Re: Wheels for Heavy Rider

LioNiNoiL_a t_NetscapE_D 0 T_NeT

> Breaking spokes is pretty much a symptom of a wheel that wasn't
> built right. The maximum load on a spoke is when the bike is empty.

The maximum load on a spoke is when you hit a pothole coming downhill
with the brake applied. Spoke breakage is not entirely preventable, but
a well-built pair of tandem wheels will go a long way for a strong,
heavy rider. Rinsing the salt off the wheels in icy climates after every
ride will help forestall corrosion, but corrosion is virtually
inevitable where the roads are salted. Plan on replacement.

Peter Cole

"LioNiNoiL_a t_NetscapE_D 0 T_NeT" <accountname.above@netscape.net> wrote in
message news:Al5dc.5628$Vo.4737@fed1read03...
> > Breaking spokes is pretty much a symptom of a wheel that wasn't
> > built right. The maximum load on a spoke is when the bike is empty.
>
> The maximum load on a spoke is when you hit a pothole coming downhill
> with the brake applied.

Braking will increase the tension on rearward spokes by about 5%. When a spoke
is fatigued enough to be close to failure, it will often fail at this point,
but that just indicates the spoke was ready to let go anyway.

> Spoke breakage is not entirely preventable, but

It is, mostly. If the spokes have been stress relieved, they won't fatigue,
since the dynamic loads are relatively low.

> a well-built pair of tandem wheels will go a long way for a strong,
> heavy rider.

If the rider wieghs as much as a tandem team, true, otherwise they're
overkill. Wheel strength is affected by spoke tension. If the rims are too
light it may be impossible to get enough tension before the spoke bed fails or
the rim distorts.

> Rinsing the salt off the wheels in icy climates after every
> ride will help forestall corrosion, but corrosion is virtually
> inevitable where the roads are salted. Plan on replacement.

Modern spokes are stainless and won't corrode, even with salted roads. Brass
nipples don't corrode heavily, nor do aluminum rims. There will be some
corrosion, but not enough to cause structural failure.

-----BEGIN PGP SIGNED MESSAGE-----

In article <s8cdc.97220$w54.580828@attbi_s01>,
Peter Cole <peter_cole_no_spam_at_all@comcast.net> wrote:
>
>> Rinsing the salt off the wheels in icy climates after every
>> ride will help forestall corrosion, but corrosion is virtually
>> inevitable where the roads are salted. Plan on replacement.
>
>Modern spokes are stainless and won't corrode, even with salted roads. Brass
>nipples don't corrode heavily, nor do aluminum rims. There will be some
>corrosion, but not enough to cause structural failure.
>

_ I'd rinse. Stainless steel can corrode in the presence of
salt water. This is a very important issue in the rockclimbing
world in relation to stainless steel bolts places in seaside
cliffs. Stress Crack Corrosion.

http://www.corrosion-doctors.org/Forms/scc.htm

http://www.safeclimbing.org/education/deepbluesea.htm

_ Maybe this doesn't apply to bicycles, but it seems
like all the elements are there. Residual stress, salt water
and disimilar metal contact.

_ Booker C. Bense

-----BEGIN PGP SIGNATURE-----
Version: 2.6.2

iQCVAwUBQHWly2TWTAjn5N/lAQFbIAP+LUOuI38y0A587Zxt6qsTRAZMS4h9sDcN
IxSCUneCEWrHNXmJHKwmZ2uJ9cTLGgVLDiBaKJeyRzcT/VjXDQmRbBm8QJROO6Vs
1VWPVxuLLcB6A6knNkGywoRjHjvNU1IZrELaAJNN2fAgLl8BGwKvPcX9r01QQw9/
ksxdMjG74hQ=
=WjMs
-----END PGP SIGNATURE-----

Tim McNamara

LioNiNoiL_a t_NetscapE_D 0 T_NeT <accountname.above@netscape.net> writes:

>> Breaking spokes is pretty much a symptom of a wheel that wasn't
>> built right. The maximum load on a spoke is when the bike is empty.
>
> The maximum load on a spoke is when you hit a pothole coming
> downhill with the brake applied.

What's the pothole got to do with it?

LioNiNoiL_a t_NetscapE_D 0 T_NeT

Tim asked:

>> The maximum load on a spoke is when you hit a pothole
>> coming downhill with the brake applied.
>
> What's the pothole got to do with it?

Mashing a pothole at speed dynamically loads the spokes greatly above
any static load on them.

Tim McNamara

LioNiNoiL_a t_NetscapE_D 0 T_NeT <accountname.above@netscape.net> writes:

> Tim asked:
>
>>> The maximum load on a spoke is when you hit a pothole coming
>>> downhill with the brake applied.
>
>> What's the pothole got to do with it?
>
> Mashing a pothole at speed dynamically loads the spokes greatly
> above any static load on them.

