Por esos leuros me pillo un Nicolai TFR, que si bien no es 100% custom (hay opciones customizables), sí es más innovador y encima te llevas el cuadro y una transmisión del copón :mrgreen:
Con esos precios es para volverse loco loco,pues estaba yo mirando que dicen los yankis de esto y me encontre con un post en mtbr,sobre cuadros de ti y la verdad siempre pense que con el titanio no podrian salir cuadros feo pero es que vaya barrabasadas, por dios!!!!!!Eso si hay alguno que es para quitar el hipo y lo msa gracioso es que son de la epoca de cuando iba con mi california xl2.El kona es la repo**a que pena no sigan con la fabricación. http://forums.mtbr.com/showthread.php?t=2814&highlight=Kona+Ti+Hei
La diferencia entre un moots y un dean es sencilla los dueños de moots tienen una mansion y los de dean un gran chalet , vamos señores seamos serios , cuanto mas os cobran por algo mas lo valorais , yo particularmente no me compro una bici de estas si no me toca la loteria , pero aun asi me lo pensaria porque luego vas a ir siempre en el grupeto de pepino de bici y no camina ni pa tras el tio. Prefiero una bike yanki mas normalita . Eso si bonitas bonitas son las merlin . Y si si tuviera dinero y comprara una seria para toda la vida , no para cambiarla luego de 5 años , para eso me quedo con mi sworks y la cambio por otra cosa de 1000 euros y listo.
Yo desde que comence con la bici estoy en ese grupeto pero al principio era conesabicicomovahatirar y ahora estoy en pepinodebiciynocaminapatras. :mrgreen: Saludos.
Linuxx, yo veo más robo 1000 euros por un S-Works M5 y nadie dice nada. Por cierto ¿que diferncia hay entre un M5 y un Orbea Scape? Te lo digo porque el Orbea cuesta la mitad, y no creo que sea el unico que piensa que es incluso mejor que el M5. Haberte comprado ese si tanto valoras el dinero a gastar en algo. ¿Y que diferencia de precio hay entre una Merlin (que si te comprarías) y una IF? ¿Y eres adivino para saber que me la cambiaré en 5 años? Drakon, a cada uno le gusta lo suyo. En una Nicolai te gastas 5000 euros y no pasa nada, a mi me gustan las rigidas y no me puedo gastar la mitad... Aun recuerdo el post de Boxxnio con su Intense M3 y nadie dijo que era una ida de olla gastarse 3000 y pico euros en ella...
Si me preguntases si yo me gastaria 3000 E en un cuadro de titanio hecho a medida mi respuesta seria que si (chulo que es uno ), otra cosa es si me preguntases que si es lógico pagar ese dineral por unos tubos de titanio soldados, seguramente te diria que no, pero el corazon y la "enfermedad" tira mas que la logica :mrgreen: . Pero la pregunta real es porque vemos "normal" que por una Specialized s-works te pidan 6000 E y uno no se pueda gastar tranquilamente 3000 E en un cuadro? Y encima te quedan 3000 E para montartela de lujo (sera petao listo y to :mrgreen: ). Lo que esta claro es que cada persona es diferente, yo soy mas del estilo de Petao, si tengo un euro me lo gasto en la bici. Saludos.
Sorry, con ese comentario lo que quería decir es que yo, puestos a gastar, me pillaba una Nicolai Nucleon TFR que anda por el precio del cuadro custom de carbono que sacarán :mrgreen:, pero porque me van más ese tipo de bicis, no porque un rígido de carbono o titanio custom sea una tontería (ya me gustaría tener la Moots "StoneKiller" Ti que han puesto unas páginas atrás :twisted. Vamos, que lo que decía lo dije por diferencia de gustos, pero siempre respetando los gustos y preferencias de los demás Un saludo: Drakon P.D: 5000 en un cuadro de bicicleta sigue siendo una burrada, tanto si es un rígido de carbono rosa como si es una burrería tecnológica con amortiguación magnética, transmisión hidráulica y un sistema de Inteligencia Artificial :roll:, pero cada cual hace lo que quiere con sus uracos :mrgreen:
Debe ser bonito tener ese dinero y poder gastarselo en una bicicleta. Tambien hay que tener esa filosofia, porque para los currantes es dificil gastarselo en un cuadro aunque tengan ese dinero en una hucha con forma de bicicleta. Yo no me lo gastaba ni loco, por muchisimo menos dinero te compras un buen cuadro al que no le vas a sacar todo el jugo que puede dar.
Puffff, esto ya si que está siendo el colmo de la desinformación. Por favor AntonioR no me digas eso a la gente e informate primero. El Colonel X-Lite tiene tubería CONIFICADA y OVERSIZE. ¿o si no de donde salen los 1.250g????? es que lo leo y ,me desespero. Macho, leete bien la web de Dean, molestate y luego rajas de ellas todo lo que quieras, pero no digas esas cosas porque no son correctas. ""Extra light - just 2.7 lbs. - the Colonel X-Lite is the lightest titanium hardtail on the market! Built with the finest titanium available - 3/2.5 Vr seamless radial aerospace grade titanium that is machine butted, cold worked and stress relieved for increased rigidity and durability. "" Y ahora viene lo mejor, la mejor respuesta que he leido en el foro: "Pues el Rigormootis y el Colonel no se pueden comparar porque no". Toma ya. El que lo haya escrito se ha quedao tan agusto. Jejejjejee, y yo dando datos, fotos de gran resolucion y otros se quedan tan panchos. Viva la objetividad. Vamos a ver, dijimos que esto iba a ser algo para sacar conclusiones serias, vamos a dar respuestas consistentes señores. Porque esta ya si que es buena: en Seven o IF no te cobran sobreprecio, esta incluido todo. jajajajajaja. De eso me rio. ¿Y entonces el catálogo de Seven que tengo yo aqui que es lo que dice? Ahi cosas, como en Dean, que son personalizables dentro de ese precio, pero otras muchas son con sobreprecio. ¿que te va a pintar el tio el cuadro por la cara bonita no? venga ya hombre, vamos a informarnos bien y decir menos cosas que no son correctas. Hombre, claro que en ese precio está incluido la geometira custom, pero muchos muchos detalles no. Y en los 300 que dije estaria metido todo lo personalizable, pintura, tallaje, todo. Otra trastada más. Comparar el Seven Verve con el Colonel X-Lite. jooooooder!!! Toma ya!, aqui la peña se pone los galones de entendidos en algo y yo es que lo flipo. Pero macho, por muy bien pulido que esté, por muy perfectisisisisimas que sean las soldaduras, aunque hayan usado ultrasonidos para medirlo, ¿como me haces semejante barbarie???????? Seven Verve: 3.5 lbs Titanio 3-2.5 espesor unico Colonel X-Lite: 2.7lbs Titanio 3-2.5 OVERSIZE y CONIFICADO + carbono Que siii, ya sé que tiene una etiqueta que pone Seven que es el sumum del titanio, ¿y que? esto es que lo flipo. Pero claro, como es más barato, es peor... Tio, enseñame más cosas que yo tambien quiero aprender. Petao, venga, te quiero colgando fotos en macro de las zonas de tu cuadro. Pero quiero que pongas muchas, no sólo las que estén mejor. (como verás he colgado la foto del portabidón a pesar de que la soldadura no era perfecta)- ¿es que acaso se va a calentar más el agua????? :mrgreen: Sólo así llegaremos a conclusiones, porque después de 8 páginas no se ha aclarado nada. Las fotos que pillais por internet estan muy bien, pero esas si que no me creo que sean de usuarios. Esas pueden ser del sueño de Moots. :wink: Lástima que las de Pariku fuesen pintadas, porque no se ven las soldaduras... venga venga, ¿no hay nadie que tenga un Moots, Merlin, Litespeed? Fotossss!!! ooootra cosa!!! Estamos hablando mucho del tema Soldaduras, pero creo que nos hemos dejado otro no menos importante: la ALINEACIÓN. Cuando tenga un rato libre me voy a molestar en montar una rueda perfectamente centrada-aparaguada y voy a coger el pie de rey, a ver qué pasa. Y pondré fotos. (y de paso le contestaré a Kabra sobre lo del paso de rueda) Estoy aportando todos los datos que puedo, porque igual se demuestra que el titanio ha de costar el doble. No estoy haciendo publicidad ni creyendo ciegamente en una marca porque yo la lleve. (si no no diria lo mucho que me gustaron las soldaduras del Moots- bueno, rectifico, del dueño de Moots. :mrgreen: ). Porque igual estoy diciendole a mis clientes que Dean es una maravilla y se demuestra aqui que es una porqueria... así es que venga, fotos y datos, pero no habladurias. Que podamos tener todos una opinion y sacar nuestras conclusiones. LA lástima es que ningun otro distri se moje en estas conversaciones... *Que alguien explique en qué consiste eso de soldar los tubos por dentro.
