----- Original Message ----- > > Has anyone used a piece of threaded rod for the boom, or is it better to > > stick with an aluminum dowel, say 1/2" in dia. ? Keep thinking "center of mass", "center of mass", "center of mass", ... And you want the "center of mass" as far as practical from the pivot. Any mass not as far from the pivot is bad - it brings the "center of mass" towards the pivot and shortens the period with no advantages gained. (Let's not get into center of gyration - same principles apply) So - a hollow boom is good - And of course the boom and supports must also be - stiff (raise its resonant frequency above some cutoff) - non-magnetic (you have enough trouble with out stray magnetic attractions confusing you further) - stable, ... so aluminum or copper tubing are among the better choices. I'm biased of course, my all time favorite long period horizontal was made of 1" rigid copper tubing soldered on the family gas stove. Your wife should be so understanding and patient. A small propane torch is probably technically and politically better! _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>