Mudcrab makes history: how a home-made electric car broke world records under water

Mudcrab makes history: how a home-made electric car broke world records under water

The Top End of Australia, particularly around Darwin, is renowned for eccentric activities and people.

There’s the Rocksitters Club, a Saturday evening tradition of nearly 5 decades’ standing to which people go for a beer to watch the weather turn spectacular. The Darwin ice hockey club, which claims to be world champions because no other team has ever taken up a challenge to play them. And there was the bull from Humpty Doo, which still holds the undisputed record for downing a two-litre Darwin stubby, the largest bottle of beer in the world.

But the people of Darwin, a city with one of the highest per-capita aggregations of four-wheel-drive vehicles, really enjoy anything to do with cars. The annual V8 races at Hidden Valley attracts thousands. In 1994, the Cannonball Run between Darwin and Alice Springs brought racers from all over the world with fast, expensive cars and, every three years since 1987, Territorians have lined the Stuart Highway to watch the World Solar Challenge, the world’s longest solar car race, from Darwin to Adelaide.

In 1983, Darwin people got really excited when a group of mates decided to drive their Toyota Landcruiser across the harbour, under water. Fitted with a 60-metre-long snorkel, the ‘cruiser made it halfway before its starter motor flooded and couldn’t get going after stalling.

Crossing 2.0

Roll forward 4 decades to Saturday 29 July, and another generation of Darwin characters and their mates decided to have a crack at the same harbour crossing, using a similar kind of vehicle – a 40 series SWB Landcruiser, dubbed the “Mudcrab”. Only this time the car was fitted with an electric motor and motor controller.

A photo of the mudcrab car's hood ornament: a gold painted crab holding a fork trident
The Mudcrab’s hood ornament. Credit: David Hancock

Engineers Finn Davy and Glen Summers were at school in Darwin when they heard about the first unsuccessful crossing. “For me, it was almost like folklore as I was growing up,” Davy says. “When Glen and another student, Tom Lawrence, called and said they were doing the project, it just ticked every box: the adventure side of things and the technical nature. It was pretty exciting.

“It was also a very ‘Darwin’ thing. You mention it down in Newcastle [where Davy is currently studying engineering] and people say, ‘why the hell are you doing that?’ You say it in Darwin and people think it’s awesome.”

The project ramped up as scores of people came on board – from a television production company to commercial divers, engineers and some really handy mechanics, fabricators and tradies around Darwin.

Engineering inspiration

Much of Glen Summers’ education was spent working on solar cars – firstly for Kormilda College, his school in Darwin, and then for the University of NSW. Solar and electric energy became his passion and, today, he works in that field for AGL in Melbourne.

Many Darwin educators credit the World Solar Challenge for introducing hundreds of Darwin kids to science and technology. It appears that when you mix science with an innovative and “can-do” Territory attitude anything can happen. And it did on Saturday, when the Mudcrab slowly crawled across the harbour, doing what Landcruisers have done for decades in the Top End – carving a track through mud, water and sand – to reach Mindil Beach around 8.30pm, nearly 12 hours after it started about 7km west, at Mandorah. More than a thousand waiting people surged into the water, surrounded the vehicle and acclaimed the crew of divers and engineers.

Photo of the engine casing of the mudcrab vehicle.
Mudcrab’s engine housing protects the EV motor conversion with silicon oil. Credit: David Hancock

According to Summers, work on converting and waterproofing the Mudcrab took about 12 months and scores of volunteers contributed hundreds of hours of their time, from writing customised circuit boards, converting the old diesel engine to electric and providing diving skills. Thirty divers tethered by airline spent 15 to 30 minutes at a time to guide the vehicle through sand, silty mud, and even over a gas pipeline. At times the seabed was 30 metres deep and just plain murky. Crocodiles and sharks were a potential hazard.

“The motor is from the world of EV conversion equipment; the kind of gear you buy to convert your car into an electric vehicle,” Summers says. “That made a lot of sense for us because the powers are matched and they are very easy to interface and control. We didn’t have the time to build the motor and controller ourselves and we would have needed a team of specialist engineers.

“On the other hand, the supply chain of the (EV) world is a lot thinner than we thought. With the motor and controller, there was only one in Australia that I hunted down out of Castlemaine, a hot rod town in Victoria.”

The motor, controller and batteries needed to be waterproofed by encasing them in silicon oil.

“A big part of what we had to do was to determine that all these components would be able to survive in oil, at pressure,” Summers says. “We had a program of pressure testing – the very first hardware work we did on the project was to build a pressure chamber and test different battery cells; we also tested capacitors that were in the motor control. Finn Davy built the pressure chamber, and the electrical team used it to test the components.

“We got this method from people who build underwater ROVs [remotely operated vehicles]. Electrical hardware companies don’t really come out with the specs saying components are deep-water, high-pressure rated. You have find out (for yourself).”

Mudcrab is go as it starts its journey beneath Darwin Harbour. Credit: David Hancock

Electric dreams

The final electrical system was very simple.

“As a pretty passionate electric car guy, these older cars are so easy to convert and they are just tough,” Summers says. “I would not be interested in going about this in a more modern Landcruiser. There is no body work, no panel work, no electrical or air bags to rip out – the amount of stuff we would have to remove (in a modern car). It [the 40 series ‘cruiser] is perfect for this. It doesn’t have to be registered and we don’t need any safety stuff, because we are driving really slowly … 1 to 3 kilometres an hour.”

The Mudcrab’s tyres were completely filled with water to ensure they wouldn’t buckle with pressure as the vehicle reached the maximum depth of 30m. Divers took the wheel on a rotational basis to ensure they didn’t stay at depth for any extended length of time and need decompression. What the team didn’t expect was the amount of time the car would get bogged in mud. Despite that, the car’s power supply remained steady and uninterrupted and the Mudcrab kept going.

“The electrical side of this project comes from solar car racing people,” Summers says. “They are the kind of people you can call up and they are very keen to come and do this kind of very experimental technology car project. You need those kinds of people to deliver this.

“The whole project was pretty adventurous but that was the spirit of every part of the team.”

After the Mudcrab crawled ashore in the ditch dark and about 5 hours later than expected, Finn Davy said the project was a testament to what can be achieved by a bunch of ordinary people in a backyard or shed without much financial backing.

“We have also proved the robustness of the electrical systems,” he says. “You can put them under a lot of pressure that they were totally not designed for and they operate as they should.”

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