David Martin wrote:
> On 20/12/04 1:27 pm, in article [email protected],
> "JLB" <[email protected]> wrote:
>
>
>>David Martin wrote:
>>
>>>On 19/12/04 10:14 pm, in article [email protected],
>>>"JLB" <[email protected]> wrote:
>>
>>[snip]
>>
>>>>This started with a discussion of chain wear. If the wear is
>>>>significant, it must also be true that the load is significant, because
>>>>the wear occurs proportionately with the load (see my other post of this
>>>>evening for more on that).
>>>
>>>
>>>Only under fixed conditions. Wear, as you describe, is proportional to load.
>>>Is it significant in the real world?
>>
>>It has to be. So long as the wear is significant, and it is apparent
>>that as the origin of this discussion it is significant in this context,
>> it is inescapable that the load is significant. The consequence of
>>insignificant load, in this context, would be insignificant wear; that
>>creates a contradiction; the conclusion is that the load is significant.
>
>
> The opposite of significant is 'not significant' not insignificant.
There is no difference. That which lacks significance is insignificant.
>
>
>>>How much does mean load vary in a bike chain? I'd guess it would be about
>>>one order of magnitude, possibly as little as a factor of two or three if
>>>one restricts activity to a specific subset of cyclists.
>>
>>Posssible, but we've gone around this way already, and it is not
>>relevant to determining if load is significant. It addresses an entirely
>>different matter: how much does load vary?
>
>
> If load doesn't vary much then it is 'not significant' with respect to a
> discussion of how fast chains wear, being essentially treatable as a fixed
> constant.
Why are you refusing to see this very simple point? The load is not the
same as the variability or range of the load. The load is significant.
You can, if you wish, treat the load as a constant; the load is still
significant, although you have decided its variation is nil. That would
make its variation insignificant, but its variation is not the load
itself. The load is significant because without it there is no wear. Fix
the load at a different value and you get different wear, although the
variation in load will be no more significant than before.
>
>
>>>How do the other environmental factors change? Potentially several orders of
>>>magnitude, and we know that dirt has a disproportionate effect on wear,
>>>depending on particle size, hardness, and concentration.
>>>
>>>So empirically, one would observe that there is a proportional relationship
>>>between load and wear, but this is not significant in the general context of
>>>environmental factors.
>>
>>Wrong again. It is inescapably significant. You are confusing the load
>>with the range of values of the load. So long as wear is taking place,
>>the load, whatever value might be measured for it, is significant
>>because it is one of the key factors that creates that wear.
>
>
> Bzzt. You mean necessary, not significant. We have been there before. Maybe
> I should just run
>
> sed -e 's/significant/necessary/g' on your posts and then I would be
> entirely in agreement.
Whatever floats your boat, but you will not escape the inevitable
physical reality that the load is significant.
>
>>>>I will now wave my big dic at you.
>>>>
>>>>Chambers 20th Century Dictionary, New Edition, 1983.
>>>>
>>>>*significant* /adj/ having a meaning: full of meaning: important, worthy
>>>>of consideration: indicative.
>>>
>>>
>>>Ooh.. let's take these one at a time.
>>>
>>>having a meaning: Nope can't see load per se as having any kind of meaning.
>>>full of meaning: Likewise.
>>
>>Another attempt at taking the ****? Your ignorance does not undermine my
>>knowledge.
>>
>>Load in this context is related to stress. It is the normal force
>>applied to the bearing surface, divided by the area. It has the same
>>units as pressure. It can be calculated from direct measurements of
>>physical properties.
>
>
> Indeed.
Well that was easy. In your last post load did not have any kind of
meaning. Now with one short word you surrender that entire position.
Air pressure can also be calculated. Air will also wear away your
> bike chain, albeit slowly. Is it significant? No. Does it occur when you
> cycle? of necessity, yes.
On the contrary: it would be possible, though pointless except perhaps
to you, to demonstrate wear in vacuo. Your proposed air effect is
neither necessary nor significant. Instead of fantasising about
irrelevances, why don't you address the point with a new rather than
discredited argument? Load is significant to the rate of wear.
>
>
>>>Inportant, worthy of consideration: If you are designing bike chains then
>>>yes. If you are just using your bike then no. Not significant. You can't
>>>change the load that goes on the bike by anything like a wide enough range
>>>*under normal cycling conditions* to make any significant difference.
>>
>>You are still confusing the range of values with the load itself. The
>>load is significant so long as the wear is significant.
>
>
> And if the wear is insignificant compared to the rest of the bike? I can
> easily envisage situations where the same load is applied to two bikes (that
> may use the same design of chain) and one wears out rapidly and the other
> doesn't wear out in the lifespan of the bike (identical lifespans assumed).
> Is load then significant?
Yes. Obviously. One might say its *blindingly* *obvious*.
>
>
>>>indicative: Here we look for correlation. given that the variation in
>>>environmetn dwarfs that in load, any correlation between load and wear will
>>>be extremely poor (at apopulation level). Load would then not be indicative
>>>of chain wear.
>>
>>On the contrary, the correlation will be good. At all times the load
>>will correlate with the wear; variation in the load will be reflected in
>>variation of wear.
>
>
> Now you have me laughing. Across a population of bikes used in a variety of
> conditions, plot chain wear vs load. My strong suspicion (based purely on
> anecdotal data as I haven't done a suitable field sampling) will be that the
> correlation is very poor because the other factors involved are far more
> significant.
>
> If you took a very restricted set of environmental conditions, then the load
> would correlate well.
Once enough was known about all the significant variables, the
relationship of any two would be easy to demonstrate. Difficulty of
measuring, or the presence of other variables, is not the issue.
>
>
>>>
>>>OK, got any more definitions to cite?
>>>
>>
>>I think it's your turn.
>>
>>>>I see no contradiction at all between my use of the word and its
>>>>definition. What definition are you following?
>>>
>>>Same ones, just applying them to a population level rather than a laboratory
>>>level.
>>
>>Perhaps I should have asked earlier and saved some time, but what colour
>>is the sky on your planet?
>
>
> Currently grey though it was blackish last night and blue first thing this
> morning.
>
> And now in the real world:
>
> Is load in itself a good predictor of chain wear?
This is not and never was the issue. The point here is whether the load
is significant. In this world, with a usual understanding of English and
a competent knowledge of engineering, it certainly is.
> Are there better predictors of chain wear?
This is not relevant. This concerns whether load is significant.
>
> If it cannot predict then it is not significant. It may be necessary but is
> not significant.
It certainly does predict. If you control or vary the load (including
fixing the load at one value) the consequence for wear is entirely
predictable.
A while ago you thought this was *blindingly* *obvious*. You don't have
much concern for consistency, do you?
>
> If you take my particular case, load is an inverse correlator to chain wear.
> My MTB is my main commuter bike and I wear chains out faster than my road
> bike. I put much greater loads into the road bike and a much higher mileage.
As you have already pointed out, without accounting for other variables
no such conclusion can be drawn. However, it indicates you can vary the
load, something you seem reluctant elsewhere to acknowledge. What do
think would happen if you varied the load by a factor of 2 on one of
those bikes, but otherwise left things the same?
--
Joe * If I cannot be free I'll be cheap