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#1
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New crank design
https://bikerumor.com/2021/05/21/sra...rative-design/
-- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
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#2
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New crank design
On Thursday, May 27, 2021 at 1:07:59 PM UTC-7, AMuzi wrote:
https://bikerumor.com/2021/05/21/sra...rative-design/ The problem as I see it is that 3D printing is not a process without errors. It can very easily have voids and weak spots. If you had the idea of using the AI for designing the lightest possible part supposedly with the highest strength per weight ratios, what does it matter? Most of the bikes in the Tour will be too light for the rules and have to carry compensating weights. If the UCI, like expected, eliminates the weight limits it would probably be the end of high end cycling because it would be like lighting a fuse on a stick of dynamite. Anyone that is close to it will be injured by the flying debris. |
#3
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New crank design
On 5/27/2021 5:01 PM, Tom Kunich wrote:
On Thursday, May 27, 2021 at 1:07:59 PM UTC-7, AMuzi wrote: https://bikerumor.com/2021/05/21/sra...rative-design/ The problem as I see it is that 3D printing is not a process without errors. It can very easily have voids and weak spots. If you had the idea of using the AI for designing the lightest possible part supposedly with the highest strength per weight ratios, what does it matter? Most of the bikes in the Tour will be too light for the rules and have to carry compensating weights. If the UCI, like expected, eliminates the weight limits it would probably be the end of high end cycling because it would be like lighting a fuse on a stick of dynamite. Anyone that is close to it will be injured by the flying debris. Yes and no. Many 3D print pieces do have some severe limits where strength, torsional resistance or pressure matter. But sintered pieces from 3D metal powder are failry well known and of a different class. I don't know but it could well be adequate and reliable. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#4
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New crank design
On Thursday, May 27, 2021 at 3:09:30 PM UTC-7, AMuzi wrote:
On 5/27/2021 5:01 PM, Tom Kunich wrote: On Thursday, May 27, 2021 at 1:07:59 PM UTC-7, AMuzi wrote: https://bikerumor.com/2021/05/21/sra...rative-design/ The problem as I see it is that 3D printing is not a process without errors. It can very easily have voids and weak spots. If you had the idea of using the AI for designing the lightest possible part supposedly with the highest strength per weight ratios, what does it matter? Most of the bikes in the Tour will be too light for the rules and have to carry compensating weights. If the UCI, like expected, eliminates the weight limits it would probably be the end of high end cycling because it would be like lighting a fuse on a stick of dynamite. Anyone that is close to it will be injured by the flying debris. Yes and no. Many 3D print pieces do have some severe limits where strength, torsional resistance or pressure matter. But sintered pieces from 3D metal powder are failry well known and of a different class. I don't know but it could well be adequate and reliable. https://3dprinterly.com/are-3d-printed-parts-strong/ |
#5
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New crank design
On Thursday, May 27, 2021 at 5:54:44 PM UTC-5, wrote:
https://3dprinterly.com/are-3d-printed-parts-strong/ Thanks for the interesting article. I had my broken ankle screwed back together with screws made of polylactic acid ("PLA") three years ago. I expect they were 3-D printed. Not only were they strong enough for the job, but they were resorbed after the joint ("tibio-fibular syndesmosis", if you *must* know!) healed. So no second surgery to remove them! |
#6
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New crank design
On 5/27/2021 4:07 PM, AMuzi wrote:
https://bikerumor.com/2021/05/21/sra...rative-design/ Pretty wild looking! A few things I wonder about: Exactly what loads did they use for inputs to the software? Did the list include forces from unplanned events, like crashing and loading the crank sideways? Or how about something really random, like whacking your crank against a rock, which might damage one of the strut members? I could envision such a load bending a small strut and making the crank look fine, but be far weaker. I wonder what results they got for mass and stiffness, and how it compared with more conventional cranks? Are the gains worth the cost and complexity? Will they put a skin over the crank to keep it from filling with mud? And: It always seems to me that even normal loads on bike parts are difficult to predict. They can even depend on design - for example, when a mountain biker lands a big jump, the peak force will depend not only on the jump and the mass and skill of the rider, but on the stiffness of the suspension (if any) and the stiffness of the crank. So how are they evaluating the prototypes, to validate the computer data? Seems they'd need some experimental stress analysis - strain gages, brittle coatings, etc. It's not simple. But it's an interesting project. -- - Frank Krygowski |
