Rooikat on the shelf

IN stealth mode, the hybrid Rooikat can tiptoe its 25-ton bulk so quietly over desert sand that the gunner’s breathing will sound louder in the turret than the soft whine of the hub motors.

Parked in peace time, the gun’s batteries hold enough charge to provide power to a small suburb for a night. And when it comes to efficiency, the old gun can teach the Nissan Leaf and Toyota Prius a thing or 400 about recycling.

In braking mode, the Rooikat’s hub motors return up to 400 kW per motor back into the system, as the heavy gun slows it down.

Despite its age, the hybrid Rooikat is still seen by all in the know as a brilliant achievement — and all of it is now gathering dust in a hired hangar at the Gerotek testing terrain west of Pretoria.

When we visited, the man who managed the development of the e-drive technology in the Rooikat, Wynand Avenant, was preparing to mothball the hybrid gun for its last resting place. It was to go to the South African Armour Corps Museum in Bloemfontein.

Wynand Avenant snr and jnr

Since then, Avenant has informed us that the gun is to stay at Gerotek for the time being. There was, at the time of printing, no clarity about what will happen to the old gun, which dates back to the nineties, when the world’s generals wondered how to apply hybrid drives to army vehicles.

The technology in the Rooikat was first tested in a truck and was then, as it is now, neither the newest nor the most powerful.

Trains use the same system, with a diesel engine driving an alternator to turn the axles, while giant mining trucks have, since the late sixties, been using much higher-powered electric motors to inch up steep inclines in open-cast mines.

But the system in the hybrid Rooikat represents an experiment by some of the finest minds then contracted to the SA National Defence Force, to see just how far they could push the envelope on electric propulsion. The system they perfected has, these past seven years, been a source of quiet pride for its designers and still garners respect from those who know their Ohms from Amperes.

The engineers explain the system to the author.

Avenant said his system is powered by an old diesel engine that has been tuned to sip diesel, and mapped to push its work rate up to 450 kW and lower its torque in order to drive the alternator at a constant high speed. The alternator generates the electric current that turns eight permanent magnet motors, one in each of the one-metre hubs of the Rooikat.

Each hub motor has as much power as a small car (80 kW) and can handle up to one megawatt of current. To get the bulk of the gun moving in thick sand is no problem either, as each motor turns with 2 200 N/m of torque from zero km/h, with the two-speed hydraulic transmissions in low range.

But all this was too late for the Cold War and is still too early for a world addicted to crude oil.

The hybrid Rooikat has never fired a shot in anger and at the last armament show, where it was displayed, the world’s buyers showed little interest.

The cockpit of the Rooikat hybrid electric drive.

Avenant has good news, however, as all this benchmark-setting technology need not be lost to transporters. For the technical wizardry that drives it has roots that stretch all the way to the Westville campus of the University of KZN, where the electric propulsion experiments started on a Ford bakkie in the mid-eighties.

Avenant said Armscor then progressed to test the first electric truck in 1996.

The truck was driven up Mpumalanga’s steep escarpments, in the Namib Desert’s shifting sands and in the depths of a snowy winter in Germany. The system finally proved itself as a tow truck for the 19-ton Ratel. The big question now is whether transporters can afford Avenant’s gas.

Bearing in mind that thousands of trucks trundle up and down the N3 each day, burning on average almost a litre of diesel for every kilometre on the 600 km up run, converting to hybrid trucks could be well-worth the investment.

Without its turrent, the Rookat looks more like a moon-buggy
than a benchmark-setting gun.