Abejaruco el que no se ha leido mi post eres tu, te lo copio aqui para que entiendas porque hago esas comparaciones... "El Colonel a secas no se puede comparar con el Moots, fisicamente es el que mas se parece por las punteras y el monostay pero olvidate de esa comparacion porque no tiene sentido. Y como el Colonel X-lite tiene el carbono enrollado alrededor del titanio vamos a pasar de el...... El colonel no lleva tubería conificada, y vamos a suponer que hacerlo a medida completamente (Cableado, Tubería, Geometría, etc...) costase 300 Euros mas: 1350 + 300 = 1650 Euros. Te lo comparo con el Seven Verve, que vale 1995 Euros y tiene tubería sin conificar y geometría Custom. 300 Eurillos de diferencia, no es poco pero no es para poner el grito en el cielo, detras de un cuadro pueden haber un monton de cosas que justifiquen esa diferencia. Te pongo otro ejemplo: En los cuadros de carretera el modelo El Diente a secas vale 1400 Euros y yo diría que es el equivalente al Colonel. El modelo El Diente Superlite vale 2350 Euros porque lleva una tubería Pata negra. Si existiese un colonel Superlite el precio seguramente sería de unos 2300 Euros y sumandole los 300 euros que supondría que te lo hiciesen a medida (Como poco) pues te plantas en los 2600 que es lo mismo que valen el Seven Sola y el IF... Conclusion que yo saco: los precios varian en un 10-20% cuando se comparan modelos similares y si las diferencias son pequeñas se compra con el corazon. Un saludo." Yo creo que el unico Colonel que lleva tubería conificada es el X-lite pero el tema es que tambien lleva carbono enrollado alrededor de los tubos. Entonces al ser un hibrido es mejor que no lo comparemos con un cuadro 100% titanio. El siguiente es el Colonel a secas, que segun las web no lleva tubería conificada y ese es el que yo comparo con el Seven Verve. Yo no he incluido pinturas ni opciones demasiado extrañas. Aun asi son muchas opciones y habría que ver cuanto cuesta tenerlas en una Dean, como no dan datos en la Web pues le planto los 300 euros y si me dices que es menos pues demuestramelo. Lo repito otra vez: La comparativa a sido COLONEL Custom - VERVE vamos yo creo que está muy claro. Un saludo.
El Colonel X-Lite tiene tubería CONIFICADA y OVERSIZE. ¿o si no de donde salen los 1.250g????? Los 1250 gramos salen de no ser solo titanio. De ser carbono y titanio y en talla pequeña. Supongo que si fuese todo titanio en esa tubería serían unos gramos más Extra light - just 2.7 lbs. - the Colonel X-Lite is the lightest titanium hardtail on the market! Built with the finest titanium available - 3/2.5 Vr seamless radial aerospace grade titanium that is machine butted, cold worked and stress relieved for increased rigidity and durability. "" Que yo sepa el mejor titanio es el 6/4, aunque excepto Litespeed, que yo conozca solo se utiliza en punteras y ejes de pedalier o direcciones. Las rigidas de titanio más ligeras son la Seven Sola Olympic Edition o la Merlin XLM o la Litespeed Tanasi o... porque son titanio 100% Cuando Antonio decía que está todo incluido en el sobreprecio (normal con lo que valen) supongo que se refería a lo que puede necesitar el 99% de los ciclistas. V-Brakes o discos, portabultos, medida de dirección, geometría, espesor de los tubos segun el peso del ciclista, guiado de cable superior o inferior, portabidones y pijadas varias. Se supone que la pintura no está incluida.
yo tb quiero saber en q consiste eso de un tubo soldado por dentro :mrgreen: yo solo quiero decir q hacer esas soldaduras no es facil,aun q soldar aluminio es mucho mas complicado,y se necesita tener mucha practica,pulso y paciencia. seguramente,alguien q sea capaz de hacer unas soldaduras asi podria ganar mucho dinero en otras empresas q no tengan nada q ver con las bicis,asi q para q trabajen haciendo bicis se les tendra de pagar un buen sueldo. lo digo por intentar justificar de alguna manera esos precios. esto tb es aplicable a las cannondale de aluminio(ya se q no biene a cuento,pero como muchas veces sale q son muy caras... :mrgreen: )
En cuanto a las diferencias de las tuberias de titanio. Creo que habria que concretar el que el 4/6 no es tanto que sea mejor que el 3/2.5 sino que es distinto. En efecto, el 4/6 es mas duro que el otro, pero en contrapartida el 3/2.5 es mas "flexible". El hecho de que Littlespeed utilice el 4/6 esta bastante relacionado con la intencion de conseguir un basculante que no fuese como la mantequilla en la Niota TI. Respecto a los pesos, el cuadro Merlin XLM en 17.5 pesa (contratado) 2.75lb (1248gr) Precio: +-2700
Que yo sepa, y puedo estar equivocado, ese titanio ni es mejor ni peor que el 3/2.5, simplemente es distinto (más rígido), y por eso se utiliza en unos sitios y en otros no (casi siempre piezas mecanizadas, no tubería, aunque hay excepciones). Un saludo: Drakon
El titanio 6.4 es mucho mas fuerte que el 3/25 pero menos ductil y resiste peor la torsion, hasta hace poco solo se podía convertir en tubo (De pequeño diametro...) a partir de una plancha por lo que llevaba una soldadura a lo largo. Litespeed fue la primera en usar este tipo de tubos/planchas en la gama alta. El tema es que Reynolds sacó hace poco una serie de tubos en 6/4 y hay fabricantes que ya la están usando. Os dejo un Texto del fundador de Seven, pero de la epoca en la estaba todavía en Merlin... [color=darkblue:d8dc723403]The Merlin Titanium Primer By Rob Vandermark A Brief History Titanium was discovered in 1790 by William Gregor, a clergyman and amateur geologist in Cornwall, England. However, it was not purified until 1910, and was not refined and produced in commercial quantities until the early 1950s. Since then, titanium production has grown by about 8% per year, and since the early 1960s its use has shifted significantly from military applications to commercial ventures. Although pure titanium was valued for its blend of high strength, low weight and excellent durability, even stronger materials were needed for aerospace use. In the 1950s, a high-strength alloy called 6-4 (6% aluminum, 4% vanadium, 90% titanium) was developed, and found immediate use in engine and airframe parts. But 6-4's low ductility made it difficult to draw into tubing, so a leaner alloy called 3-2.5 (3% aluminum, 2.5% vanadium, 94.5% titanium) was created, which could be processed by special tube-making equipment. Today, virtually all the titanium tubing in aircraft and aerospace consists of 3-2.5 alloy. Its use spread in the 1970s to sports products such as golf shafts, and in the 1980s to wheelchairs, ski poles, pool cues and tennis rackets. In the 1970s, commercially pure, or CP, titanium was used for the first time in bicycle frames. The frames were light and resilient, but they were not nearly strong enough to withstand the rigors of racing. In 1986, the first frames made from 3-2.5 titanium were manufactured by Merlin Metalworks. 1990 saw the first double-butted 3-2.5 seamless tube set, also created by Merlin. Cost of Titanium Titanium is expensive, but not because it is rare. In fact, it is the fourth most abundant structural metallic element in the earth's crust, after aluminum, iron, and magnesium. It is extremely common in the form of titanium dioxide, and is widely used as a whitener in pigments, paper, and food colorings. Titanium's high cost arises from three main factors: 1. Refinery costs-titanium is never found in its pure form. It must be extracted from other compounds, which requires a significant amount of electrical energy and human labor. 2. Tooling costs-whether pure or alloyed with other metals, titanium is a tough material that requires specially made forming equipment, and an oxygen-free atmosphere for heat-treating and annealing (heating and cooling at a controlled rate to eliminate work-hardening and restore ductility). 3. Processing costs-titanium work hardens easily, and so must be annealed a number of times during the tube forming process. Unfortunately, there are no market forces at work to cut prices significantly in the foreseeable future. The slowdown in the aerospace and defense industries has created a slight surplus in capacity, which in the short term should cause more competition and lower prices. However, if these industries keep shrinking, as all signs indicate, the market for titanium will also shrink. In addition, there are design forces at work, including fly-by-wire systems, that will further reduce the total consumption of titanium alloys in the aerospace industry. It is unlikely that the titanium sports industry can make up the difference. One Boeing 747 uses about 95,000 pounds of titanium, which is an eight-year supply for bicycle frames at current usage rates. The Grades and Sources of Titanium Titanium alloys vary widely in their properties and appropriate applications. The alloy most suitable for bicycles is 3-2.5, due to its strength, resiliency, and durability. In addition, 3-2.5 can be drawn readily into small-diameter tubing. Merlin bicycles also employ 6-4 titanium plate in the dropouts, and 6-4 or CP titanium for some non-load-bearing fittings. CP Commercially Pure, or CP, is titanium in its purest form, unalloyed with any other elements. It is available from many sources in the United States, Europe, Russia, and the Far East. It is relatively easy to form into tubing, and it is currently used in a few bonded bicycle frames in Europe and Taiwan. Although CP has many industrial applications (primarily arising from its excellent corrosion resistance), its strength-to-weight ratio is substantially below that of 3-2.5, and actually worse than many modest steels. There are four grades of CP in the U.S., which are distinguished primarily by oxygen content. CP's yield strength ranges roughly from 25 to 65 ksi (thousand pounds per square inch). Grade 4 has the highest yield strength; Grade 1 is the weakest. Only Grade 4 is useful for bicycle frames, and only in areas that see minimal stress. 