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Active Suspension For The Masses

Out of the realm of concept cars and into production - an Australian-developed active sway bar system.

By Greg Brindley

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It's taken a humble Aussie inventor to be the first to design and develop a user-friendly active suspension system. Impressed? I was, certainly when I became aware that while it is a first in Australia, is also just happens to be a first for mankind! But what makes it even more exciting is that the fully patented system may well - and certainly should - have a huge impact on the global market.

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The design of the G-Force Anti-Body Roll Control (ABRC) suspension system by hydraulics technician, Phil DiMaria, has been a 15-year project. Amazingly, Phil's interest has never waned, even though he has been faced with considerably angst. For example, in 1994 one of the world's larger corporations took Phil to task, attacking one of his patents. Some months, many hours of blood, sweat and tears, a flight to Munich to fight the complaint in court and $300,000 later, Phil had won the battle while walking away almost penniless!

The Long and the Short

It was when Phil was working at a large power generation plant in the role of hydraulic technician that he cottoned onto the idea of developing/transforming a poorly executed suspension system into something that would work in any almost situation and in any type of motorised vehicle. Early electronic/hydraulic prototypes were tried but found to offer somewhat slow response times while also lacking a reliable interface between the electronics and hydraulics.

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The concept revolved around sway bar manipulation, whereby sufficient lateral g-forces would cause a ram to apply hydraulic pressure on the 'loaded' end of the sway bar/s. This would result in radically reduced body roll, in particular in off-road 4WD vehicles, which of course tend to roll around like barges. By actively controlling the sway bars and reducing body roll, the suspension could be altered in other areas - such as by the use of softer springs - without reducing the efficiency of the total handling package.

The system worked in theory, while offering acceptable performance in practice. Along the way, Phil dropped the electronic valving in favour of a patented pendulum-based control valve with pressure feedback. Considerable fine-tuning meant that the system worked well, however one obstacle remained. It was harshness that was the obstacle - the design of the hydraulic ram meant that the pressure feedback was too slow and cumbersome. The concept was great, with significant improvements achieved in handling. However, in targeting the 4WD market, Phil could not afford to offer a system that in fact added to the harshness of the suspension. Sure, body roll may have been radically reduced, however the side effect was too much against it.

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In 1998 a revised (patent-pending) system came on stream, an all-hydraulic system employing well-proven technologies. It kicks off with a hydraulic power steering pump driven by belt or electric motor. This plugs away at the same speed regardless of demand. When there is no demand (ie no cornering), the pressure is almost zero, with resulting extremely low power absorption. And because of the low maximum working pressure, even under maximum cornering, the demand remains low when compared to a typical power steering system. This lower pressure also means a reduction in Noise, Harshness and Vibration (NVH).

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The "microprocessor" of the system is the Central Hydraulic Processing Unit (CHPU), which converts cornering g-forces into a proportional pressure. The CHPU consists of a pendulum, spool valve and that clever patented feedback piston. Deadband, damping, and non-linear gain are all provided for by careful attention to the spool design.

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On the test vehicle an electrically operated solenoid was fitted, allowing the system to be easily turned on and off.

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The G-Force kit consists of two large diameter sway bars. Each bar is fitted with a patented Shock Ram at one end. As the cornering g's increase, the pressure across the internal piston within the Shock Ram forces the sway bar to react against the fixed body connection, opposing body roll. (The Shock Ram pictured here is partly covered by a prototype dust cover.)

Now comes the part that sees this system behaving very differently to a traditional heavy-duty sway bar package. It was found with earlier versions that it's fine reducing the body roll on a smooth road - but truly smooth roads are few and far between! A single bump in the road can cause a vehicle to become unstable, especially when a stiff sway bar is holding the vehicle level. To overcome this, G-Force developed their Shock Ram, which as the title suggests, works both as a hydraulic ram and a shock absorber.

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There are a total of three hydraulic lines attached to the ram, one at the top, another at the bottom, and a third line that runs through the centre of the Shock Ram shaft. This third line delivers instantaneous pressure to the centre of the piston. In other words, as opposed to when a vehicle is travelling in a straight line and there is no communication with the ram, when cornering, the pendulum valve moves in the opposite direction to the turn and in doing so blocks off one side of the port, therefore removing the pressure off one side of the pump and delivering it through the middle of the piston through a central shaft.

While the piston high side pressure generally equals the internal piston pressure, if while cornering, a bump in the road is encountered resulting in a pressure spike, it opens the shock absorber valving as in a conventional shock absorber, allowing dampened wheel movement while always maintaining a corrective force. Also advantageous is how the system operates on a lower pressure than many other systems (for example OEM self levelling systems). The result is low noise, therefore no increase in NVH.

Does It Work In The Real World?

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I was fortunate enough to be offered as much time as I needed in the G-Force demo vehicle - and I have to say I was impressed. As a consequence of G-Force's initial design being targeted at the four wheel drive market, the test vehicle was just that - a Toyota Landcruiser. "The idea behind the system was and always will be safety. Sure, vastly improved handling in a family sedan or high performance road car is a by-product and one we are currently working very hard on, however safety was always our primary concern," explained G-Force distributors Joe Beninca and Burt Van Dyk.

By 'safety' Joe relates to the task of eliminating body roll which in itself often reduces 'push' or understeer. More predictable handling, a much more positive tyre foot print and significantly increased manoeuvrability will increase the confidence and ability of many 4WD drivers, hence giving improved safety.

For the sports enthusiasts it's a very different story. Safety, while an issue, is overwhelmed by our desire to own a vehicle offering impeccable handling. Unfortunately, as a general rule, the use of after-market shock absorbers and lowered heavy duty springs often results in a harsh ride. So, on one hand we have improved handing, on the other our teeth are shaken out of their sockets.

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The G-Force ABRC system offers a very good alternative. While using traditional extra heavy duty sway bars normally results in less body roll, it also has a tendency to transmit bump from the loaded wheel to the other side, resulting in a reduction in the compliance of the tyre. In other words, it effectively detracts from the independence of the suspension. The ABRC differs in that thanks to the 'weight' and 'active' control of the sway bars, suspension compliance can be heavily enhanced via the use of lower rate springs, giving a much plusher ride. Turn a corner and the ride remains the same! What's more, by eliminating body roll, it also results in a significant improvement in virtually eliminating camber and other geometry changes.

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The ABRC system is fitted parallel to the vehicle's own suspension and consists of front and rear stabiliser bars fitted on one side in a traditional manner, and on the other side with the patented 'Shocker Ram' located between the bar and body. The rams are capable of providing upward and downward forces, while not limiting the operation of the vehicle's own shocks. The rams are connected to a patented G-Force HCPU that is activated by lateral forces and provides instantaneous pressure to the rams.

Simple in theory, difficult in execution, G-Force has performed miracles with their ABRC system. Of course the acid test will be seeing how well the system works in a high performance application where minute and instantaneous reactions are necessary.

For the time being I've given it the thumbs up and suggest that anyone interested in the G-Force should contact Joe Beninca or Bert Van Dyk at The Auto Edge in Melbourne, Australia. Bert has combined his manufacturing expertise with Joe's long term racing experience (with too many wins and successes to mention here) to embark on a development program that includes a large range of road vehicles with current projects including Porsche, Alfa Romeo and others.

Contact:

The Auto Edge
+61 3 9836 1519
0409709 006

Fax +61 3 9830 1779

Bertvijk@aol.com

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