Solving long-term gearbox challenges in asphalt mixing

Gearbox failures in heavy industrial equipment can result in costly downtime and reduced productivity — issues McQuillan Quarries knew all too well. Its asphalt mixer, vital to operations, was hindered by frequent gearbox breakdowns, driving up maintenance costs and delaying production. Seeking a durable, efficient solution, McQuillan Quarries partnered with Technidrive, which engineered a custom planetary gearbox system that resolved these challenges while setting new standards for reliability and performance in asphalt production.

Since it was founded as a quarrying operation in 19^th century Belfast, family-run McQuillan Quarries has grown into a significant player in construction, waste treatment and recycling. Today, the company is a multi-million-pound operation that serves several industries including quarrying, civil engineering, waste management, demolition and environmental services.

Among the most crucial pieces of equipment McQuillan Quarries relies on an asphalt plant mixer, which is vital in combining aggregates from the quarry with bitumen to create durable, reliable road surfaces across Northern Ireland. However, McQuillan Quarries was experiencing issues with downtime in this essential piece of equipment.

For over a decade, McQuillan’s mixer suffered frequent gearbox failures, with gearboxes often lasting as little as a year and a half before failing. Each failure incurred significant costs, including expensive replacement parts, as well as extensive labour and downtime.

Further issues arose from the gearbox system’s design. Its two shafts were causing problems due to misalignment and uneven load distribution, which led to excessive wear on bearings and other components. This resulted in premature failures, increased maintenance and operational downtime.

“We were losing faith in the existing setup due to the high rate of failures and the extensive stock of left- and right-sided gearboxes we had to maintain just to stay operational,” says Colin Mitchell, general manager at McQuillan Quarries.

Deciding on a solution

McQuillan Quarries didn’t just require a new gearbox system, it needed a whole new design engineering concept. That’s why it approached Technidrive to engineer a solution that could handle the high-impact load of mixing bitumen and stone.

Technidrive began by assessing the mixer’s needs and the constraints of McQuillan’s production schedule. Several considerations shaped the final approach.

First, the new system needed to withstand substantial shock loading from each three-tonne batch drop, a major stress point for the previous gearboxes. Second, the existing configuration had limited space for additional equipment, so Technidrive’s solution required precision engineering to fit seamlessly within the existing footprint. Third, to reduce the downtime associated with frequent gearbox replacements, Technidrive aimed to design a system with a life expectancy of ten years or more.

Several options were considered before deciding on a final solution. One possibility was to upgrade the existing gearbox to a heavier version, but that didn’t address the shortcomings of the current system such as excessive wear. Another idea was to use a single gearbox to drive synchronised gears on the shafts, but this idea would potentially concentrate stress and lack the flexibility needed for reliable operation.

Ultimately, Technidrive’s chosen solution was to implement two planetary gearboxes that utilised the existing motors to independently drive the shafts. Custom synchronising gears were added to keep the shafts aligned, creating a robust solution capable of handling the system’s demands while delivering maximum benefits.

“We designed the planetary gearbox arrangement to absorb impacts more effectively and minimise stress on the system,” said Andrew Ritchie, technical sales manager at Technidrive. “Our goal was to provide a solution that wouldn’t just solve the immediate issues but would ensure long-term reliability.”

Durability for high-impact applications

For manufacturers, any change to a long established production process or equipment setup invites risk. So, there were understandably concerns within McQuillan’s team that the new planetary gearboxes design wouldn’t work. However, in the end, Colin Mitchell and his team decided to trust Technidrive’s expertise.

“It wasn’t an easy decision,” remarks Mitchell. “But we wanted a system that could handle the shock loading and last for years. This planetary gearbox setup had the highest service factor and shock-loading capabilities.”

Installation of the new system was completed over a long weekend to minimise production interruption. The key challenge was ensuring the new system could fit within the existing plant configuration, especially since space was quite limited.

“Technidrive played a crucial role in this by coming on-site, measuring the necessary mounting heights, and working with us to design the setup,” explains Mitchell. “Once the design was complete, we had a mechanical contractor fabricate the mounting arrangement, and when it came time to install, Technidrive didn’t just leave us to it—they were involved every step of the way. They helped us with the installation, ensuring everything was correctly aligned, fitted properly and functioned as intended.”

The selected gearbox for the new solution was a Bonfiglioli 300 Series heavy-duty planetary gear unit. This series is noted for its durability and adaptability to high-impact applications. This was used with the existing motors and switchgear. The entire installation was smooth, with only minor adjustments, and has since proven exceptionally reliable.

A game-changing solution

Since its installation in 2018, the system has far exceeded expectations, drastically reducing downtime and maintenance issues.

Technidrive’s gearbox solution has not only eliminated the frequent gearbox failures but also reduced wear on the mixer’s bearings, which previously endured strain from the coupled gearbox design.

According to Mitchell, the gearboxes have required no replacement or significant repair, a stark contrast to the previous system. “We initially feared the synchronised gears would wear out quickly, but five years in, they’re still in perfect condition. The solution has been an absolute game-changer,” he says.

Ritchie added, “The planetary gearboxes and synchronised shafts solution gave McQuillan Quarries the robust performance needed for a high-impact environment. Hearing about the zero failures since installation reinforces our commitment to durable, high-performance designs.”

Long-term reliability

By eliminating the need for frequent gearbox replacements, Technidrive’s solution has significantly reduced downtime, with lower maintenance costs for McQuillan Quarries. Moreover, biggest benefit of this improved reliability is that McQuillan now has peace of mind when the equipment runs at nights and weekends; a critical advantage when fulfilling time-sensitive government contracts.

“We work with government authorities on projects where reliability is essential,” said Mitchell. “This new system has given us the confidence to run the mixer without worrying about breakdowns.”

Technidrive’s innovative drive solution has proven a resounding success for McQuillan Quarries. The company has continued to collaborate with Technidrive on other projects, confident in its expertise and commitment to long-term reliability.

Reflecting on the project, Mitchell emphasised, “Technidrive’s contribution to this project was exemplary — they guaranteed their solution would work and it has exceeded our expectations. From a reliability and maintenance standpoint, it has exceeded all expectations.”