3-2.5 Titanium 3-2.5 is an alloy of 3% aluminum, 2.5% vanadium, and 94.5% pure titanium. The strongest grade, called AMS 105, has a minimum yield strength of 105 ksi, and a minimum ultimate tensile strength of 125 ksi. It has an annealed elongation of 15-30%, and a cold-worked minimum elongation (ductility) of 10%. It does not respond well to heat-treatment. Instead, increases in strength come solely from cold working. Its fatigue strength-to-weight ratio is roughly twice that of the 4130 chrome-moly steel used in bicycles. It has excellent resiliency, which can be controlled by changes to the tube diameter and wall thickness, allowing the bicycle designer to accurately tune the ride. This latitude is a direct result of titanium's superb margin of fatigue strength, and is unique to the metal; neither steel nor aluminum enjoys the same "tunability." As with most titanium alloys, 3-2.5 is corrosion resistant, and it does not need to be painted. 6-4 6-4 alloy (6% aluminum, 4% vanadium, 90% titanium) was the original miracle metal of the aerospace industry, due to its outstanding strength-to-weight ratio. Its primacy is such that it currently represents 50% of all titanium alloy usage in the U.S. However, 6-4 has several severe drawbacks as a bicycle frame material. Compared to 3-2.5, 6-4's ductility is roughly 30% lower, which makes it extremely difficult to draw into seamless tubing. In fact, there is no such thing as seamless 6-4 tubing in the sizes needed for bicycles. All small-diameter 6-4 is made from annealed sheetmetal, which is rolled into a tube shape and welded. Fatigue strength in tubing made from sheet is also compromised. The weld area suffers from a random crystallographic texture (grain structure), with reduced fatigue endurance (see Butting considerations in titanium on page 9). And the texture in the sheet cannot be controlled, as it is in seamless tubing. In addition, 6-4's shear modulus (stiffness in torsion) is considerably lower than 3-2.5's, which is problematic in a bicycle frame that is repeatedly stressed in torsion. Finally, it should be noted that cost is a limiting factor, too; 6-4 is more expensive to machine and process. Russian Titanium Russia has recently been identified as a possible source of low-cost, high-strength titanium alloys. The appeal seems to be twofold: First, in theory, Russia's costs of labor and electricity are lower than the West's. However, costs are also lower because those manufacturers offering tubing for sports applications have not invested in up-to-date equipment and processes for optimum quality. Second, Russian producers reportedly have a more extensive array of high-strength alloys. This, however, is a misunderstanding that arises from Russia's labeling system for its 200 alloys. In fact, many Russian alloys are similar to U.S. alloys, but carry different names or slightly different formulations. For example, Russia's equivalent to 6-4 is called VT-6. The properties of these alloys are nearly identical. And Russia's VT-5 alloy has similar performance specifications to 3-2.5. In 1993, the Raleigh Cycle Company began distributing a frame featuring tubing manufactured in Salda, Russia (the frame is welded in England). This tubing, called BT01, is a Commercially Pure titanium approximately equivalent to U.S. Grade 4, or Russian grade VT1-1 (64 ksi yield). The yield strength is roughly 70,000 psi, an increase of 40,000 psi over U.S. Grade 1. The tubing is strengthened to this level through oxygen induction (or -oxygen hardening); oxygen content tolerance is 2.6 times higher for Grade 4 than Grade 1. Nitrogen induction is also employed in BT01 to increase yield. Although yield does increase with oxygen induction, ductility is reduced by about 80%; that is, elongation falls from 27% to 6%, creating a much more brittle structure. Fatigue strength is also reduced. Merlin has worked with a few groups from Russia for the past four years, but so far the quality of their products has been unacceptably low. Raising the quality will require heavy investments in tooling, processing and equipment, which in turn will increase costs, probably to levels equal to or greater than those in the U.S. Reliable delivery is also problematic, in part due to Russia's political situation. With no assurance of a stable supply or guaranteed shipments, the immediate future for Russian titanium seems questionable at best. 3-2.5 Tubing Comparison In the U.S., the three most common grades of 3-2.5 titanium used in bikes are: 1. 3-2.5 AMS grade 105, the same stuff you would find under the hood of a 747. This material must meet all AMS specifications (Aerospace Material Specifications, as issued by the Society of Automotive Engineers) for hydraulic tubing. Theoretically, buying AMS 105 tubing directly from the mill allows the designer an unlimited choice of diameters and wall thicknesses. In reality, there are large minimum order requirements and long lead times involved, and only the largest titanium fabricators, such as Merlin, can afford this luxury. Buyers sometimes add to or modify the standard specifications for AMS tubing. Merlin's MTS325 tubing varies from AMS grade 105 in that it has more stringent tolerances for straightness and surface texture. Merlin's tubing also exceeds AMS specs for minimum ultimate tensile strength and minimum yield strength. 2. 3-2.5 -sports grade. Sports grade tubing is marginally less expensive because it is subjected to fewer processing steps, which is supposed to cut costs. However, the cost savings to date have had a detrimental effect on material formability and surface texture, both inside and out. 3. Scrap 3-2.5. This is material which has not met aerospace and/or sports grade specifications, or is simply a small amount of overrun. One of the problems in using scrap tubing is that there are no certifications or specifications, and thus no means for the buyer to determine whether any structural anomalies exist. 3-2.5 Tubing Processing Variables Although AMS standards prevail for all certified aerospace tubing, there is a window of acceptable performance, and processing plays a large role in the quality of the final product. There are three manufacturers of 3-2.5 tubing in the U.S., and each makes its tubing in a different way. These processing differences create a wide range of 3-2.5 tube quality. There are three main processing variables in U.S.-manufactured 3-2.5 titanium tubing: 1. The crystal grain orientation of titanium, sometimes referred to as its texture, affects some of its properties, and can be controlled by processing. Crystal orientation is measured by testing the material+s contractile strain ratio (CSR), which is a numerical index of crystallographic texture determined by the ratio of diametral strain to radial strain. A small value, such as 0.3, denotes tangential crystalline grain texture, while values above 1.8 can be considered radially textured. A CSR from 1.7 to 1.9 promotes the highest fatigue strength possible while maintaining excellent bending ductility. Additional radial texturing can push the CSR past 2.0, which improves bending ductility even further, but only at the expense of fatigue life; fatigue endurance drops dramatically at CSR levels above 2.0. For best results, CSR should be controlled and determined at the mill when the tubing is made. Tubing diameter and wall thickness are always reduced at the same time, but not always at the same rate, and it is the difference between diameter reduction and wall reduction that determines the direction of grain texture. Larger reductions in wall generate a radial grain texture, while larger reductions in diameter offer greater circumferential grain texture. Tube texture can be detrimentally affected by cold working after the tubing has run through its final cold-worked, stress-relieved (CWSR) cycle at the mill. For example, forcibly reducing a tube (as by swaging or tapering) after it has completed its final CWSR cycle rotates the crystals out of their radial orientation and lowers CSR. Reduction processes like these, often used to taper main tubes and chainstays, diminish the endurance limit of the tube. 2. Surface finish, both inside and outside, is directly affected by processing. Titanium is more notch-sensitive than steel. A defect-free surface makes a significant contribution to longer fatigue life. The inside diameter of most titanium bicycle tubing also plays an important role in promoting fatigue endurance; typically, the tube wall is so thin that both the outside and inside diameters undergo a cycle of relative compression and tension. The tension, or pulling, causes micro-cracking, which in turn can cause the tube or joint to fail. If the inside surface texture is much rougher than the outside, crack growth can begin on the inside. 