In a message dated 10/05/2009, shammon1@............. writes:

Try  using a bubble level to know when the boom is level. Then tilt the end 
of the  boom down, never up. I normally start by using a level to make sure 
the  vertical upright is at zero degrees and then I level the boom. I then 
add  about 1-5 degree of tilt in the upper most point of the upright in the  
direction of the boom. I have three level screws the base plate and a 
machine  screw in the end of the boom to make the adjustment. 
Regards, Stve Hammond  


Hi Steve,
 
    The period is not effected by the angle of the boom  itself. It is the 
angle between the local vertical and the line joining the two  centres of 
rotation which is critical for determining the period.
 
    In 
_http://jclahr.com/science/psn/chapman/2008%20lehman/lehman_prototype.jpg_ 
(http://jclahr.com/science/psn/chapman/2008%20lehman/lehman_prototype.jpg)  this  line joins the centre of the 1/2" ball bearing on the upright 
with  the fine wire at the top where it is clamped by the edges of the brass  
variable rotating clamp washers. The horizontal arm is set up parallel to 
the  base bar just for convenience.
 
    Regards,
 
    Chris Chapman






In a message dated 10/05/2009, shammon1@............. writes:
Try 
  using a bubble level to know when the boom is level. Then tilt the end=
 of the 
  boom down, never up. I normally start by using a level to make sure the=
 
  vertical upright is at zero degrees and then I level the boom. I then ad=
d 
  about 1-5 degree of tilt in the upper most point of the upright in=
 the 
  direction of the boom. I have three level screws the base plate and a ma=
chine 
  screw in the end of the boom to make the adjustment. 
Regards, Stve=
 Hammond 
  

Hi Steve,
 
    The period is not effected by the angle of th=
e boom 
itself. It is the angle between the local vertical and the line joining th=
e two 
centres of rotation which is critical for determining the period.
 
    In http://jclahr.com/science/psn/chapman/2008%20lehman/lehman_prototy=
pe.jpg this 
line joins the centre of the 1/2" ball bearing on the upright with 
the fine wire at the top where it is clamped by the edges of the=
 brass 
variable rotating clamp washers. The horizontal arm is set up parallel to=
 the 
base bar just for convenience.
 
    Regards,
 
    Chris Chapman