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Horst link bending forces



 
 
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  #11  
Old February 3rd 18, 01:41 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 3,967
Default Horst link bending forces

On Fri, 2 Feb 2018 08:21:36 -0800, sms
wrote:

On 2/1/2018 8:37 PM, jbeattie wrote:
On Thursday, February 1, 2018 at 3:38:32 PM UTC-8, Joerg wrote:
On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.


All parts made by a decent company are tested to failure or to the end of a test protocol. Call the company and see how many fatigue cycles it took to fail your linkage. Then count your cycles and go from there. When you get to the magic number, don't ride anywhere near mountain lions.


I would put in an optical sensor to count the cycles and then do a
replacement after every 10,000 cycles.


If you look closely practically every part on a bike bends under a
load. Notably, the front forks, the handle bars, the brake arms, the
main frame .....

Few of which cause failure and physical injury that the O.P. mentions
in a separate post.
--
Cheers,

John B.

Ads
  #12  
Old February 3rd 18, 01:50 AM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 5,551
Default Horst link bending forces

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:

On 2018-02-01 17:07, John B. wrote:
On Thu, 01 Feb 2018 15:38:39 -0800, Joerg
wrote:

On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.

[...]

True that all large aircraft wings flex - the outriggers on a B-52
will be some 6 feet above the ground with empty tanks :-)

If you are worried about your bike's rear strut why not just reinforce
it. You have explained how clever it is to use a hose clamp to prevent
a nut from loosening why not use the same technique to hold a
reinforcing brace on your MTB?

https://tinyurl.com/yaklvuy6

Figure 14 shows a bridge using plates attached with clamps as
reinforcement.



I know how to do that but wanted to know how much bending is normal. IOW
whether reinforcement is necessary. Hence my post here. Clamping a
reinforcement to the bar back there ain't as easy as a steerer hose
clamp. That area can't have anything protruding and potentially slicing
open a leg in case of a crash.


If you are seriously worried about injuries resulting from a crash it
would seem logical to simply get rid of the bike before the
anticipated failure.


As someone who has done aircraft maintenance you surprise me. Ever heard
the term crashworthiness?

Mountain bikers do crash once in a while. Par for the course. It has
been more than a year for me I think but some day my number will come up
again. All it takes is a violent tire blow-out.


As for clamps see https://tinyurl.com/y97t6n2b
The 19th shows a clamp that can be installed without protruding parts
and several other examples are shown further down the page.



The kind with the "U-turn screws" is what I'd probably use if needed and
then cap nuts on the ends. Towards the wheel it'll be tight, not much room.

--
Regards, Joerg

http://www.analogconsultants.com/
  #13  
Old February 3rd 18, 03:33 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 3,967
Default Horst link bending forces

On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote:

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:

On 2018-02-01 17:07, John B. wrote:
On Thu, 01 Feb 2018 15:38:39 -0800, Joerg
wrote:

On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.

[...]

True that all large aircraft wings flex - the outriggers on a B-52
will be some 6 feet above the ground with empty tanks :-)

If you are worried about your bike's rear strut why not just reinforce
it. You have explained how clever it is to use a hose clamp to prevent
a nut from loosening why not use the same technique to hold a
reinforcing brace on your MTB?

https://tinyurl.com/yaklvuy6

Figure 14 shows a bridge using plates attached with clamps as
reinforcement.


I know how to do that but wanted to know how much bending is normal. IOW
whether reinforcement is necessary. Hence my post here. Clamping a
reinforcement to the bar back there ain't as easy as a steerer hose
clamp. That area can't have anything protruding and potentially slicing
open a leg in case of a crash.


If you are seriously worried about injuries resulting from a crash it
would seem logical to simply get rid of the bike before the
anticipated failure.


As someone who has done aircraft maintenance you surprise me. Ever heard
the term crashworthiness?


Nope, never heard the term used in conjunction with the word
"aircraft". I've heard the term "preventative" and even seen aircraft
with what are called "Egress" systems but never an aircraft designed
to be "crashworthy".

