We took the wrong turn to Roach Manufacturing and arrived on Keith Roach’s driveway via a campsite. I wondered if the big cheeses from Audi’s immaculate HQ in Ingolstadt had done the same when they visited their latest project. And, even if they arrived via the correct farm track, what would they have thought of the wonderful labyrinth of workshops that have evolved there during the last 50 years?

We’re greeted by Keith Roach, wife Heather and the ‘guard mutt’. They lead us through the main workshop – we do our best to dodge Formula Juniors, Austin Seven specials and Bugattis – and into the special projects area that’s usually sealed off to visitors. The doors open, and there is the recreation of the last-ever variation on the legendary Auto Union theme, the pre-war V16s and V12s that revolutionised racing and produced some of the most memorable sights, sounds and results in the history of grands prix.

The first of the breed, the A-type, was designed by Ferdinand Porsche to conform to new regulations that specified a 750kg weight limit but left capacity and layout free: clearly no-one was expecting Auto Union to design a rear-engined V16 that was capable of an unprecedented 174mph.

It would be foolish to say that this is run-of-the-mill to the craftsmen at Roach Manufacturing, but they’ve been living with the project long enough to be surprised at the width of the grins that this vision in bare aluminium has prompted on the faces of myself and photographer Matthew Howell. The size, the shape, the stories that surround these cars. Fantastic.

The replica is based on the Auto Union D-type V12s that were raced in 1939. The V12s replaced V16s in 1938, when regulations changed to limit capacity to three litres, but the last of the 1939 cars also featured a twin-stage supercharger and additional air intakes on the top and along the length of one side of the engine cowl – intriguing enough for The Motor to refer to ‘the mystery of the new bulges’ in July 1939.
Having commissioned restorations and recreations of earlier Auto Unions, Audi decided to complete the set with this last-ever variant, despite earlier claims that its spending days were over. Sure, it’s not yet finished, but the chance to see it receive a few finishing touches, and to reveal this previously secret project, were too good to miss.

So there we are, setting up cameras and exploring the car, when Audi’s representative arrives. He has one last surprise. ‘Of course, you know the original’s here, don’t you David?’ he drops into the conversation. I’m not sure what he’s on about.

‘Look, look through there!’ he urges. I peer through a tiny window in the workshop, into another, smaller workshop. I can make out an Austin Seven and a selection of car-like shapes. We nip round the front, the doors are heaved open, a cover whipped off, and there, under a muddy HRG trials car on a four-poster ramp, is an original 1938 Auto Union D-type – the sight of it, so unexpected, is breathtaking.

Audi has supplied the ’38 car, logically enough, to help with the creation of the 1939 replica, but the way the latest project came around is a little convoluted. Some years ago, Audi commissioned an Auto Union rolling chassis for its museum from historic engineering company Crosthwaite & Gardiner, which had been involved in the very first Auto Union project well over a decade ago. There was no question of having a body or engine built – having spent hundreds of thousands of Euros on Auto Union and Wanderer recreations, Audi had drawn the line at any further expenditure.

But then it was pointed out to them that, with all the moulds for engine block, transmission and so on still in existence from earlier projects, the costs for a fully built-up car would be significantly lower than for previous recreations. Gradually the Audi bosses were won over; the realisation that the last D-types, campaigned just before the outbreak of WW2, were significantly different was the final decision maker.
The chassis was handed over to Roach Manufacturing, along with a handful of pictures of the 1939 cars. Sounds daunting.

‘We just use normal procedures,’ understates Keith Roach. ‘We look at the pictures and try to scale things – we knew the wheelbase, which helps. Then we draw sketches, make patterns and produce a plywood buck.’

The collection of photographs of the 1939 car on the workshop wall prove just how little there was to work from. And the plywood buck, whose remains are now stashed out of reach in the roof of the workshop, is a complicated ‘skeleton’ design, which took a full four weeks to produce.

With the buck attached to the chassis, Steve Parmiter, the coachbuilder assigned to the project, started on the centre section of the car before moving onto the nose, then the complicated tail section and then, according to Steve, ‘filling in the gaps’. But once again it’s a difficult, skilled, labour-intensive procedure that has taken months to get to the ready-for-paint-preparation stage that you see it at now.

