Below are a few words from the Scientific American Amateur Scientist article of
April, 1967.  The "Complete Collection of The Amateur Scientist" is 
available on
CD-ROM for $40, which is quite a bargan.  See:
http://shop.store.yahoo.com/explo/amsciencdrom.html

Scientific American
by C. L. Stong
April, 1967

---------------------

........

Figure 1: Horizontal pendulum of long period devised by Nils E. Lindenblad



......
One of these is Nils E. Lindenblad of Princeton, N.J., who took up the 
study of pendulums two years ago at the age of 70 after a career of 45 
years as an electronics engineer. Lindenblad writes:

.....

"It is just as valid, and on occasion more helpful, to think of the period 
as a function of the curvature of the arc through which the bob swings. ....

..... The linkage, as modified, consists of a horizontal bar supported at 
one end by a hinged lever and suspended at the other end by a flat ribbon 
of spring steel [see Figure 1]. The ribbon in turn was hinged in the middle 
by means of a short length of spring stock turned at right angles to give 
the suspension lateral freedom. If the ribbon and the lever are equal in 
length, the midpoint on the horizontal bar will move in a straight line 
when pushed along its axis through a limited distance. A bob that has a 
hole through its center of gravity and is slid into position at the middle 
of the bar will move as though it were suspended by a wire of infinite 
length forming a pendulum of infinite period.

Cheers,
John

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