#7
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New crank design
On 5/27/2021 8:12 PM, Frank Krygowski wrote:
On 5/27/2021 4:07 PM, AMuzi wrote: https://bikerumor.com/2021/05/21/sra...rative-design/ Pretty wild looking! A few things I wonder about: Exactly what loads did they use for inputs to the software? Did the list include forces from unplanned events, like crashing and loading the crank sideways? Or how about something really random, like whacking your crank against a rock, which might damage one of the strut members? I could envision such a load bending a small strut and making the crank look fine, but be far weaker. I wonder what results they got for mass and stiffness, and how it compared with more conventional cranks? Are the gains worth the cost and complexity? Will they put a skin over the crank to keep it from filling with mud? And: It always seems to me that even normal loads on bike parts are difficult to predict. They can even depend on design - for example, when a mountain biker lands a big jump, the peak force will depend not only on the jump and the mass and skill of the rider, but on the stiffness of the suspension (if any) and the stiffness of the crank. So how are they evaluating the prototypes, to validate the computer data? Seems they'd need some experimental stress analysis - strain gages, brittle coatings, etc. It's not simple. But it's an interesting project. I, like you, have seen a lot of things and seen a lot of things fail. I agree that modern 'modeling' seldom accounts for real world outliers with relatively high probabilities. Which is to say 'unexpected' describes the designer more than the event. -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 |
#8
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New crank design
Frank Krygowski writes:
Pretty wild looking! Many topology optimization results look much wilder. Exactly what loads did they use for inputs to the software? Did the list include forces from unplanned events, like crashing and loading the crank sideways? I cannot comment on SRAM, but I do know something about Trek: https://www.3ds.com/fileadmin/PRODUC...MULIA-trek.pdf Adaptive manufacturing becomes really high-end once you start to simulate the process itself (which you should, but I am biased, since I am working for this company): https://blogs.3ds.com/simulia/print-...ence-platform/ Best regards Axel |
#9
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New crank design
On Thursday, May 27, 2021 at 4:07:59 p.m. UTC-4, AMuzi wrote:
https://bikerumor.com/2021/05/21/sra...rative-design/ -- Andrew Muzi www.yellowjersey.org/ Open every day since 1 April, 1971 That looks to be an accident waiting for a place to happen. To me it looks like a very weak design. I wonder too what'll happen when the bicycle goes over obstacles or if there's a twisting force on the crank. Cheers |
#10
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New crank design
Am 28.05.2021 um 00:09 schrieb AMuzi:
On 5/27/2021 5:01 PM, Tom Kunich wrote: On Thursday, May 27, 2021 at 1:07:59 PM UTC-7, AMuzi wrote: https://bikerumor.com/2021/05/21/sra...rative-design/ The problem as I see it is that 3D printing is not a process without errors. It can very easily have voids and weak spots. If you had the idea of using the AI for designing the lightest possible part supposedly with the highest strength per weight ratios, what does it matter? Most of the bikes in the Tour will be too light for the rules and have to carry compensating weights. If the UCI, like expected, eliminates the weight limits it would probably be the end of high end cycling because it would be like lighting a fuse on a stick of dynamite. Anyone that is close to it will be injured by the flying debris. Yes and no. Many 3D print pieces do have some severe limits where strength, torsional resistance or pressure matter. But sintered pieces from 3D metal powder are failry well known and of a different class. I don't know but it could well be adequate and reliable. I've read somewhere that the aricraft industry is using 3-D printed Titanium joints which weigh about half as much but are double as strong as the previous generation of joints. Rolf |
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