Re: Suspension losses

On 1/4/2025 6:20 PM, Jeff Liebermann wrote:

On Sat, 4 Jan 2025 16:28:21 -0500, Frank Krygowski
<frkrygow@sbcglobal.net> wrote:
 

On 1/4/2025 2:52 PM, AMuzi wrote:

On 1/4/2025 1:36 PM, Jeff Liebermann wrote:

On Sat, 4 Jan 2025 12:35:20 -0600, AMuzi <am@yellowjersey.org> wrote:
>
User manual on an early analog computer including a few useful
examples.  Try to visualize what those problems might look like on a
slide rule or today's personal computers:
<https://www.analogmuseum.org/english/collection/eai/tr10/>
<https://www.analogmuseum.org/library/eai_tr-10.pdf>

>
Ah, such as a slide rule. Got it, thanks.

>
The device I was talking about was nothing like a slide rule.

 I called the analog computer that I build in a briefcase an
"electronic slide rule".  I didn't want to, but that made it more
acceptable to the college bureaucracy.
 

It looked
vaguely like the one in Jeff's last link above, but the classroom
demonstrator was much larger - maybe 3' x 4' IIRC - with much bigger
knobs (4" diameter?) and meters.

 I couldn't find anything with such huge knobs.  Maybe something like
these from Edmund Scientific?
<https://www.google.com/search?q=edmund+scientific+analog+computer&udm=2>
 Would you believe a Heathkit EC-1 analog computer?
<https://www.google.com/search?q=heathkit+ec-1&udm=2>
<https://www.nutsvolts.com/magazine/article/may2016_heathkit_restoration>
Fig 7 is a bouncing ball simulation, which is similar to the bouncing
bicycle simulation.
 

We were talking about electrical analogies for vibrating masses, and
that's one of the things the analog computer could simulate. One would
have to calculate the values of voltage, inductance and resistance to
correctly simulate the damped spring-mass system, set initial
conditions, then let the circuit run. The system's meters would then
swing back and forth in a manner analogous to the position of the mass.
All this was before digital computers were desktop devices.

 Meters?  Too crude.  We used an oscilloscope or X-Y pen plotter.
 

(In those days, the programs I wrote for vaguely similar problems were
room sized and run by full time technicians, and I'd turn in a program
stored as a thick deck of punched cards, hoping output would be ready
the next day.)
>
As I recall, we students never did any actual work with that analog
computer.

 We did.  My guess(tm) that would 1969.  We had groups of 5 or 6
students sharing one machine.  I got some extra experience because I
worked for the "calibration department" repairing them.  The problem
was we had a large number of foreign exchange students from Iraq. Most
had never done any manual labor or learned to use tools.  When faced
with a knob that had reached its end of rotation, they simply applied
more force to help it rotate.  That usually broke the expensive 10
turn potentiometer (Helipot).
<https://www.google.com/search?q=helipot&udm=2>
 I was the idiot who found a solution to the broken potentiometer
problem.  Between the knob/turn_counter and the pot was a short shaft
extension.  I machined a few of these and added a plastic shear pin.
If they hit the end of rotation and break the pin, all they had to do
was rotate everything full counter clockwise, push the pin out of the
hole, and replace it with a new pin (or toothpick).  The reason I was
an idiot was because I had found the solution, I sentence to working
overtime retrofitting all the analog computers with shear pins.
 

I worked with a curmudgeonly older engineer many years ago who quipped "do a shitty job well and it's yours forever".