Large Binocular Telescope Project

Questions & Answers

concerning the RFP for the

Elevation Structure Windbracing Structure

October 17, 1997

Question 1. (received 23 Sep 97)
We do not appear to have sufficient detail information (i.e. pipe diameter, pipe length, plate thickness) to complete a material take-off that would allow us to cost these structures accurately. We have been supplied with a typical connection detail (drawings 512e078 - 081) which shows the information we require. Is this information/drawing detail available for the balance of the Elevation and Windbracing Structures?

Answer 1. The remainder of the detailed drawings of the connection nodes of the Windbracing Structure are now in production. However, we do not expect them to be available before the deadline for proposals. You are encouraged to make your best estimate based on the drawings that you have. The detailed drawings will be available when we issue the manufacturing contract. Our feeling is that the cost of these structures is not dominated by the material, but rather by the labor of welding and machining.

Question 2. (received 1 Oct 97)
Could you please clarify what is intended for the pre-assembly of this component as specified in paragraph 9.0 of 401e030. Is it expected that the bracing subassemblies are assembled together with the C-Ring Structure? What is really required for the proof asssmebly?

Answer 2. Our intention is that the individual structural sections of the Elevation Structure Windbracing Structure will be pre-assembled to assure their overall geometry before shipment to the Telescope Pre-Erection site. Clearly there is room for flexibility in the assembly sequence if the same company is supplying several of the work packages. In the dialect of LBT "pre-assembly" refers to individual components such as the Elevation Windbracing Structure or the Azimuth Ring, while "pre-erection" refers to the erection of the entire telescope in a factory location.

Question 3. (received 3 Oct 97)
What are the supply limits on the central instrument rotators?

Answer 3. On some drawings there are the six instrument rotators on the Elevation Platform with the vertical bearings depicted. The drawings of the Central Rotator structure will come soon from EIE, but, at the moment, the supply limits are well identify by the Elevation Platform frame. This Central Rotator structure will be part of another Request for Proposals to be issued late in 1997.

(See also question #2 under the Mirror Cells RFP.)

Question 4. (received 13 Oct 97)
The Elevation Platform and Windbracing mainly consist of pipes which are open at the ends and the C- Ring Structure has a lot of holes and open cavities. How is your planning to protect these inner surfaces against corrosion?

Answer 4. All the internal surfaces should be protected according to section 8.7 of the Technical Specifications --- that is by painting. The supplier can propose alternative protective methods that would be more cost effective.

Question 5. (received 13 Oct 97)
On drawing 512e078 (Horizontal Bracing) the pipe ends are marked as NE3, NE4 and NE5. We could not find a reference to the main drawing 512e000 because all nodes are marked as Pi or Pe. Additionally there must be a mistake in the item list on drawing 512e078 because the quantity of item 7 is 24 and of item 8 is 21. Which quantity is correct?

Answer 5. As defined in section 8.0 of Technical Specification (dwg 512e078) NE3, 4 and 5 are only an example indicating the feasibility typology. The bidding drawings reppresent the connection sketches, the node and flange numbers and the type of pipes utilized, and define the dimensions and geometry. The working drawings will be supplied before the manufacturing phases.

Question 6. (received 17 Oct 97)
Apart from the shims for the connection of the windbracing structure to the C-Rings during the pre-erection stage, is it acceptable to insert shims during the preassembly of the windbracing?

Answer 6. We certainly do not wish to fill the entire structure of the Elevation Windbracing structure with shims at every joint. Shims at a few selected locations to improve the pre-assembly process would be acceptable.