Rail Industry Focus


Intelligent ways to extend wheel and track life

Source: Rail Technology Magazine Jun/Jul 2012

Sophisticated lubrication can have a massive impact on wheel and track wear, extending operating life and reducing maintenance requirements and frequency. RTM spoke to David Rowe, senior engineer at Rowe Hankins, about a long-term trial on Manchester Metrolink that has proven the value of ‘intelligent’ wheel flange lubrication.

A study conducted on the Kuala Lumpur Express link to its airport has previously shown how trackside lubrication can nearly double wheel life compared with no lubrication – and on-train lubrication increases wheel life by a factor of six. Rowe Hankins has been undertaking a long-term trial on one of Manchester Metrolink’s T68s showing that more ‘intelligent’ on-train lubrication systems can improve these results even further, incorporating GPS, curve detection, tram direction detection and other features to dispense lubrication only when and in the amount it is needed.

The headline result of the trial into wheel flange and track wear over the past 18 months has shown that, compared to a solid lubricant based system, the distance a tram could cover before needing its wheel flanges reprofiling was extended by over 50%, from 55,000km to 87,000km.

There were also significant benefits in terms of noise reduction, with a spectral analysis of train curving noise showing the high frequency ‘squeals’ eliminated, leaving only the lowerfrequency sounds, which are much less grating for passengers and pedestrians nearby.

Principal design engineer David Rowe has recently produced a 17-page white paper explaining the mechanisms behind track and wheel flange wear, and how lubrication can reduce it. The results of this trial have been incorporated into the report, which is based on a report given by Rowe to the North West branch of the Institution of Mechanical Engineers.

He told RTM: “We’re extremely pleased with the trial.”

He described the findings of the Kuala Lumpur study into the effects of lubrication on wheel wear and wheel life as “incredible” – with on-train lubrication extending wheel life to 1,000,000km, compared to just 170,000km with no lubrication – but noted that the Rowe Hankins system trialled on the Metrolink T68 was being compared with the same kind of solid lubricant that achieved those top results in Kuala Lumpur.

Its trial uses ‘intelligent wheel flange lubrication’, iWFL, which combines measurement of distance, curve radius detection and GPS technology to pinpoint precisely where the problems of potential wear and noise occur. Measured pulses of lubrication, variable according to the severity and duration of the curve, are applied to the flange of the wheels on the leading axle just ahead of the curve. Traces of this lubrication are conveyed to other wheels and are sufficient to moderate friction and wear without affecting traction or braking efficiency.

Proportionately more lubrication is therefore applied on the outer edge of the curve and lubrication is switched to the leading wheelset when the tram reverses direction.

Stick lubricants, by contrast, are in permanent contact with the wheels.

From T68s to M5000s to heavy rail?

Rowe said: “Metrolink are also very pleased, and they are looking for us to do another trial.”

The new trial will be on Metrolink’s new stock: the Bombardier M5000s, based on the Flexity design. There will be a bidding process for wheel flange lubrication on the new fleet, which Metrolink has confirmed it “definitely wants”, Rowe said.

The new trial will be able to utilise some of the existing trial equipment, but Rowe added: “Every kind of stock has a unique mounting requirement. We go into discussion with the customer, we talk about precisely where they’re getting problems on their network, and because we can do location-based dispensing, we can very much customise the use of our equipment to match their requirement, then customise the equipment to mount onto the vehicle.”

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 distancebased 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.

“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.”

Trial results

Extract from the white paper ‘Wheel Flange Lubrication: Benefits, Advances and Trials’, by David Rowe.

The use of intelligent wheel flange lubrication has brought a 50% improvement in the wheel life of a T68 LRV working over a network of street and conventional rail track. This 50% improvement is relative to vehicles using onboard stick lubricants; stick lubricants have been shown in the past, when compared to unlubricated vehicles, to extend wheel life by up to a factor of 5.

The application of GPS and inertial sensing techniques to flange lubrication has proven to be cost effective on the basis of wheel savings alone; more as yet unaccounted savings will be being made by its use from the rail infrastructure.

The study has identified that on the T68 LRVs that vehicle reversal would be beneficial. Additionally, a wheel turning scheme based around a reduced amount of turning at 50,000km should be looked at. This would also reduce the amount of back of flange contact and noise being generated.

The trial did not reduce the level of flange wear to the point at which flange wear stopped being the primary cause for wheel turning. It is possible that a different type of lubricant may bring further reductions in flange wear.

It is also possible that changes in the yaw stiffness of the vehicle, conicity of the wheels and durability of the wheel steels could reduce the flange wear further.

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