Large Binocular Telescope Project

Questions & Answers

concerning the RFP for the

Telescope M1 Mirror Covers

updated 25 May 2004

Questions answered on 18 May 2004

Question 1. (received 12 May 04)
Can English units be substituted for the metric.

Answer 1. Yes you are welcome to do shop drawings in English units. And we will only complain a little bit if you use English fasteners. But you still have to match the metric interface points to the telescope, and you still have to respect the metric tolerances.


Question 2. (received 12 May 04)
What are the electrical requirements?

Answer 2. The motors and the simple electrical controls are described in section 3 of the Technical Specification 401a022d. The idea is to have just a test cabinet for moving the motors back and forth and stopping them with the limit switches at the end of travel. The sizing parameters for the motors are described in Technical Report 727a010c.


Question 3. (received 12 May 04)
The "ties" on drawing 727a011 are not called out or shown.

Answer 3. These ties are meant to be made of the same material as the fabric cover. They are designed to limit the opening of the sectors.


Question 4. (received 12 May 04)
Line 36 on 727a011b says "COVERING TH. 0.4mm, Kevlar", what and where is this item? (Is there a view that shows the fabric?)

Answer 4. Line "36" has been put on the list, to state that a fabric cover must be placed above the metallic frame. The purpose of the cover is to stop dust from entering either the hinges or the ends of the folding sectors. There is not a specific fabric layout drawing.


Question 5. (received 12 May 04)
The quantities on items #1,2,3,15 should be two not one on sht. 727a009b.

Answer 5.
Item 1: the dwg 727a048 contains 2 pieces
Item 2: the dwg 727a049 contains 2 pieces (Left-Right)
Item 3: the dwg 727a050 contains 2 pieces (Left-Right)
Item 15: the dwg 727a061 contains 2 pieces (Left-Right)


Question 6. (received 12 May 04)
From the drawings 727a007, 008, 009, 011 and 012, can you confirm that all the parts required to build this are all shown?

Answer 6. We think it is complete. Please send specific remarks, if any.


Question 7. (received 12 May 04)
Can an alternate hinge system be substituted?

Answer 7. Yes, we are open to the proposal of an alternate hinge system. But make sure that the alternate system is similar in function, in stiffness and in smoothness of motion.


Question 8. (received 12 May 04)
8a) On drawing 727a072a the "chain" in the upper detail shows a length of 12293.6 with a space 203.2 typical and a 101.6 space where and at what end?

8b) Where does item #2 go?

8c) The travel is 12192 on each side, what happens at the ends, is there a stop?

8d) Have the holes already been placed in the cell?

8e) Is the 25.4 mm pitch set? That is not a standard chain link 1mm less is.

Answer 8.
8a) The short space (101.6) occurs where the two chains meet. Zoom in near the sprockets on the left side of drawing 727a072a to see this.

8b) Item 2 is the support bracket for the chain, it must be supplied and it will be attached to the cell (by the customer).

8c)There are electrical limit switches. Mechanical stops can be added if needed: specific tailoring must be foreseen at factory testing.

8d) The mounting holes for the chain mounting brackets have not yet been placed in the cell.

8e) An equivalent standard chain could be implemented keeping the same gearing ratio and other design parameters. (We still think a 1-inch chain has a 25.4 mm pitch.)


Questions answered on 25 May 2004

Question 9. (received 21 May 04)
In the BOM on sht 727-a011 line 36 , 2 ea., cover, th.0.40 Kevlar:
a) There are several (9) types of Kevlar,
b) There are a variety of thicknesses,
c) The closest to the call out, that we see working is K129-731, 0.37mm thk. X 54" wide, 8.1 oz. per sq. yard , ballistic fabric, water repellant finish. @ $45.00 per sq. yd. material cost.

Is this what you have in mind? How did you intend for the fabric to be attached to the st.st. fan covers and is the ends covered and how do you see that folding up with the st.st. fan covers.

Answer 9. Yes, that is the general idea.
The thickness is OK (it must be < 0.4mm). The fabric must be attached to the metallic cover; no specific design has been finalized.


Question 10. (received 21 May 04)
We are missing sheets 727a030 and 727a031 (items #2 & #3 0n 727a011).

Answer 10. Item 2 drawing 727a030 is the first sector fixed to the fixed arm.
Item 3 drawing 727a031 is the last sector fixed to the moving arm.
These 2 drawings depend on the hinge design that will be adopted. They have not been drafted.


Question 11. (received 21 May 04)
On sheet 727a009 item #15 is not called out on the drawing.

Answer 11. The BOM is in the left lower side.


Question 12. (received 21 May 04)
On sheet 727a011 item #16 & #36 is not called out (#16 has no details and quantities).

Answer 12. Item 16: OK see the updated drawing which is available on the web..
Item 36: OK see the updated drawing which is available on the web.
727a011c

See also the updated drawing.
727a045b


Question 13. (received 21 May 04)
What does the word "GLISSA" refer to on drawing 727a052?

Answer 13. This is an impregnated bushing. (I haven't been able to translate "glissa".)


Question 14. (received 21 May 04)
They are showing # for the machining tolerances but do not make any sense (uni-iso 8015 and uni-iso 2768-mk) What are these?

Answer 14. These are the italian general construction tolerances for steel structures. You may propose an equivalent US standard.


Question 15. (received 21 May 04)
Has the second cell been sent up the Mountain?
If not can we use that as a test fixture to test the covers, it would save a lot of money doing that, instead of building a separate machined structure.

Answer 15. The second cell has not been sent to the mountain. It is still in the Mirror Lab in Tucson. However, the schedule of the second cell is quite tight, so it seems unlikely that using the second cell to test the mirror cover will be practical.

However, we are always willing to discuss creative alternate proposals.