Bike adjustments

David Scheidt writes:

Mark J. wrote:
:On 12/13/2019 8:34 AM, Frank Krygowski wrote:
: On 12/13/2019 11:01 AM, Radey Shouman wrote:
: John B. writes:
:
:
: I remember a story that at Wright-Patterson AFB (one of the
: development bases) they had a 10 foot long slide rule in a temperature
: controlled room for doing really accurate calculations I don't know
: whether that is true, however it does sound possible.
:
: That sounds like a tall tale to me.
:
: ISTR hearing of oversized slide rules being used for additional
: accuracy. But I never heard they were in a temperature controlled room,
: and I doubt they would need that. The relevant parts would expand or
: contract at the same rate.
:
: Even back in the thirties heavy
: computations were done digitally by rooms full of "computers", many of
: them mathematically inclined women, using ten key adding machines and
: passing slips of paper to one another.Â* Richard Feynman describes this
: kind of work during the Manhattan project.
:
: The excellent movie _Hidden Figures_ covered that in great detail.
:
: There were other shortcut computation methods before calculators and
: computers became so cheap.Â* Graphs for actual lookup were popular.Â* You
: could buy graph paper at a technical book store with half a dozen
: variations on the scales: log-log, semi-log, probability ...
:
: :-) And I still have - somewhere! - my stock of at least a dozen types
: of graph paper. (Not that a retiree has much use for them...)Â*Â* But I
: did appreciate an unusual Christmas gift: Graph paper sticky notes.
:
: Building nomograms was a useful art, and using them a basic skill.Â* In
: the chem lab, functions were integrated by cutting them out in filter
: paper and weighing them on the analytical balance.Â* Every field had its
: set of graphical methods for calculation, from the really graphical,
: like lofting plans for ships or planes, to the more mathematical, like
: designing distillation columns.
:
: I wonder how many people here have used a planimeter?
: https://en.wikipedia.org/wiki/Planimeter
: An analog one with a vernier scale?

:I've used a planimeter, but I think it was just for demonstration in a
:teaching situation. It was a nice "Made in West Germany" model - which
:attests to both its quality and its age. As an undergrad I had to do an
:exercise deriving the theoretical basis for a planimeter's operation,
:but I never saw one until years later, when it was essentially obsolete.

I've used one in the last decade. Except it wasn't the sort of
mechanical device you're thinking of it. it was a rather large pen
thing, that you pushed a button, and then traced your object of
interest. After you were done you pushed the button (or maybe another
one). it then told you the perimeter and area of the shape you'd
traced, both the atual values, but also according to the scale you'd
told it. It belonged to an interior designer, she used it to make
material estimates from drawings done at the client's site. In the
office the cad software did all that for her/ I think ti stored the
data so you could import the traced shapes into the cad system later.

Years ago I wrote a program to convert polygon data collected by hand on
a digitizer tablet to area and arclength. Surprisingly simple with the
help of Dr. Green. Never used a real mechanical planimiter.