John was "the great student hands-on demonstrator". My guess was this
device was intended for a classroom and student interaction. Did you
happen to also receive the very long 12-inch wide sandpaper cover board
and red brick attached to a rubber cord and large hand-crake-real? John
used that one to demonstrate how strike slip faults would lock and then
suddenly leap forward. I saw John for the first time at IBM in San Jose
talking in front of 1,000 people about earthquake preparedness. He was
in the middle of his pitch when he setup this long board and placed the
brick at one end and started cranking on the real at the other. As he
talked about locked faults in the Bay Area he mentioned how the brick
and the board represented two sides of a fault and he kept talking and
talking and the cord got more and more tension. Then, suddenly, the red
brick leaped into the air and flew up the board. It was a very
convincing demonstration on stored tension. In later years John told me
he had figured out how many turns on the handle it took to make the
brick move so, he would time cranking the real with his pitch so that it
leaped forward at the right point in his talk. 

Regards, Steve Hammond  PSN San Jose, Aptos, California

-----Original Message-----
From: psnlist-request@..............
[mailto:psnlist-request@............... On Behalf Of Karl Cunningham
Sent: Wednesday, September 08, 2010 9:38 PM
To: psnlist@..............
Subject: Re: Question about John Lahr's work


Kay,

My guess is that this device was simply to demonstrate wave propagation,

and reflection at the ends (representing media boundaries). I doubt that

the wave is torsional is important to the demonstration.

Another fact that might have been mentioned during a demonstration is 
that the motion of the end of each dowel appears up-and-down, for small 
amplitudes when viewed from the side. I have seen demonstrations using 
the same type of apparatus, where a few of the dowel ends are painted 
with bright colors so their motion can be more easily followed when 
observed from the side.

Karl


Kay Wyatt wrote:
> Dear friends,
> 
> John Lahr's wife, Jan, gave me much of John's earthscience activities
> and experiements.  I'm familiar with most of them, but there is one in

> particular that I could use some help on.  I have posted some pictures

> at http://www.oregonshakes.com/temp/Lahr/ for your review.
> 
> The device appears to be a torsion wave generator but I'm not familiar
> with torsion waves generated by earthquakes (which was John's primary 
> focus). Could this be something else related to earthquakes?
> 
> Be sure to look at the move link on the website so that you can see it
> in action.
> http://www.oregonshakes.com/temp/Lahr/MOV04260a.MPG
> 
> If any of you have ideas, please let me know.
> 
> Thanks so much,
> Kay Wyatt

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