I did some research and the term seems to be primarily associated with
airbags in the Sikorsky UH-60 Black Hawk and the Boeing AH-64 Apache
helicopters but no mention in other aircraft ranging from large
aircraft like the B-52 to small ones like the F-15. In fact one
reference reported that air bags were not built into commercial
aircraft at all. Given the reliability of air bags, as evidenced by
the recall of more then a million air bag equipped automobiles,
perhaps a different term should be applied.



Mountain bikers do crash once in a while. Par for the course. It has
been more than a year for me I think but some day my number will come up
again. All it takes is a violent tire blow-out.


As for clamps see https://tinyurl.com/y97t6n2b
The 19th shows a clamp that can be installed without protruding parts
and several other examples are shown further down the page.



The kind with the "U-turn screws" is what I'd probably use if needed and
then cap nuts on the ends. Towards the wheel it'll be tight, not much room.


Well, then don't spend any time or effort in strengthening the struts.
After all it is not as though a huge portion of the 18 million
bicycles sold in the U.S. between 2013 and 2015 have broken.
--
Cheers,

John B.

  #14  
Old February 3rd 18, 04:39 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 5,551
Default Horst link bending forces

On 2018-02-02 18:33, John B. wrote:
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote:

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:

On 2018-02-01 17:07, John B. wrote:
On Thu, 01 Feb 2018 15:38:39 -0800, Joerg
wrote:

On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.

[...]

True that all large aircraft wings flex - the outriggers on a B-52
will be some 6 feet above the ground with empty tanks :-)

If you are worried about your bike's rear strut why not just reinforce
it. You have explained how clever it is to use a hose clamp to prevent
a nut from loosening why not use the same technique to hold a
reinforcing brace on your MTB?

https://tinyurl.com/yaklvuy6

Figure 14 shows a bridge using plates attached with clamps as
reinforcement.


I know how to do that but wanted to know how much bending is normal. IOW
whether reinforcement is necessary. Hence my post here. Clamping a
reinforcement to the bar back there ain't as easy as a steerer hose
clamp. That area can't have anything protruding and potentially slicing
open a leg in case of a crash.

If you are seriously worried about injuries resulting from a crash it
would seem logical to simply get rid of the bike before the
anticipated failure.


As someone who has done aircraft maintenance you surprise me. Ever heard
the term crashworthiness?


Nope, never heard the term used in conjunction with the word
"aircraft". I've heard the term "preventative" and even seen aircraft
with what are called "Egress" systems but never an aircraft designed
to be "crashworthy".


Seriously? jaw drops

https://flightsafety.org/hs/hs_jan-feb90.pdf


I did some research and the term seems to be primarily associated with
airbags in the Sikorsky UH-60 Black Hawk and the Boeing AH-64 Apache
helicopters but no mention in other aircraft ranging from large
aircraft like the B-52 to small ones like the F-15. In fact one
reference reported that air bags were not built into commercial
aircraft at all. Given the reliability of air bags, as evidenced by
the recall of more then a million air bag equipped automobiles,
perhaps a different term should be applied.


This term is very widely used in aircraft design and also the design of
components. Almost everything inside an aircraft must be designed with
crashworthiness in mind or it will (hopefully) be flagged down in the
design review.

Among the things I do for a living is also the design of aerospace
parts. For example, critical devices that are supposed to remain intact
after a not quite "wrinkle-free" landing have to withstand some of
G-force and nothing is allowed to come loose in the process.



Mountain bikers do crash once in a while. Par for the course. It has
been more than a year for me I think but some day my number will come up
again. All it takes is a violent tire blow-out.


As for clamps see https://tinyurl.com/y97t6n2b
The 19th shows a clamp that can be installed without protruding parts
and several other examples are shown further down the page.



The kind with the "U-turn screws" is what I'd probably use if needed and
then cap nuts on the ends. Towards the wheel it'll be tight, not much room.


Well, then don't spend any time or effort in strengthening the struts.
After all it is not as though a huge portion of the 18 million
bicycles sold in the U.S. between 2013 and 2015 have broken.



