Horst link bending forces

On Tue, 06 Feb 2018 07:32:50 -0800, Joerg wrote:

On 2018-02-05 21:20, dave wrote:
On Sun, 04 Feb 2018 09:59:47 -0800, Joerg wrote:

snip

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.

Maybe the application of some thread lock may be beneficial.


Loctite didn't help. This is on the side of the upper Horst link part
that flexes when braking hard. It happens on steep stretches of trail.
Though usually only every few hundred miles so a 5mm Allen wrench
carried in a quickly accessible pocket is fine. You just have to watch
for the symptoms before something down there eats itself.

Still. It shouldn't be undoing itself. There are several grades of thread
lock available. Maybe up the goop strength or investigate different
fasteners. Checking every couple of hundred miles is fine till it comes
out 50 after the last check.

Good luck with that.
--
davethedave

On 2018-02-06 11:21, dave wrote:
On Tue, 06 Feb 2018 07:32:50 -0800, Joerg wrote:

On 2018-02-05 21:20, dave wrote:
On Sun, 04 Feb 2018 09:59:47 -0800, Joerg wrote:

snip

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.

Maybe the application of some thread lock may be beneficial.


Loctite didn't help. This is on the side of the upper Horst link part
that flexes when braking hard. It happens on steep stretches of trail.
Though usually only every few hundred miles so a 5mm Allen wrench
carried in a quickly accessible pocket is fine. You just have to watch
for the symptoms before something down there eats itself.

Still. It shouldn't be undoing itself. There are several grades of thread
lock available. Maybe up the goop strength or investigate different
fasteners. Checking every couple of hundred miles is fine till it comes
out 50 after the last check.

Good luck with that.


Yes, seems I have to either find better Loctite or have a better set of
parts machined for the rear shock pivot.

Having to use wrenches a lot happens to other riders as well, the ones
that put a lot of miles on their MTBs. Though no complaints since the
MTB affords me a lot more fun per mile than the road bike does. Nice
scenery, no cars, no Diesel stench, technically interesting rides and I
get to meet many animals.

--
Regards, Joerg

http://www.analogconsultants.com/

Joerg wrote:
On 2018-02-01 11:26, jbeattie wrote:
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.

Do the structural parts of the wing really last that long, or do they get
replaced during service? I know nothing about aircraft.


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.

The aircraft wing flexing is pretty low frequency compared with hammering a
bike down a cobblestone road. It does much fewer load cycles per unit time.

robert

Emanuel Berg wrote:

When everything brakes because of abuse and
lack of maintenance, she will not care one bit,
except for when it brakes to the point that she
cannot use it - then there will be sudden PANIC
because how will she now get to the university,
shop for clothes, her boyfriend, etc.???

That (and many other) boys will scramble to fix the bike for
her.

Fact is that the urban young women who ride all those "vintage" bikes these
days get sold junk for too much money. Especially the brakes need lots of
maintenance to function acceptably, and the frame-mounted friction shifters
are so inconvenient to use that the chain often stays in the unsightly
left-right (small-small) constellation. Also the old frames tend to be quite
large, and compact handlebars didn't exist back then, which makes for an
awkward riding position. Since aesthetics is all this is about one
SHOULD care about posture and proper chain alignment.

robert

On 2018-02-06 12:13, Robert Latest wrote:
Joerg wrote:
On 2018-02-01 11:26, jbeattie wrote:
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.

Do the structural parts of the wing really last that long, or do they get
replaced during service? I know nothing about aircraft.


They get repaired when corrosion, cracks or other deficiencies are found
and replaced after a structural damage event such as a landing where a
wing made ground contact like he

https://www.youtube.com/watch?v=trrUkKUyhl4

Otherwise not AFAIK.


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.

The aircraft wing flexing is pretty low frequency compared with hammering a
bike down a cobblestone road. It does much fewer load cycles per unit time.


