I think you just described a sonic delay line. IBM was using these for storage in the late 60's with lengths up to about 500 ms. That size was touchy, the 50 ms units were rock solid. John Ferrell http://DixieNC.US ----- Original Message ----- From: "jsand" To: Sent: Thursday, July 29, 2004 2:50 PM Subject: [OT] : Challenging...(another thought) > Hello Jay & PIC.ers, > > > > >A better experiment would be to take a long metal rod that is restricted > >to only move in one dimension. Then hit one end and measure when the other > >end moves. With precision timing you don't need that long a rod. > >-- > > This can be made really easy too. > Hang any old length of off-cut material (steel, copper rod) horizontally > on a couple of strings. When you knock one end of the piece longitudinally with > a hammer, the impulse sends it away from the hammer head. > This appears to be `instantaneous' but there is a delay due to the need > for the impulse to reach the far end of the strike-ee rod, > change phase 180degree and reflect back to the hammer. > Once it gets there, the two metal pieces separate for the first time. > > The time delay can be measured by closing a circuit (hammer / rod) and > monitoring by scope. Voila, speed of sound in metals. > > > best regards, John > > email from the desk of John Sanderson. > JS Controls, PO Box 1887, Boksburg 1460, Rep. of S. Africa. > Tel/Fax 011 893 4154, > Cell 082 741 6275, > web http://www.jscontrols.co.za > Manufacturer & purveyor of laboratory force testing apparatus & > related products & services. > > -- > http://www.piclist.com hint: To leave the PICList > mailto:piclist-unsubscribe-request@mitvma.mit.edu -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads