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From: lbjostad@ops.agsci.colostate.edu ()
Subject: Mech Simulation
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Message-ID: <Dec27.155905.19815@yuma.ACNS.ColoState.EDU>
Date: Mon, 27 Dec 1993 15:59:05 GMT
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From wurtz@sgi510.msd.lmsc.lockheed.com:

:For real-time dynamic analysis and graphical display of mechanical systems,
:check out

                  Working Model

            from  Knowledge Revolution
                  San Francisco, California,
                  (415)553-8153

This runs on Macintosh platform, with minimums of System 7, 4 MB RAM, 
4 MB hard disk.

I finally got a chance to try the demo version (available from several ftp 
sites), and I think it's some of the most exciting software I've seen.  For 
those of us who are used to modeling mechanisms with stiff card, paper clips,
and soda straws, it's a giant step upward.  Fairly easy, intuitive 
tools.  It took me about an hour to learn all the tools (by playing around) 
at about 6 pm yesterday evening, and it was so much fun I didn't quit until 
2 am.

The simulations are quite realistic, whether you use pulleys, springs, or 
whatever in your Rube Goldberg.  It took me a while to figure out how 
to simulate gear trains.  No gears are in the demo, but you can set 
circular masses in contact with one another, set the static and sliding 
friction as you like so you get no slip, attach the axles with a spring 
(remembering to set the spring length about 50% shorter than the 
axle-to-axle distance, so the spring is under tension), and anchor 
the "gears" on pivots as needed to make them stay put.  I couldn't find 
a simpler way.

The "pulleys" work well, but they seem to allow only infinitely small radii 
for the pulley wheels.  I never could find a way to simulate belts running 
over different sizes of pulley wheels.  However, the titles of the complex 
demos that come with it seem to imply that this can be done, too.  Two 
tutorials come with the demo, but they are sparsely written.  I learned 
more by playing around (maybe that's the way it should be).

It's a big sucker (1.6 MB just for the basic application), and runs a little 
slow on my Centris.  I only have 4 meg of RAM at present, and about 6 meg 
free on my hard drive, and some of the complex demos that came with it would 
not run on my machine, because of memory limitations.  The simpler demos ran 
just fine.  I can't wait to try the complex ones on the faster machines in 
our computer lab.

At $1000, it seems expensive, and there is an additional package called 
"Lincages" (sic) for an additional $3000.  Clearly not an app for the 
"financially challenged".  Still, quite impressive.

I found references to the demo through Gopher>Veronica.  I downloaded 
it through gopher to keep from burdening ftp.  
Couldn't find any US ftp sites.  Non-US FTP sites are as follows:

-----------------------------------------------------------------------
Name=working-model-10-demo.hqx
Path=0/INFO/pub/mirror/info-mac/Science-Math/working-model-10-demo.hqx
Host=gan.ncc.go.jp
-----------------------------------------------------------------------
Name=working-model-10-demo.hqx
Path=0/mac/info-mac/Recent/working-model-10-demo.hqx
Host=swdsrv.edvz.univie.ac.at
-----------------------------------------------------------------------
Name=working-model-10-demo.hqx  [18Oct93, 1983kb]
Path=0/pub/mac/info-mac/Science-Math/working-model-10-demo
Host=ftp.sunet.se
-----------------------------------------------------------------------
Name=working-model-10-demo.hqx
Path=0/pub/mac/info-mac/Science-Math/working-model-10-demo
Host=metten.fenk.wau.nl
-----------------------------------------------------------------------
Name=working-model-10-demo.hqx
Path=
0/eri/LK/Macintosh/funic-maclib/info-mac/Recent/working-model-10-demo.hqx
Host=tukki.jyu.fi
-----------------------------------------------------------------------

The only similar software I've used is the software for 4-bar, 5-bar, and 
6-bar linkages (for DOS machines) that comes bundled with Robert L. Norton's 
book Design of Machinery.

Does anyone know of software that allows realistic mechanical 
simulation, other than Working Model?  It's the first I've seen.

Lou Bjostad
LBJOSTAD@ceres.agsci.colostate.edu

