JIM MARTIN wrote: > Gentlemen, > > I am experiencing rather frustrating problems in getting my Lehman set up. > I just finished the construction, and am now trying to get the boom to > center. The boom is setup so that it has a VERY slight downward slant from > level. I have leveled the base plate and it seems that no matter what I do > to the leveling screws, the boom either performs a major swing to either the > right or left. It takes almost NO turning of the leveling screw and the boom > will go from a center of about 30 degrees to the right, to a center that is > about the same except to the left. It seems as though I just can't get the > darn thing to center up. > > I know a lot of you out there have built the Lehman, so I'm hoping that > maybe someone can give me some assistance. > > Please help if you can.... > > Jim D. Martin > New Haven, Indiana Jim, The important tilt is the position of the upper and lower pivot points with respect to vertical. The action you describe is consistant with the upper pivot point being further from the mass in the horizontal direction than the lower pivot point. The angle of the boom itself is not particulary important. You should be able to use the leveling screws to adjust out your problem by lowering the mass end of the instrument. Then you can adjust the screws for tilt right or left to center the mass. There are actually two different adjustments made with the leveling screws. The centering which you are trying to do, and the period adjustment which you now have set to somewhere beyond infinite. Lowering the mass end of the instrument will decrease the period. -- Jim Hannon http://soli.inav.net/~jmhannon/ 42,11.90N,91,39.26W WB0TXL _____________________________________________________________________ Public Seismic Network Mailing List (PSN-L)
Larry Cochrane <cochrane@..............>