3. Any surface or chemical defect will affect the tubing. The only way to avoid this is through rigorous quality-control procedures throughout manufacturing. These factors, individually or in combination, greatly affect the longevity of a 3-2.5 seamless tube, and, in turn, the quality of the finished product. Resiliency, Flexibility and Fatigue Historically, titanium frames have been more compliant than most steel or aluminum frames, and this has given titanium a reputation for being inherently flexible. But the so-called flexibility of any material is measured by its elastic modulus (Young's modulus). And the three most common frame materials-steel, aluminum, and titanium-actually have similar modulus-to-density (stiffness-to-weight) ratios. Steel's ratio is only about 10% higher than titanium's. This similarity means that a titanium tube of the same diameter and the same weight as steel or aluminum will have similar stiffness. But of course, no one builds frames that way-nor can they, because modulus isn't the only governing variable. The other property that must be considered is fatigue strength. Fatigue strength can be loosely defined as the level at which a material can withstand an infinite number of stress cycles. It so happens that titanium has exceptionally high fatigue strength. Since titanium can endure a higher level of stress without damage, bicycle designers can create resilient frames with less concern that flexure will cause failure. Conversely, metals that have poor fatigue strength cannot be given much room to flex. Aluminum has the worst fatigue strength of these metals, and so aluminum frames tend to be very stiff-not because the metal itself is stiff, but because allowing an aluminum frame to flex will significantly reduce its service life. For a simplified example of this phenomenon, compare two aluminum frames, one very flexible, the other very stiff. Assuming everything else is equal-rider weight, terrain, frame geometry, and so on-the flexible frame will fail from fatigue much quicker than the stiff frame. The ultimate failure of each frame is caused by the cycles of stress it endures, with the more flexible frame cycling through higher stress peaks than the stiffer frame (the greater the deflection, the greater the stress). The higher the stress peaks, the shorter the theoretical fatigue life. Steel has much better fatigue strength than aluminum, so allowing the frame to flex isn't as much of a problem. But steel is twice as dense as titanium, so it is more difficult to tailor the stiffness of the ride without running into weight problems. Put another way, since titanium is half as dense as steel, more of it can be used to tune the ride by juggling tube diameters and wall thicknesses, while still creating a frame that is lighter than an equivalent made from steel. And if the 3-2.5 frame were designed to be as stiff as the same steel frame and weigh roughly the same, it could have roughly twice the fatigue life. Thus, it is not resiliency per se that is the issue, but rather how the designer is able to exploit the fatigue properties of the material. Although the modulus-to-density ratios of the materials may be virtually the same regardless of strength or alloy, a bicycle's tubing diameter and wall can have a profound effect on the stiffness or resiliency of a frame-assuming the fatigue strength of the material allows this design latitude. This model is simplified greatly, and there are many factors beyond material choice that affect fatigue life. The tube diameter, wall thickness, butted sections, surface finish, and tapering all influence fatigue life, as do frame geometry, weld quality, braze-ons, component choice, and rider style. The net benefit of titanium's high fatigue strength-to-weight ratio is the ability to modify the tube geometries in pursuit of a lighter frame that is stiff as a steel frame, or, alternatively, designing a more resilient frame without sacrificing fatigue life. Finally, it follows that given the freedom to modify tube geometries, a titanium frame can be stiffer than a steel frame, too, if that is the goal. Titanium Use and Abuse Titanium's amazing strength, light weight and exotic origins have created a bizarre mythology, and led to its appearance in some odd places. As with any material, there are good applications and bad applications. The trick is to use titanium in the right place for the right reason. Some of 3-2.5 titanium's strengths are: 1. Excellent fatigue strength (twice that of 4130 steel) 2. High strength-to-weight ratio 3. Excellent elongation (ductility) of 15-30% 4. Excellent corrosion resistance Titanium's high fatigue strength gives the designer a wide latitude in choosing how the bicycle will perform. A frame can be made relatively resilient or very stiff, depending on the need, simply by modifying the thickness and shape of the tubes. Unfortunately, there are many areas on a bicycle that have design constraints, due to the use of standardized components. Most of the geometries used in bicycle tubing were created to exploit the best properties of the steels available 40 or so years ago. Today, any deviation from those standards requires an enormous commitment of energy and resources to convince component manufacturers that a change is necessary, and retail dealers that it is worthwhile to carry a separate inventory of non-standard replacement parts. Nevertheless, there is no current frame application that is not well suited to titanium, assuming the designer has the freedom to specify an appropriate tubing geometry. In areas of the bike where design latitude is restricted, the advantage is not always as great. Forks are a good example of an area where geometry restrictions bias the material application toward steel. Assuming the designer is restricted to a one-inch steerer, and the goal is to create a titanium steerer as stiff as its steel counterpart, the titanium steerer will have to weigh over 60% more than the steel equivalent. Increasing the size of the steerer and headset does not necessarily improve the equation. With a 1.25-inch headset, a titanium steerer is roughly 25% lighter than a steel steerer of equal stiffness. However, the 1.25-inch headset is heavier than a 1-inch version, and the larger head tube required is also heavier. Apart from expense, there is no net gain. These complications occur because titanium's modulus, or stiffness, is roughly half that of steel (given identical tube cross sections). To explain the steerer issue another way: Doubling the wall thickness of a given tube almost doubles its bending stiffness. That is, the relationship is close to linear. However, doubling the diameter of the same tube-without altering wall thickness at all-increases the bending stiffness by the third power, or roughly 800%! Thus, the most efficient way to increase the stiffness of any metal is to enlarge the diameter, not the wall thickness. Of course, there is a limit to diameter increases versus wall thinning; if the ratio between diameter and wall becomes too great, the tube will collapse under pressure, like an aluminum can. When designers run up against diameter and wall thickness limitations, they often turn to shape manipulation as a way to locally strengthen the tube. Flaring, ovalizing, and tapering are common strategies, but, as we will see in the following section, each has significant limitations and problems. Ovalizing and Tapering Ovalizing An oval tube is stiffer in its major axis and more flexible in its minor axis. Although ovalizing is often touted as a major contributor to stiffness, it is actually more useful as a means to improve flexibility. Ovalizing does add some bending stiffness in the major axis, but at the same time it reduces torsional stiffness. Since most frame tubes see both bending and torsion, ovalizing is not a panacea. Also, tubes see bending stress along their entire length. Ovalizing a tube over a very short section-for example, ovalizing a seat tube at the bottom bracket shell-results in marginal bending stiffness improvements along the tube+s major axis while making it more flexible through its minor axis. And of course torsional rigidity suffers as well. Tapering Tapering was first used on steel bikes to help soften the ride over the poor road conditions at the turn of the century. At that time, virtually all bicycles had tubing with relatively thick walls, primarily because the cost of more accurately drawn thinwall tubing was prohibitive. Tapering was a less expensive way to bring resiliency to the frame, since a tube becomes more flexible as it tapers (that is, its moment of inertia drops). Tradition and cosmetics have continued this practice in modern bicycles, but tapering serves little purpose in improving the ride of any high-quality frame, whether steel or titanium. Perhaps the easiest way to see why tapering is not generally meaningful is to imagine a hypothetical standard steel frame which has enough stiffness to ensure good ride characteristics. The only way to remove weight from this frame without altering the ride (ignoring fatigue issues for the moment) is to juggle tube diameters and wall thicknesses along the entire length of each tube; otherwise, the torsional and bending stiffnesses will change, spoiling the ride. Tapering a tube can give the illusion of greater overall stiffness, but it really depends upon which end of the tube you view. From the small end it appears as if you have increased the stiffness. From the large end it appears that you have created a more flexible tube. Certainly, a tapered down tube that is larger at the bottom bracket shell will be stiffer in that area than the same tube with no taper. But it must also be thicker, and therefore heavier, to avoid upsetting the tube's diameter-to-wall ratio; otherwise, the tube will collapse. Thus, the most weight-efficient way to limit flex is with a tube of constant diameter and wall thickness. For example, say you want to increase the stiffness of a 24-inch down tube by 50%. One approach would be to taper half of the tube until the 50% stiffness increase (viewed from the larger end) was met. This method would also increase weight by roughly 25%. A second approach would be to increase the overall diameter of the entire tube, which would raise weight by 20%. In the end, both tubes would display the same deflection under a given load, but the untapered tube would be lighter. When resiliency is the goal, a better approach is to start with a smaller diameter tube with a thinner wall. This can give the same flexibility over the length of the tube while saving weight. Tapering in titanium also creates problems with grain orientation in the metal (see -3-2.5 Tubing Processing Variables). Tapering forces the molecules to align with the longitudinal axis of the tube, rather than to maintain their optimum radial orientation. This has a detrimental effect on fatigue life. There are some good uses for tapering, however, particularly in the seatstays. The main function of seatstays in a rigid frame is to provide a place to put the brakes. A tube that is very rigid in bending and torsion at the brake mounts is useful, but the rest of the tube does not contribute much to the ride of the bike. A tapered seatstay could cut weight slightly without harming performance. Any weight savings would have to be carefully balanced against losses in fatigue endurance, however. The evolution of suspension frames may trigger more