Corratec Inside Link 2013

Todos los años por estas fechas se presentan muchísimas novedades, pero casi todas utilizan sistemas ya conocidos, y es que se puede decir que ya está casi todo inventado. Este año uno de los cuadros que mas me han sorprendido es el de la Corratec Inside Link. El sistema a simple vista es un Pivote Virtual muy similar al VPP, pero con las bieletas colocadas de una manera un poco diferente. Esta configuración de las bieletas situa el IC dentro de la rueda trasera, y hace que la bieleta inferior gire en el mismo sentido que la superior durante la primera parte del recorrido, por lo que no creo que exista ningun problema de Patentes con Santa Cruz.





Como podéis ver en los gráficos la nueva Corratec Inside Link es uno de los cuadros de XC mas radicales de toda la historia. La eficacia de pedaleo es impecable, con un porcentaje de Anti-Squat en torno al 100% pero por si eso no fuese poco, el cuadro tiene un recorrido trasero de tan solo 60mm y la posibilidad de bloquear el amortiguador desde el manillar. Si os fijais en la gráfica del Anti-Squat podéis ver como no se parece en nada a la típica curva del VPP, la gráfica de la Corratec es mucho mas parecida a la de un sistema de Pivote Virtual como el Maestro. El Brake Squat (100%) y el Pedal Kickback (6.5º) son un poco elevados, pero en un cuadro con tan poco recorrido no suponen ningun problema.

En la gráfica del Leverage Ratio vemos como el sistema es regresivo (1.7-2.15), pero en un sistema de este tipo yo lo veo bien. Es el típico LR que aplicado a un cuadro de XC sacrifica un poco de comodidad, para conseguir mayor eficacia de pedaleo. En fin, un cuadro sin concesiones, un cuadro 100% de competición, y una autentica rareza con tan solo 60mm de recorrido. Hace algunos años se veían cuadros de 80mm de XC (Para 29'' pueden ser suficientes...), pero poco a poco han ido desapareciendo.


Un saludo.

10 comentarios:

Josep Barberà dijo...

Bastante de acuerdo en las conclusiones... aunque 60mm son muuuuuy pocos, para justificar la inclusión de un sistema trasero de suspensión, que además, depende totalmente del amortiguador.
Alguien puede asegurar, que con ese recorrido se obtiene alguna ventaja objetiva en el transcurso de una carrera?. Objetivo es, el hecho que respecto una bici rígida de igual material, metes entre 500 y 600gr de peso.

Y no creo que se vaya más lento... quizás, un poco más rapido.

Bueno, después de tantos palos... decir que es una bici preciosa y altamente "molona".

Un saludo.

Antonio Osuna dijo...

Yo no diría que el cuadro depende del amortiguador. Si el objetivo fuese la comodidad entonces si habría que hilar muy fino con el Tune... pero es que el concepto es justo el opuesto. Es un cuadro tan radical que el LR está hecho asi a proposito y no creo que el tune sea nada especial.

Con ese recorrido y esa efectividad el bloqueo tambien es un poco redundante, pero ya puestos no cuesta nada meterlo...

Un saludo.

Josep Barberà dijo...

A mi, lo que me inquieta Antonio... son los 1000 N de fuerza máxima que se necesita para hacer tope!!.
Creo que el amorto tiene que ser muy progresivo, por que si no, el machaca que la lleve cuesta abajo (que los pros corren mucho también en bajada), se va a llevar más de un topeteo desagradable.

La parte buena, quizás es ese bajo LR.

Un saludo.

Antonio Osuna dijo...

Pueden reducir volumen con espaciadores por dentro, o simplemente meter mas presión y llevar algo menos Sag...

Un saludo.

Chris dijo...

Slowly, slowly every permutation of how two links might swing in relation to each other is being considered, implemented and patented. This new linkage is one permutation that up until now has had little attention.

My main surprise is that nobody came out with it earlier. I've been playing around with a modified Scott Spark simulation in Linkage that is a lot like the Corratec in form and function, so I would appreciate it if my name could be included on the patent award alongside the other patent holders.

Un saludo

Antonio Osuna dijo...

Yep, It's weird that nobody tried this until now, but I guess that SC Patents are a bit scary. Anyway, the problem with this system is that it is going to be difficult to build all the bikes around it. Having a regressive LR on a XC bike is ok.... but if they want to design a trailbike or something bigger, they need to change that.

Un saludo.

Unknown dijo...

I saw a new B'Twin prototype (B'Twin Peak) reported on in the cycling media the other day. It reminded me of the Inside Link so I looked at this again. While Corratec has not done much with the design (i.e. no longer travel versions yet) it really does seem to be alright (your comments about LR curve notwithstanding). It would be good to see a longer travel implementation - the way the pedal kickback curve is tapering off suggests that the trade off between AS and PK could be pretty good. That can only be confirmed with a longer travel bike though and it doesn't look like Corratec will be making one any time soon.

Of course the revised B'Twin might turn out to be alright too.

Un saludo
Chris

Antonio Osuna dijo...

I've just uploaded it to the online Library.... Give it a try and see if you can do a longer travel version with a better LR. The new Btwin is on my waiting list too, but I haven't done it yet.

Best regards,
Tony.

Unknown dijo...

Gracias Antonio

Unknown dijo...

I've tinkered with the Inside Link simulation in the Linkage Library now and I can report that longer travel implementations of the linkage are straightforward. I messed around with the linkage in a 160mm and 200mm implementation with corrected SAGs etc. and it works, sort of.

With the 160mm implementation reorientation of the leverage rate curve to a primarily progressive rate - rearward shock eye needs to go behind the link and forward shock eye gets dropped a bit lower - wasn't hard although I had to go to a coil shock, due to the limited choice, to settle down the crazy forces graph. In the 200mm implementation I set the shock up in a manner similar to the KROSS Moon, just to see what was possible. It worked fine with an LR curve not dissimilar to the one just mentioned. Long shocks (222mm and 270mm) were used and it wasn't hard to achieve low leverage ratio implementations in either case.

How did things look overall? Well, the good news is that in longer travel implementations the AS curve naturally breaks down into three parts - a declining curve initially then a somewhat flatter part of the curve mid travel and finally another declining curve deeper into travel. It turns out that achieving successful control of this curve or putting the promise of the three part AS profile to good ends is challenging - maybe that is why Corratec is taking its time.

What is the problem? In longer travel implementations the upper link swings through a larger arc and this works the lower link much harder in turn. With the DW-link or Yeti Switch or the recent AVP implementation on the BMC Trailfox this seems to lead to mostly propitious results in practice. Not so with the Inside Link. It does not appear to be as easy to time the relative interaction to links to achieve useful results. What I have described as a flatter middle section of the curve is actually more bowl shaped dipping at first where it needs to hold up immediately post-SAG then rising again briefly before dipping again in the latter portion of travel. A much longer lower link (in the same orientation) will settle things down a bit but tends to rob the linkage of some of the features that make it interesting - with a long lower link the AS picture is more one of a continual decline in the AS rate albeit a slower decline in the middle part.

I was hoping to see a simultaneous pedaling and pedal feedback result in the vicinity of that provided by the Yeti SB-66. I did not achieve that with the simulated 160mm bike and can now see significant obstacles to achieving such a result without fairly major changes to the linkage. Something that I didn't check was whether this kind of linkage can be used to achieve a very low kickback design that provides adequate AS at SAG (but not notably elsewhere) in the style of the Mondraker Zero linkage. Worth looking at I suppose. Anyway, I will be very interested to see what Corratec comes up with, but I wish they would get on.

Cheers
Chris

 

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