TerraGlide suspension: A new offroad suspension system by Premcar
One of Australia’s leading automotive development companies, Premcar, has released a new offroad suspension set to shake up the local industry. Its TerraGlide system is available now and has started shipping on some Urban Caravan models.
Sometimes, it takes a fresh set of eyes to solve a problem. When the engineers at Premcar were tasked with improving caravan suspensions, they realised that a lot of the accepted design was astonishingly old hat. Their solution might be a game changer for many caravanners with its innovative design and vastly improved maintenance schedule.
Based in Epping Victoria, Premcar is part of the global RLE International engineering group specialising in product development and engineering, primarily for the automotive industry. The business evolved from the Tickford and Prodrive to produce enhanced high-performance Ford vehicles. These days, they add styling and suspension enhancements to Navaras and Patrols, turning over 6000 of them into the Warrior variant beasts for Nissan.
But it was a meeting in the shared carpark with Urban Caravans that Premcar’s Head of Engineering, Andrew Lynch, and Urban owner, Steve Trajcevski, hatched a plan for a better caravan suspension. When Lynch delved into the accepted engineering around systems available for caravans, it surprised him that modern automotive technology had yet to cross over to caravans.
ADAMS software
Lynch was confident Premcar could do better, and it had the suspension experience, the proper digital design and testing equipment and the engineering facilities to follow through. Importantly, it had deep expertise with Automated Dynamic Analysis of Mechanical Systems (ADAMS ) software, which enabled modelling and virtual testing of a suspension as applied to a van.
The research led them to the semi-trailing arm system similar to that seen on the new Ford 150 Lightning, and while the concept isn’t new, it translates well to an offroad caravan. Many commentators describe semi-trailing arms as simple and elegant, and while multi-link technology now dominates the auto scene, semi-trailing arms are better suited to the wheel layout of a trailer.
Semi-trailing arms are set at an angle on the chassis that points outward to the wheel hub and differ from a trailing arm that angles back in line with the direction of movement. The semi-trailing arm delivers better tyre alignment with the road (camber) and adds some negative toe-in in bump mode for improved steering.
The modelling delivered the optimum length and angle of the arm for best performance. Months of real-world testing followed, again supported by computer analysis to land on the best spring and damper rates, arm dimensions, and placement of anti-roll bars. Dampers were tested on a rig to simulate two million cycles, and track testing with an accelerometer showed a shock and vibration improvement of up to three times less than current premium offroad suspensions.
As part of the process, Premcar engineered its own jounce bumps — or bump stops — to progressively control compression reducing shocks, noise and vibration to the chassis and the van’s internals.
The TerraGlide system has an impressive 230mm of travel and supports weights up to 4500kg, making it an ideal application for heavy-duty offroad vans. Coil and airbag springs are options. A single specially rated Monroe twin-tube shock absorber or damper on each arm helps control movement. The team insists that their single properly rated and quality Monroe shock is all that’s needed, suggesting that twin shocks are more show than go.
Importantly, the team didn’t stop with the new suspension design. It asked why caravan wheel bearings are such a high maintenance item when modern cars are virtually set and forget. Again, it came up with a solution. The TerraGlide uses a specially retooled 12in brake drum to fit heavy-duty sealed dual roller bearings with a projected life of over 200,000km. A disc brake option is on the way as well. Their bushes too have a lifetime endurance.
When we visited Premcar recently, production was well underway. Urban Caravans was rewarded for its input by getting first access to the TerraGlide units, and we report elsewhere in this issue. We call the new suspension a game changer, and it will be if only for those hundreds of caravanners stuck on the side of the road with a failed wheel bearing.
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