Large Binocular Telescope Project

Questions & Answers

concerning the RFP for the

Enclosure Cable Chain & Support

January 5, 2000


Question 1. (received 03 Dec 99)
a) Referring to drawing 310e001d, Zone E9-11 shows the chilled water and electrical cable plate detail. What material type/thickness/grade is required?

b) What is the spacing interval along the length of the two cable chains for this detail to allow proper operation? Is the spacing requirement for the chilled water and electrical chains the same?

Answer 1.
a) The materials usually used, and the ones we prefer, are aluminium and its alloys. The thickness etc. depends on the kind of the chain used.

b) Normally one "plate" is inserted every two passes (links) of the chain.

Question 2. (received 03 Dec 99)
Referring to drawing 310e001d, Zone B8 shows a cross section of the Cable Chain and towing bar. Is the "floor" area considered to be part of the deliverable items? If so, what is the material and thickness? It is understood that the shim area at the interface to the Pier Upper Ring leg will vary in thickness according to site conditions. There is a nominal elevation change shown of 45 mm. However the required floor thickness prior to shimming needs definition.

Answer 2. The supply includes everthing that is interfaced with the Pier Upper Ring (dwg 421e029d) above level 21055 mm, and with the enclosure structure (dwg 302m009b). So, the threaded base plates (to be welded on site) and the thicknesses of adjustment are part of the supply. The thicknesses for shimming will need a maximum adjustment of 6 mm*. The 45 mm includes the base plates and shims mentioned above and the thickness of the basic "floor" structure relevant to the fixed part (External Chain Guide Structure, #3.0 of the Technical Specification) of the Enclosure Cable Chain, that you will have to define according to your construction standards.

* 6 mm shim thickness to be confirmed at the issue of the contract.

Question 3. (received 03 Dec 99)
Referring to drawing 310e001d, Zone B8 shows a cross section of the cable chain and towing bar. There is a structure shown interior to the cable chains. The structure has caster wheels on the bottom that interface to the "floor" at elevation 21100 mm. It is assumed that this is a deliverable item, and that there is one such structure that interfaces the driven cable chains to the tow bar assembly. Please confirm. Also, definition is needed for this structure. What is the material type? What are the sizes of the members used? What is the configuration (i.e. cross brace locations, work points, etc.) of the members? What type of material should be used on the caster wheels?

Answer 3. The Inner Distance Structure (#3.0 of the Technical Specification) with relevant swivel wheels is part of the supply. These structures are usually realised in tubular steel with wheels made of a plastic material.

Question 4. (received 03 Dec 99)
Referring to drawing 310e001d, Zone B8 shows a cross section of the Cable Chain and towing bar.

a) The Cable Chains appear to have some roller mechanisms on each corner of the chain where it interfaces with the stationary structure. What materials are used for the mechanisms and the wheels? Please provide details of the mechanism including the spacing interval along the length of the cable chain.

b) The Cable Chains appear to have caster wheels on the bottom. What type of material should be used on the caster wheels? Are they a swivel caster type? If so, please specify bearing type on the swivel. What is the load rating of the caster?

Answer 4. a) Yes, these guiding rollers are indispensable to limit the friction of the rotation. Normally they are made of steel.

b) The caster wheels are of the swivel type. For both the Inner Distance Structure and the Cable Chains, their choice depends on the loads applied to them, due to the movements and to gravity.

Question 5. (received 03 Dec 99)
a) Referring to drawing 310e002d, Zone E11: Section B-B shows a cross section of the Cable Chain assembly at a location between the Pier Upper Ring structure legs. There is a bracket shown connecting the outer portion of the stationary structure to the concrete roof of the Telescope Pier. What is the material thickness/type? What is the spacing of these brackets? Does the fabricator supply the anchor bolts to attach the brackets to the concrete? Is the bracket bolted or welded to the stationary structure? If bolted, are slotted holes required? If welded, would this be a field weld?

b) There is a support bracket shown in this sectional detail under the floor. Please provide material type, thickness, and attachement details of this bracket. Does it bolt or weld to the floor?

Answer 5. Section B-B represents some auxiliary supports in order to grant the planarity of the sliding surface relevant to the mobile part of the cable chain. The number and kind of supports depends on the building characteristics of the fixed part. The supports will have to be made in steel and fixed to the concrete with anchor bolts (Hilti or Fisher). (LBT will provide the concrete anchor bolts.)

Question 6. (received 03 Dec 99)
a) Referring to drawing 310e003d, Zone A11: Provide details on the two pivot brackets that allow the tow bar to adjust in the horizontal plane. Please specify bearing type, size of bearing, material thickess/type, number and size of attachment bolts, pin details, and lubrication scheme if required.

b) For detail E, provide details on pin and sleeve diameters, material grade, clevis dimensions, bushing type, clearances between pin and bushing, weld sizes to attach pin to tow bar.

Answer 6. In the drawing 310e003d are reported the main characteristics of the "Towing Arm Structure", you will have to propose its details according to your manufacturing standards and specific characteristics of the towed structure (friction, loads etc.). The system will have to be self-lubricating.

Question 7. (received 03 Dec 99)
Does the designer have a source for buying the cable chain assemblies as a complete mechanism? If so, what is the source? Can another supplier provide an equivalent cable chain? If so, please provide the specifications for the cable chain so alternate sources could be investigated.

Answer 7. There are several suppliers of this type of cable chain. These include Igus, Stendalto, Gortrac, etc.. The drawings are based on a chain that would be typical of Stendalto, but a particular brand of chain is not required for this supply.

Question 8. (received 03 Dec 99)
Various parts of Technical Specification 401e047c dated 24Nov99 make reference to material options and/or the supplier determining material types. Referring the above questions to the Technical Specification would not be sufficient reply since the loads of the mechanisms are not known. The cycle times are not know as well as other pertinent design factors like the minimum bend radii of cables, installation constraints, etc..

As presented, the RFP requires significant engineering (not detailing) to provide a product that will meet all specifications. Is this level of engineering going to be required to perform this contract?

Answer 8. The bid foresees the development of all the engineering activities needed to be able to supply the complete and functional product, as per specification.

The Technical Specification lists the environmental conditions under which the Cable Chain must operate. Aside from being in a colder mountaintop environment, these conditions are typical of what would be required of a typical industrial cable chain. The maximum velocity of rotation is 1.5 degrees per second with a maximum acceleration of 0.2 degrees per second per second. We expect a typical duty cycle of 10 full cycles of rotation per day. All cables and hoses to be installed in the cable chain will have minimum bend radii compatible with the dimensions of the chain shown in the drawings.

Question 9. (received 21 Dec 99)
The 60 mm diameter hole on the "electrical" chain, is very near to the lateral rollers having the function of containing the chain. Can it be lowered 5 mm?

Answer 9. Yes.

Question 10. (received 21 Dec 99)
Half of the load relevant to the towing arm rests on the chains. Is it possible to realise a support to the towing arm that slides on the lower track, by previous widening of the track itself?

Answer 10. Yes.

Question 11. (received 21 Dec 99)
What is the estimated weight of the cables and tubes?

Answer 11. For each chain, the weight is about 50 - 55 kg per meter.

Question 12. (received 05 Jan 00)
May we have an extension to the proposal due date in order to obtain and review a subcontractor proposal?

Answer 12. Yes, we will postpone the proposal due date from January 12, 2000 until January 19, 2000.