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New crank design



 
 
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  #1  
Old May 27th 21, 09:07 PM posted to rec.bicycles.tech
AMuzi
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Posts: 13,447
Default New crank design

https://bikerumor.com/2021/05/21/sra...rative-design/
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Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

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  #2  
Old May 27th 21, 11:01 PM posted to rec.bicycles.tech
Tom Kunich[_4_]
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Posts: 2,196
Default 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  
Old May 27th 21, 11:09 PM posted to rec.bicycles.tech
AMuzi
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Posts: 13,447
Default 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  
Old May 27th 21, 11:54 PM posted to rec.bicycles.tech
Tom Kunich[_4_]
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Posts: 2,196
Default 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  
Old May 28th 21, 01:03 AM posted to rec.bicycles.tech
Steve Weeks
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Posts: 97
Default 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  
Old May 28th 21, 02:12 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
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Posts: 10,538
Default 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  
Old May 28th 21, 02:23 AM posted to rec.bicycles.tech
AMuzi
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Posts: 13,447
Default 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  
Old May 28th 21, 08:22 AM posted to rec.bicycles.tech
Axel Reichert
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Posts: 28
Default 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  
Old May 28th 21, 09:12 AM posted to rec.bicycles.tech
Sir Ridesalot
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Posts: 5,270
Default 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  
Old May 28th 21, 09:34 AM posted to rec.bicycles.tech
Rolf Mantel[_2_]
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Posts: 267
Default 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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