I was stood on Patricroft station this morning and could see three different types of gantries. What's the difference between the types, I just thought they were steel girders welded/bolted together to hold up the wires?
Pete
The project is still unfolding, but there are a variety of structures depending on the ground conditions and forces acting on the OHL.
The simplest arrangement is a thin post and cantilever over each track, but that seems to be used only in the most favourable conditions (the western end of the line has a lot of these).
There is a lot of larger L-shaped stuff going up, with a heavy lattice post and cantilever over both tracks - maybe the ground conditions are poor on one side.
This dominates around Eccles and over Chat Moss itself.
The even bigger stuff is often positioned to support extra switchgear or the termination point of a wire run (carrying tensioning weights etc).
These crop up regularly along the route.
Then at significant junctions, there are massive portal structures over all tracks.
There are about 12 of these across Ordsall Lane Jn, and some for the Weaste branch at Eccles (anywhere with multiple tracks, basically).
Track curvature brings other complications, but the Chat Moss line is practically straight except for the junctions at both ends.
My guess is that this scheme is more "heavy duty" than would have been used in the past, to give a more robust system.
Given this is the first scheme with the new design, it's very important that the design "works" and gets completed on time and budget or it will impact all the later schemes.
