B
Ben C
Guest
On 2007-02-13, [email protected] <[email protected]> wrote:
> Ben C? writes:
[...]
>>>>> Placing the caliper in from of the fork would result in the
>>>>> reaction force driving the axle into the dropout and eliminating
>>>>> the ejection force altogether.
>
>>>> Of course true, but although not impossible, undesirable.
>
>>> Why is that undesirable?
>
>> Because it puts the mounting point in tension as explained by jim beam.
>
> Every bending element is subject to tension. Thee is nothing wrong
> with tension or we couldn't build anything right from the Golden Gate
> Bridge to the elevator next to the stairs. There is nothing wrong
> with tension as we see in spokes that don't fail at mid span where
> they are entirely in tension. It is unintended bending that causes
> most failures and these fail on their tensile side. Don't give
> tension a bad name or we can't play tennis or listen to stringed
> instruments.
I think jim beam's point was that this was a tensile fatigue cycle,
which tends to be worse than a compressive one, especially for things
that are cast.
>> Also I am concerned about grit, brake dust etc. coming out of the
>> back of the caliper being thrown upwards towards the rider's face.
>> With the caliper behind the fork it's directed towards the road
>> behind the front wheel.
>
> For a particle to fly into your face, it would need to be at least as
> large as a grain of coarse sand that flies of the front tire all the
> time when on road edge pavement or dirt roads. This is not a hazard.
Anyway I got it the wrong way round-- it would be thrown downwards by a
front caliper, and upwards by a rear caliper!
> Ben C? writes:
[...]
>>>>> Placing the caliper in from of the fork would result in the
>>>>> reaction force driving the axle into the dropout and eliminating
>>>>> the ejection force altogether.
>
>>>> Of course true, but although not impossible, undesirable.
>
>>> Why is that undesirable?
>
>> Because it puts the mounting point in tension as explained by jim beam.
>
> Every bending element is subject to tension. Thee is nothing wrong
> with tension or we couldn't build anything right from the Golden Gate
> Bridge to the elevator next to the stairs. There is nothing wrong
> with tension as we see in spokes that don't fail at mid span where
> they are entirely in tension. It is unintended bending that causes
> most failures and these fail on their tensile side. Don't give
> tension a bad name or we can't play tennis or listen to stringed
> instruments.
I think jim beam's point was that this was a tensile fatigue cycle,
which tends to be worse than a compressive one, especially for things
that are cast.
>> Also I am concerned about grit, brake dust etc. coming out of the
>> back of the caliper being thrown upwards towards the rider's face.
>> With the caliper behind the fork it's directed towards the road
>> behind the front wheel.
>
> For a particle to fly into your face, it would need to be at least as
> large as a grain of coarse sand that flies of the front tire all the
> time when on road edge pavement or dirt roads. This is not a hazard.
Anyway I got it the wrong way round-- it would be thrown downwards by a
front caliper, and upwards by a rear caliper!