Felt Virtue & Compulsion 2012

Si repasáis los archivos vais a ver como el año pasado hice un pequeño analisis sobre la Felt Virtue 2011, pero al ser un sistema que no se podía analizar correctamente en el Linkage ya os avisé de que los cálculos no iban a ser exactos. Esta vez sin embargo tengo la nueva Versión del Linkage y puedo analizar el sistema directamente, por lo que la precisión va a ser mucho mayor, aunque nunca es del 100%...













Como podéis ver en las tablas de Excell y en las gráficas de Anti-squat el sistema Equilink tiene un funcionamiento "de manual", cuando lo analicé el año pasado el porcentaje era bastante mas alto, muy efectivo en desarrollos grandes, pero se puede decir que iba un poco sobrado. El caso es que yo estaba convencido de que el análisis iba a ser bastante exacto, y al ver los gráficos me he llevado una pequeña sorpresa. El Pedal Kickback es un poco elevado, como es lógico, y el Brake Squat también está en un valor bastante alto (es muy raro ver a un Pivote Virtual por encima del 100%).

En la gráfica del Leverage Ratio vemos como el sistema es del tipo progresivo (3.0-2.4). Un dato muy bueno para una Trailbike. En el análisis antiguo tambien me salía un poco mas alto, pero el amortiguador no llegaba a la carrera que le correspondía asi que ya sabía lo que estaba pasando.

Un saludo.

14 comentarios:

Josep Barberà dijo...

Me quedo con las gráficas y por tanto la bici Compulsion... estan un poco mejor (rectificame si me equivoco, claro) en todos los apartados.

Creo que es un claro ejemplo de lo que a veces has estado hablando aquí en el blog, sobre que los mayores recorridos de las bicis, no tienen por qué ser un impedimento al buen funcionamiento general del sistema.

Y ahora la duda:
El pedal kick back y el brake squad son muuuuuy altos.
En la práctica, cuales cres que seran las sensaciones del piloto dando pedales cuesta arriba, y frenando cuesta abajo.
Por que no termino de verlo claro.

Un saludo.

Antonio Osuna dijo...

El Kickback yo lo veo en un valor normal, lo típico en un cuadro con un 100% de Anti-Squat en plato mediano. Y el Brake Squat si es verdad que es muy alto, asi que en teoría es un cuadro en el que la suspensión se va a endurecer un poco en bajadas.

Un saludo.

Anónimo dijo...

Adriano

Me alegro de que se hayan currado una buena bici en general, pedalea de forma impresionante, yo creo que ahi esta luego que tenga un kickback alto, el que se atranque un pelin creo que es normal, en la ibis hd pasa también.

Me alegro por FELT

Antonio echa un vistazo a la specialized enduro sworks 2013 a ver como la vés....

Josep Barberà dijo...

Buah!, Con tanta pregunta se me olvido perdirte eso tambien.

Pinta genial esa spezialized!!.
Me sumo a la petición de Adriano.

Un saludo.

Antonio Osuna dijo...

La tengo en la lista para este mes. Una cosa curiosa es que la EVO 2013 es distinta, no solo es que tenga muelle, es que la bieleta tambien es distinta... Asi que supongo que haré una comparativa entre las dos.

Un saludo.

Chris dijo...

For a long time, I thought the Equilink was a joke. Based on these numbers I can see I was wrong. I still doubt the complexity of the design serves a useful purpose but I'll keep an open mind for now.

It would be nice to know what is essential and what is incidental in the design. Is any important function served by that faux-bar-like pivot near the rear axle? Are the anti-squat or brake-squat curves affected if you get rid of that pivot and use a split pivot say (for the structural advantages that it would offer) instead? Would the brake-squat curve change if the caliper was moved from the lower suspension arm (chainstay) to the upper one (seatstay) assuming a split pivot implementation is possible?

I would very much like to see this one in Linkage.

Un saludo

Antonio Osuna dijo...

I think the problem is that the explanation of the system in their website is a joke, but that happens all the time. There are a few nice system out there awfully explained in their websites.

And most of the time you get the feeling that the guy who designed the bike is a good engineer, but then they try to explain it like we were six years old???

It's not rocket science.

Chris dijo...

I've looked for a long time at this linkage only to realise that it is very simple. The defining idea that makes the Felt bikes different also turns out to be easily generalisable to other four bar bikes very different in form to the Felt bike.

