The construction of the rotating spiders is part of the construction of the LBT (Large Binocular Telescope) - 2X8,4m
For the first light configuration it is planned to equip the telescope with the M2/F15 and M3 spiders only.
The proposal shall assume a unique time schedule for the delivery of the four rotating spiders.
Each spider shall be completed with a cylindrical dummy at its vertex simulating the mass of the supported mirror with the relevant electronic and mechanical components.
The supply of the dummies is part of the present call for tender.

More in detail, the supply consists in :

1.1 The execution of all the workshop drawings on the base of the design drawings included in the call for tender.

1.2 Purchasing all the commercial components being part of the rotation mechanisms. The motor and the limit switches are part of the supply, but no cabling or electrical control units are demanded to be supplied. The necessary equipment for the acceptance tests shall be provided by the supplier. A provisional control box for pre-assembly tests will be supplied by the LBT P.O. (Project Office).

1.3 Manufacturing of all the structural and mechanical parts.
Every rotating spider shall be fully preassembled including the rotation and preload mechanisms and presented for the acceptance functional tests in horizontal position (telescope zenith pointing).

1.4 Delivery of the four tested units at the workshop of pre-erection and integration of the telescope structure.

A prototype unit of M2/F15 Spider has been built and successfully tested.

The selection of the Supplier will be driven only by the cost and delivery time parameters.

In the following chapter are listed the dimensional and load constraints along with the minimum design stiffness requirements.

Working conditions- The Spiders are required to grant the required performance in the following environment conditions:

The following design drawings shall be supplied to the Manufacturer (files in AUTOCAD dwg. Format) to be the base for the cost evaluation and the further development of the workshop drawings.

On the spiders assembly drawings is resumed the suggested construction procedure to obtain a structure accurate in the geometry and stable in the long period to grant a repeatable positioning of the optics and a global shadow over the mirror not larger than the single spider dimensions. In other words, the main beams and the diagonals of each layer of the single spider and the ones of M2/F15 and M3 when overlapping must coincide with a tolerance max. of ±1 mm. For this reason is mandatory the geometry control after the stress releasing of the welded spiders with the acceptance of the LBTP.O.(Project Office), before proceeding with the pretensioning and machining operations.
The machining of the interface surfaces and connection bolting must be performed on N.C.machines to grant dimensional tolerances. more accurate than 0,1 mm to allow the final assembly on site of the mirror supports that shall be manufactured by Others.
At the manufacturer workshop each single spider complete with the dummy of the mirror must be preassembled with its rotation and preloading mechanisms; to this purpose the Manufacturer shall provide a suitable temporary supporting frame where to anchor the four supports and the driving mechanisms. The assembling operations can be done both with the spider axis horizontal or vertical according the Manufacturer working procedure, but it has to be remembered that the acceptance tests shall be performed rotating the spider with the axis in Horizontal position (that corresponds at the telescope zenith pointing).

First acceptance test is concerning the geometric accuracy of the steel structure before pretensioning, as above described.
The final acceptance tests shall be full functional tests with the spider rotating with the axis horizontal, demonstrating preload mechanisms and limit switches performances within the design requirements.
According to the Manufacturer Quality Control Planning - delivered to P.O. according to Item 3.2 -, at the delivery of the spiders shall be included all the materials and tests certificates produced during the manufacturing.
The LBT Project Office has the right to witness to all the tests that shall judge interesting, and shall inform the Manufacturer of his program at the approval of the workshop drawings and the planning for construction.

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Title:Technical Specification of Secondary and Tertiary Spiders with Rotation Mechanisms
Document Type: Technical Specification
Source:ADS Srl
Issued by:E.Anaclerio
Date_of_Issue:04/30/99
Revised by:
Date_of_Revision:
Checked by:D.Gallieni
Date_of_Check:04/21/99
Accepted by:J.Hill
Date_of_Acceptance:05-28-99
Released by:
Date_of_Release:
File Type:MS-WORD 7
Local Name:
Category:Telescope Azimuth Platform
Sub-Category:General Telescope
Assembly:Technical Documentation
Sub-Assembly:Technical Specification of Secondary and Tertiary Spiders with Rotation Mechanisms
Part Name:
CAN designation:401a005
Revision:D

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