They might not yet be matching the times of Formula One pit crews, but railway maintenance teams are set to exchange bogies – sets of four wheels at each end of a railway carriage – in record time.

This is due to new processes made possible by equipment developed specifically for the purpose by Andrew Engineering. Driven by the flexibility and precision of the SEW-Eurodrive Movidrive B drive inverter, the latest bogie exchange system (BES) 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, when traditional methods are used, it takes a team of maintenance workers an hour and a half for each changeover. Using the new BES, a single operator can remove and replace a set of bogies and have the train ready 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 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 lifting and positioning movements requiring great precision.

When equipped with an absolute encoder feedback mechanism, the inverter can be configured for fine or course movements in any direction, says 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 says. “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.”

During the system design phase, Boehringer and his team enlisted their supplier to assist. “If it’s a complex design that you can’t do yourself, they support you,” he says.

SEW-Eurodrive employed its Workbench software in producing the designs. Castiello says that by feeding in parameters like the speed of movements, the weights lifted and the type of friction to be encountered, the designers could easily select 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,” says 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,” says Lincoln Oxer, Senior Electrical Designer at Andrew Engineering.

Field bus flexibility

Oxer says another major advantage of the design was the ability to control the motors and drives via a field bus, 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 is 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,” says Oxer. “You can limit the current if you need to do a soft stop. And it also has the grunt to lift heavy weights.”

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 12-16 weeks, whereas SEW-Eurodrive could deliver in one week because its local operation holds stock. The ability to source all components from one supplier was also important, says Boehringer, who has selected gears, motors and drives from SEW-Eurodrive 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 – working from a 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 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,” says Oxer, adding that working under a heavy jacked-up train is not pleasant either, regardless of the precautions in place. “It always makes me nervous.”

In stark contrast, the new Andrew Engineering BES, powered by the SEW-Eurodrive 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 bogie exchanges in a safer, faster and more cost-effective manner.