OUR LOVELY A9X TRIBUTE CAR NOW HAS A NEW OWNER, BUT THERE ARE A FEW ASPECTS OF THE BUILD THAT WE HAVEN’T YET COVERED. HERE’S ONE OF THEM W alk around the back of any selfrespecting A9X – real or tribute – and you’ll be looking for the inevitable racer-rep drop tank. They look tough and bring to mind the halcyon days of these cars, when they battled for supremacy across the crest of Mount Panorama with drivers like the legendary Brock at the helm.
Our car had one when we bought it, though it was of unknown heritage and felt a little on the flimsy side. It was doing its job, but we had some doubts about whether it met anything that resembled a design rule.
What to do? Pretty obvious, really. We blundered into Brown Davis in Vic, and had a chat with Kevin Sharp, who’s been with the crew since the start some 30-odd years ago.
“We started doing a lot of touring car work in the Group C days,” he says. They now have around 20 employees, have branched out into the 4WD world, and still do a lot of tanks and roll cages. The fact that many of the crew race themselves not only gives them a bit of street cred, it sometimes provides a useful testing ground.
The company has a lot of off-the-shelf gear for popular Aussie and American cars, right up to VT Commodores.
If it’s a custom job, they get you to bring in the car and go over what you need. “What we basically do is get the donor car and get the customer
requirements, and find out things such as whether it’s carburettor or EFI to see what we have to do internally. Some like drop tanks, or they could be looking to move everything further forward, closer to the centre of gravity. It could be baffled or foam filled.”
There might be other considerations, such as making room for a Watts linkage or a different diff.
“We work that out, come up with a shape, tack it together and see how we’d mount it.”
The customer is invited in again to check everyone is on the same page, before any final decisions are made.
“It all depends on what the customer wants,” says Sharp.
“With the Torana, that is an iconic shape. That drop tank style has been around since the 1970s and a lot in the day were our own products.” In fact, he was able to point to a 1976 tank that was in for repair.
Much of the work goes on the internals. “Anyone can make the outside,” says Sharp.
“It’s what’s inside that’s most important.” That includes a number of options when it comes to baffling, plus a decent swell pot. Eh ? That’s an area specifically designed to contain fuel around the pick-up, so the engine isn’t being starved under hard use.
For some race machinery, that can make the difference between finishing with or without melted pistons.
The overall construction is done with 2mm-thick marine grade aluminium sheet, chosen for its resistance to oxidisation. “It’s very strong,” says Sharp, “You’ll see on the tank that it’s all 45 degree corners – that’s so the weld is not taking the load and it keeps the heat-affected zone away from the corner.”
That TIG welding is done by one person, who manages an incredibly consistent result, which Sharp says is an art form in itself.
Mounting is done via brackets rather than straps, because you get a much more rigid result that doesn’t move around. And it’s less prone to theft!
Each tank comes with a serial number, so its history can be traced, and Brown Davis keeps a record of pressure testing and other ADR data. That is important if the car you’re building is subject to an engineering examination.
There’s no doubt the tank we installed was a much better and safer product than the one we took out.
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