On Jan 23, 2009, at 12:31 PM, Ed Barkmeyer wrote: (01)
> Matthew West wrote:
>
>>> This is a slight generalization of Matt's characterization, in
>>> that it
>>> recognizes the existence of parts with subfunctions, without
>>> requiring
>>> substitutability
>>
>> MW: Can you give an example of a system with parts that were not
>> substitutable?
>
> I mentioned in fact that good systems engineering gives rise to
> subsitutability by encapsulating the mechanisms used by a subsystem
> and
> defining only their functions, interfaces, and constraints.
>
> There are many examples, particularly in civil engineering, of systems
> with parts that are not substitutable, precisely because the
> engineered
> system was conceived as "one-off". (02)
A classical example might be the wooden frames of farm buildings, the
timbers of which were individually numbered precisely because they
were not interchangeable. Japanese temple construction followed the
same practice for centuries. (03)
> The analog is 16th-18th century
> European manufacturing, in which all parts were hand-made and
> hand-fitted. (I think Eli Whitney is credited with developing the
> 'standard parts' concept for his machines. (04)
It seems to have occurred to a number of people around the same time.
Eli Terry revolutionized clock-making and the Springfield rifle did
the same for firearms, and a little later in the UK, I.K. Brunel did
the same for boat manufacturing. In each case, the critical advance
was mechanical uniformity and precision in manufacturing resulting in
intersubstitutable 'standard' parts. BTW, the industrial revolution
was brought about by steam power, which was made possible only by
there being machine tools which could make metal components with an
unprecedented degree of precision. There is a wonderful book about all
this history: Tools for the Job: A Short History of Machine Tools By
L. T. C. Rolt, 1965. (05)
PatH (06)
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