In many four bar suspensions (those with rigid rear triangles or horst-links) the floating bar performs two important functions. It provides a structure to carry the wheel and it controls the relative movement of upper and lower links (rockers, bars or whatever). It turns out that these two functions can be separated with one floating link bonding together and controlling the relative orientation of upper and lower links and another second link providing a structure to carry the wheel.

The wheel carrying 'link' like the controlling link (which Felt calls the Equilink) is joined to the upper and lower links but necessarily unlike the controlling link it must be expandable or collapsable so as not to interfere with the operation of the control link. As the contolling equilink determines the relative orientation of all points of the upper an lower links it will also determine the relative position and orientation of the mount points (i.e. pivots) for the wheel carrying link. This link will in practice always turn out to be a two piece linkage (it is the chainstay and the seatstay in the Felt implementation) so that there is allowance for the expandability or collapsability of the wheel link already mentioned. This expandability / collapsability of the wheel linkage is under the control of the equilink and doesn't imply that the suspension linkage lacks rigidity. The slight recasting of the form of the rear triangle (one of whose arms is not a bar but rather the equilink governed distance between the upper seatstay pivot and lower chainstay pivot) with the vertex near the rear axle opening slightly over the course of suspension compression on the Felt bike is just part of the necessary reformation of the rear triangle for the rigidity of this sort of four bar to be properly realized.

So why would you want to separate these two functions? Certainly not for most of the strange reasons that Felt has offered in its thorough misdescription of the linkage. They do mention (but don't explain) linkage 'bias' in a video somewhere and that would seem to be the real issue. The lower and upper rocker links can impart greater or lesser movement in their conjoined partner depending on the distance the equilink mount points are placed from the anchoring frame pivots for those links. The Felt bikes are biased to provoke greater angular movement in the upper link because the equilink mounts to the upper rocker at a very small radius from the anchoring frame pivot. The mount point to the lower rocker is at a greater radius. This effect which has implications for both wheel path and anti-squat curve (and other matters) then is further amplified in the Felt design by placing the mount point / pivot for the seatstay on the upper rocker at a far greater radius from the rocker anchoring frame pivot than the equilink mount point / pivot. So, there is a potentially vast range of wheel path and anti-squat tuning that can go on.

Whether this results in a better suspension is another matter. That may become clearer in time. In the meantime, it should be obvious that the same modification (of adding a floating control link) can readily be applied to any existing four bar (whether it employs short or long links) as long as the wheel carrying link (in the unmodified design) is a floating bar (or triangle).

Anyway, I offer this as one account of some of the implications of the Felt design, or is that the Brian Caulfield design improperly appropriated by Felt?

Un saludo

Antonio Osuna dijo...

Well, I think the pivot points of the Equilink are adjusted so they swing almost together... maybe the distance is different, but the speed of the rotation is diffent too, so you have to take that into account...

I have the feeling that an equilink system can be designed to work almost the same as a frame with a "vertical seat-stay and the same 4 main pivots...

You can use the 5th bar to tune the system a little bit, but it's not a very good idea, because it put a lot of pressure on the Equilink bar, and I've seen a couple of them broken. The pivots of the Equilink are very close to the main pivots, so if you want to transfer some forces from the upper to the lower link you have a very high "Leverage ratio" on the Equilink.

Un saludo.

Chris dijo...

I noticed a prototype bike at http://www.pinkbike.com/news/Random-Products-Part-Seven-Interbike-2012.html (designed by Brian Berthold, previously responsible for the truly awful Kona Magic Link) that similarly separates the wheel carrying link from the control link (Equilink on the Felt bike).

Thats where the similarity ends though. The control link of the prototype, which determines the relative orientation of upper and lower rocker links, is very short and in front of the down tube.

It is not hard to imagine different implementations.

Un saludo

Antonio Osuna dijo...

Yes, I saw that bike a couple of days ago, but it's going to be difficult to check it out with the Linkage program.

Maybe with the working model...

jaaral dijo...
Este comentario ha sido eliminado por el autor.
jaaral dijo...
Este comentario ha sido eliminado por el autor.
jaaral dijo...

Hola a todos, el brake squat puedes comprobarlo poniendo la bici boca arriba y haciendo girar al maximo la rueda de atrás y frenas de golpe. Hay muchos videos en internet donde se ve claramente como traga el amortiguador al frenar debido al brake squat:

https://www.youtube.com/watch?v=cY2j2gDiZQY

En mi caso, un amortiguador fox float rp 23 abierto del todo ni se ha inmutado. En mi opinión no se tiene en cuenta en estos cálculos el funcionamiento de la barra del equilink, como ya dije hace bastante tiempo. Saludos y gracias

 

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