How does that happen? Which spokes see an increase in tension? Where
is the load affected zone of the rim? What is the effect of the load
affected zone on spoke length and tension? Do you actually understand
how a wheel supports a load?

jobst.brandt@stanfordalumni.org

Mr Cryptic writes:

>> Breaking spokes is pretty much a symptom of a wheel that wasn't
>> built right. The maximum load on a spoke is when the bike is
>> empty.

> The maximum load on a spoke is when you hit a pothole coming
> downhill with the brake applied. Spoke breakage is not entirely
> preventable, but a well-built pair of tandem wheels will go a long
> way for a strong, heavy rider. Rinsing the salt off the wheels in
> icy climates after every ride will help forestall corrosion, but
> corrosion is virtually inevitable where the roads are salted. Plan
> on replacement.

Let's not try to turn back the clock into the dark ages of wheel
building. The greatest load on a spoke is when the wheel is idly
standing there with no load on it. When applying rim brakes that
value rises slightly but not significantly. Shock loads only slacken
spokes in the ground contact zone.

Where have you seen stainless spokes corrode on salted roads. I spent
much time riding on such roads and still have the wheels, non of which
has the slightest corrosion on their spokes or spoke nipples.

Jobst Brandt
jobst.brandt@stanfordalumni.org

LioNiNoiL_a t_NetscapE_D 0 T_NeT

Tim wants to know:

> Do you actually understand how a wheel supports a load?

Do you actually understand the concepts of inertia, momentum, and force?

LioNiNoiL_a t_NetscapE_D 0 T_NeT

> Shock loads only slacken spokes in the ground contact zone.

Inertial shock loads are different from static loads. Strain is
propagated through a rigid structure subject to inertial shock, and is
not localised as it can be with static load.

jobst.brandt@stanfordalumni.org

LioNiNoiL_a t_NetscapE_D 0 T_NeT (aka Condoleza Rice) writes:

>> Do you actually understand how a wheel supports a load?

> Do you actually understand the concepts of inertia, momentum, and force?

Hey, that's the way Dr. Rice answers questions. Are you sure you
aren't one and the same. The silly code name looks like it...
national security at all times! If you don't know the answer just say
so.

Jobst Brandt
jobst.brandt@stanfordalumni.org

jobst.brandt@stanfordalumni.org

LioNiNoiL_a t_NetscapE_D 0 T_NeT (aka anonymous) snipes:

>> Shock loads only slacken spokes in the ground contact zone.

> Inertial shock loads are different from static loads. Strain is
> propagated through a rigid structure subject to inertial shock, and
> is not localised as it can be with static load.

Oh! Please explain how this is so and why it is different from static
loads. At what rate of change, input through an inflated rubber tire
does strain start propagating through a "rigid" structure differently
from static strain?

As I said, let's not go back into the dark ages of wheelbuilding.
Maybe we do need Mr. anonymous's Bicycling Physics to explain that a
bicycle is the same as other machines and follows the same stress
versus strain relationships. If this were better understood fewer
bicycles at the +$5000 range would be sold. All the "space age"
materials cannot change the mechanics of the beast. It's the rider
that is weak in the knees and head.

Jobst Brandt
jobst.brandt@stanfordalumni.org

carlfogel

Lioninoil_a T_n wrote:
> > Shock loads only slacken spokes in the ground contact zone.
> Inertial shock loads are different from static loads. Strain is
> propagated through a rigid structure subject to inertial shock, and is
> not localised as it can be with static load.



Dear L.,

Everyone else seems to know the answers, but I'm just curious.

As I understand it, a pre-tensioned bicycle wheel works by its lowermost
spokes losing tension under load from the axle, a sneaky trick that
means that more tension is better than less tension (more tension to
lose before going slack).

Of course, if a wheel under a rider slams into a nasty enough pothole at
a high enough speed, the rim presumably collapses and all bets are off.

But you seem to be talking about something else, something that I'm not
following about impacts.

I doubt that it's anything to do with speed per se, since the fleeting
loss of tension occurs smoothly at high speeds.

Can you go through what you have in mind?

Thanks,

Carl Fogel



--

Tim McNamara

LioNiNoiL_a t_NetscapE_D 0 T_NeT <accountname.above@netscape.net> writes:

> Tim wants to know:
>
>> Do you actually understand how a wheel supports a load?
>
> Do you actually understand the concepts of inertia, momentum, and
> force?

Yes. And I also understand how a wheel supports a load. I notice
that you are dodging the questions I asked, conveniently snipping
them out in hopes that they will be forgotten. You've presented a
hypothesis, now back it up or shut up.