Gearing up for quick changes

They might not yet be matching the times of Formula One pit crews, but railway maintenance teams are set to do their work in record time. This is due to new processes made possible by equipment developed specifically for the purpose.

A single operator carries out the bogie exchange in a safer, faster and more cost-effective manner.
Driven by the flexibility and precision of the SEW-Eurodrive Movidrive B drive inverter, the latest exchange system enables faster, safer and more economical turnaround in railway maintenance sheds throughout Australia.

Changing bogies is a demanding business. According to Neil Boehringer, Project Manager at Andrew Engineering, the company that manufactures the bogie exchange system (BES), the new design halves the changeover time.

He said that when traditional methods are used, it takes a team of maintenance workers an hour and a half for each changeover. Using the new equipment, a single operator can remove and replace a set of bogies and have the train ready to leave the shed within 45 minutes. This makes it easy to carry out maintenance on the wheels or other components away from the train.

Precise movements
The older methods rely on jacking the whole train up or working from below in specially constructed pits, but thanks to the precise movements controlled by the Movidrive B drive inverter, the car need only be lifted by 50mm. The bogie is then easily removed from the carriage and brought out sideways. This combination of movements requires a complex set of drives, motors and gears, working in all three axial directions (x, y and z), with some of the lifting and positioning movements requiring great precision. 
“When equipped with an absolute encoder feedback mechanism, the inverter can be configured for fine or coarse movements in any direction,” said Mauro Castiello, Sales/Application Engineer at SEW-Eurodrive.
“The absolute encoder gives us the ability to lift and position with a tolerance of 0.1mm, in real time,” he said. “In other cases, when we don’t need that level of precision, it’s more like manually operating a crane. You press the button and the motor runs, and then you release the button to stop it.”
Design support
During the system design phase, Boehringer and his team at Andrew Engineering enlisted their supplier to assist. “If it’s a complex design that you can’t do yourself, they support you,” he said. 
The company employed its Workbench software in producing the designs. Castiello said that by feeding in parameters like the speeds of the movements, the weights to be lifted and the type of friction to be encountered the designers could easily select the appropriate motors and drives. To cater for the range of movements, the system design included a combination of helical bevel and helical worm gearboxes.
“After the equipment selection was made, we reviewed the calculations together with the Andrew Engineering designers. Once approved, a three-dimensional CAD model of the system was provided and then used directly into their own design software,” said Castiello. “Their skilled designers could use this input to engineer a complete BES, with no additional information from us.”

Because the movements are sequenced when the bogies are changed over, the designers requested a single inverter to control the individual movement of four different motors. This resulted in considerable savings for the overall project.
“Rather than asking you to buy a Rolls Royce version, SEW-Eurodrive optimises its designs to suit our needs every time we work with them,” said Lincoln Oxer, Senior Electrical Designer at Andrew Engineering.

Fieldbus flexibility
Oxer said another major advantage of the design was the ability to control the motors and drives via a fieldbus, with acceleration times, deceleration times and other parameters easily managed. Similarly, any adjustments that become necessary as conditions change during the lifecycle of the machine can be carried out remotely or by the operator at the human-machine interface (HMI). 
The complete system controls 15 different motors through seven drives. Some of the motors have brakes; some have absolute encoders for extra precision and others don’t. Consequently, there are a wide variety of power and current requirements during the bogie changeover and it is essential that all the parameters can be switched simply. 
“You get complete parametrisation and adjustability at your HMI without having to connect up a laptop to do the tweaks. You can limit the current if you need to do a soft stop. And it also has the grunt to lift heavy weights,” said Oxer.

Delivery time was an important factor in the success of the project. According to Oxer, the industry norm is to deliver this kind of equipment in 12 to 16 weeks, whereas SEW-Eurodrive was able to deliver in one week because their local operation holds stock. 
The ability to source all of the components from a single supplier was also important said Boehringer, who has selected gears, motors and drives from the company for complex projects over many years. It simplified the design process and there were no concerns about different suppliers arguing over warranty responsibilities.

Safer, cheaper and faster
While the cost, speed and labour-saving advantages of the BES are clearly important, improved safety is the number one benefit. The two traditional methods of exchanging bogies, that is, working from an underground pit beneath the train car or working beneath the jacked-up train, require special precautions. This is not the case with the new system.

When a pit is installed in a maintenance shed – an expensive civil construction exercise – special work practices must be put in place to maintain the trains. Working in a pit beneath the train means working in a confined space. Occupational health and safety (OH&S) regulations for confined spaces include requirements for quick and easy exit in case of emergency. At the same time though, the maintenance crews are working at height to change the bogies, and there is a requirement for scaffolding to ensure their safety. 
“These two requirements are fighting against each other, and maintenance might be delayed because the issue is too hard to resolve,” said Oxer.
He said that working under a heavy jacked-up train is not pleasant either, regardless of the safety precautions in place. “It always makes me nervous,” he said.

In stark contrast, the new Andrew Engineering BES, powered by the Movidrive B drive inverter, overcomes this safety dilemma. In railway maintenance sheds around Australia, it is now possible for a single operator to carry out the bogie exchange in a safer, faster and more cost-effective manner.

SEW Eurodrive
03 9933 1000

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