JIM MARTIN wrote:

> To anyone who wishes to help:
>
> Is 18" too tall for the main support with the Lehman?
>
> 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. ?
>
> Is the angle of the boom support wire, in relationship to the boom,  a
> critical item,  or is it just desirable to keep it somewhere around 30
> degrees?
>
> Thanks,  and sorry for the elementary questions.
>
> Jim Martin
> New Haven, Indiana
>

It is best to avoid all magnetic materials in and on the boom. If your
threaded rod is steel I would not use it. Otherwise it is a matter of
mechanical stability and not having stray mechanical resonances in the
system. In other words stiffer is better. The other dimensions are not
critical. Except the location of the upper and lower pivot points. The upper
pivot, when adjusted for proper period is slightly closer to the mass in the
horizontal direction than the lower pivot point. Normally this adjustment is
made with the levelling screws on the base. So if you build the pivots to be
vertical when the base is horizontal the correct adjustment can be made by
slightly inclining the base down at the mass end.
--
Jim Hannon
http://soli.inav.net/~jmhannon/
42,11.90N,91,39.26W
WB0TXL



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