cherenkov-bosch-4-4-01

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					Support Structure Construction Using Bosch Aluminum Beams, a Second
Iteration Design




Figure 1 – An isometric view of the proposed support structure attached to the existing Ferris wheel
           structure.

Rather than supporting each Čerenkov detector separately in each octant, a frame similar to the Ferris wheel
itself could be constructed and attached (see fig 1). This type of design would be better able to support the
weight load of Čerenkov detector boxes and shielding. It also offers the advantage of serving as a general
support framework to which the CED detectors and other equipment could be attached.

Instead of fabricating the Čerenkov support structure from scratch using welded tubing, a more versatile
solution would be to use pre-made Bosch aluminum frame members. The same type of frame member was
used to construct the magnetic verification gantry used to survey the GØ magnet. All of the components are
modular, and are easy assemble.

Some of the advantages of using the Bosch components are:
         Other supports and components can easily be attached to the structure
         Structure may be assembled and disassembled repeatedly
         Fabrication shop delays are avoided
            Greatly decreased cost over fabrication from scratch.

Some disadvantages are:
         May require time on the part of engineers or experimenters to assemble.

The Čerenkov support structure could be held to the Ferris wheel structure by means of standard Bosch
gussets and long (100mm) 8mm bolts and nuts.

The Bosch aluminum framing system



The aluminum framing elements incorporate a central hole in each beam. Bosch has part available to turn
the beams into a compressed air distribution system. The beams themselves could be used to help distribute
dry air or N2 to the Čerenkov detector boxes.
Attachment of the Čerenkov Detectors




Figure 2 – A close-up, isometric view of the attachment of the Čerenkov detector to the Bosch framing.
           Notice the aluminum plate supporting the detector has a number of holes in the top portion,
           allowing angular adjustment of the Čerenkov detector.


The Čerenkov detectors may be mounted by means of aluminum plates (see fig 2) attached to the support
structure, featuring adjustable angles. The plate would be attached to the frame element with Bosch gusset
hardware. The plate design will give adequate support to the detectors in each of the octants.
Assembly




Figure 3 – An isometric explosion of the Bosch components required to construct the Čerenkov detector
           support structure in one octant.

Part list from figure 3:
           (1)     Bosch 30x30 profile, structural aluminum beam. Cross-section:




         (2)      Bosch 30mm multi-angle connector
         (3)      Bosch 45º angle connector
         (4)      Bosch 30x30 gusset

See table in figure 5 for quantities, prices and numbers of these parts.
Clearance to Existing or Planned Apparatus




Figure 4 – An isometric view showing how the frame and Čerenkov detector would fit with the CED
           detectors, light guides and other supports.


Based on the current models, adequate clearance exists between the proposed support structure and the
CED detectors, light guides and existing support hardware. (see fig 4)

This support structure could simplify the attachment and support of much of the other equipment and
apparatus to this area.
Cost




Figure 5 – Pricing estimate for Bosch aluminum structural framing system components taken from
           ‘boschframing.com’.

The pricing and quantities in the table found in figure 5 represent a minimum order for the structure alone,
any additional brackets and fasteners used to attach other supports or components would have to be
included.
Additional Forces on Existing Structures

The approximate total mass for this proposed structure would be:
        For the beams    62.8m x 0.8kg/m =            50.2 kg
        For the hardware      ~0.2kg x 188 =          37.6 kg
        Total                                         87.8 kg

A revised estimate of the total mass of a single Čerenkov detector is:
         Approximately 10 000cm3 aluminum @ 2770kg/m3 ~29 kg
         4 x 17” – Ø5” schedule 40 steel pipe @ 18.97lb/ft      48.9 kg
         Fasteners and miscellaneous                              ~5 kg
         Total                                                   ~ 84kg each

This gives an approximate total mass on the support structure of (8x84) + 87.8 = 760kg.




Figure 6 – A side view of the Čerenkov detectors, support structure and Ferris wheel, showing a static
           balance of forces.
If the Čerenkov detector support structure is added to the side of the Ferris wheel structure with out
additional supports (‘Possible frame supports’ in Fig 5), we can expect the Čerenkov detectors and support
structure to produce a moment about the rightmost rail:

MB = (760kg x 9.81 m/s2) x (0.796m + 1.417m) = 16.5 x 10 3 N·m

Reactions on the guide rails of the Ferris wheel would then be:

RA = MB / 1.417m = 11.6 x 103 N compression on rail A

RB = W - RA = 4.9 x 103 N tension on rail B

It must be verified that the guide rails of the Ferris wheel structure could support these additional forces
before this solution could be implemented. Note that the force on rail B is tension. If the rails only support
weight, but do not prevent lifting off, this would not work and would be dangerous. A counter-balancing
mass of some kind could be used to get around this problem.

Alternatively, if extra frame supports were included on the bottom octant of the Čerenkov support structure
this would eliminate the moment and the statics would simplify to:

RA = RB = Reaction on supports = W/3 = 5.5 x 103 N compression on rails and support

If a spot could be found to position the support, or an extra rail installed, this would be a superior solution.
Vertical deflections of the support structure could be compensated for by adjustable feet on the extra
supports (‘Possible frame supports’ in Fig 4).

Again, it must be verified that the guide rails of the Ferris wheel structure could support this additional load.


Assembly

Assembly of the structure could be problematic. It would be better, but more difficult, to assemble the
Čerenkov support structure directly on the Ferris wheel. More likely, the Čerenkov support structure would
be pre-assembled and then lifted into place on the Ferris wheel. Adequate stress analysis for the lifting
should be done before it is attempted.

The Čerenkov detector boxes themselves are quite heavy, and must be lifted into place at a variety of
different angles. Assembly of the detectors into the support structure before it is installed on the Ferris
wheel would increase its weight dramatically and make it unlikely that lifting the assembly would be safe.

A lifting jig should be designed for the installation and removal, if necessary, of the Čerenkov detectors.

				
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posted:9/26/2012
language:English
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