A spare (new) inclinometer was mounted directly on the track about midway
between two wheels and was pushed along as the antenna was rotated.
Measurements were made in May 1995 and are readily converted to a track
profile. Fig.6 shows the data, and Fig.7 the resulting track profile.
A sinusoidal curve of the form 4
*sin(az-150) is subtracted -
representing
a plane tilted 4
towards azimuth 60
E of N - and the
residuals
are plotted in Fig.8.
The parameters for this plane may be compared with 2 of the parameters of
the 7-parameter antenna model that describe the antenna azimuth axis as
deviating from the vertical by 8
to the North and 16
to
the East,
ie 18
to azimuth 63
.
The largest step is between track segments 14 & 1, showing a drop of
500
m. Fig.1 shows that when wheel 1, on the the right A-frame, rolls over
this joint the tilt induced is about 8
, which implies a drop
from segment 14 to segment 1 of only 270
m. The difference between the
static measurement made by the direct inclinometry, and the dynamic
measurement implies a dynamic component to the joint that reveals itself
only under load. This implies that the track segments probably sit upon a
foundation (grout) that is not stable. This observation alone provides
justification for the Azimuth Track Improvement Project, which aims to secure the track
segments, and in the process, reduce or remove the (possibly variable)
dynamic component of the joint effects.