[TheForge] Bedtime reading

[Andrew Vida]

David E. Smucker wrote:
> Andy,
> Think about the friction a bit.  Start with just "simple" flat rolling 
> (not shapes). On one side of the roll bit we have the thicker entry 
> metal going at a "slow" speed, we have the roll surface turning at 
> another speed, called "medium" and we have the exit thin material moving 
> at a third speed "fast".

	Ah, yes I see what you're talking about.  It would seem, at a very 
superficial glance, that the traction point would be at the poiace where 
the speeds were equal, which I would imagine as a line comtact 9in 
theory) similar to that of a railway wheel and rail.  But all that 
constantacceleration along the surface of the roll...

 >  All of the energy from the moving roll has to
> be transferred to the metal by the friction between the roll and the 
> metal with a film of lubrication between the surface of the roll and the 
> surface of the metal.  The pressures are very high and the type of 
> lubrication vary dependent on speed, film strength of lubrication, 
> temperature, viscosity of lubricate etc. etc.  Way over my head at this 
> point, like I said I was an equipment guy, but I could run the models to 
> find pass schedules, required horsepower, separating force, metal 
> temperature etc. etc.

	Does this modeling difficulty also exist for hot rolling?  I would also 
imagine it would be the case for drawing wire as well, no?

	Fluid shear phenomena is amazing stuff.  I studied this extensively 
when I was designing infinitely variable power transmissions for 
bicycles back when I was 20 years old.  I was a fixture at the 
Engineering Societies Library in those days... even worked there for a 
while.  There was a British automobile, the Hilliard  or Hillman as I 
recall, that had an infinitely variable transmission whose rolling 
surfaces employed a fluid shear traction mechanism.  Those cars were 
produced in the 1940s or 50s as I recall.  Examination of transmissions 
with over 200K miles on them showed ZERO measurable wear.  That is how 
powerful thin fluid films are.  Amazing.

I find it amusing that some car manufacturers are now offering variable 
trannys and hyping them on their commercials as if they'd invented them. 
  Seems they are using split sheave type transmissions.  I don't get it, 
they are so complex compared to using toroids.

> Dave Smucker
> ----- Original Message ----- From: "Andrew Vida" <osan at netlabs.net>
> To: "Sponsored by ABANA" <theforge at mailman.qth.net>
> Sent: Saturday, February 12, 2005 8:33 PM
> Subject: Re: [TheForge] Bedtime reading
> 
> 
>>
>>
>> David E. Smucker wrote:
>>
>>> Andy,  Just my point -- what used to be an "art" and the use of 
>>> "experience based rules of thumb" is today being handle by computer 
>>> models of the process.
>>
>>
>> Ah, I was being thick.  I completely agree, but computerization isn't 
>> all bad.  It does open avenues of technology that would otherwise be 
>> impossible to traverse.  It's not the technology per se that disturbs 
>> me, but rather the context in which it is used.  Were people sane on 
>> the whole and were we as a race not sucking every last bit of life out 
>> of this world, the technology would not be bothersome.  But it is 
>> being used as a lever to perpetuate insane ways of living.  OTOH, were 
>> we living in a manner more consistent with my own definitions of 
>> sanity, perhaps we would not covet all this high technology.  Perhaps 
>> doing things the "old fashioned way" would hold greater appeal on the 
>> broad basis.  I don't know.
>>
>> > Development of these models has been very active
>>
>>> since the early 1970's and they have gotten better and better.  Many 
>>> of the models have been very closely held "trade secrets" for 
>>> sometime by various companies.  This is true of not just rolling both 
>>> shape and flat rolling but also close die forging.  One of the areas 
>>> that remains the hardest to model is the friction between the metal 
>>> and rolls or dies.  In many cases models still depend on experience 
>>> based data models for the friction factors.
>>
>>
>> Really?  I'm not in the mode to think about this right now... or maybe 
>> I'm just clueless.  Do you know what the difficulties are with 
>> modeling roll friction?  That it would be a significant problem is not 
>> immediuately apparent to me.  Then again, I've never really thought 
>> about it.
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-- 


	-Andy V.

Trust I seek, and find in you
Everyday for us something new
Open mind for a different view
And nothing else matters