MTB? You've got to be kidding. That's why MTB riders carry cable ties
and sometimes duct tape.

http://www.socaltrailriders.org/inde...n-frame.21124/

--
Regards, Joerg

http://www.analogconsultants.com/
  #15  
Old February 3rd 18, 11:53 PM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 3,967
Default Horst link bending forces

On Sat, 03 Feb 2018 07:39:28 -0800, Joerg
wrote:

On 2018-02-02 18:33, John B. wrote:
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote:

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:

On 2018-02-01 17:07, John B. wrote:
On Thu, 01 Feb 2018 15:38:39 -0800, Joerg
wrote:

On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.

[...]

True that all large aircraft wings flex - the outriggers on a B-52
will be some 6 feet above the ground with empty tanks :-)

If you are worried about your bike's rear strut why not just reinforce
it. You have explained how clever it is to use a hose clamp to prevent
a nut from loosening why not use the same technique to hold a
reinforcing brace on your MTB?

https://tinyurl.com/yaklvuy6

Figure 14 shows a bridge using plates attached with clamps as
reinforcement.


I know how to do that but wanted to know how much bending is normal. IOW
whether reinforcement is necessary. Hence my post here. Clamping a
reinforcement to the bar back there ain't as easy as a steerer hose
clamp. That area can't have anything protruding and potentially slicing
open a leg in case of a crash.

If you are seriously worried about injuries resulting from a crash it
would seem logical to simply get rid of the bike before the
anticipated failure.


As someone who has done aircraft maintenance you surprise me. Ever heard
the term crashworthiness?


Nope, never heard the term used in conjunction with the word
"aircraft". I've heard the term "preventative" and even seen aircraft
with what are called "Egress" systems but never an aircraft designed
to be "crashworthy".


Seriously? jaw drops

https://flightsafety.org/hs/hs_jan-feb90.pdf

:-) You are reading a document that was published by Bell as part of
a sales pitch made 30 years ago. The seat test and the required dummy
standards were resulted from knowledge gained during the Works on
effects of deceleration carried out by Colonel John Paul Stapp some 70
years ago.


I did some research and the term seems to be primarily associated with
airbags in the Sikorsky UH-60 Black Hawk and the Boeing AH-64 Apache
helicopters but no mention in other aircraft ranging from large
aircraft like the B-52 to small ones like the F-15. In fact one
reference reported that air bags were not built into commercial
aircraft at all. Given the reliability of air bags, as evidenced by
the recall of more then a million air bag equipped automobiles,
perhaps a different term should be applied.


This term is very widely used in aircraft design and also the design of
components. Almost everything inside an aircraft must be designed with
crashworthiness in mind or it will (hopefully) be flagged down in the
design review.

Among the things I do for a living is also the design of aerospace
parts. For example, critical devices that are supposed to remain intact
after a not quite "wrinkle-free" landing have to withstand some of
G-force and nothing is allowed to come loose in the process.



Mountain bikers do crash once in a while. Par for the course. It has
been more than a year for me I think but some day my number will come up
again. All it takes is a violent tire blow-out.


As for clamps see https://tinyurl.com/y97t6n2b
The 19th shows a clamp that can be installed without protruding parts
and several other examples are shown further down the page.


The kind with the "U-turn screws" is what I'd probably use if needed and
then cap nuts on the ends. Towards the wheel it'll be tight, not much room.


Well, then don't spend any time or effort in strengthening the struts.
After all it is not as though a huge portion of the 18 million
bicycles sold in the U.S. between 2013 and 2015 have broken.



MTB? You've got to be kidding. That's why MTB riders carry cable ties
and sometimes duct tape.

http://www.socaltrailriders.org/inde...n-frame.21124/


And how many of the 18 million or so bikes sold from 2013 - 2015
broke. Or even easier, how many bicycles in California broke in the
same period?
--
Cheers,

John B.

  #16  
Old February 4th 18, 04:17 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 5,551
Default Horst link bending forces

On 2018-02-03 14:53, John B. wrote:
On Sat, 03 Feb 2018 07:39:28 -0800, Joerg
wrote:

On 2018-02-02 18:33, John B. wrote:
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote:

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:

On 2018-02-01 17:07, John B. wrote:
On Thu, 01 Feb 2018 15:38:39 -0800, Joerg
wrote:

On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.

[...]

