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Radial-arm Inclinometry of 970707 & 970712
970707 inclinometry imc
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18:00 high wind & cloud prevent observing.
Include the radial arm inclinometer :
wheel 2 (back right) +ve X-axis radially outwards Ch 7 = RADX
+ve Y CW Ch 8 = RADY
18:30 inc970707a CW 5" glitch in TY at az=139
21:25 inc970707b CCW
970712
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03:35 inc970712a.dat - CW, with radial arm inclinometer on
beam between central bearing and back-right wheel.
mid temperature of antenna legs 0.6 deg C
interrupted at az = 388. R-l-b done between (20,27) and (380,387)
Plots of TX TY LX LY in the difference c970707a-0630 shows +-1.5" systematics correlating to the track segments. There is excellent synchrony in the differences of TX TY LX, whereas LY is essentially 0.0" except in the azimuth range 110 - 190 and, to a much lesser degree 300 - 340, where 3" systematics occur. The glitch in TY occurs close to but not exactly coincident with the joint at 139 where wheel 4 meets traverses the joint 7/8. The difference between the CW and CCW runs, c970707cw-ccw, shows large and systematic deviations in TX, TY, LX, LY, RADY , with rms values between 0.6" and 1.9". The scatter in Ch 7 = RADX , by comparison, is only 0.3". A detail of this plot, around azimuth 271 , where wheel 2 traverses the joint 5/6, shows that the joints are still encountered differently in CW and CCW rotations - at the 0.7" level in this case. Other steps observed in this figure are :
Azimuth 13 94 115 142 169 196 217 271 319 322 346
step size 0.6 0.3 0.2 0.2* 0.2 0.5 0.1 0.7 0.4 0.1* 0.3 "
wheel 2 2 2 2 2 2 2 2 2 4 2
joint 9/10 12/13 13/14 14/1 1/2 2/3 3/4 5/6 7/8 14/1 8/9
* - a spike rather than a step
Further repeated CW & CCW radial-arm inclinometry are needed to determine the repeatability of this behaviour at the joints, but the single CW run on 970712 was readily compared with the 970707 CW run :
Ch 1 2 4 5 7 8
TX TY LX LY RADX RADY
rms 0.7" 0.9 1.0 0.5 0.2 1.0 "
showing that again, the radial-arm data is considerably more repeatable
than any other inclinometer measure. This might be taken to
imply that the track itself is almost invariant
between CW rotations of the antenna, and also between CW and CCW rotations.
RADX - the inclinometer on the radial arm between the
central bearing and the rear-right wheel - might just be
so close to the
action that it suffers less from (I speculate) intermediate
structural hysteresis than the other inclinometers.
Our inclinometry database suggests that consecutive CW runs are usually in
excellent
agreement, while those from one day to the next often show systematic
(segmental) differences that provoke explanations involving
differences in ambient temperature or humidity or something . . . ,
From this list of suspects we cannot eliminate hysteresis.
A comparison of this new radial arm data with older (pre-welding) stuff should throw light on the efficacy of the welding - see the report of 970731. imc 970731 |
