[AT] Transmission oil, 90-wt? Now: drawings

[Larry D. Goss]

It's a little bit more fundamental than that, John.  The coordinated
standards committees outlawed fractional tolerances, and in later
modifications they eliminated "sheet tolerances" altogether. That also
meant that implied tolerances were no longer allowed.  As a result, you
have to specify the tolerance on every dimension on a part and you have
to adhere to a hierarchy of tolerances based on guaranteeing
interchangeability of parts.  My students used to think that if a little
tolerancing is good, a lot ought to be better.  So they would specify
everything to four-place decimals without realizing that they had just
increased the production costs of the part by an order of magnitude or
two (10 to 100 times the original cost) if it had a larger tolerance.

The change isn't all bad.  With the proper application of linear
tolerances, geometric tolerances, and statistical process control, we're
seeing product life of engines, transmissions, and other major
assemblies that far exceeds anything we could have reasonably expected
50 years ago.  Remember when Ford and Studebaker engines were basically
worn out at forty or fifty thousand miles?  Now, it's not uncommon for
an engine to go for over 200,000 miles without an overhaul and
six-figure warrantees are fairly common.

I must admit to being an advocate for getting rid of dimensioned
drawings, John.  It became obvious to me when I was doing computer
graphics for a large supplier to the AEC in 1969 that the real data
resided in the computer program, not in the drawing.  It took 20 years
for industries and standards organizations as a whole to recognize that,
but in 1989 the unified professional societies made it official -- a
drawing is no longer required of a part before it is manufactured, and
the electronic database can be approved by a licensed engineer.

But I too enjoy the look and feel of the old drawings.  They are an art
form.  Just this week, I went through a closet full of materials that I
used to treat with reverence, but that now has no utility -- a roll of
tracing cloth from the Korean War era, a roll of drafting film, a roll
of tracing vellum.  Bear and H. L. Staples stopped by on their way to
Portland five years ago and I shipped all my drafting materials off with
them -- thousands of dollars-worth of tools and equipment that was
absolutely essential for engineering in a by-gone era but that now is
archaic.  I have never shed a tear over letting go of it all, but like
you, I still appreciate and value some prints of farm equipment from now
defunct manufacturers.

Larry

-----Original Message-----
From: at-bounces at lists.antique-tractor.com
[mailto:at-bounces at lists.antique-tractor.com] On Behalf Of John Hall
Sent: Tuesday, September 05, 2006 5:17 PM
To: Antique tractor email discussion group
Subject: Re: [AT] Transmission oil, 90-wt?

I remember back in the '70's when they gave all the teachers kits with
wood 
blocks painted different colors so they teach us kids the metric system.

Funny, maybe they should have taught us math first!!!

We rarely see drawings in fractions any longer. I think the reason they 
disappeared is the tolerances are pretty much too loose. I forgot about 
dealing with metric surface finishes. The one that blew my mind is the
third 
type of surface finish--ISO I think. First time we saw it (and there
have 
only been a few) it took our customer about a half a day to tell us what
it 
was supposed to be. They finally suppled me with a nice conversion chart
for 
the 3 methods.

To get this post tractor related, WHS supplied me with several drawings
for 
my Titan 10-20. It was definetly different looking at all those 80+ yr
old 
prints. Normally we don't see prints over 10 years old and most are cad 
drawings--although not very good ones!!

John Hall
----- Original Message ----- 
From: "Larry D. Goss" <rlgoss at evansville.net>
To: "'Antique tractor email discussion group'" 
<at at lists.antique-tractor.com>
Sent: Monday, September 04, 2006 8:44 PM
Subject: RE: [AT] Transmission oil, 90-wt?


> Back in 1975 when we were "supposed" to make a concentrated effort to
> convert to metric measurements, I gave my college freshmen a test that
> covered both the US customary units and the ISO metric.  Guess what!
> They didn't have a clue about either one of them.  So I figured they
> needed to learn at least one and I tried to teach some fundamental ISO
> measurements for the next 20 years or so.  It was an exercise in
> futility.  What really muddied the waters was when we started working
> with the decimal inch system (standard everywhere except at Home Depot
> and Lowes).  I finally ended up letting the students work with either
> the ISO or the decimal inch.  Those students who insisted on working
> with the fractional inch system abandoned it within a matter of
minutes
> when they found that no computer system supported it as a default mode
> of operation.
>
> Bottom line: students know more about how to text message each other
> than they will ever learn about any measurement system.
>
> Larry
> 

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