Power transmission in transport — whether it’s pedalling a bicycle or driving a train — is a familiar concept to most of us.
The energy generated by the engine (or pedals) has to be converted into power, often torque, at the business end, and that some mechanical system — maybe of couplings, chains, shafts and gears — gets the job done.
This also applies to many industrial scenarios. Direct drive motors are not always practical, due to spatial and environmental constraints among others, and what may appear to be rudimentary mechanical linkages are often the most practical option. Power is also transmitted via hydraulics and pneumatics in many applications, but those areas are for another article.
Like many other aspects of engineering, European manufacturers are facing stiff pricing pressure, both from Asian and eastern European manufacturers able to take advantage of cheaper labour and lower operating costs. A recent report on the European market for gearboxes and geared motors by Frost & Sullivan highlights these challenges.
The report also notes that the need for improved productivity is driving investment into more efficient power transmission systems, and that demand for more efficient components, such as planetary gearboxes, is expected to remain healthy. And it’s a sizeable and growing market.
The report predicts the European gearboxes and geared motors market to be worth some €3.13bn (£2bn) in 2011, up from around €2.48bn in 2004.
One area where technology is excelling is in aiding the specification and selection of power transmission components. Much of the calculation (and with it the possibility of error) has been taken over by software, either as standalone packages or via code sitting behind a website.
There are many examples of these types of software. For example, Alpha Gear Drives has developed a package called Cymex which can interrogate a database of some 6,000 motors from a variety of manufacturers — a database the company claims is the largest library of its kind in the world.
Working from input application data, the software will calculate and design a complete drive train — and allow users to experiment with different loadings to test the train in detail.
Zero-Max also produces software aimed at taking the strain out of selecting components for power transmission. Again, the user inputs application data, such as coupling speed, peak torque, angular, axial and parallel misalignment, a service factor and shaft sizes. The software will recommend a coupling model for a particular application.
Neeter Drives has put its 3D CAD Product Configurator online (see http://www.powerjacks.com/). Users can view and configure a solid model of Neeter Drives gearboxes in real-time then download the required 3D solid model or 2D drawing. Once a gearbox is selected the user can configure the technical specification for his or her exact requirements and generate a model which can be imported directly into most popular CAD software — over 20 formats are supported.
One inherent feature of power transmission components has been material degradation (often leading to failure) often enhanced by the local environment in which the components are placed. Of course, failure of components leads to downtime, which can be very costly in industrial processes.
Advances in materials science have gone some way to combating the problem — one example being the use of PEEK (polyetheretherketone), a polymer made by Victrex, in gear wheel manufacture.
The replacement of metal gears by polymer ones enables reductions in noise, cost and weight. For example, in one application actuators are used for controlling the air intake louvres of automatic aircon systems in cars. Inside the actuator the highly-loaded gear wheels are made of PEEK, with its high mechanical strength, good creep resistance, low water absorption and minimum wear.
Additional benefits are that due to the low coefficient of expansion, engineering clearances can be reduced, resulting in components such as oil pump rotors achieving their optimum operating conditions almost straight from cold. This in turn eliminates engine oil starvation.
Wear is not the only factor that limits the lifetime of power transmission components. Manufacturer Renold Chains advises its clients to consider all the factors involved in the mechanics of the application. It’s all-too easy to specify components based on breaking load, but it doesn’t necessarily ensure the best solution in terms of service life.
Renold Chains’ David Turner said: ‘You can’t blame engineers for using breaking load as a criteria for selecting chain. Breaking load was one of the earliest chain standards, so engineers became used to specifying it that way — and many of them still do.
‘What we have to do now is to re-educate engineers that breaking load is no guide to chain performance, and that chain strength is not the best measure of chain life. In fact, high-tensile strength can lead to a shortened working life if component strength has been achieved by making parts hard but brittle.’
To enable specifiers to optimise their chains, the company has produced a program (downloadable from www.renold.com), which can choose from 11 product types and 400 chain variations depending on the use — from relatively undemanding applications right up to the most arduous environments where chains such as the highly-engineered Synergy range are ideal.
Looking at how power transmission is a vital part of many plant systems, it becomes obvious how downtime will equal huge financial losses. At Corus Steel’s tandem cold mill in Port Talbot, new gearboxes supplied by David Brown Engineering have contributed to an increase in production capacity of around 50 per cent. And the combined gearbox and AC motor configuration occupies the same footprint as the old DC motors.
Couplings are also an important part of many systems. Mayr Transmissions’ couplings are claimed to have improved reliability of underfloor pulpers and calendar roll drives at paper mills. These rigid couplings feature a patented cone seating arrangement with backlash-free, high-capacity torque transmission.
And for a more down-to-earth example, Brevini has recently supplied a bespoke gearbox system at Yorkshire Water’s Rawcliffe sewage treatment plant which treats waste for some 45,000 households.
Failures were previously frequent on the plant’s aerator gearboxes, largely due to vibration and the large stresses involved in moving the half-tonne aerator paddles. A planetary gearbox — engineered to extend the mean time before failure — was designed that incorporated anti-vibration components. This contributed to an estimated payback time of around two years for the whole project and minimal downtime.
Power transmission components may not be seen as exciting, but specifying the wrong parts can mean wasted money. With the wealth of electronic help available there is now less excuse than ever for getting it wrong.
With European manufacturers facing stiff pricing pressure from Asia and Eastern Europe, technology is available to help with the choice of more efficient power transmission systems.