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Re: Malcolm's ruler machine

Hi Terry,

You have probably thought of this already.  Why not add a second much
shorter wire (may need thicker wire) with a mass on one end so it vibrates
at  the same fundamental frequency as the long wire.  Then link the two
together say half along the short wire. You then have a primary and
secondary.  When you pluck the short wire at the end you should see the
classic interchange  between the two. Much more illustrative than the double
pendulum.  I will leave you to work out how to add quench.

You should be using glass rods for the best Q and bolt the apparatus to a
large concrete block for a good ground plain :).

Don't you have a cam.  A few minutes of uncompressed cam should even slow
your link down.

Regards Bob

-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Thursday, May 25, 2000 10:55 PM
Subject: Malcolm's ruler machine


>Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>Hi All,
>
>I have built sort of a fun toy to study secondary resonance.  Going off
>Malcolm's analogy of a bent ruler model for secondary oscillation, I built
>a simple device.
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/Mach.jpg
>
>It is simply a wooden base with a spring steel wire pressed into a hole.  A
>"woofer" speaker is connected to the base of the wire by a rubber band and
>some small powerful magnets to couple the speaker cone to the base of the
>wire.  The wire is 30.0 inches long and weighs 11.7 grams.  The wires
>natural frequency is 1.81 Hz.
>
>The speaker is driven by a DC-50kHz amplifier from a low frequency
>oscillator with a scope attached to measure frequency:
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/drive.jpg
>
>The first harmonic occurs at 1.81Hz where the wire swings with great
>amplitude.  Decreasing the amplitude did not change the resonant frequency:
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/1st.jpg
>
>The third harmonic occurs at 12.11Hz with far less amplitude.  The nodal
>point is 23.5 inches from the base:
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/3rd.jpg
>
>The fifth harmonic is at 34.13Hz with nodes at 15.25 and 26.0 inches:
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/5th.jpg
>
>The seventh harmonic is at 66.23 Hz with nodes at 10.75, 19.25, 27.0
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/7th.jpg
>
>it is interesting to compare this to actual secondary coil measurements at:
>
>http://users.better-dot-org/tfritz/VoltDistBare.jpg
>
>Is is also interesting to note the similarity of the wire bending profile
>to the graph profile of the measured results:
>
>http://users.better-dot-org/tfritz/site/misc/MalRulMa/Wire.jpg
>
>It is interesting to also note the measured profile is concave rather than
>convex as would be expected in a 1/4 wave sine function as shown in the
>comparison graph here:
>
>http://users.better-dot-org/tfritz/DistGraph.jpg
>
>I don't know what all this means or anything but I wanted to pass this
>information I had on for everyone's enjoyment...  Maybe it will all mean
>something to someone.  I have been so busy getting the thing working that I
>have not thought much about the implications...
>
>For reference, there are many web sites with spring, mass, and oscillation
>information such as:
>
>http://www.futuresouth-dot-com/~mhenders/physics/Simple_Harmonic_Motion.htm
>
>http://www.cs.wright.edu/~fdgarber/199/Spring_Mass_3/
>
>I will try adding weight at the top (like a terminal load) and such in the
>future.  I have to start working on the cap bulk buy first ;-))
>
>Cheers,
>
> Terry
>
>