abril 27, 2014 11 Comentarios
Descifra el código de las ruedas eternas.
¿Cuál es la característica que más se pasa por alto al construir ruedas? ¿La aprovechas? Apuesto a que no, pero aun así, te vendría bien un recordatorio. Una pista: se trata de los radios.
Hechos
#1 - La mayor debilidad de las ruedas que piensan en los costos es la rotura de los radios (también para muchas ruedas de alto rendimiento).
#2 - Los radios se rompen principalmente en el codo (cubo) y, secundariamente, en las roscas (llanta).
#3 - Un material de radios más resistente, un mayor número de radios y radios más gruesos disminuyen la tendencia de una rueda a romperse.
Solución: ¡Codos musculosos!
Los constructores eligen la marca y el calibre de los radios, así que veamos qué es posible.
La solución obvia son radios tan resistentes en el codo como en la rosca. ¿Existen? Claro. Ejemplos: Alpine (DT), Strong (Sapim) o DH13 (Wheelsmith).
¿Alguien los usa hoy en día? ¡Casi nadie! Pregúntenles a los fabricantes.
Esto es ignorancia a un nivel que no podemos permitirnos. Necesitamos maneras de que la gente use bicicletas (nuevas o viejas), convencerlos de que lleven su equipo, añadir características como motores de asistencia al pedaleo, luces y suspensión, y los radios se rompen por todas partes.
¿Cómo funcionan los codos musculosos?
Los tres modelos que acabamos de mencionar tienen codos de 13 g (2,3 mm de diámetro) pero son de 14 g (2,0 mm de diámetro) en el extremo de la rosca (por lo que son compatibles con todas las llantas).
Sorpresa para muchos, los bujes de 2,3 mm encajan en bujes perforados para radios de 2,0 mm. ¿Cómo? La rosca laminada de un radio de 2,0 mm tiene un diámetro exterior de 2,2 mm. Al laminar una rosca, como al arar la tierra, se crean picos y valles (sin quitar material). Para que la rosca quede bien en los radios, los bujes se perforan más grandes, generalmente a 2,5 mm. Si se usa un radio de 2,3 x 2,0 mm, el codo encaja perfectamente.
Los radios de codo robustos funcionan con el 99.9% de los bujes y llantas diseñados para radios estándar. ¡Aprovechémoslos!
Los radios de codo robustos no cuestan más que los conificados. Un juego de 32 radios DH13 (de un solo conificado) pesa 7 g por rueda (32) más que los 14 g de un juego de radios rectos. Esto es menos que el peso de un radio, y ese pequeño peso se concentra en el buje, donde tiene el menor efecto dinámico.
¿Cuánto mejores son?
Recuerde que la resistencia a la fatiga de un radio no es proporcional a su diámetro sino a su área de sección transversal.
Eso supone un enorme aumento del 32 % para unos míseros 7 g por rueda. Equivale a añadir 10 radios a la rueda. La experiencia demuestra que esta característica casi elimina la rotura de radios. Combínala con neumáticos más grandes y tendrás una solución para cualquier rueda mal construida, sobreutilizada o sobrecargada.
Para una revisión de la ingeniería detrás de la longevidad de los radios, consulte esta publicación nerd .
¿Cómo empezar?
¡Empieza a usar radios de codo robustos mañana mismo! Comunícaselo a otros constructores, mecánicos y gerentes de producto de inmediato. Convence a las empresas de radios de que NO dejen de usar estos calibres como hicieron con muchos modelos de 15 g. Las ventas lentas llevan al desistimiento de cualquier producto.
Date una palmadita en la espalda por ser un experto en ruedas, por saber trucos baratos, soluciones ingeniosas y opciones que pasan desapercibidas, y por difundir el mensaje. Nada de dar vueltas a ciegas, eres un experto seguro. Demuéstralo poniendo a prueba tus codos.
Por cierto, como muy pocos distribuidores de radios conocen los codos robustos, Wheel Fanatyk ahora vende piezas en bruto Wheelsmith DH13. Córtelas a medida con sus máquinas Morizumi o Phil. También encontrará productos equivalentes de otras empresas de radios.
febrero 12, 2024
The killer for rear derailleur wheels is the left-right tension difference. Single-butted 13/14g spokes deal well with the extra tension on the right, but you don’t really need them on the left and there’s a reason the wheel should last even longer if you use more elastic double butted spoke on that less tight side.
The trick is to match the spoke stiffness to the tension, so that both sides have the same elongation – just like a front wheel. And how often does anyone break a front wheel spoke?