True that all large aircraft wings flex - the outriggers on a B-52
will be some 6 feet above the ground with empty tanks :-)

If you are worried about your bike's rear strut why not just reinforce
it. You have explained how clever it is to use a hose clamp to prevent
a nut from loosening why not use the same technique to hold a
reinforcing brace on your MTB?

https://tinyurl.com/yaklvuy6

Figure 14 shows a bridge using plates attached with clamps as
reinforcement.


I know how to do that but wanted to know how much bending is normal. IOW
whether reinforcement is necessary. Hence my post here. Clamping a
reinforcement to the bar back there ain't as easy as a steerer hose
clamp. That area can't have anything protruding and potentially slicing
open a leg in case of a crash.

If you are seriously worried about injuries resulting from a crash it
would seem logical to simply get rid of the bike before the
anticipated failure.


As someone who has done aircraft maintenance you surprise me. Ever heard
the term crashworthiness?


Nope, never heard the term used in conjunction with the word
"aircraft". I've heard the term "preventative" and even seen aircraft
with what are called "Egress" systems but never an aircraft designed
to be "crashworthy".


Seriously? jaw drops

https://flightsafety.org/hs/hs_jan-feb90.pdf

:-) You are reading a document that was published by Bell as part of
a sales pitch made 30 years ago. The seat test and the required dummy
standards were resulted from knowledge gained during the Works on
effects of deceleration carried out by Colonel John Paul Stapp some 70
years ago.


The principle is still the same. As is the law.

[...]


As for clamps see https://tinyurl.com/y97t6n2b
The 19th shows a clamp that can be installed without protruding parts
and several other examples are shown further down the page.


The kind with the "U-turn screws" is what I'd probably use if needed and
then cap nuts on the ends. Towards the wheel it'll be tight, not much room.

Well, then don't spend any time or effort in strengthening the struts.
After all it is not as though a huge portion of the 18 million
bicycles sold in the U.S. between 2013 and 2015 have broken.



MTB? You've got to be kidding. That's why MTB riders carry cable ties
and sometimes duct tape.

http://www.socaltrailriders.org/inde...n-frame.21124/


And how many of the 18 million or so bikes sold from 2013 - 2015
broke. Or even easier, how many bicycles in California broke in the
same period?



Only a small fraction, mainly because most bikes become garage queens.
Garage queens become dusty but they don't get hurt.

There is one guy here in the NG who broke several Cannondale frames. One
of the more serious accidents in our family happened when my dad's
bicycle frame broke.

--
Regards, Joerg

http://www.analogconsultants.com/
  #17  
Old February 4th 18, 06:41 PM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 3,429
Default Horst link bending forces

On Sunday, February 4, 2018 at 7:17:29 AM UTC-8, Joerg wrote:
On 2018-02-03 14:53, John B. wrote:
On Sat, 03 Feb 2018 07:39:28 -0800, Joerg
wrote:

On 2018-02-02 18:33, John B. wrote:
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote:

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:

On 2018-02-01 17:07, John B. wrote:
On Thu, 01 Feb 2018 15:38:39 -0800, Joerg
wrote:

On 2018-02-01 11:26, jbeattie wrote:
On Thursday, February 1, 2018 at 10:24:16 AM UTC-8, Joerg wrote:
Yesterday on the MTB I had to look downwards between my legs to see
what made a rattling noise on the bike, saw some brush tangled in
the rear and hit both brakes quite hard. That's when I noticed how
much the upper diagonal strut in a Horst link bends when applying a
lot of brake force. The center of it bows down several tenths of an
inch and also outward a little. It's a pretty beefy strut:

http://www.analogconsultants.com/ng/bike/Muddy4.JPG

Similar on other bikes:

https://ep1.pinkbike.org/p5pb9586988/p5pb9586988.jpg

One can see such bowing also on aircraft wings which as built and
tested to high stress standards. They make the spars out of stuff
such as 7178 which I assume bike mfgs don't:

https://www.popularmechanics.com/fli...-stress-tests/



Has anyone else with a Horst link bike taken a look while applying the
rear brake hard? Can this fatigue the strut to the point where it
eventally breaks? Should I shore that up with maybe an L- or
U-profile strapped around it?

I am asking because I use my MTB for transportation a lot and ride
about 2000mi a year on it, hard, not just the occasional weekend
loop. It'll see hundreds of such strut load cycles per ride.

