TRACK TECHNOLOGY
He said the results should be of real relevance to heavy rail, too, especially since the T68 has something of the profile of a heavier train, rather than a light tram, with weight per wheel contact at around six tonnes.
He said the particularly innovative thing about iWFL was the way lots of different kinds of information was combined intelligently. He said: “You can do time-based dispensing, which is historically done. You can do distance- based dispensing, which is also historically done. You can even do detection-of-bend sensing and dispensing, which has done more recently done, and in very recent times, you can get systems that pick up information from the
Passenger Information Systems, but they tend to be few and far between.
Below: City trams often follow tracks with tight radius curves that cause greater noise and wear on track and wheel flanges.
“What you haven’t got on those systems is the analysis of the track, the network situation, the speed of the vehicle, all brought into one, so we can avoid dispensing when they’re going to be putting out sand, to avoid making a grinding paste. You haven’t got the additional dispensing on corners: if you’re going for a longer distance you don’t have the detection of the more gradual bends, where you can get wear, which we have got in Manchester. More particularly, you don’t get the concentration of dispensing onto the specific locations where it’s needed, rather than the rest of the track, so you’ll end up with a smaller volume of consumable being used for our system, as compared to the rest of the systems.”
Braking distances
One particular issue with lubrication methods is the risk of over-lubrication having an effect on braking distances by reducing friction too much.
Trials were done using the iWFL system, but the conditions required to produce a significant increase in braking distances were so unlikely and specific as to be “vanishingly small”,
Rowe said: they would involve lubrication dispensing nozzles on both sides of the tram becoming misaligned at the same time on multiple trams on the same stretch of track, to build up enough grease to have an effect on braking.
He said: “We ran the trial for effectively two years, and we’ve never had either of the nozzles move. If you look at the inspection period for checking the nozzles, the chance of having two nozzles moved and not being detected is vanishingly small.
“Then, just to cap it all off, even if a tram has both nozzles spraying onto the tread, to get a slippable surface, we had to run that vehicle over that track six times over before we got enough grease on the track to actually get the extension in braking distance. You’d really have to have six vehicles all with identical double faults, following each other over a piece of track, before you’d get an extension in braking distance.
“Because of the intelligence of the system, we don’t dispense on braking areas anyway: we positively avoid them, because we want to avoid mixing the sand with the grease.”
FOR MORE INFORMATION
For details or to obtain the white paper call 0161 765 3000.
rail technology magazine Jun/Jul 12 | 73
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