Working 3 digit mechanical computer built from LEGO Technic...

A truly stunning achievement!  Charles & Ada would be proud of you.  Not
wishing to get you to start rebuilding or anything but what does it do if
b^2 <4ac?

It doesn't solve for roots, it evaluates for x = 1, 2, 3, etc.  It
would be used to build a table of results for a polynomial.

The most common one I run for testing is x^2.  It outputs:  1, 4, 9,
16, 25, 36, 49, 64, etc.

I am considering expanding it to 4 digits and adding another set of
adders so it can evaluate cubic polynomials.

---- Andy

Your table:

f(x)
x        2*x^2 + 3*x + 5 First Difference    Second Difference
1        10                    9                        4
2        19                    13                      4
3        32                    17                      4
4        49                    21
5        70


Why don't you look @ it this way:

f(x) = a*x^2 + b*x + c

First Differance:   a*(2x-1) + b
Second Differance:  a*2

Always...


:)
Wouter



<Andy Carol> wrote in message

You are correct that would be more general.  I did it with actual
numbers simply for the ease of conveying the basic principle to people
who want an overview of how the machine works.

--- Andy

   Some of us over in LUGNET noticed it as well - *very* nice, and a
lot of us are very curious about the details. It needs about a 100
turns?!? Use an RCX as a dumb battery box to motorize it ;-). Someone
on LUGNET also recently posted a working knitting machine. Now we need
the machine inbetween (Jaquard [sp?] loom).

--
Brian Davis

I'm guessing that's becuase lego gears are small and weak. A big
gear for a big crank would probably help a lot.


The one I've seen:

http://homepage.mac.com/aklego/PhotoAlbum22.html

Does spool knitting, which is trivial compared to a regular knitting
machine -- even one without a ribber. Mind you, I'm impressed, but it
is a baby step towards knitting. All you get is a lucet cord.

Elijah
------
can see a Jacquard loom being much more difficult

There is a LOT of friction in moving 200 gears, along with the
mechanisms they drag along.  There is also a detent which causes each
digit to "click" into place.

The original Babbage design was 1:1.  The version of his machine made
by the London Museum was 1:4.  Mine is about 1:105

On the other hand, the movement is very smooth and light.  Part of the
issue is that I only have a specific set of gear sizes available.  I
would have been happy to have 1:80, but I had a choice between too low
or too high and too high simply won't work, so I'm stuck with too low.

--- Andy

Andy Carol writes:


It's very impressive.  I sent the link to our High Performance
Computing group, so they can see how to make real calculators. :-)


I didn't quite understand how it works.  I suppose it takes a bit of
experimenting to figure it out.  Please let us know, if you expand the
explanation.

Play well,

Jacob
--
City X'ers mail van (building instructions):
               http://lego.jacob-sparre.dk/CityXers/Postbil/

Andy:

What a fascinating thing this is. I gave a quick study of the device and am
amazed what can be built with Lego. Being a student of mathematics myself,
this is really quite exciting!

Great Work!

Best Regards,

Mark


<Andy Carol> wrote in message