Yes, everything breaks after enough fatigue cycles, particularly
aluminum -- which has no fatigue threshold. Even small amplitude
fatigue cycles will affect aluminum. It will break.


Not necessarily. Next time you fly sit right behind a wing and watch
closely what happens at rotation time (when the pilot pulls up and the
aircraft becomes airborne). The wing will bend so much that its tip is
now several feet higher than it was in its resting state. In turbulent
weather it'll then continue to flex up and down like he

https://www.youtube.com/watch?v=tr5qkjlE77Y

https://www.youtube.com/watch?v=NYsFk4I14N8

Yet these aircraft have a service life of 30 years. And then typically
get sold to the freight dogs or lesser devloped countries for another 30
years or so.

It's aluminum. My question is whether the typical upper Host link strut
on a MTB can take similar dynamic stresses and for how long. If Boeing
made them I'd have no doubt but Boeing does not build MTBs.

[...]

True that all large aircraft wings flex - the outriggers on a B-52
will be some 6 feet above the ground with empty tanks :-)

If you are worried about your bike's rear strut why not just reinforce
it. You have explained how clever it is to use a hose clamp to prevent
a nut from loosening why not use the same technique to hold a
reinforcing brace on your MTB?

https://tinyurl.com/yaklvuy6

Figure 14 shows a bridge using plates attached with clamps as
reinforcement.


I know how to do that but wanted to know how much bending is normal. IOW
whether reinforcement is necessary. Hence my post here. Clamping a
reinforcement to the bar back there ain't as easy as a steerer hose
clamp. That area can't have anything protruding and potentially slicing
open a leg in case of a crash.

If you are seriously worried about injuries resulting from a crash it
would seem logical to simply get rid of the bike before the
anticipated failure.


As someone who has done aircraft maintenance you surprise me. Ever heard
the term crashworthiness?


Nope, never heard the term used in conjunction with the word
"aircraft". I've heard the term "preventative" and even seen aircraft
with what are called "Egress" systems but never an aircraft designed
to be "crashworthy".


Seriously? jaw drops

https://flightsafety.org/hs/hs_jan-feb90.pdf

:-) You are reading a document that was published by Bell as part of
a sales pitch made 30 years ago. The seat test and the required dummy
standards were resulted from knowledge gained during the Works on
effects of deceleration carried out by Colonel John Paul Stapp some 70
years ago.


The principle is still the same. As is the law.

[...]


As for clamps see https://tinyurl.com/y97t6n2b
The 19th shows a clamp that can be installed without protruding parts
and several other examples are shown further down the page.


The kind with the "U-turn screws" is what I'd probably use if needed and
then cap nuts on the ends. Towards the wheel it'll be tight, not much room.

Well, then don't spend any time or effort in strengthening the struts..
After all it is not as though a huge portion of the 18 million
bicycles sold in the U.S. between 2013 and 2015 have broken.


MTB? You've got to be kidding. That's why MTB riders carry cable ties
and sometimes duct tape.

http://www.socaltrailriders.org/inde...n-frame.21124/


And how many of the 18 million or so bikes sold from 2013 - 2015
broke. Or even easier, how many bicycles in California broke in the
same period?



Only a small fraction, mainly because most bikes become garage queens.
Garage queens become dusty but they don't get hurt.

There is one guy here in the NG who broke several Cannondale frames. One
of the more serious accidents in our family happened when my dad's
bicycle frame broke.


Everything breaks after enough fatigue cycles. I've failed a bunch of frames, but have never been injured because of one, and for you, a failed rear linkage will not put you over the bars.

I've seen injuries with fork failures (TK being a prime example) and with early Al MTB front-end failures. I saw some front-ends detach, although after big impacts that would have ejected the rider in any event. I'm not in the know with MTBs, but it seems that suspension failures would just result in a crippled bike rather than a crippled rider.

If you are concerned, you need to buy a steel hard-tail fat bike -- or a full rigid steel fat bike.

-- Jay Beattie.

