A versatile industrial transmission used in Australasia for conveyors, crane drives, lifting equipment and process automation applications has found a unique use in bridge engineering. Bonfiglioli Transmission , a part of the international Bonfiglioli group, report on how the F series parallel shaft drive was employed on the Bizkaia suspension bridge in Spain.
In 1893, industrial expansion led to the construction of one of the earliest river crossing systems in the world, the Bizkaia suspension bridge. This transporter bridge with gondola connects two towns without disrupting the maritime traffic of the Port of Bilbao. The bridge, the world’s oldest transporter bridge, is constructed from riveted steel girders (with a structural design not dissimilar to that of the Eiffel tower).
A bogey runs under the span of the bridge and carries a gondola suspended on 18 steel cables, which transports pedestrians and vehicles from one side of the river to the other. The empty weight of the gondola is 20 tonnes. It has been calculated that since the bridge first opened, it has carried some 650 million passengers across the river Nerviòn, in crossings that have continued uninterrupted 365 days a year, 24 hours a day. The gondola departs every eight minutes and takes one-and-a-half minutes to complete the crossing.
The bridge is now driven by twelve Bonfiglioli F302 UH40 24.4 P112 H3 gearboxes powered by 2.2 kW, 3000 rpm electric motors with encoder control. Rated torque is 176 Nm and the duty cycle is 1.9. The gear motors are controlled by closed loop vectorial frequency converters (a technology used in Australasia for applications such as industrial process control).
The main challenges of the application are continuous operation all year around, massive inertia (varying from 20 to 50 tonnes), and an aggressive marine environment. Another strict requirement is the need to ensure passenger comfort in addition to reliability. Bonfiglioli parallel shaft helical F series gearboxes were selected as the suitable product for the application because of their low noise operation and reduced angular play (which translates into greater comfort) in suspended installations.
The Bonfiglioli parallel shaft helical F series ensures that the installation is unaffected by radial loading generated by alignment errors between the bogey frame and its wheels. A high duty factor was calculated to suit input power and the installation position was chosen to ensure that all gearbox components run in a permanent oil-bath. This helps to ensure the operational reliability that the application demands.
To ensure that the drive system is adequately protected against the salt air, the gearboxes are fitted with Viton seals and are externally finished in a 200µm thickness coating of RAL9010 white epoxy paint. Applications like the Bizkaia suspension bridge, which has been put forward for World Heritage listing by UNESCO, reinforce Bonfiglioli Transimission’s confidence to accept such challenges.
The F series drives used in the Bizkaia suspension bridge form part of Bonfiglioli Transmission F series of easily installed modular shaft-mounted gearboxes in capacities from 140 Nm to 14,000 Nm. The F series of speed reducers and gear motors features high efficiency gears, sturdiness, quiet operation and a broad range of sizes, ratios and configurations to fit numerous applications.
The Bonfiglioli Transmission F series can be used in the following applications:
- Materials handling and lifting equipment
- Roller conveyors
- Belt and chain conveyors
- Screw conveyors
- Mixers
- Aerators and batchers used by the food and chemical industries
- Industrial crane travel drives
Advantages of the Bonfiglioli Transmission F series’ shaft mounting include simple, neat and easy installation and removal plus avoidance of costly machining of mating surfaces and shaft alignment. The series has compact axial dimensions, low weight and high torque outputs. With its modular design and reduced number of components, the F series facilitates easy assembly, quick delivery and a high level of customer service.