The unequal elongations when the same type of spoke is used in both sides of a dished wheel means it doesn’t take much of a bump in the road for any left spokes in the bump zone to go completely slack, while the right spokes still have tension, so that part of the rim doesn’t simply move toward the hub, it also kicks over to the right! And if you build wheels, you’ll know how far a rim can deflect sideways in response to a modest difference in left-right spoke tension. This is why rear wheels go out of true and can even collapse in a Pringle shape without being hit sideways at all, but just from running straight over a bump in the road. A bit of rim is pushed toward the hub, the left spokes attached to it go completely slack and then the still quite tight right spokes yank it over in their direction!
Please think about it and give ‘Dish-Matched Spoking’ a try. Single butted are good for high stress wheels, but are even better IMHO with double butted on the less stressed side.
noviembre 02, 2021
Hi Ric,
Excellent article, though I’m obviously a bit late to the game.
Any thoughts on actually building with beefy elbows? The 2.3 J-bend can make hard work of bedding down the spokes along the flange. They just don’t lay down snug like a 2mm gauge.
I recently built up a touring wheel with Alpine 3s and an Shimano LX hub. Had to resort to head washers to get the spokes to set decently. Not sure if that was ultimately necessary, but it seemed to help.
noviembre 02, 2021
Just ordered some Sapim Force spokes to build up to some Velocity Ailerons to White Industries CLD hubs. 36h rear, 32h front. Should work out to a very long lasting wheelbuild. Interested to see how the Force spokes build up.
noviembre 02, 2021
Ric, the benefits of extra meat at the elbow end are negated by the straight-gauge nature of the spoke at the thread end. The purpose of that but at the thread end is to protect the place with the lowest diameter, which is the thread valley. The diameter there is something like 1.8mm IIRC. By having the spoke shaft at 2mm, the strain is concentrated in the thread valley, By reducing the shaft to 1.8mm or lower, the strain is concentrated on the shaft where the smooth surface provides no stress risers and thus few cracks at either end of the spoke.
I doubt the durability of a 2.3mm – 2mm spoke has been proven, whereas the durability of a 2.0mm – 1.8mm – 2.0mm spoke has.
Making it thicker at one end may make it stronger (but we already have ample strength) but reduces durability, which is what we are after.
noviembre 02, 2021
Ric,
I’m kind of stunned at the above comments… Having personally built about 6 touring wheelsets and a TON of Ebike wheels with Mostly Alpine3s I have never had one come back with a broken spoke! Many of the E-bikes are daily transportation.
I’m not sure why any one would say differently if they haven’t at the very least used them on a build. I do still build with mostly 2.0/1.8/2.0 and think for most of my applications they are adequate, but i Never hesitate to pull out the 13/14 when someone whispers E-bike… I don’t believe any wheel is forever though. Especially under those heavy commuter situations, and I’m very curious when/if I will see one of the wheels built with Alpine3 come back with a spoke issue. Have you seen any?
Anyways, haters gonna hate… so keep posting because I really enjoy all the WF Blog posts. Thanks!
noviembre 02, 2021
DT Super comp spokes are widely used by many wheel builders, and at ~ 86% the diameter of the DH 13, are plenty stout for many applications. Just ask the Enduro racers…. This seems like a non-issue.
noviembre 02, 2021
Care to elaborate on that last bit? Is their patent of PSR the reason we’re not seeing reinforced elbows on light spokes from the usual three for instance?
noviembre 02, 2021
Ric, Always enjoy your site and blogs! Thank you… With regard to spoke gauge, my personal preference for wheel longevity is 36 × 14/16 gauge. The greater spoke count over 28 or 32, requires correspondingly less tension in each spoke, which in turn places less stress on aluminum rims and hubs, and more evenly distributes “shock” loads among a greater number of spoke resulting from encounters with pot holes, curbs, rocks and the like. Regards, BikinBobS
noviembre 02, 2021
Beg your pardon, but the statement re. reletive cost does not hold water. The DH13 spoke is only marginally less expensive (at retail cost, anyway) in comparison to the DT Supercomp. And again, the later is widely available and utilized by many wheels builders for amateur (not pro) riders.
Further, the mathematics shown above appear to be in error; 2.3 mm is not 32% greater than 2.00 mm in ‘cross section’…that term (cross-section) typically equates to diameter. So; .3 mm increase from 2.00 mm is .15 or 15%—not 32%.
No debate from me that heavier gauge spokes can produce wheels that are less likely to fail at the ‘elbow’. Only certain details in this post appear to be a bit askew.
noviembre 02, 2021
Ric, do you have any thoughts on Pillar spoke and their PSR (big elbows) series? Seems a lot of factory built wheels tend to use Pillar so I never gave them much thought, but after a look on their site they seem to have very progressive design.
Off topic: Spent part of the morning on a Moizumi today, and man alive, what a dream! Love using great tools!!
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PeteComo
febrero 12, 2024
One way around is to use washers on the bent end. Quality sold/sells a version from Bossard in packs of 1000. Part number S10332170011.
And yes, it’s a wheel business.