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On Wednesday, 14 March 2018 19:30:12 UTC, Gareth's Downstairs Computer  wrote:
> We certainly covered the principles in my
> electronics degree ('69 - '72), but AIUI
> there was a pre-war mechanical analogue
> computer made with the Meccano erector set.

Yes, indeed.  One unit of it was on display 
in the South Kensington Science Museum the 
last time I was there.  There's a picture 
of it on pp. 60-61 of Christopher Evans' 
splendid book "The Making of the Micro".

On 14/03/2018 19:29, Gareth's Downstairs Computer wrote:
> We certainly covered the principles in my
> electronics degree ('69 - '72), but AIUI
> there was a pre-war mechanical analogue
> computer made with the Meccano erector set.

Also covered in my degree in the Control theory modules, it was easier 
to use the analogue computer to simulate control systems than try to 
simulate it on the PCs of the time.
Our analogue computer was a shiny steel table with various 
electromechanical doodahs* on magnetic bases. We stuck them down. 
connected them up with string, rods, cables and belts and tried to make 
sense of all the calculus and control equations we worked out theoretically.
Legend has it that somewhere in the mists of time somebody actually 
managed to get it to make sense.

*Genuine technical term by the way


Andy

On Thu, 15 Mar 2018 07:38:37 +0000, AndyW <An...@nojunqmail.com> wrote:

>On 14/03/2018 19:29, Gareth's Downstairs Computer wrote:
>> We certainly covered the principles in my
>> electronics degree ('69 - '72), but AIUI
>> there was a pre-war mechanical analogue
>> computer made with the Meccano erector set.
>
>Also covered in my degree in the Control theory modules, it was easier 
>to use the analogue computer to simulate control systems than try to 
>simulate it on the PCs of the time.
>Our analogue computer was a shiny steel table with various 
>electromechanical doodahs* on magnetic bases. We stuck them down. 
>connected them up with string, rods, cables and belts and tried to make 
>sense of all the calculus and control equations we worked out theoretically.
>Legend has it that somewhere in the mists of time somebody actually 
>managed to get it to make sense.

I took that course a few years later and we had an electronic analog
computer, from TI IIRC.  It was kind of fun but by the time I got my
first engineering job digital was "in" and just suggesting the use of
analog anything marked one as some kind of reactionary, at least in
the place I worked.
>
>*Genuine technical term by the way
>
>
>Andy

On Thu, 15 Mar 2018 07:09:07 -0400
J. Clarke <jclarke...@gmail.com> wrote:

> I took that course a few years later and we had an electronic analog
> computer, from TI IIRC.  It was kind of fun but by the time I got my
> first engineering job digital was "in" and just suggesting the use of
> analog anything marked one as some kind of reactionary, at least in
> the place I worked.

	Makes sense, once a digital computer is fast enough to solve a
given problem it will do a more repeatable and reliable job than an
analogue computer.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/

Ahem A Rivet's Shot wrote:

> On Thu, 15 Mar 2018 07:09:07 -0400
> J. Clarke <jclarke...@gmail.com> wrote:
> 
>> I took that course a few years later and we had an electronic analog
>> computer, from TI IIRC.  It was kind of fun but by the time I got my
>> first engineering job digital was "in" and just suggesting the use of
>> analog anything marked one as some kind of reactionary, at least in
>> the place I worked.
> 
> Makes sense, once a digital computer is fast enough to solve a
> given problem it will do a more repeatable and reliable job than an
> analogue computer.
> 
Well, there's two kinds of analog computing.  For solving problems in an 
analytical way, digital has the HUGE advantage that you get the same answer 
every time, and debugging and documenting what you did is easy.

However, once the IC op-amp came out, analog computing for production 
control systems got a huge boost.  Today (and, really, from the late 1980's 
or so) digital computers with a couple ADC and DAC chips can do a very 
cheap, reliable, and reproducible job with a minimum of pots and 
adjustments.  But, back in the 70's and into the 80's you could do a lot 
with a couple op amps.  I retrofitted a cruise control on a car I had, it 
was an all analog solution, and worked very well.  About a 2 x 3" PC board 
with 5 8-pin DIPs and some passives did the whole thing.

Jon

On 14/03/2018 19:29, Gareth's Downstairs Computer wrote:
> We certainly covered the principles in my
> electronics degree ('69 - '72), but AIUI
> there was a pre-war mechanical analogue
> computer made with the Meccano erector set.

I think this is pretty well known. Hartree and one of his students, 
Arthur Porter built a Meccano differential analyser which they used to 
solve the the Hartree-Fock equations for the Helium Atom.

The results were good, so they managed to obtain a grant to build a copy 
of Vannevar Bush's differential analyser. Bush had given Hartree access 
to all the drawings on a visit to the USA. The full six machine was 
built at Trafford Park by Metropolitain Vickers. The initial version had 
four integrators and was later expanded to six.

If you have a copy of Flash you can see a video of part of the machine 
operation at the Museum of Science and Industry in Manchester...

http://www.cs.man.ac.uk/~chl/hartree.html

the section of the machine that was on display in Manchester is 
currently in storage. The other part is I believe still on display at 
the Science Museum in London.

