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Auxiliary drive systems – a hidden opportunity?


Dayco, a leading engine products and drive systems supplier for the automotive, industrial and aftermarket industries, has the technical knowledge and expertise to highlight the challenges and the resulting opportunities facing the aftermarket as modern vehicles incorporate the latest power transmission developments.

In common with many aspects of vehicle design and engineering, the auxiliary drive systems used in both the heavy duty and automotive sector have changed considerably over the last 25 years. Whereas in the past vehicles might have used several belts that only had three or four pulleys/components to drive, the belts used in modern systems can have as many as 10.

By their very nature, these complicated, multi-component drive systems are far more susceptible to issues such as pulley misalignment, which can lead to unacceptable noise levels and premature wear, and therefore require belts that are able to operate efficiently under the challenges they present.

This evolution, combined with the requirement to cover greater distances between replacement compared to their predecessors, has meant that the construction of the auxiliary belt has also had to develop. So where previously the belts would be made with a neoprene rubber compound that would last between 50,000 and 80,000 miles, contemporary designs incorporate an EPDM (ethylene diene propylene monomer) compound that is able to cope with the multiple pulleys and smaller radii inherent in these new drive system layouts and last between 90,000 and 100,000 miles before they need to be replaced.

When it comes to the likely cause of failure, traditionally it would very likely to have been as a result of the belt cracking, as opposed to the loss of rubber material more common with current design. The effects of belt failure also reflect these drive system developments as previously a belt failure would not generally be catastrophic as the multiple belt design would mean that fewer vehicle systems would be disabled. This is in stark contrast with the modern single belt layout in which every system would suffer.

What’s the Problem?
Due to the demands of multi-component drive layouts, original equipment (OE) suppliers such as Dayco have to develop the high-quality belts and accessories that are necessary to ensure the reliable function of the systems the vehicle manufacturer’s engine design teams specify.

In some cases, these layouts are well designed and have generally equal spacing between the pulleys and rarely cause problems. However, some design solutions are less ideal and combine both very short and very long spans between these points, which is where the problems of both noise and wear can arise.

As an example, belt misalignment – from a pulley being out of plane or due to a worn bearing – such as between a power steering pulley and backside driven water pump pulley over a long span and the water pump to crankshaft pulley on a short span, will cause problems.

In this scenario, any misalignment between the power steering pulley and the crankshaft pulley will NOT be corrected as the belt enters the backside water pump pulley. The belt will travel around the backside pulley in the same plan that it enters, which means the belt will have to make up the misalignment angle in the very short span that enters the crankshaft pulley. This will generate higher pressure on one side of the belt’s ribs than the other as it is being forced into the crankshaft pulley grooves, thus creating the conditions for both excessive wear and noise.

So, What’s the Answer?

Armed with this background information, the workshop is able to make sound decisions that both prevent possible belt failure, and the subsequent cost and inconvenience caused by a vehicle breakdown, and provide legitimate sales opportunities, as a direct result of following industry best practice.

Despite their design life, auxiliary belts should be regularly inspected once the vehicle has covered 60,000 miles and irrespective of their condition, replaced at 90,000 miles, along with any associated component that shows of wear. Naturally, should the belt become noisy, the cause must be investigated as they rarely emit noise that is unrelated to other factors within the system. Once the root cause is established, any worn component must be replaced to prevent unnecessary damage.

As a global leader in power transmission technology, Dayco has both the tools to identify potential problems and the replacement belts and components to rectify them. For more information regarding the OEM quality power transmission products in the Dayco range, please email: info.uk@dayco.com or visit: www.dayco.com