MA3 rim failure, where to now

On Fri, 10 Oct 2003, PK wrote:
Ian Smith wrote:
On Thu, 9 Oct, Martin Jervis wrote:

Let me explain the flaw in the logic of the standers argument by
looking again at the spoke forces. Say all the spokes are stressed
to a force level of 100. If we just consider a 4 spoke wheel

As has been stated over and over again, considering the behaviour of
wheels that aren't bicycle wheels does not necesarily give you any
insight into teh behaviour of bicycle wheels.

Ian, take a moment to re-read what you wrote and reflect upon it.

Don't be patronmising. I know what I wrote, and it remains true.

Workable bicycle wheels are but a subset of a much wider set of Wheels,
considering the properties of the wider set (Yes, even Naomi's rubber band
wheel) does exactly what you claim it doesn't. It gives you insight into the
real physics and engineering rather than the narrow sub-set of phenomena you
observe in the special case of the workable bicycle wheel.

Nonsense. It gives you an insight into the bahviour of wheels that
don't behave like bicycle wheels. You're welcome to think about them
if you want, but the conclusions reached don't usefully translate into
insights aboutthe behaviour of bicycle wheels. The question is not
"how doe all wheels work", nor even "do most wheels stand or hang", it
was (and is) "do bicycle wheels hang or stand on their spokes.

Example, there is no _fundamental_ difference between a very elastic spoke
and a real wire spoke.

Indeed, and I have never claimed otherwise, but there ARE
fundamentally different behavious in wheels depending upon whether you
have very elastic spokes and near rigid rims or vice-versa, or some
intermediate case.

Similarly, there is no essential difference between a rigid rim and a real
flexible rim

Not of itself (assuming that be 'rigid' you mean 'near rigid'), but
there is in teh behaviour of the wheel. One distributes the load
evenly round the spokes, and teh other doesn't. The one that really
exists in real bicycle wheel sin teh real world doesn't distribute
load evenly round all teh spokes.

variable rim rigidity. There is no step change threshold of rigidity at
which the physics changes, it varies continuously.

Indeed, and at anything approaching real bicycle wheel component
rigidities, it behaves as decribed, with teh resisting action
concentrated in the lower spokes.

I really do think you would be wise to step back and stop defending for a
moment and revisit the basic physics/engineering and look at the problem
anew without delving into the esoterics of FEA, which are after all just a
mathematical tool to solve difficult problems.

I'm still waiting to know:

1: How you elongate your wire in teh latest 'explanation' without the
tension changing.

2: Why you think the 'rigid rim' case gives you a useful insight into
wheel behaviour but the 'rigid spokes' case doesn't.

3: What conclusion you got from your last bounding box thought
experiment (the strange tensions / infinite acceleration one).

I think you would be wise to get your basic physics right before
lecturing other people on teh topic. I really am interested in teh
answers to those questiosn, you know. Please do answer.

regards, Ian SMith
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On Fri, 10 Oct 2003, PK wrote:
Ian Smith wrote:
On Thu, 9 Oct, Martin Jervis wrote:

Let me explain the flaw in the logic of the standers argument by
looking again at the spoke forces. Say all the spokes are stressed
to a force level of 100. If we just consider a 4 spoke wheel

As has been stated over and over again, considering the behaviour of
wheels that aren't bicycle wheels does not necesarily give you any
insight into teh behaviour of bicycle wheels.

Ian, take a moment to re-read what you wrote and reflect upon it.

Don't be patronmising. I know what I wrote, and it remains true.

Workable bicycle wheels are but a subset of a much wider set of Wheels,
considering the properties of the wider set (Yes, even Naomi's rubber band
wheel) does exactly what you claim it doesn't. It gives you insight into the
real physics and engineering rather than the narrow sub-set of phenomena you
observe in the special case of the workable bicycle wheel.

Nonsense. It gives you an insight into the bahviour of wheels that
don't behave like bicycle wheels. You're welcome to think about them
if you want, but the conclusions reached don't usefully translate into
insights aboutthe behaviour of bicycle wheels. The question is not
"how doe all wheels work", nor even "do most wheels stand or hang", it
was (and is) "do bicycle wheels hang or stand on their spokes.

Example, there is no _fundamental_ difference between a very elastic spoke
and a real wire spoke.

Indeed, and I have never claimed otherwise, but there ARE
fundamentally different behavious in wheels depending upon whether you
have very elastic spokes and near rigid rims or vice-versa, or some
intermediate case.

Similarly, there is no essential difference between a rigid rim and a real
flexible rim

Not of itself (assuming that be 'rigid' you mean 'near rigid'), but
there is in teh behaviour of the wheel. One distributes the load
evenly round the spokes, and teh other doesn't. The one that really
exists in real bicycle wheel sin teh real world doesn't distribute
load evenly round all teh spokes.

variable rim rigidity. There is no step change threshold of rigidity at
which the physics changes, it varies continuously.

Indeed, and at anything approaching real bicycle wheel component
rigidities, it behaves as decribed, with teh resisting action
concentrated in the lower spokes.

I really do think you would be wise to step back and stop defending for a
moment and revisit the basic physics/engineering and look at the problem
anew without delving into the esoterics of FEA, which are after all just a
mathematical tool to solve difficult problems.

I'm still waiting to know:

1: How you elongate your wire in teh latest 'explanation' without the
tension changing.

2: Why you think the 'rigid rim' case gives you a useful insight into
wheel behaviour but the 'rigid spokes' case doesn't.

3: What conclusion you got from your last bounding box thought
experiment (the strange tensions / infinite acceleration one).

I think you would be wise to get your basic physics right before
lecturing other people on teh topic. I really am interested in teh
answers to those questiosn, you know. Please do answer.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|