applications for tapered tubing. Clearance issues arising from ergonomics and standardized components may require some interesting tube configurations. Finally, it is worth noting the one drawback of a straight-gauge tube is that, compared to the large end of a tapered tube that is equally stiff in bending, the straight-gauge tube will have higher stress at the joint. This concentration can be resolved through butting. Double Butting The mechanical properties in the welded or brazed joints of any steel or titanium frame are always lower than in the unheated areas. This loss in strength is an important consideration because the joints are usually the most highly stressed areas on the frame, and most frame failures occur at the joints. Fortunately, titanium retains a greater percentage of its raw yield strength after welding than steel, so the drop in strength is not severe. Nevertheless, it is desirable to minimize stress levels at the joints whenever possible. Butting the tube-making it thicker at the ends and thinner in the middle-is an efficient way to strengthen the heat-affected zone (HAZ) at the joints without adding appreciable weight. Put another way, applying proper butting techniques to a thinwall non-tapered tube allows a significant weight reduction without sacrificing fatigue life. This is not to say that butted tubing is always necessary. Since, under a given load, a stiffer tube has lower stress and, therefore, improved local fatigue life, there are some areas of the frame in which a tube can deliver the desired ride characteristics and also have more than enough bending stiffness at the joints. That is, the tube's geometry (its inside and outside diameter) can be adequate to keep joint stresses reasonable. For example, the performance requirements for road bikes and mountain bikes are very different. A mountain frame built from a butted road tube set could have adequate fatigue life, but it would not be stiff enough in bending or torsion. Adding stiffness to this frame in any optimal way would also increase its ability to resist bending stresses, which in turn would help improve its fatigue life. In this case, the need for butted tubing would be greatly reduced. However, when a tube is designed for a given application, there is usually more than one goal, and the goals often conflict: weight vs. stiffness, weight vs. strength, stiffness vs. resiliency, and so on. In these cases, butted tubing can be an excellent solution. Engineering Principles of Butting Butting is a process that varies the wall thickness of a tube to provide local reinforcement. It was first applied to steel tubing in the 1890s, and was patented by Alfred Reynolds and J.T. Hewitt in 1897. When properly applied, butting can significantly enhance the fatigue endurance, and thus the service life, of a frame tube. Fatigue endurance is improved because the thicker tube wall in the butted area is stronger. Butting can reduce weight, too, since the unbutted areas of the tube are lighter than the butted areas. And it can improve ride quality if the thinner center sections of the tube are allowed to flex somewhat. Butting always makes a tube stiffer locally, at the butt, but only locally. Contrary to common opinion, any local stiffness increase gained through butting does not have much effect on overall tube stiffness. That is, frames with butted tubing are not automatically stiffer than frames with straight-gauge tubing. Tubing can be butted at one end (single butted), at both ends (double butted), or can have any number of wall thicknesses to solve specific problems (leading to triple butting, quadruple butting etc.). Generally, true butted tubing is considered to be seamless and cold-worked to shape. Other externally or internally applied reinforcement methods, such as gussets or sleeves, are sometimes referred to as butts, but this is a misnomer. In this discussion, butting will only refer to tubing made with seamless starter stock, and without gussets, sleeves, or other secondary reinforcements. Internal and external butting Tubing can be butted internally, which is the traditional method patented by Reynolds and Hewitt, or externally, which is a more recent approach. Internal butting is useful for lugged construction where the reinforcing lug slips over the outside of the tube. Internal butting is also cosmetically appealing, since wall thickness variations are not apparent to the eye. And the forming mandrels for internal butting are less expensive than external rolling dies. However, external butting offers certain advantages, and is a superior method for tube reinforcement. If two tubes of identical bending stiffness and which offer equal fatigue endurance at the joint are butted, one internally and one externally, the externally butted tube will be lighter. If these same tubes are modified slightly to offer identical weights, the externally butted tube will be stronger, and will also exhibit lower stress at the joint. To see why this is so, it is important to consider all of the variables that affect fatigue strength, stiffness, and weight. The most efficient way to improve the specific fatigue strength of a tubular joint is to make it stronger. A stronger tube handles loading better, and is generally more resistant to fatigue failure. Strength can be gained by increasing the thickness of the tube, and indeed, an internal butt performs just that function. This is not an ideal strategy, however, because making a tube thicker adds strength and stiffness rather grudgingly. When wall thickness is doubled, for example, the stress level in the tube per given load is cut roughly in half. The most efficient way to improve strength without a significant weight penalty is to increase the tube+s diameter, which improves the picture rapidly at a ratio of about 1.6:1, strength to weight. If all things were equal, then, it would seem that the best way to butt a tube would be to simply flare the tube ends. Though this might be the case in a lower grade tube that has not been optimally designed, any tube that has been properly engineered for minimum weight and maximum fatigue endurance will already be at its maximum diameter limit. At this point, if the diameter is increased by flaring without a corresponding increase in wall thickness, the tube will surpass its buckling limit, and will collapse like an aluminum can when heavily loaded. Thus, the optimum strategy is to simultaneously increase the tube wall thickness and the tube diameter in an ideal proportion-which is to say, to externally butt the tube. The external butt provides maximum strength with minimum weight. It cannot be surpassed. External butting also offers the greatest flexibility in choosing optimum wall thickness differentials between the butted and unbutted sections. To see why this is so, it is important to understand that internally butted tubes are manufactured not by adding material to the ends of the tube, but by displacing material from the center of the tube to make the tube thinner in that area. When this process is complete, the internal mandrel that is used to thin the center sections must be withdrawn past the thicker ends. Typically, internally butted tubes are limited to a 40 percent thickness differential to allow the mandrel to be pulled out. Externally butted tubes suffer from no such differential limitations. Indeed, only external butting allows every possible permutation of tube diameters and wall thicknesses, and an optimum strength-to-weight ratio. Butting considerations in titanium With the possible exception of mercury, no metal likes to be pushed around too much, but titanium is especially sensitive to manipulation. In fact, its properties are radically altered by cold working. This is both good and bad. It's good in the sense that strength increases can be achieved through simple cold working. But it's bad in that any cold work after final anneal and stress relief will change the tube properties, often for the worse. At the root of this behavior is titanium's crystallographic texture (CT), which is determined when the tubing is made. The measure of crystallographic texture is called "contractile strain ratio" (CSR), which compares the tubing's diametral strain to its radial strain. The tubing's CSR, and thus its CT, is optimized by controlling the rate of size reduction. During the manufacturing process, a reducing die is rolled over the outside of the tube while the inside of the tube is supported by a mandrel. The titanium is squeezed between the die and mandrel like cookie dough under a rolling pin. As deformation occurs, the titanium molecules are forced to rotate and realign. Only so much of this manipulation (called rocking, because the die rocks back and forth along the tube), can take place at one time. For Merlin MTS325 tubing, the process starts with titanium tube hollows roughly 2.375 inches in diameter, with a wall roughly 0.8 inches thick-a long way from the thinwall small-diameter tubing used in bicycle frames. Getting to the final dimension takes many reducing, or pilgering, steps, each step followed by a trip through an annealing oven to eliminate excessive hardness and loss of ductility due to the cold working of the tube. The rate of pilgering is the primary way in which CSR is controlled. Pilgering control of CSR can be accomplished through either wall ironing or diameter sinking. Wall ironing takes place when the reduction in wall thickness is proportionally greater than the reduction in diameter. Diameter sinking results when the reduction in diameter is proportionally greater than the reduction in wall. Ironing pushes CSR up. Sinking forces CSR down. Cold working is, therefore, a good way to fine-tune the tubing+s bending characteristics and fatigue strength. But too much cold working at the wrong rates can destroy those properties, weakening and embrittling the tubing significantly-even radically. The useful window for CSR in bicycle tubing is narrow, and tubing that falls outside a CSR of 1.6 to 1.9 suffers from poor fatigue endurance. The