Australia’s fastest truckie
He’s hoping to top 300km/h in SA dash
TOUCHING 200km/h in a modern sedan is illegal but do-able, running 250km/h in a high-performance sports or muscle car is not too difficult and hitting 300km/h is a doddle in a supercar but in a truck? Never. Unless that truck is Diesel Arrow, a one-off, land speed record-grabbing mega-truck built to go ultra-fast (and then some) at Dry Lake Racing Australia’s annual Speedweek event on South Australia’s Lake Gairdner salt flats.
In 2010 owner/builder Gavin Manning piloted Diesel Arrow to the national Unlimited Class record with a 251km/h (156mph) pass on the Lake Gairdner salt – and with plans to take the record north of 300km/h (186mph) next March he is in no hurry to give it up.
The brainchild of the self-taught engineer and go-fast guy, Diesel Arrow is based on an early 1990s Ford Cargo converted for truck racing. Over the years it has morphed into a monster that would look right at home on a Mad Max movie set.
The staunchly upright Ford cab is landfill, in its place a low, centrally mounted single-seat cab sitting forward of the front axle line with the massive 23-litre, six-cylinder, Cummins-based engine bolted right behind.
That huge, twin-turbocharged engine, mid-mounted in the chassis for optimum weight balance, develops an estimated 1500-kilowatts (about 2000 horsepower), enough to push the eight-tonne, 8.0-metre long, 2.5-metre wide and 1.9-metre high rig to a potential 340km/h (210 miles per hour) top speed.
Manning, Diesel Arrow’s designer, development engineer, builder and test pilot, built his Cargo circuit racer for the Australian Truck Racing Championship in the late 1990s, giving it a spaceframe rear end, quick-change differential and coil-over suspension to help achieve the kind of handling needed to compensate for its lack of sheer grunt against the bigger outright trucks.
“The level of chassis sophistication in Diesel Arrow comes from its race truck days. It doesn’t need all of that to go fast in a straight line but it was there, so we kept it,” Manning said.
The quick-change diff, a simple alternative to swapping gearboxes to achieve ratio alterations is, he says, the biggest quick-change anyone is ever likely to see.
When truck racing went into decline, the first steps were taken to convert the Cargo six-shooter into a ballsy ballistic missile. A 12.7-litre turbo-diesel was bolted-in, a few aero mods made and Diesel Arrow Mark One headed for the 2005 Dry Lake Racing Association’s National Speed Trials.
“We learned a lot about what we shouldn’t do on that first trip to the salt and when we got home we started all over again, keeping the basic chassis and pretty much changing everything else,” Manning said.
Since then, the single-seat “aero” cockpit went on, the 23-litre engine replaced the “small” donk and a second turbo was added.
The truck sprouted wide aerodynamic sidepods to both keep it stable and enclose the coolant tanks for the multiple radiators used to cool the engine, automatic transmission and turbochargers.
Tyres from a Boeing 737 aircraft were fitted up front and 747 rubber went on the back, filled with nitrogen and pressurised to 200psi to manage both the speed and heat that would destroy conventional tyres. Aerodynamics, including a full undertray and sidepod rear endplate extensions, were used to maximise straight line speed and stability.
“A big rear wing might have looked good and given us downforce but it would have slowed us down. We have about two miles (3.2km) of track to build speed so we use the truck’s weight to keep it on the surface and keep it stable,” Manning said.
Diesel Arrow was scheduled to run at Speed Week in March this year but a workshop accident just days before the event threw a giant spanner in the works and ruled Manning out of proceedings.
But every cloud has a silver lining and the extra time – a full year between
❝ The level of chassis sophistication in Diesel Arrow comes from its race truck days. — Gavin Manning
runs – has allowed even more development on the weapons-grade monster truck.
The “cargo bed” has sprouted an aerodynamic cover and a Jabsco marine water pump has been fitted to flow even more coolant through the giant engine.
“Warming it up,” says Manning, “will be our biggest problem and it’s an excellent problem to have.
“If the radiators are right and the oil’s at the right temp we’ll let the rest take care of itself.”
The long break has also allowed more engine running time on a rolling road dynamometer, giving Manning’s small crew time to run systems checks, a luxury simply not available in the harsh, 38-degree South Australian outback.
Unfortunately, the dyno is unable to be used to find extra power and torque because it is simply not able to handle the engine’s mammoth output, whatever that may be.
“When we get it on the salt in March next year we’ll just run it, see what sort of speed we get and go from there,” Manning said.
INNOVATOR: Gavin Manning, Diesel Arrow’s designer, developer, fabricator, engineer, builder, test pilot and tea lady.
Stripped of its panels, Diesel Arrow reveals what lives beneath its aerodynamic sidepods. The tanks hold engine coolant and transmission radiators as well as the turbocharger intercoolers.
Diesel Arrow’s engine room. The 23-litre engine delivers its plentiful power to the back wheels through an automatic transmission.