[Dsg-rich] RICH lift calculations

[Tyler Lemon]

Hello, 

Amanda, Pablo, and I have reviewed the calculations for the forces during RICH rotation. Using AutoCAD models and a Python script we developed, we were able to compare the lift parameters and lift forces to the safety ratings of the pulley and winch we have on hand for RICH rotation. The calculations were done assuming the only the winch was used to rotate the detector. PDFs containing the simplified AutoCAD diagrams and Python-generated plots are attached. 

We set the weight of the fully assembled RICH at 1500kg. This total includes 1000 kg for the fully assembled RICH, 200 kg for the stiffening frame, and 300 kg for a 25% safety margin. Please let us know if we should use a different weight for our calculations. 

Our findings are as follows: 

1.) As RICH is rotated from horizontal to vertical, the force on the pulley decreases. This is shown in "01 force on pulley vs. RICH module angle.pdf". Despite the force decreasing as RICH is rotated, the force on the pulley at when nearing horizontal position is ~20000 N. This is greater than the 10000 N rating of the pulley on hand. While Sandro and Dario were at JLab, we were able to find a pulley that has the weight rating we need (model VB7000, rated for 3175 kg, pulley specs attached as "new pulley - VB Series Blocks.pdf"). Sandro and Dario also gave us the dimensions of the plate used to anchor the pulley to the assembly structure. If we were to procure the new pulley, we would be able to have the anchor plate prepared in time for the fully assembled RICH rotation. 

2.) As RICH is rotated from horizontal to vertical, tension on winch cable decreases. This is shown in "02 cable tension vs RICH module angle.pdf". The tension on the cable also directly relates to the force on the winch. Therefore, the maximum force on the winch will be ~11700 N or ~1170 kg. This exceeded the maximum lift rating of the fourth winding layer (1000 kg) and third winding layer (1100 kg) of the winch but not any other layer (layers 1: 1300 kg, layer 2: 1250 kg). When rotating RICH back to horizontal on March 24, 2017, we noted that the winch started on layer 3 (lift rating of 1100kg) and ended on layer 2 (lift rating 1250 kg). We are still checking our calculations regarding the load on the winch and confirming what winding layer the cable is on when during the rotation. 

In summary, by DSG's calculations, to use only the winch to rotate the RICH, we will have to procure a new pulley rated for a higher load. A suitable pulley has already found and we have the information needed to modify the assembly structure for the new pulley. DSG just needs approval to procure the new pulley. We may be able to use the winch we have on hand to rotate the fully assembled RICH from vertical to horizontal. DSG is still checking our calculations for the load on the winch. Despite the winch potentially being able to handle the fully loaded RICH rotation on its own, we still expect to use the gantry as a safety precaution. 

Best regards, 
Tyler 

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