Design & Analysis Ltd were contracted to design and structurally verify a modified version of the Jubilee Line operator’s seat for fitment to the London Underground Northern Line 1995 Tube Stock fleet. The modifications required for this installation were to alter the cushion frame fabrication to mount reprofiled cross member bracketry to suit the existing Northern Line pedestal. This modification allowed commonality between the two fleets thereby bring the associated operational and cost benefits.
To allow our customer to build the new seats for the Northern Line we fully reverse engineered the existing Jubilee line seat from a physical sample including all detailed manufacturing drawings. Below are some rendered images from the CAD model we created. Believe it or not, the images are rendered CAD models and not photographs of the actual seat!
Structural analysis undertaken to verify that the design has sufficient structural integrity to meet the requirements of:
1. Railway Group Standard GM/RT2100 Issue 5 [Ref. 2].
2. Clause 3.10 of Transport for London Standard S1180-A8 [Ref. 1].
The analysis uses a combination of finite element analysis and manual calculations to determine structural integrity. The image below shows the stress from the 2000N seat back load. The point of note here is that there was a significant area of stress above the yield stress of the material. A plastic strain assessment was therefore undertaken (right hand images) to investigate the amount of permanent deformation that would be expected.
