The Generative Design Challenge: Build a Better Bicycle Frame
Roopinder Tara posted on December 31, 2018 |
Splendor in the grass. The author's bike rests during a recent trip through Marin County, Calif. The diamond-shapedbike frame with tubular construction may be the optimum shape. Made of titanium, this bike has withstood a hundred thousand miles. It will, without a doubt, outlast and outlive its owner.
Splendor in the grass. The author's bike rests during a recent trip through Marin County, Calif. The diamond-shaped bike frame with tubular construction may be the optimum shape. Made of titanium, this bike has withstood a hundred thousand miles. It will, without a doubt, outlast and outlive its owner.

A road bike frame is a study in elegance and minimalism. It uses the minimum amount of material but is rigid and strong. You'll break before your bike does. Its diamond shape has not been improved upon in a hundred years. No better solution has been found to transmit the compressive and tensile loads from the ground and the rider. Its tubular members keep the bike frame in plane even when a thousand watts (the peak power of a Tour de France sprinter) try to twist it. There's simply nothing better to resist twist than a round cross section. As little as two pounds of material can support a 150-pound rider, even in a tight downhill turn, even if they hit a bump…. 

The $4,000 Litespeed T1SL frame is made of 6Al/4V titanium alloy. The small size frame weighs 995 grams. (Imagecourtesy of Litespeed.)
The $4,000 Litespeed T1SL frame is made of 6Al/4V titanium alloy. The small size frame weighs 995 grams. (Image courtesy of Litespeed.)

The bike frame as we know it—perfect as it may be—came into being without the benefit of CAD, simulation and certainly without generative design. The originator may have cut tubes to length, brazed them into lugs, and voilà! The diamond frame was born. 

Was this the first diamond frame bicycle? CAD and generative design were not in the picture. (Imagecourtesy of Wikipedia.)
Was this the first diamond frame bicycle? CAD and generative design were not in the picture. (Image courtesy of Wikipedia.)

Sure, there were a number of design attempts that led to the diamond frame. Frame members may have been solid rather than made of hollow tubes. There were different materials used for bikes, including wood. Grainy black and white photos show many sub-optimum designs. The penny farthing, for example.  

But have we thought of every possibility? Could there be a better design than the diamond, tubular frame? Have we settled on the diamond frame without doing design diligence? In our human weakness, we often assume the last solution is the best. We can stare at something long enough and convince ourselves it is the best way. We’re human. But is it optimum? Is it perfect? 

Enter a class of design software that should, in theory, throw away the limits and restraints of human design, and not be bound by stock material on hand, like tubes; or joining methods, like welds; a very limited library of shapes, like round; or a few materials, like metal.  

Generative design has the potential to explore design possibilities without bias, without limitations. It doesn't care what looks good, if it is symmetrical, if it can be manufactured by any mortal means. Its sole raison d'être is to find an optimum solution, and being computerized, it can subject endless possibilities to discerning tests. 

The Attempts

There have been a number of attempts at making a more perfect bike frame. Many have yielded fanciful, even beautiful structures. Some may have been suitable for at least being considered for mountain bike frames. A whole different animal, mountain bikes have frames with more members and can be nonrigid, incorporating rotational links and suspensions. But no generative design to date seems to have achieved the same strength-to-weight ratio of the diamond, tubular frame for a road bike.

Watch as generative design tries in vain to improve upon a pure diamond frame construction. One immediate failing of the state of the art in generative design: you cannot specify a type of frame member, such as round tubes, the main factor in the torsional rigidity of a road bike frame. There is no hope that the algorithms used, which “create” material on a cellular level, would be able to come up with anything like a round tube. 

The Challenge

With this post, we propose that generative design companies see if they can one-up the tubular, diamond bike frame. Is there another shape we poor human engineers have not thought of that weighs less yet can still support the dynamic mass of the rider? On a bumpy road—one that stretches over mountains and which is a hundred thousand miles long? 

Recommended For You