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Horst link bending forces



 
 
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  #1  
Old February 1st 18, 07:24 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,854
Default Horst link bending forces

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.

--
Regards, Joerg

http://www.analogconsultants.com/
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  #2  
Old February 1st 18, 08:26 PM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 2,900
Default Horst link bending forces

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. You will died. Mountain lions will eat your corpse. Or it will break and you'll buy a new one, which is what most people do. If this is a problem, buy a steel hard-tail.

-- Jay Beattie.

  #3  
Old February 1st 18, 10:05 PM posted to rec.bicycles.tech
Frank Krygowski[_4_]
external usenet poster
 
Posts: 5,657
Default Horst link bending forces

On 2/1/2018 1:24 PM, Joerg wrote:


Has anyone else with a Horst link bike taken a look while applying the
rear brake hard?


Someone somewhere has, certainly.

Can this fatigue the strut to the point where it
eventally breaks?


Yes. Not for most people, but certainly for you.

Should I shore that up with maybe an L- or U-profile
strapped around it?


Use steel channels, say C3x4.1, one on each side. Hold them in place
with hose clamps. Remember, weight doesn't matter.

--
- Frank Krygowski
  #4  
Old February 2nd 18, 12:38 AM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,854
Default Horst link bending forces

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.

[...]

--
Regards, Joerg

http://www.analogconsultants.com/
  #5  
Old February 2nd 18, 02:07 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 3,787
Default Horst link bending forces

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.
--
Cheers,

John B.

  #6  
Old February 2nd 18, 02:40 AM posted to rec.bicycles.tech
James[_8_]
external usenet poster
 
Posts: 5,674
Default Horst link bending forces

On 02/02/18 12:07, John B. wrote:

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.



Sounds like something I did to keep my Land Rover going to the workshop.

I've never had to do anything like that to my Jeep, so maybe it is made
by Boeing? LOL

--
JS
  #7  
Old February 2nd 18, 05:37 AM posted to rec.bicycles.tech
JBeattie
external usenet poster
 
Posts: 2,900
Default Horst link bending forces

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.

-- Jay Beattie.


  #8  
Old February 2nd 18, 05:01 PM posted to rec.bicycles.tech
Joerg[_2_]
external usenet poster
 
Posts: 4,854
Default Horst link bending forces

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.

--
Regards, Joerg

http://www.analogconsultants.com/
  #9  
Old February 2nd 18, 05:21 PM posted to rec.bicycles.tech
SMS
external usenet poster
 
Posts: 8,107
Default Horst link bending forces

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.
  #10  
Old February 3rd 18, 01:35 AM posted to rec.bicycles.tech
John B.[_3_]
external usenet poster
 
Posts: 3,787
Default Horst link bending forces

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 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.
--
Cheers,

John B.

 




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