Orthopedic tech (cycling)

On 1/27/2019 10:10 AM, Zen Cycle wrote:
On Friday, January 25, 2019 at 9:24:37 PM UTC-5, AMuzi wrote:
On 1/25/2019 8:01 PM, Frank Krygowski wrote:
On 1/25/2019 5:09 PM, Zen Cycle wrote:
On Sunday, January 20, 2019 at 7:30:11 PM UTC-5, Sir
Ridesalot wrote:
On Sunday, January 20, 2019 at 4:36:46 PM UTC-5, Mark J.
wrote:
Check out the ninth photo in this gallery, apparently an
orthopedic
device. I don't know anything beyond the caption, but
the visuals are
quite striking.

https://www.velonews.com/2019/01/new...ng-camp_482921


Mark J.

Thank you for something BICYCLING related! LOL

I found the image with the derailleur hanger between the
frame and the cassette to be pretty interesting. I(t's
the first image that doesn't have riders in it. I've
never seen such derailleur a setup before.

Cheers

It's a 'thru-axle' set up. They've been around on MTBs for
quite a while. They offer greater stiffness at lighter
weight. It's one of "standards" that aren't (like various
BB 'standards'). The UCI has been allowing them in lieu
of open dropouts with 'lawyer tabs' so expect to see
greater cross compatibility as time goes on. Here's a
primer on the technology:

http://www.bikebug.com/blog/everythi...ut-thru-axles/


Nice to see some bike tech discussion.

I note in that article, "Thru Axles (TA) originally were
designed for downhill riders years ago who were popping
their front wheels out of their front axles."

Does anyone remember the intense debates here about whether
that problem actually existed? Seems it's now well recognized.


ISTR that we agreed here on RBT it was a front disc specific
problem. With the ubiquitous behind-the-blade mount on
current popular discs, through axles make sense.

I'll leave rear through axle explanation as an exercise for
the reader.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

I did a bit of research into the thought this being a disk-specific problem, and learned a few things (always good to learn new things).

A brake mounted _behind_ the fork will cause the whee to pivot down around the . Placing the brake in front of the fork will cause the wheel to pivot up. So, not a disc specific problem per se. IT may have been seen if a substantial number of manufacturers placed rim brakes behind the fork, but of course that's impractical for a number of obvious reasons.

I remember seeing a few manufacturers placing disk brakes on the front of the fork which minimized the problem by forcing the pivot up _into_ the dropout, but this also led problems of the brake be more exposed to potential damage (not likely on a road bike, but easily conceivable on a MTB). At the time I hadn't considered the issue of the wheel popping out, but since my MTB philosophy is "I I don't crash at least once, I'm not riding hard enough", I didn't consider a front mounted brake to be a tenable option.

As far as the rear brake, it's simply a case of through axles offering better strength/rigidity at less weight. The possibility of A wheel popping out could only be an issue if the frame had a rear-facing open dropout. Every mounting position on the rear stays would force the wheel back and up.

As I recall, the disc brake debates were one of the very few times this
discussion group was referring to Free Body Diagrams. That made it
qualify as _real_ "tech."


--
- Frank Krygowski

On 1/26/2019 4:26 PM, Zen Cycle wrote:
On Friday, January 25, 2019 at 9:24:37 PM UTC-5, AMuzi wrote:
On 1/25/2019 8:01 PM, Frank Krygowski wrote:
On 1/25/2019 5:09 PM, Zen Cycle wrote:
On Sunday, January 20, 2019 at 7:30:11 PM UTC-5, Sir
Ridesalot wrote:
On Sunday, January 20, 2019 at 4:36:46 PM UTC-5, Mark J.
wrote:
Check out the ninth photo in this gallery, apparently an
orthopedic
device. I don't know anything beyond the caption, but
the visuals are
quite striking.

https://www.velonews.com/2019/01/new...ng-camp_482921


Mark J.

Thank you for something BICYCLING related! LOL

I found the image with the derailleur hanger between the
frame and the cassette to be pretty interesting. I(t's
the first image that doesn't have riders in it. I've
never seen such derailleur a setup before.

Cheers

It's a 'thru-axle' set up. They've been around on MTBs for
quite a while. They offer greater stiffness at lighter
weight. It's one of "standards" that aren't (like various
BB 'standards'). The UCI has been allowing them in lieu
of open dropouts with 'lawyer tabs' so expect to see
greater cross compatibility as time goes on. Here's a
primer on the technology:

http://www.bikebug.com/blog/everythi...ut-thru-axles/


Nice to see some bike tech discussion.

I note in that article, "Thru Axles (TA) originally were
designed for downhill riders years ago who were popping
their front wheels out of their front axles."

Does anyone remember the intense debates here about whether
that problem actually existed? Seems it's now well recognized.


ISTR that we agreed here on RBT it was a front disc specific
problem. With the ubiquitous behind-the-blade mount on
current popular discs, through axles make sense.

I can't imagine what disk brakes would have to do with it, but I haven't seen those arguments. The issue was that even with a solid bolted axle, the fact that the dropouts were open meant the wheel could dislodge. The through axle design offer better rigidity, and of course an infinitesimally small probability of the wheel popping out of a fork with a closed dropout.


I'll leave rear through axle explanation as an exercise for
the reader.

Similarly, a broken rear axle could dislodge from an open dropout, so the same philosophy applies to rear hubs/dropouts. It seems to be a bit of overkill to apply that to a road bike except for the fact that the thru axle will give more rigidity at less weight.



Rear axle failures will slow the bike when the tire rubs on
a chainstay; almost never a rider injury absent aggravating
external factors. Annoying, yes, deadly no.

But think about forces and directions of a front disk during
braking. The wheel really wants to go down and the fork up.
Bad thing, that.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Sunday, January 27, 2019 at 2:17:17 PM UTC-5, AMuzi wrote:
Snipped

Rear axle failures will slow the bike when the tire rubs on
a chainstay; almost never a rider injury absent aggravating
external factors. Annoying, yes, deadly no.

But think about forces and directions of a front disk during
braking. The wheel really wants to go down and the fork up.
Bad thing, that.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Back in the early 1980s I broke the rear axle on my MTB. I climbed a fairly long hill with it and thought that the cones had come loose. It wasn't until I got home and took the wheel off to get at the cones that I discovered that it was the axle that was broken and not loose cones. It was a nutted axle not a quick release one. I'm just glad I didn't remove the wheel a the top of that hill. I still had some distance to ride to get home.

Cheers