only way to obtain a consistent CSR of 1.6 to 1.9 throughout the tube is to create a constant wall thickness and a constant diameter. It is not possible to change the dimensions of the tube through material manipulation without affecting molecular structure, and thus CSR. Both wall ironing and diameter sinking destroy the ideal CSR of the starter stock and thereby shorten the service life of the tube. The effect can be dramatic, with the drop in fatigue endurance alone exceeding 10 percent. Internally butted tubes are created at the mill through wall thinning, or ironing. Tapered tubes are created by diameter sinking. Even though the tube may have had ideal properties before pilgering, the ironed or sunken sections of the internally butted or tapered product will exhibit significantly poorer properties. Merlin MTS325 butted tubing is created through proprietary processes that do not alter the ideal CSR range. Because CSR remains constant, there is no loss of fatigue strength or ductility. What of the claim that CSR should be altered for different parts of the frame? Under this argument, chainstays that need to be bent would use tubing with a different CSR, or radial texture, than, say, the down tube, which does not require bending. Although this argument may sound plausible, further examination reveals a fundamental problem: the CSR that offers the highest fatigue strength also offers excellent ductility. High ductility supplies the best bending characteristics. Thus, while enhanced bending is sometimes touted in higher CSR tubes, ductility actually falls as CSR rises. From where, then, did an argument for using a range of CSR values arise? Most bicycle frames are built with tubing obtained from more than one mill, and the range of CSRs is an inevitable byproduct of this multiple sourcing. To make the best of a bad situation, some manufacturers have touted these varying CSRs as a virtue. In reality, however, there is no advantage to using tubing with any CSR outside the optimum range. Tubing production speed, and thus final cost, also plays a role. Tubing costs can be reduced through faster pilgering. Unfortunately, though, running the tubing through the mill faster also leads to higher CSR values and greater radial texture. To keep costs down, most "sports grade" tubing is produced in this way, and the high radial texture that results is sometimes proclaimed a benefit. However, slower pilgering and lower CSRs create a stronger, more durable frame. Comparison of butted properties There are three common types of butted titanium tubing. Two are butted internally and one, Merlin MTS325, is butted externally. To distinguish the internally butted methods, we have designated the configurations type 5I and type 3I. Type 5I tubing: This internally butted tube is made with high-strength starter stock (125 ksi UTS). The tube is butted by wall ironing. As noted above, wall ironing disturbs the titanium's molecular grain structure; thus, only the thick, unironed ends of the tube retain the starter stock's original properties. The tubing will also be subject to internal scratching, gouging, or notching, due to the action of the supporting mandrel. Notched surfaces create stress nodes in the tubing, leading to premature failure. Unfortunately for the consumer, once the frame is built there is no nondestructive way to determine whether the tubing has a poor internal finish. Notches, gouges and scratches are of less concern in the thin center sections of the tube than in the transition zone, or butt taper, between the thin center and the butted tube ends. This area is highly stressed and extremely sensitive to surface degradation. Notching here will lead to almost certain tube failure. Type 3I tubing: Another internally butted tube, but made with annealed or low-strength starter stock. Butting is also performed by wall ironing. The thinned section of the tubing has slightly better properties than 5I tubing, but the thicker end sections suffer from extremely low strength. Type 3I tubing is less expensive than 5I tubing, because the low-strength starter stock is easier to manipulate. Aside from price, it offers no real advantages. Like 5I tubing, 3I tubing is subject to notch failure from damage caused by the supporting mandrel. Merlin MTS325 tubing: Merlin tubing is externally butted without mechanically altering material properties or CSR. No internal notches or stress nodes are created during or after butting, so full fatigue strength and CSR are maintained. Tapering versus external butting As noted earlier in Ovalizing and Tapering, tapering is a convention inherited from traditional frame design, where it was used to provide a softer, more flexible ride over the rough roads common at the turn of the century. It is of limited value in a modern titanium frame. Titanium tubing can be tapered by diameter sinking; the tubing is forced through a die (swaged) until the final dimensions are reached. Tapered tubing can also be created by rolling titanium sheet into a tapered tube form and welding the seam. Both processes have drawbacks. The molecular structure of the metal is severely affected during the tapering process, altering the CSR and thus the fatigue endurance and the ductility of the tubing. Diameter sinking reduces CSR, and decreases fatigue strength. In fact, the negative effects of diameter sinking on fatigue endurance are quite dramatic. Tapered tubing can be of some use where severe clearance restrictions exist due to component design or geometry constraints. However, every effort should be made to employ untapered tubing instead, with the need for tapering to be carefully weighed against the shorter service life of a tapered tube. Welding Material strength is always lower within a welded joint, whether the metal involved is titanium, steel, or aluminum. The drop in ultimate tensile strength (UTS) for 3-2.5 titanium in the heat-affected zone (HAZ) is roughly 12-15%. Note that UTS drops 40-50% in a high-quality steel tube. Aluminum also suffers a significant loss, but in many alloys strength can be recovered by solution heat-treating and aging. Titanium weld quality depends on many factors: 1. Cleanliness has the single biggest impact on weld quality. The surface metal must free of grease, chlorides, and all contaminants, and the entire weld area must be free of oxygen, nitrogen, and hydrogen during the process of welding. Even fingerprint oil can contaminate the weld area, so scrupulous cleansing standards must be maintained at all times. 2. Complete penetration of the filler material is critical. Only a skilled welder using proper equipment on a well-designed joint can assure that the base metal has been properly fused with the filler material. 3. The type of bead plays an indirect role in penetration, and thus in final welded strength. A smooth bead disperses heat, and makes full penetration harder to achieve. Puddle welds heat a smaller area, focusing the bead and improving penetration. An excessively thick or uneven bead will create a harsh transition in relative stiffness between the bead and tube. Since the weld bead acts as a stress riser in any case, it is best to minimize the sharpness of the transition area. 4. The rate of post-weld cooling theoretically affects weld quality, but there is no evidence that cooling rate plays a large role in post-weld fatigue strength. Welding versus Bonding The loss of strength due to welding begs the question of substituting bonded lugged joints for welded beads. The primary drawback to bonded construction is added weight. For example, the titanium lugs used in the Specialized Epic Ultimate carbon fiber/titanium mountain frame, designed for minimum weight, weigh 1.5 pounds per set. If the frame were built from welded Merlin Extralight double-butted tubing, the butted sections would weigh a fraction of the titanium lug set. This relationship is true of any material, whether metal-matrix composite, aluminum, steel, or carbon fiber. Anodizing There are many different types and purposes of anodization, but for titanium bicycles the primary use is decorative. The process creates an anode out of the titanium in a chemical bath and progressively builds an oxide film through electrolysis. As voltage is varied, the oxide thickens and a color spectrum is created. The final product is a dense adherent titanium oxide film. There are three basic variations of this oxide, determined by voltage levels and electrical dispersion. The titanium oxides are composed chiefly of anatase and/or rutile crystals; anatase and rutile are the main ores from which pure titanium is separated. Unfortunately, titanium oxide is extremely brittle (regardless of color), and the oxide film is not easily separated from the titanium substrate due to titanium dissolution into the oxide. The normal bending loads seen in a frame will cause slip lines in the brittle colored surface and ultimately create cracks in this anodized shell. The failed oxide film propagates the cracks through the dissoluted titanium oxide mixture and finally into the uncontaminated titanium below the oxide. Once the cracks have moved into the tube wall, they propagate further, ultimately causing frame failure. Thus, it can be seen that an anodized titanium substrate acts in exactly the same way as an oxygen-contaminated weld zone. The outermost titanium fibers, which see the greatest stress and therefore need the best ductility, become the most brittle. The potential for stress failure is vastly increased. For these reasons, Merlin strongly suggests avoiding the anodization of any structurally important titanium part. Merlin's lifetime frame warranty is voided if the frame has been anodized. 3-2.5 versus Other Materials Steel Although the ultimate tensile strength of many premium steels is greater than 3-2.5 titanium, this raw strength is meaningless in the final bicycle frame because: 1. The strength advantage is lost in welding. 