The diamond form of a bicycle body hasn’t modified a lot because it was first invented. Triangles are an enormously robust form and may also be simply modified to accommodate riders of various statures. Every rider’s wants might fluctuate, however the essence of the design needn’t change drastically.
A well-built bicycle transfers energy effectively via the drivetrain, steers predictably and is snug to journey for lengthy durations of time. Overemphasizing stiffness creates a motorbike that turns each variation within the street floor into numbing vibrations whereas focusing an excessive amount of on compliance makes a motorbike that handles unpredictably and loses power via undue body flex. It’s within the harmonious center floor between these two extremes that good bicycles exist.
Experience high quality as an idea is extremely subjective. Moreover, the sensations you are feeling whereas driving a motorbike can’t be simply attributed to anyone part or half. In sum, one may really feel some mixture of the next whereas driving: tyre casing, air strain, spoke and rim interaction, body design, seatpost flex, saddle padding and situation of chamois (or lack thereof). And that’s simply the rear half of the bike.
There’s a cause why many bike evaluations deal with goal traits, like weight, geometry and aerodynamic efficiency. Attempting to isolate the efficiency of the body from your entire system is considerably akin to attempting to discern a person thread in a sock with the underside of your foot. Nonetheless, we attempt our greatest.
Some ideas on flex
Stress testing being carried out on a body as Argonaut Cycles in Bend, Oregon.
(Picture credit score: Argonaut Cycles)
We spoke with body builder Corey Lowe of Eyewater Bicycles to be taught extra about body composition. Lowe began within the bike trade with Parlee Cycles as an engineer and body builder, then moved to Cannondale and Specialised as a design engineer with the high-performance street crew. He has additionally carried out contract engineering work for locations like Allied and Cervelo and at present builds customized carbon bicycles beneath the Eyewater title.
Lowe emphasised that the body “should all the time [be considered] as an entire. There are occasions when isolating a part helps get a transparent understanding of its impression, however the finish results of how a body rides may be very a lot a sport of the entire bundle.” As he says, “It’s comparatively simple so as to add stiffness whereas including weight. The trick is so as to add stiffness with out including weight. The fabric properties of carbon could be adjusted with the layup schedule with out essentially including weight.”
We additionally requested him about balancing stiffness and compliance: “Frames could be designed for each aims, bettering one or the opposite utilizing layup modifications. I attempt to design frames to fulfill the efficiency objectives set out after which work to optimize journey high quality and compliance from that time. These two parameters are usually not all the time mutually unique, particularly with working with carbon layup schedules and spherical tubing.”
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Finally, Lowe says, “match and geometry are the biggest components in rider consolation.”
Which tubes should be versatile, and which should be stiff?
(Picture credit score: Andy Jones)
Structurally, the best focus of stress on the body happens on the joints, particularly the backside bracket, with the center of the tubes in between seeing the least quantity of stress. The fabric used, its form and its thickness all decide the way it will react to pressure and stresses.
If the purpose of the design is to place the correct amount of fabric in the appropriate locations, then this implies utilizing much less materials within the locations the place it’s going to expertise the least quantity of stress.
With a traditional body design, the downtube considerably impacts the general really feel of the bicycle. It’s the essential structural aspect tying the underside bracket to the top tube, so it’s liable for sustaining torsional stiffness and stopping an excessive amount of lateral flex. If it’s too stiff, it gained’t monitor the bottom nicely, but when it’s too versatile, it’s going to really feel imprecise (i.e. scary) at excessive speeds or beneath heavy cornering masses.
The difficult factor to remember is that the appropriate stiffness for a rider depends on their dimension and weight. Chainstays should be robust sufficient to carry the wheel in place whereas transferring the power going via the drivetrain. The highest half of the bicycle, notably the highest tube and seat stays, add to the energy of the entire by finishing the triangles, however much less inflexible materials right here may help with discovering the appropriate steadiness of vertical flex.
The stiffness of the fork additionally considerably impacts consolation. Curiously, the seat tube does little or no to offer consolation or construction. Its main objective, exterior of finishing the triangles, is basically simply to put the saddle in the appropriate place for the rider.
Strategies
(Picture credit score: Future)
How does one change the stiffness of a tube? There are basically three rules in play: materials form, thickness and diameter. Shaping is used each for aerodynamics and to encourage motion in particular instructions and ranging the thickness of the fabric at completely different factors in every tube is used for weight financial savings and adjusting journey high quality and rigidity. All else being equal, bigger diameter tubes are stronger than smaller ones. By utilizing thinner materials with a bigger diameter producers could make bikes which are each mild and powerful.
There are additionally a number of different design parts to think about along with journey high quality: aerodynamics, impression resistance, and weight all play an element, and relying on the appliance a designer might skew extra towards the route of a number of of those so as to meet particular goals.
Conclusion
(Picture credit score: Future)
Experience high quality is an attention-grabbing matter of debate partially as a result of it’s so subjective. What works for one rider might not work for one more. Bicycles from giant trade gamers are designed for many who match inside a sure vary of constraints. Riders on both finish of the peak and/or weight bell curves would require changes to discover a bike with their desired journey high quality, and may have to hunt options to mass manufacturing choices.
Finally, the most important positive aspects to be made on the subject of rider consolation are within the seatpost and tires. A seatpost designed to flex will take away way more street vibration than the body, and ditto for tires: greater quantity tires at decrease pressures are key. On the subject of body design, match is the primary most crucial aspect. A nicely designed-frame strikes a wholesome steadiness between stiffness and compliance so as to fulfill its true objective: making cyclists completely happy.