Not really. Look at the 2nd video. That's a lot more flexing per minute
than a full-suspension MTB could ever do. On Horst-Link MTB any serious
flexing only happens during hard braking and hard upright cornering
(where you have a foot on the ground).

Cobblestones cause a rattle of the whole bike but not much flexing. In
fact, my MTB runs over such roads with the comfort of a Lincoln Towncar
or a Citroen DS21. Very different story on the road bike but that's so
stiff that not much can flex. What does flex on the road bike is the
front end which begins a slight shimmy somewhere above 30mph. So I try
to avoid that speed range or hold on tight while going through it on a
downhill stretch. At 40mph and above the shimmy stops.

--
Regards, Joerg

http://www.analogconsultants.com/

On Tue, 06 Feb 2018 07:32:50 -0800, Joerg
wrote:

On 2018-02-05 21:20, dave wrote:
On Sun, 04 Feb 2018 09:59:47 -0800, Joerg wrote:

snip

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.

Maybe the application of some thread lock may be beneficial.


Loctite didn't help. This is on the side of the upper Horst link part
that flexes when braking hard. It happens on steep stretches of trail.
Though usually only every few hundred miles so a 5mm Allen wrench
carried in a quickly accessible pocket is fine. You just have to watch
for the symptoms before something down there eats itself.

When a fastener is used where there is movement in the joint a pinned
fastener is usually used. See
https://tinyurl.com/ybrca92g
--
Cheers,

John B.

On 6 Feb 2018 20:13:10 GMT, Robert Latest wrote:

Joerg wrote:
On 2018-02-01 11:26, jbeattie wrote:
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.

Do the structural parts of the wing really last that long, or do they get
replaced during service? I know nothing about aircraft.


In Vietnam I worked on a DC-3 (gun ship) that was nearly as old as I
was and there was no evidence that there had been any major
maintenance or replacement done on the aircraft.


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.

The aircraft wing flexing is pretty low frequency compared with hammering a
bike down a cobblestone road. It does much fewer load cycles per unit time.

robert
--
Cheers,

John B.

On 2/1/2018 3:38 PM, Joerg wrote:

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 not years, it's cycles, as Aloha 243 demonstrated.
https://www.aerotime.aero/upload/content-assets/images/aloha%201.jpg.

On 2018-02-07 06:44, sms wrote:
On 2/1/2018 3:38 PM, Joerg wrote:

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 not years, it's cycles, as Aloha 243 demonstrated.
https://www.aerotime.aero/upload/content-assets/images/aloha%201.jpg.


Could have been a materials defect but this is what I'd like to avoid
and why I posted my question.

https://en.wikipedia.org/wiki/Aloha_Airlines_Flight_243

Quote "During an interview, passenger Gayle Yamamoto told investigators
that she had noticed a crack in the fuselage upon boarding, but did not
notify anyone". Now that I don't understand. Whenever I see something
unusual or potentially defective on an aircraft I notify someone from
the crew. That has happened more than once.

--
Regards, Joerg

http://www.analogconsultants.com/

On 2018-02-06 18:24, John B. wrote:
On Tue, 06 Feb 2018 07:32:50 -0800, Joerg
wrote:

On 2018-02-05 21:20, dave wrote:
On Sun, 04 Feb 2018 09:59:47 -0800, Joerg wrote:

snip

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.

Maybe the application of some thread lock may be beneficial.


Loctite didn't help. This is on the side of the upper Horst link part
that flexes when braking hard. It happens on steep stretches of trail.
Though usually only every few hundred miles so a 5mm Allen wrench
carried in a quickly accessible pocket is fine. You just have to watch
for the symptoms before something down there eats itself.

When a fastener is used where there is movement in the joint a pinned
fastener is usually used. See
https://tinyurl.com/ybrca92g


That's how I would have done it but designers haven't. At least there
should be a locking nut. Some day I might re-do that linkage in a more
secure fashion. Not easy, the heads of the screws are sunk into recesses
because serious leg injury could otherwise happen.

--
Regards, Joerg

http://www.analogconsultants.com/