2. Steel's strength-to-weight ratio is lower than that of titanium, both before and after welding. When comparing materials, strength after welding, or heat-affected strength, must be considered first, because the highest stresses in a frame are at the joints or heat-affected zones. For example, Columbus SL steel tubing has a cold-worked (as received) ultimate tensile strength of roughly 135 ksi, making it equal to Merlin 3-2.5. Ignoring for a moment that Merlin's strength-to-weight ratio is almost double that of the Columbus SL, we find that SL's yield strength drops to 70-78 ksi after welding. Merlin 3-2.5 has a post-weld yield of 97-100 ksi. In addition, for a given weight 3-2.5 titanium has roughly twice the post-weld fatigue strength of 4130 chrome-moly steel. External and internal reinforcements, such as gussets, butts and lugs, can improve steel's fatigue strength somewhat. Internal butts move the weakest points away from the areas of highest stress. In some cases, however, it is not possible with current manufacturing equipment to create a butt of optimum thickness. The maximum differential between the butted and unbutted sections of a production premium steel tube is about 40%; any further improvement must be achieved in some other way-with gussets, lugs, or some variant of these. An optimally butted steel tube will outperform a gusseted or lugged tube because: 1. A gusset or lug does not reduce the heat-affected zone (HAZ) at the sides and end of the reinforcement. An ideally butted tube provides equal strength and equal or lower weight with no HAZ. 2. Gussets and lugs create stress raisers at their endpoints, with a further reduction in fatigue life due to the HAZ. An ideal butt with a properly designed taper eliminates the stress raisers and also saves weight. Whether gussets and butts are employed or not, there is still a wide gap between the fatigue strength-to-weight ratio of 4130 steel and 3-2.5 titanium. Claims that it is possible to create a steel frame of comparable weight and strength as a titanium equivalent are unsupportable, as proven by raw objective data, and by the fact that no such frames exist. Aluminum Unlike titanium, aluminum's fatigue strength declines continuously with increasing cycles. Therefore, aluminum designs must include a greater design safety factor, which inevitably increases weight and bulk. A related issue is the failure mode of aluminum, which is catastrophic, rather than gradual. Again, the design safety factor must be increased to compensate. Aluminum is a good material for low-stress components that see little to no fatigue cycling. MMC (Metal Matrix Composites) There are many available types of MMCs, but only one, a particulate-type from Specialized/Duralcan, is presently being used in bicycle frames. Particulate-type MMCs are the least-expensive form in current production. The Duralcan MMC is an aluminum oxide particulate matrix in an aluminum medium. Other MMCs under development for bicycle use are also particulate types. One employs silicon carbide, the other boron carbide, both in an aluminum base. MMCs vary in the base metal from aluminum to titanium to copper, and in matrix additives as noted above. The formats of the additives also vary, from particulates, whiskers and wires to continuous and discontinuous fibers. Each factor plays a large part in the strength and other mechanical properties of MMCs. One thing common so far to all particulate and whisker MMCs is a loss of ductility and fracture toughness, which has had a negative effect on potential fatigue life. Duralcan's 6061-T6 15% particulate MMC has the following advantages over pure 6061-T6 aluminum: Tensile modulus is increased 30% to 12.7 ksi. The higher modulus helps offset the material's low fatigue life, since a stiffer frame has a lower stress cycle. Yield is increased by 15%, from 40 to 46 ksi. Disadvantages of the Duralcan MMC include: Elongation hovers at a meager 5.4%, potentially decreasing fatigue life. (Theoretically, if the frame were designed for no flexure whatsoever, elongation would not affect fatigue life, since the joints would not move. In practice, however, this seems unlikely.) Elongation drops another 50% or more for other MMCs. The lower the number, the less ductile the material. 6061-T6 aluminum has 14-17% elongation after welding and heat treatment. High-quality bicycle steel is 10% before welding, 20-25% after welding. Titanium's elongation is 10-19% before and 15-30% after. Stress vs. Number of cycles (S-N) fatigue curves remain almost identical to off-the-shelf 6061-T6: 17 ksi at 107 cycles for Duralcan MMC vs. 16 ksi for 6061-T6. Therefore, the fatigue strength-to-weight ratio is almost identical to standard 6061-T6. Note that this fatigue strength is hypothetical because, like monolithic aluminum, MMCs do not have true fatigue endurance. Instead, they must be designed with a much more conservative safety factor. Fatigue strength is the most important consideration in frame design, regardless of which frame material is under consideration. Most frames fail through fatigue, not from one-time overloading, as in a crash. Ultimate strength is of secondary importance, because a high UTS alone does not and cannot make a durable frame. The most obvious theoretical benefit of any MMC is the potential to create a stiffer material, as in an engine block where rigidity can reduce noise and vibration. This, however, is not necessarily desirable in a bicycle frame. Ride quality is an important consideration that must be incorporated, even if the fatigue issues are satisfactorily resolved. Welding is also a complication. Most MMCs lose strength after welding, and some of that strength remains unrecovered after heat treatment. In the area closest to the weld (as well as in the weld itself), the particulates become dispersed, which can cause anomalies and strength problems. Heat treatment cannot restore these particulates to their pre-welded state because the metal does not liquefy during heat treatment. Finally, it should be noted that a bonded MMC frame can never match the weight of a welded MMC frame. Thus, it is doubly unfortunate that many MMCs have serious mechanical degradation after welding. Titanium Metal Matrix Composites There are very few titanium-based MMCs in current production, with only two basic types of matrices. One, intermetallic-matrix composite (IMC), uses continuous fiber. The other is formed from titanium carbide particulates. Both have been developed primarily for high-temperature applications, as in engine components and skins for military aircraft. IMCs are formed from a series of titanium-aluminide foils consolidated with boron-coated silicon carbide continuous fibers. With a starting price of $2000-3000 per pound, it is unlikely they will soon find applications in the bicycle field. Interestingly, raw ingots of titanium cost only $10-12 per pound, so the processing costs to create IMCs are obviously formidable. Titanium carbide MMCs present similar cost issues. They also suffer from a severe loss of ductility which arises from the induction of carbon into titanium. Titanium-aluminides are another newly publicized group of aerospace alloys. Strictly speaking, these are not MMCs, but they do boast very high strength and good resistance to loss of mechanical properties at high temperatures. However, they suffer from abysmal ductility at room temperature and exorbitant cost. The ductility issue may soon be resolved; cost, however is unlikely to drop within the foreseeable future. Beryllium Beryllium is a light, stiff, and expensive metal that has received recent attention as a potential frame material. Merlin began cooperative work with a beryllium tube manufacturer two years ago, but our preliminary investigation revealed that the stiffness-to-weight ratio of beryllium is extremely high-so high that it would be difficult to build a frame with adequate flex for good ride characteristics. Furthermore, beryllium's cost is so prohibitive that the financial wherewithal necessary to develop a frame is beyond the resources of the bicycle industry. Even those alloys that incorporate beryllium as their major element are so expensive that it is doubtful any of them will ever find their way into the frame tubing market. In addition, beryllium is toxic, although this can be managed with proper manufacturing procedures. Carbon Fiber Carbon fiber is a blanket term for a wide variety of carbon-impregnated polyesters, graphite fibers, and polymerized carbon fibers that are used within a matrix of adhesive to create a clothlike structural material. Within the family of fibers considered appropriate for bicycle frame use, the raw fibers' stiffness-to-weight ratio is roughly 3.5 times higher than 3-2.5 titanium. The ultimate tensile strength is roughly 70% higher. However, these figures apply only to the raw fiber strand, before it is impregnated by and retained within an epoxy resin matrix. The epoxy adhesive's structural properties are significantly lower. Moreover, epoxy normally occupies 50% or more of the cross-sectional area of a sheet of carbon fiber cloth. This ratio of resin to carbon must be maintained to hold the fibers together; a lower epoxy content reduces the fiber weave's layer-to-layer shear strength. A 50% volume of adhesive reduces the finished product's strength-to-weight ratio by a factor of two. In addition, carbon fiber is anisotropic, which means that it displays directional properties. For example, a fiber with a modulus of 20,000 ksi when measured longitudinally will have, at best, a transverse modulus of 4,000 ksi. Similarly, the ultimate tensile strength may measure 220 ksi longitudinal, but will be, at best, 10 ksi transverse. This anisotropic property can be exploited beneficially in some structures, such as leaf springs. However, bicycle tubes must be able to carry stress loads in many planes at once-in tension, compression, fully reversed bending and clockwise and counterclockwise torsion. Thus, it is virtually impossible to utilize anisotropy to any significant extent in a frame. In addition to the modest structural properties displayed by the epoxy resin, carbon