Panels can’t just be bent around that plywood buck, because they’re full of compound curves that can only be produced on a wheeling machine. Steve demonstrates the centuries-old skill of wheeling, pushing a sheet of aluminium backwards and forwards through the wheels in a serpentine fashion, changing the pressure on the metal with his foot on the adjusting wheel below. The shape of the wheels means that one side of the metal is stretched slightly each time it’s pushed through and it doesn’t take too many goes to produce something with a respectable compound curve. But to have control over the exact shape of that curve is a different matter.

‘Emotionally, you’re up and down with this car,’ says Steve. ‘It’s like a crossword; you spend so much time searching for clues. When you don’t know what’s going on under the skin of a car in a photograph you do have to freestyle it a bit, but usually you get the magnifying glass out and you see a line of rivets, perhaps, and say, yeah, there’s something going on under there. Keith often mentions the “mindset of the car” and of the people who built it, and that is what you have to think about.’

There are countless examples of this detective work: one photograph clearly showed a fixing screw through the top of the engine cowl, which earlier D-types were known to have done without, sticking with rubber fixing hoops instead. Why? The Roach team realised that, at speed, air flowing through the extra vent on top of the cowl would have caused the cowl to lift, stretching the rubber fixings – the screw was a crude modification, probably added during testing.

Keith mentions the nose of the car. ‘See the handle on the front? What was that for? It might have been a jacking point but, by examining photographs and thinking about how Auto Union worked, we realised that it moves a splitter inside the nose, to block off the oil cooler.’

It takes some time for a visitor to start taking in these details but when the initial wow factor dies down, a new admiration kicks in. The grille, for example, consists of a multitude of delicate bars. Each bar has wrapped edges, each one a different shape and each drilled through for the curved crossbars to pass through exactly. It took several days to make.

The nose itself is a work of art while, at the other end, the engine cover is made from eight separate panels, beautifully stitched together by gas welding. With the exception of a few TIG welds on the framework, all the construction techniques are just as Auto Union would have used.

But the resulting panelwork isn’t totally faithful to the original, created as much by racing needs and pit-lane modifications as by factory craftsmen. Over to Stuart, son of Keith and overseeing the project: ‘This is much better than the original would have been; it’s not as ripply as it would have been, but we had to be careful not to produce something too clinical. The louvres in the engine cover, for example, were hand cut, not machine cut.’

Over at Crosthwaite & Gardiner, meanwhile, where a labyrinth of buildings are overflowing with parts from and for some of the world’s best-known historic race cars, the Auto Union’s running gear is in the final production stages.

Years ago, the company produced castings of everything from engine blocks to bonnet catches, using factory blueprints, photos and original parts to aid pattern maker Derek to carve out intricate wooden models. Derek is still there and the hundreds of patterns have been dug out of storage, to produce block, heads, carbs, transmission casing, suspension parts... You get the idea.

 

The twin-stage supercharger, with its two Roots-type screws within one casting, is unique to the 1939 cars and is being built from a combination of blueprints and engineering logic. Audi wants to use this recreation to demonstrate the look and sound of the most iconic cars to fall under their multi-brand heritage. Consequently, there are variations from standard.

John Gardiner explains: ‘In the original V12, the crankshaft assembly consists of 1100 parts [there are roller bearings on every journal] and it takes days to assemble into the engine. We’ve used modern shell bearings; some people may object, but it won’t have to be rebuilt after every 80 hours of running!’
Similarly, the ineffective gauze oil filter of the original engine is now supplemented by a modern remote filter hidden out of sight – another bit of protection for a very expensive engine.

This engine really is a neat design. It has three camshafts in a cast cambox that straddles the two cylinder heads, one down the middle of the head to operate the inlet valves and the two exhaust camshafts lying on either side. The intake manifold runs down the centre of the casting, underneath the cambox.
So when will it all be bolted together? When will we hear the famous crackle of the Auto Union V12? No-one’s willing to confirm it but next year’s Goodwood Festival of Speed seems the popular prediction. Make sure you’re there to witness it.

Thanks to Roach Manufacturing (+44 (0)2380 814287, www.roachmanufacturing.co.uk) and Crosthwaite & Gardiner (+44 (0)1825 732240, www.mdr.co.uk/candg.