The expanded machine was used to determine the structure of larger 
atoms. They also tackled a range of other problems including aero 
dynamic stability and noise in electrical transmission systems. These 
are detailed in the commissioning notes which are in the archives at MSI 
Manchester (was MOSI) and can be viewed by appointment.

Several other machines were built, both in Meccanno and as full sized 
machines

Dave

On Thu, 15 Mar 2018 15:56:55 +0000, Ahem A Rivet's Shot
<ste...@eircom.net> wrote:

>On Thu, 15 Mar 2018 07:09:07 -0400
>J. Clarke <jclarke...@gmail.com> wrote:
>
>> I took that course a few years later and we had an electronic analog
>> computer, from TI IIRC.  It was kind of fun but by the time I got my
>> first engineering job digital was "in" and just suggesting the use of
>> analog anything marked one as some kind of reactionary, at least in
>> the place I worked.
>
>	Makes sense, once a digital computer is fast enough to solve a
>given problem it will do a more repeatable and reliable job than an
>analogue computer.

     Knowing about a different way can help sometimes.

Sincerely,

Gene Wirchenko

On 2018-03-15, Jon Elson <jme...@wustl.edu> wrote:
> Ahem A Rivet's Shot wrote:
>
>> On Thu, 15 Mar 2018 07:09:07 -0400
>
> However, once the IC op-amp came out, analog computing for production 
> control systems got a huge boost.  Today (and, really, from the late 1980's 
> or so) digital computers with a couple ADC and DAC chips can do a very 
> cheap, reliable, and reproducible job with a minimum of pots and 
> adjustments.  But, back in the 70's and into the 80's you could do a lot 
> with a couple op amps.  I retrofitted a cruise control on a car I had, it 
> was an all analog solution, and worked very well.  About a 2 x 3" PC board 
> with 5 8-pin DIPs and some passives did the whole thing.
>
> Jon

I have a memory of reading that in the early days, calculations wee
done twice or thrice to check on the results.


-- 
greymaus.ireland.ie
Just_Another_Grumpy_Old_Man

Jon Elson <jme...@wustl.edu> wrote:
> Ahem A Rivet's Shot wrote:
> 
>> On Thu, 15 Mar 2018 07:09:07 -0400
>> J. Clarke <jclarke...@gmail.com> wrote:
>> 
>>> I took that course a few years later and we had an electronic analog
>>> computer, from TI IIRC.  It was kind of fun but by the time I got my
>>> first engineering job digital was "in" and just suggesting the use of
>>> analog anything marked one as some kind of reactionary, at least in
>>> the place I worked.
>> 
>> Makes sense, once a digital computer is fast enough to solve a
>> given problem it will do a more repeatable and reliable job than an
>> analogue computer.
>> 
> Well, there's two kinds of analog computing.  For solving problems in an 
> analytical way, digital has the HUGE advantage that you get the same answer 
> every time, and debugging and documenting what you did is easy.
> 
> However, once the IC op-amp came out, analog computing for production 
> control systems got a huge boost.  Today (and, really, from the late 1980's 
> or so) digital computers with a couple ADC and DAC chips can do a very 
> cheap, reliable, and reproducible job with a minimum of pots and 
> adjustments.  But, back in the 70's and into the 80's you could do a lot 
> with a couple op amps.  I retrofitted a cruise control on a car I had, it 
> was an all analog solution, and worked very well.  About a 2 x 3" PC board 
> with 5 8-pin DIPs and some passives did the whole thing.
> 

ISTM digital solutions are akin to integrating a function that the analog
computer models directly. The more steps you use and the smaller the
interval the closer the digital solution approaches the reality.

-- 
Pete

Peter Flass wrote:


> ISTM digital solutions are akin to integrating a function that the analog
> computer models directly. The more steps you use and the smaller the
> interval the closer the digital solution approaches the reality.
> 
Yes, but digital has some big advantages, too.  One thing that is REALLY 
hard in analog is holding a sampled value for a long time.  In digital, 
especially with battery-backed or non-volatile memory, you can hold that 
setting for years.

Jon

On Thu, 15 Mar 2018 14:33:18 -0500
Jon Elson <jme...@wustl.edu> wrote:

> However, once the IC op-amp came out, analog computing for production 
> control systems got a huge boost.

	Very much so, I've seen (and made) some surprisingly simple control
systems that way, also real time data analysers - and I was only dabbling.

>  Today (and, really, from the late
> 1980's or so) digital computers with a couple ADC and DAC chips can do a
> very cheap, reliable, and reproducible job with a minimum of pots and 
> adjustments.

	Reproducible is of course the big win in production - if you can
get the adjustments to zero then the production rate shoots up and cost
shoots down.

>  But, back in the 70's and into the 80's you could do a lot 
> with a couple op amps.  I retrofitted a cruise control on a car I had, it 
> was an all analog solution, and worked very well.  About a 2 x 3" PC
> board with 5 8-pin DIPs and some passives did the whole thing.

	Neat.

-- 
Steve O'Hara-Smith                          |   Directable Mirror Arrays
C:\>WIN                                     | A better way to focus the sun
The computer obeys and wins.                |    licences available see
You lose and Bill collects.                 |    http://www.sohara.org/