Inclinometry on the evening of 970417

Summary : CW inclinometry following the welding of track joint 1/2.

Inclinometry started at 20:20 - mean temperature of antenna legs 5.4C, falling to 4.4C at end => an average of 4.9C.

Changes by as much as 4" are seen, principally at azimuths 72, 169 and 252, where the wheels 3, 2 and 1 traverse the joint 1/2. The behaviour of the inclinometry at azimuth 169 is highly illustrative of the sign of the changes introduced by the welding. Recall that the 2-axis inclinometers are oriented with their Y-axes pointing towards the front of the JCMT building, the X-axes pointing right. Tilting the front end of each inclinometer up from the horizontal produces a more negative output.

As wheel 2, the back right wheel, now moves over joint 1/2 the implications for the motion of the right A-frame and/or wheel 2 specifically are as follows :

• TX is deflected to a more negative value than it did previously. This implies that the right A-frame stays higher than it did before, when the ends of track segments presumably deflected beneath the load. The sharp vertical feature in the TX plot at azimuth 169, together with the shallower approaches just before and just after, are due to the step across the joint - now hopefully absent.
• RY and TY both go more positive, indicating that the right A-frame is rocking further forward now than before - indicating that wheel 2 is staying higher than before.
• LY also goes positive - perhaps reflecting the (relative) rocking forwards of the sub-frame.

A new track model was created and installed. The difference between this model and the previous one of 970412 is shown here .

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imc 970418