Station rotations, and central plane crossing

In the Monte Carlo, the stations are rotated by multiples of 7.5°/8. From the model, we read the following angles:

MC rotation
× 0.9375° 		Support plane edge supp. to HDIsum-5.046/0.937
Station 10 5.830° 2.029° 7.859° 2.813° 3
Station 23 2.366° 2.68° 5.046° 0.0 0
Station 31 4.241° 2.68° 6.921° 1.875° 2
Station 42 3.303° 2.68° 5.983° 0.937° 1

The absolute angles are dictated by having to stay clear of mounting posts and pins. Station 1 is different from 2,3,4, but in the end the sensors are rotated correctly.

Station 1:

In white is the big wheel support plate, which has an exact vertical edge 1 mm to the right of the midplane.

The station-1 support plane is shown in green with yellow outline. Because of the rotation of the plane, its leftmost point crosses the midplane by 10.107 mm. The HDIs protrude beyond the support plane, with the leftmost point at -23.296 mm.

Click to enlarge →

Station 2:

Same as above - big wheel support in white (+1 mm), station 2 support plane in green with yellow outline (-7.266 mm), HDI in pale yellow (-25.307 mm).

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Station 3:

Same as above - big wheel support in white (+1 mm), station 3 support plane in green with yellow outline (-13.015 mm), HDI in pale yellow (-30.876 mm).

Click to enlarge →

Station 4:

Same as above - big wheel support in white (+1 mm), station 4 support plane in green with yellow outline (-10.142 mm), HDI in pale yellow (-28.095 mm).

Click to enlarge →

Summary:
support plane HDI
Station 1 -10.107 -23.296
Station 2 -7.266 -25.307
Station 3 -13.015 -30.876
Station 4 -10.142 -28.095


Added 15 January 2014:

On the left, I show the mechanical model, in an exact x-y projection. You can see that disk 0 is rotated more than the other disks (more than a multiple of 360°/96/4). The additional rotation is 0.6515°.

On the right you see that in the model, the silicon edges are all rotated by a multiple of the same small angle.




Click on the pictures to get the full size →

In Pisa however, the disks are evenly spaced (red), and the edge of the small disk silicon overlaps with the edge of the ST2 disk (blue). (sili_use_survey = 0 in phnx.par)
The solution is to add 0.6515° to the small station rotation.