Find content
Not Telling
wintermute, on 2012-03-24 22:36:41, said:
What exactly are people "wrong" about ?
wrong + wrong = right
Posts I've Made
In Topic: Express Trains To Suvarnabhumi Airport Suspended
2011-04-02 23:46:35
ginjag, on 2011-04-02 19:34:29, said:
unless we are lucky, there isn't an expert to tell us in one sentence who takes the blame.
Not in one sentence, no.
My knowledge dates from quite a few years back but I doubt much has changed, so here goes...
To complete the electric circuit there are two kinds of brushes:
The first one is on (some of) the axles. I very much doubt those are the problematic ones as there's not a lot of force on them, speeds are low, and they're kinda self aligning. However, if it *is* actually the problem then it is obviously Siemens who are to blame.
The second one is mounted on the pantograph (the arm thingy on the roof) that connects to the catenary. That one is much more vulnerable and tolerances to make it all work are surprisingly tight. Failure modes are legion. for ex.:
- catenary too high and your graphite arcs to vapor
- catenary too low and it wears out rapidly
- catenary too straight and it wears away in one spot
- out of spec catenary alloy could be wearing out the shoe
- bumpy line section crossovers will chip away the graphite
I understand that the airport link's wear problem has been known for quite a while and the root cause should have been addressed instead of just keep replacing parts. But then, that root cause may very well be 30 km not-so-easy-to-fix overhead wiring. Still, I don't see why as some have suggested it should be on Siemens to alter their production and/or stocking policies simply because some other contractor failed to deliver.
I remember reading somewhere that the tracks and catenary were contracted out to some Chinese outfit whose name escapes me, but I could be wrong.
Anyway, my bet is on whoever built the catenary.
(back to lurking)