  #18  
Old February 4th 18, 06:59 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 5,551
Default Horst link bending forces

On 2018-02-04 09:41, jbeattie wrote:
On Sunday, February 4, 2018 at 7:17:29 AM UTC-8, Joerg wrote:
On 2018-02-03 14:53, John B. wrote:
On Sat, 03 Feb 2018 07:39:28 -0800, Joerg
wrote:

On 2018-02-02 18:33, John B. wrote:
On Fri, 02 Feb 2018 16:50:56 -0800, Joerg
wrote:

On 2018-02-02 16:35, John B. wrote:
On Fri, 02 Feb 2018 08:01:18 -0800, Joerg
wrote:


[...]



As for clamps see https://tinyurl.com/y97t6n2b The 19th
shows a clamp that can be installed without protruding
parts and several other examples are shown further down
the page.


The kind with the "U-turn screws" is what I'd probably use
if needed and then cap nuts on the ends. Towards the wheel
it'll be tight, not much room.

Well, then don't spend any time or effort in strengthening
the struts. After all it is not as though a huge portion of
the 18 million bicycles sold in the U.S. between 2013 and
2015 have broken.


MTB? You've got to be kidding. That's why MTB riders carry
cable ties and sometimes duct tape.

http://www.socaltrailriders.org/inde...n-frame.21124/



And how many of the 18 million or so bikes sold from 2013 - 2015
broke. Or even easier, how many bicycles in California broke in
the same period?



Only a small fraction, mainly because most bikes become garage
queens. Garage queens become dusty but they don't get hurt.

There is one guy here in the NG who broke several Cannondale
frames. One of the more serious accidents in our family happened
when my dad's bicycle frame broke.


Everything breaks after enough fatigue cycles. I've failed a bunch of
frames, but have never been injured because of one, and for you, a
failed rear linkage will not put you over the bars.


It's the top strut that could break. Won't put me over the bar but could
cause an all day (or night) walk. BTDT, after a rear tire blew and lost
a chunk of material.


I've seen injuries with fork failures (TK being a prime example) and
with early Al MTB front-end failures. I saw some front-ends detach,
although after big impacts that would have ejected the rider in any
event. I'm not in the know with MTBs, but it seems that suspension
failures would just result in a crippled bike rather than a crippled
rider.


It depends. If my rear shock detached the bike would bottom out. The
posterior mount of that loosened twice, last time on Wednesday, but now
I learned the symptoms and carry a 2nd 5mm Allen wrench in a pocket so I
can check tightness once in a while without having to unpack the tool kit.


If you are concerned, you need to buy a steel hard-tail fat bike --
or a full rigid steel fat bike.


I need full-suspension because of a lower back issue. I am hoping some
day there will be a Ti-frame for a 29er, or at least 27-1/2" suitable
for 3" tires. However, I am thankful that my current bikes are not
carbon fiber (the road bike is Reynolds steel, as it should).

Fat bikes aren't suitable for the trails I use because their tires would
fail very soon.

--
Regards, Joerg

http://www.analogconsultants.com/
  #19  
Old February 5th 18, 12:17 AM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 6,335
Default Horst link bending forces

On 2/4/2018 12:59 PM, Joerg wrote:
On 2018-02-04 09:41, jbeattie wrote:

If you are concerned, you need to buy a steel hard-tail fat bike --
or a full rigid steel fat bike.


I need full-suspension because of a lower back issue. I am hoping some
day there will be a Ti-frame for a 29er, or at least 27-1/2" suitable
for 3" tires. However, I am thankful that my current bikes are not
carbon fiber (the road bike is Reynolds steel, as it should).


FWIW, the fork that broke on our tandem was Reynolds 531.

I don't blame Reynolds. I blame the custom frame builder, Jim Bradford,
who without telling me substituted track-gauge fork blades in place of
tandem gauge. The wall thickness was only 1/3 what it should have been.

--
- Frank Krygowski
  #20  
Old February 5th 18, 01:26 AM posted to rec.bicycles.tech
Emanuel Berg[_2_]
external usenet poster
 
Posts: 1,035
Default Horst link bending forces

Frank Krygowski wrote:

FWIW, the fork that broke on our tandem was
Reynolds 531.


BTW I've heard that number (531) doesn't
specify some property of the steel but is
a designation/name so one can refer to
the product.

--
underground experts united
http://user.it.uu.se/~embe8573
 




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