-squat y la del Pedal Kickback no son las correctas, ya que están calculadas sin tener en cuenta el sistema Pendbox. La pieza que sujeta el eje de pedalier gira un poco hacia atrás al principio del recorrido, y hacia delante en la parte final. El cambio de sentido se produce en la zona de Sag y por lo tanto el porcentaje de Anti-squat en esa zona es muy parecido al de un monopivote, pero la gráfica evidentemente es muy distinta. En fin, lo que quería comentar es que el punto de giro principal en la nueva versión está un poco mas bajo que antes, y por eso creo que el porcentaje de Anti-squat y el del Brake Squat también habrán bajado un poco, aun así la eficacia de pedaleo va a ser muy buena, porque el modelo antiguo iba incluso sobrado, sobre todo en la parte final del recorrido. Lo ideal sería analizar el sistema con el Working Model, pero no he tenido tiempo.

En la gráfica del Leverage Ratio vemos como el sistema sigue teniendo una buena Progresividad (~3.6-2.4). El LR Medio sale un poco mas alto porque tenemos 20mm mas de recorrido y se está utilizando el mismo amortiguador, pero en principio la gráfica es muy similar a la del modelo anterior. Cuando en la presentación se hablaba de que el sistema es mas lineal tal vez se referían al hidráulico, que puede ir un poco mas abierto, o tal vez a la sensación que genera tener un poco mas de recorrido, pero el sistema ya veis que sigue teniendo una buena progresividad.

Un saludo.

5 comentarios:

Unknown dijo...

Lapierre's account and justification of the pendbox remains elusive several years after its introduction.

First, it is an anti-bob mechanism - chain tension is said to exert pressure on the pendbox mechanism pulling and locking the FBB in its rearmost position resulting in excellent pedaling performance. Still, Lapierre grant that without sound kinematics chain tension would not rise sufficiently to provoke FBB movement. So, the effect could be considered minor and perhaps redundant.

Then, there are the somewhat odd claims that the pendbox returns the FBB to the equilibrium position (SAG). Trouble is the shock does that too and the pendbox will never achieve what it is said to achieve without the support of the shock. Allowing that Lapierre has treated us to some descriptive oversimplifications of the pendbox it seems clear that the general idea is that the pendbox permits an increase in the degree of acceleration (assuming pedaling is uninterrupted by ongoing suspension activity) over what would be possible without such a mechanism (whether the suspension is currently compressed, extended or at equilibrium). So far, there has been no attempt at quantitative justification of the claim.

Finally, there is the claim that the pendbox can deliver its benefits (anti-bob and enhanced acceleration) without noticeable costs - the suspension will respond normally to bumps and dips because of the clever inclusion of a bypass mechanism into the pendbox which means that bump force will always have precedence overriding other modalities. However, this can't be quite right because when bump force "overrides" the designed functions of the pendbox the FBB moves forward raising chain tension and increasing kickback above what would normally be caused by chain growth as the wheel swings though its path. That surely increases both the likelihood of impairment of suspension function and the degree of such impairment when it occurs.

In the end the pendbox starts to appear to be more trouble than it is worth. For DH it seems to be a particularly dubious proposition. The small gains come at a high cost - elevated pedal feedback and chain tension have the effect of limiting suspension action. Where chain growth and pedal feedback are lesser concerns the pendbox makes more sense i.e. short travel bike.

These comments do not preclude that the pendbox may serve some useful function that Lapierre has so far failed to explain.

Un saludo

Antonio Osuna dijo...

Well, the thing is that nobody explains "anything", so it would be unfair to expect a good explanation from Lapierre, when their system is so complicated.

VPP explained anywere? No.
FSR?? No.
DW?? Not really...

The Pendbox has a lot of Kickback at the end of the travel, but the rider is probably not pedaling at that time, so it's not very important. The key of the system is low Pedal Kickback below Sag and having a different shape in the A1 Curve (It goes up...) and that's something that can't be analyzed with Kinematics, but it could make a difference in the dynamic response.

Best Regards,
Tony.

Unknown dijo...

Concerning the dynamics of the Lapierre DH Team. Is it something that you can model in WM? Will it be one of the bikes in the library of models you are working on?

Cheers
Chris

Antonio Osuna dijo...

I'm working mostly with Trailbikes, so I'll probably model the X-Flow.

Best Regards,
Tony.

Unknown dijo...

Great!

 

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