Detector mounting

I - Joining the boxes

The top image shows the brackets used to join the boxes, and to mount to the posts. These are the joints of the 80-bar boxes (station 1), looking at the upstream face.

The second image shows the brackets used to join the boxes, and to mount to the posts. These are the joints of the 50-bar boxes (station 2), looking at the downstream face.

The assembly procedure to join the boxes is as follows:

  1. For each box, lay it down, with the upstream face up.
  2. Mount the brackets on the upstream face
    1. For the double-wide bracket in the very center, use 2 single-wide brackets for now.
    2. Note that the brackets on the vertical center line will touch those on the adjoining box - this means one screw hole each needs to be moved.
    3. After the new screw holes have been made (and the double nut slid over to match), tape the side panel, and then mount all the upstream brackets.
  3. Flip the box over; note that each bracket on the upstream face is 3" high, they function as legs.
  4. Mount the downstream brackets
    1. Again, a hole for each of the center-line brackets needs to be drilled.
    2. After drilling, tape the downstream cover sheet.
    3. Mount the brackets of on the downstream face.
    4. On this side, not all brackets are 3" high, so on these corners, mount temporary 3" brackets.

Now join the boxes, and connect the vertical posts:

  1. Join box pairs
    1. Boxes are paired horizontally first: 1+2, 3+4 (and later 5+6, 7+8).
    2. Downstream face up, connect centerline brackets between 1&2
    3. Flip the pair over, and join the upstream face brackets.
    4. Same for 3&4
  2. Join the pairs into 4's.
    1. Connect brackets on the horizontal center line
    2. In the very center, replace the pairs of single-width brackets with the double-width bracket.
  3. Attach the vertical posts. You need some 9" blocks to raise them off the floor while doing this.
  4. With the crane, raise the combined units on its side
  5. On the downstream side, swap out the brackets in the center, and remove temporary 3" brackets
  6. Lay the detector back down, and attach the lifting bar
  7. Raise the detector by the lifting bar and install.


Raw measurements made in the hall

II - Station 2 location

Station 2 is lifted by the top crossbar, and dropped down onto the steel of the A-frame, leaving a 3" gap to the box beam.

On the floor, the posts are anchored with a pair of brackets each. We have marked where the posts and anchors are located.

The vertical beams are 171.75" (from the CAD drawing), as in this drawing from the safety document. However, we measured to the top of the I-beam (11 May '17) to be 173.5", 1.75" higher.

To fix that, we mounted a foot tothe bottom of the posts, consisting of 1.5" 80/20, plus 1/8" shim plates.

III - Station 1

The measurements in black are taken from E906spectrometer2-17.EASM. The measurements in green are taken in the experimental hall. There are a number of significant differences.

In red is the position of the detector. Note there is some almost-interference at the top with the box that covers the magnet power leads. However it clears the detector corner in the x-direction by 3.125", and I moved the detector out so that the upper coax cables remain easy to service.

The top of our posts is 3.25" below where they should be if we want to bolt to the center of the 8" I-beam. More on that below.

For the extenders, we need to leave enough transverse space to lift the station-1 drift chamber out. This chamber would be raised a hair, then moved downstream until it clears the big I-beams, and then lifted up and out. This means our extenders need to be mounted out a bit to provide enough clearance width. See this picture - the drift chamber is the Al box, 10'8" wide. Near the top, just visible behind this black hose, is a bracket that sticks out 5.25", on both sides. Plus a little over 3" on both sides for slack, gives a clear space of 145" between our extenders. In this sketch, I just draw flat pieces, but this could be C- or I-beams, or 80/20. We have to provide these, they will drill bolt holes in the I-beams (behind the weld of the current I-beam extension).
The actual extenders are made of 3×3" 80/20. The bracket that mounts to the steel I-beam has 4 holes for 5/16 bolts. There are various options for attaching the extender arms to the I-beam, more on that below.

The installation procedure is:

  1. Prepare the steel I-beam with posts or holes or a plate, and bolt brackets into the floor.
  2. Mount the extender arms loosely to the I-beams; they will hang down a bit.
  3. Lift the st.1 detector by the crossbar, and drop it into place. Attach it to the floor brackets.
  4. Raise the downstream end of the extender bar to the lifting crossbar and attach it.
  5. Tighten all bolts.
Mounting the extenders to the beam:

First, we have to come down by 3.25" from the calculated position. By changing the way the short piece connects to the extender arm, we gain 3" - close enough.  →

There are 3 ways to attach this extender assembly to the big I-beam

  1. Drill 4 holes, and mount with the 80/20 bracket with nuts and bolts. (the original plan)
  2. Instead of drilling 4 holes, spot-weld 4 threaded posts, and attach the 80/20 bracket with nuts. (5/16 thread)
  3. Instead of using the 80/20 bracket, weld a 3×3" plate (with 4 holes pre-drilled) to the I-beam instead.
The 80/20 arm runs alongside the I-beam for 30", and protrudes for another 30". So the holes, posts or plate should be located at ~27" from the I-beam end.
This is a view upstream towards the st1 wire chamber and the I-beams, in grey. In red is indicated where the I-beams really are (the inside of the beams lines up with the edge of the chamber, as indicated. The chamber was measured at 128.5, the beam is 6.5" wide with a 1/4" web, so the extender spacing should be 135.25". Our mounting frame is made for 134.5" - close enough.
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Cable trays: We have a rack (red) to either side of each of our detectors. Shown here is a beam's eye view of the first station. We propose to have cable trays (orange) mounted to the top of our racks, and on the other end supported by some bracket coming off our vertical post. Cables and fibers (yellow) go down (3 bundles) or up (1 bundle) to the cable tray.
Brackets mounted, and racks placed (25 Apr 2017):

Hubert van Hecke
Last modified: Fri May 12 08:57:37 CDT 2017