fiber has extremely low ductility and poor abrasion resistance. Historically, low ductility in those bicycle frames that do not use separate lugs has led to joint failure and stress cracking. Abrasion is a particularly thorny problem since composites are notch-sensitive, such that even minute inconsistencies in the material can develop into large cracks, eventually leading to failure. Abrasion problems can be reduced at the cost of added weight by a protective skin or veil of fiberglass or, at higher cost and somewhat greater strength, Kevlar fiber, but the abrasion resistance of these and similar polyester and aramid fibers is also low. Abrasion and impact damage can be repaired with epoxy-based fillers and additional cloth. However, since the integrity of the structure is dependent upon continuous fibers in tension, the strength of the repaired area will be lower than the original material, and the weight of the repair will be higher. Carbon-wrapped Titanium and Aluminum Titanium or aluminum tubing wrapped with a bonded layer of carbon fiber composite has been proposed as a method to achieve a synergistic improvement of material properties. (In fact, carbon-wrapped aluminum tubing was produced by Easton for Raleigh for two years, before the withdrawal of that frame from the market.) The main objectives of this approach are: 1. To improve the performance of a low-strength tube. Aluminum's low strength-to-stiffness ratio, for example, can be boosted appreciably with a layer of high-modulus composite fiber. 2. To protect the abrasion-sensitive carbon within a metal exoskeleton. These approaches have a number of drawbacks: 1. External carbon wraps do not solve the problem of abrasion damage to the composite. 2. Internal carbon wraps do not necessarily protect the composite from impact failure either. To create a frame of reasonable weight, the titanium or aluminum tube must be very thin, and consequently not resistant to denting. Since titanium is very ductile, it can spring back from minor impact with no appreciable damage. However, the internal wrap will suffer local cracking, which can spread into a serious fault. In addition, delamination of the composite from the tube surface is a serious long-term problem. It has at least three sources: 1. Delamination can occur from impact. Once the composite has cracked, it will continue to fail along the fiber orientation. The fissure created by the initial fault becomes a point for peeling or cohesion. 2. Delamination can occur at the ends of the supporting tube due to applied bending and torsion during use. Adhesives are weakest in peeling and cleaving. 3. Delamination can occur from stress. When used in a wrap, the adhesive must perform two duties, first as the bonding agent between the fibers, and second as the glue between the composite and the tube. Ideally, two different adhesives and primers would be specified, but this is not always possible. Carbon-wrapped tube frames also suffer from a weight disadvantage, since these tubes cannot be welded once the composite has been applied, and so must be bonded in a lugged frame. Honeycomb-Reinforced Titanium Honeycomb-reinforced titanium tubing is conceptually similar to internally wrapped composite tubing, with the primary objective being increased stiffness. The only frame that currently employs this construction uses a lightweight fiberglass honeycomb bonded to a carbon fiber skin, which in turn is bonded to the inside wall of a thin titanium tube. The frame is lugged. In the current design, the honeycomb lends anisotropic reinforcement properties to the tube. Unfortunately, it is not possible to create layers of directional honeycomb, as can be achieved with carbon fiber. Thus, the honeycomb is inevitably unidirectional, but lies within a structure that demands more isotropic properties. Since the frame must be lugged for assembly, frame weight is not ideal; a current 54-cm example weighs 3.0 pounds, with the honeycomb and carbon representing 0.75 pounds of this total. A 54-cm Merlin Extralight, with double-butted tubing and similar rigidity, weighs 2.6 pounds. Titanium Parts No discussion of materials is complete without considering the reasonable cost of improvement. When does improvement, in any material, fall so far behind its price to a consumer that it can no longer really be termed improvement? Forks The biggest hurdle to building a titanium fork that is as stiff as a steel fork and lighter than an aluminum fork is the steerer tube, as discussed earlier under Titanium Use and Abuse. There are other geometry restrictions that make titanium forks unattractive: 1. The compact shape of the conventional road fork crown was optimized for steel, and has been modified somewhat for aluminum. Duplicating the shape of an aluminum crown in titanium will make it stiffer, but not lighter. Removing enough weight from the titanium crown to make it competitive with aluminum involves considerable casting or forging complexities that raise the cost significantly. 2. To compensate for the lower modulus of 3-2.5 (compared to steel), the fork legs need to be larger in diameter. This creates an opportunity to save weight, but tire clearance can become an issue. 3. The dropouts must be larger to fit the oversized fork legs, adding weight. At best, then, a titanium fork can weigh about the same as an aluminum fork, with the stiffness of a steel fork, at a cost of five conventional forks. Unless the titanium fork can demonstrate some additional advantage, it appears to be a bad bargain. Seatposts The important properties in a seatpost are light weight, high strength, good failure resistance, and adjustability within the seat tube. Reliable aluminum mountain bike seatposts weigh as little as 220 grams. The lightest titanium post is around 195 grams. The titanium post will have better fatigue life, but it will also be more flexible. A titanium seatpost is also very sensitive to head design and weld quality. Finally, if the titanium post is used in a titanium frame, it will gall, although proper lubrication can minimize the problem. Chainrings Chainrings must be light, stiff, and wear resistant. A titanium chainring of the same weight as an aluminum ring will not be as stiff for two reasons. First, aluminum's modulus-to-density is a few percent higher than titanium's. Second, to meet the weight restriction, the titanium ring must be 30% thinner. A titanium ring of standard thickness could be more durable than aluminum, both in its wear properties and in its ability to survive impact damage from rocks and other trail debris. But this survivability comes at a significant premium in cost and weight. Metal-matrix composites, whether aluminum or titanium-based, could be ideal materials for chainrings. Brakes Brake calipers need to be stiff, failure resistant, and light. Due to clearance issues and other design constraints, it is very difficult to make a titanium caliper that can match the light weight and stiffness of an aluminum equivalent. Aluminum or metal matrix composites appear to have the ideal properties here. Bottom Bracket Spindles and Pedal Axles The properties that are important in a spindle are failure resistance, precision, and light weight. A Shimano Dura-Ace or XTR spindle, made from heat-treated 4140 steel, has excellent fatigue characteristics, roughly twice that of current 6-4 titanium spindles. A 6-4 spindle can be considerably lighter, but its fatigue endurance is not acceptable. An additional drawback is that titanium cannot be surface hardened to create a durable bearing surface. Thus, any titanium spindle must employ sealed bearings, leading to added weight, expense, and complexity. Bolts Lightweight titanium bolts, generally made from 6-4 alloy, have demonstrated excellent durability and strength in bicycle applications. Titanium's corrosion resistance is an added plus. Titanium's lower modulus compared to steel is not a serious drawback, as virtually all bolts are used in tension against fully seated parts, where the bolt's flexibility is not an issue. However, titanium bolts will gall, or seize, when threaded into other titanium parts. This can be avoided by liberal application of anti-seize compound or other appropriate lubricant to the bolt threads before installation. Handlebars Titanium's high fatigue strength can be exploited to create mountain bars with excellent flexibility. The bars will transmit less shock and deliver a more comfortable ride. However, if the goal is to create bars of equal stiffness as existing bars made from steel or aluminum, then the weight of the titanium bars will be uncompetitive. Stems Forged aluminum road stems and welded steel mountain stems are light and rigid, and have a good safety margin. It is possible to make titanium stems as light, but rigidity suffers. Increasing the rigidity adds weight. A welded, one-piece bar and stem combination can be lighter and as rigid as any current equivalent; the only drawbacks are cost and adjustability. Future of Titanium Although new alloys of titanium are under development, the 3-2.5 alloy retains excellent potential. Double-butted steel was patented in 1897, but butting was never applied to seamless 3-2.5 titanium until 1990. The potential for advancement is further illustrated by the Merlin Suspension frame, which uses the chainstays as integral springs, eliminating the weight of
tais tos chalaos!!! tais desfasaos!! un buen cuadro de carbono!! :wink: jajaja..todo esto es una pequeña broma pero si q os digo una cosa al hilo del cuadro Litespeed..el mas ligero del mundo q sale a 4100$ la broma(solo el cuadro!!) gastarse eso en un cuadro cuando ahora todo el panorama carretero mira hacia el carbono por sus propiedades..rigidez, comdidad de marcha.. me parece un atraso.. y comprendo q sea elitismo y una pasada y demas.. un saludo! VIVAN LOS POLIMEROS!!
Pssssssssssss ya he visto el nuevo Ghisalo, es raro que no hallan cogido otro nombre pero ellos sabran, y me parece un chollo al lado de una Serotta Ottrot ST:::::::: 5295$ :roll: :roll: :roll: Un saludo.
