
When mechanical analog computers ruled the waves (2014) - tosh
https://arstechnica.com/information-technology/2014/03/gears-of-war-when-mechanical-analog-computers-ruled-the-waves/
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klodolph
> When assembled precisely, analog computers can be much more accurate than
> digital computers on these types of questions.

Stopped reading here... whoever wrote the article is missing some critical
pieces of the theory of how computers work or what computers are, as well as
some basic understanding of how materials work. Mechanical computers are made
with parts that have some finite tolerance in their manufacture as well as
some measurable amount of flexibility in their parts and connections.
Increasing the accuracy of analog computers requires developing new
manufacturing techniques to reduce this error. On the other hand, making a
digital computer more accurate just requires some extra memory and CPU time.

These analog machines are beautiful computers... but they are not more
accurate than digital computers.

~~~
pavel_lishin
Maybe they meant contemporary digital computers?

Although you're right, the claim that

> _Because they use physical rather than digital inputs and outputs, they can
> represent curves and other geometric elements of calculations with an
> infinite level of resolution_

is obviously bullshit, although the article does point this out:

> _(though the precision of those calculations is based on how well their
> parts are machined, and loss from friction and slippage)._

~~~
klodolph
This is just a really roundabout way of not saying anything at all. "Analog
computers can have infinite resolution, except for the fact that this is
physically impossible." I could just as easily say, "I am a millionaire,
except for the fact that I do not have that much money," or "My house is red,
except for the fact that it is actually green, and no part is actually red,
and I do not even have a house."

~~~
cix_pkez
While I found your comment funny, I could stand to be a bit more charitable. I
think it's an interesting side point they're trying to make about analog
computation, but to be accurate should maybe be written more like "A
theoretical perfectly-machined set of gears could perform calculations to
infinite precision."

~~~
klodolph
I don't know how to be charitable here, the side note is completely wrong, and
I'm not sure what interesting point could be made here.

A theoretical perfectly-machined set of gears is a mathematical construction,
not a physical construction. It seems reasonable to me that a mathematical
construction could have infinite precision, but it is obvious that a physical
device has limited precision. An analog computer is a physical device. We
might as well pretend that a digital computer has infinite RAM and an
infinitely fast CPU, if we are in the business of assuming that an analogue
computer is infinitely precise.

In general you can make many of the same engineering tradeoffs with simple
analogue computers. A cam wheel can encode a function, and by adjusting the
size, manufacturing tolerances, and materials you can control the amount of
error that the cam wheel gives you when calculating the function. Similarly,
with a digital computer you can adjust the number of digits used to represent
numbers, the size of lookup tables, the number of iteration for iterative
methods, etc. and control the amount of precision a digital computer provides.

~~~
cix_pkez
I mean, you could definitely convince me that it's not an aside worth
including in the article for the sake of staying on point.

I'll still take Ars at its worst over most general news sites' tech reporting
at its best.

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boomlinde
The whole training film on mechanical computers, for navy mechanics I believe:
[https://www.youtube.com/watch?v=s1i-dnAH9Y4](https://www.youtube.com/watch?v=s1i-dnAH9Y4)

It illustrates the problems and solutions near perfectly, and I've watched it
way too many times.

~~~
nick_m
Thanks, being a long-time lurker, I've just signed up now to say that's great.
What a video - I've been writing software for the past 31 years, and I love
the simplicity among ingenuity of this. If you've not read it already, you
might like
[http://www.mayofamily.com/RLM/txt_Clarke_Superiority.html](http://www.mayofamily.com/RLM/txt_Clarke_Superiority.html)

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Bjartr
I did not see any link to the full training video[0] the clips in this article
were taken from. I highly recommend it. It's a fascinating trip into
engineering, computing, and the past.

[0]
[https://www.youtube.com/watch?v=s1i-dnAH9Y4](https://www.youtube.com/watch?v=s1i-dnAH9Y4)

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dang
Two previous discussions:

[https://news.ycombinator.com/item?id=11460672](https://news.ycombinator.com/item?id=11460672)

[https://news.ycombinator.com/item?id=7419837](https://news.ycombinator.com/item?id=7419837)

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stcredzero
The XC-142 tilt wing VTOL airplane, basically the 60's version of the V-22
Osprey, used an analog computer to mix the control continuously outputs
between vertical wing mode and horizontal. (For example, differential thrust
means roll in vertical mode, but yaw in horizontal mode, whereas ailerons go
from roll in horizontal mode to yaw in vertical.)

[https://en.wikipedia.org/wiki/LTV_XC-142](https://en.wikipedia.org/wiki/LTV_XC-142)

I am even more impressed by this, having implemented the control mixing for a
model XC-142 on a microprocessor.

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Animats
This equipment in use: [1]

[1]
[https://archive.org/details/0436_Radar_Secrets_01_20_16_00](https://archive.org/details/0436_Radar_Secrets_01_20_16_00)

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vmh1928
Imagine if self-driving cars used an analog mechanical computer such as these.
"bicycle bearing one niner zero at 1.5 knots, intercept in .0025 seconds...."

