Climax flat - 16

BRM had attempted it with disastrous results, but the allure of 16 cylinders was still strong 15 years later. Wally Hassan's new F1 Engine showed lots of promise; Trouble was, his old unit was still showing the rest the way home. By Keith howard

When Wally Hassan stood to address the combined powerplant and transportation meeting of the Society of Automotive Engineers in Chicago in October 1966, it must have been with mixed emotions.

His paper The Coventry-Climax Racing Engine, 1961-1965 - described much to be proud of. In those five memorable seasons, Hassan and his colleagues had played a central role in cementing the ascendancy of British grand prix teams, notching up two drivers' championships (Jim Clark, 1963 and '65) and two constructors' titles (Lotus, in the same years). But the pleasure of those achievements was tinged with regret. Regret that Coventry-Climax had quit F1 at the close of the 1.5-litre era, and regret that what should have been its last great racing engine was stillborn.

The story of the FWMW flat-16 is a curious echo of what happened to the first Hassan F1 engine, the FPE `Godiva' V8. Both were destined for a clutch of needy British racing constructors (Brabham, Cooper and Lotus in the case of the 16-cylinder); both, in the event, never ventured beyond the factory because it was decided they should not be released. In the first instance Hassan and his team were bluffed into a no-show; in 1965, they were victims of their own success.

To justify its existence the flat-16 had to put a clean 10-20bhp between itself and the latest-generation FWMV V8, which it signally failed to do. With sufficient development the necessary power jump could surely have been realised, but time was short and the flat-16 needed to deliver straight out of the box. When it didn't, it was set aside with little consequence: Clark and Lotus triumphed regardless. None of which detracts from what was a startling vision, and given another season would have been honed into a remarkable swansong.

Sixteen is remembered as an unlucky number for post-war racing engines, conjuring up visions of the BRM V16 fiasco and the barely more happy episode of Tony Rudd's H16. The Climax flat-16 would have redressed the balance and, who knows, might even have inspired others to venture beyond 12 cylinders. Certainly it would have become an indelible audio memory for all who heard it.

Hassan's decision to opt for 16 cylinders was based on two design factors: engine speed and piston area. Both could be greater for a 16 than for a 12 or an eight, and both should express themselves as increased power. Preliminary calculations suggested that, with its tiny stroke of 1.6in (chosen to retain the 1-to-0.76 bore :stroke ratio that had proven itself in the V8), a 16 should rev safely to 13,100rpm as opposed to 11,870rpm for a 12 and 10,340rpm for an eight. Total piston area was 56.6 sq in (cf 52 and 45) suggesting that, at a conservative 12,000rpm, the 16 should deliver 240bhp an unheard of 160bhp/litre with yet more to come at higher crank speeds and with the planned four valves per cylinder (64 valves and tappets, 128 valve springs!).

Design work began in late 1963. In Hassan's own words, although the flat-16 looked complicated, it was effectively four four-cylinder engines joined together. At its heart was a split block/crankcase, to which were bolted four cylinder heads attached to four exhaust systems. This allowed known exhaust tuning techniques to be used to improve cylinder scavenging.

Two flat crankshafts, phased at 90 degrees, were joined end-to-end using a novel coupling technique developed by SKF, the Swedish bearing company. Hydraulic pressure was used to expand a cup onto the end of each crank, into which the stub of the mating component (a spur gear) was inserted. Removing the hydraulic pressure then caused the cup to shrink, clamping the two pieces together.

To quell torsional resonances and reduce clutch speed, power take-off was from the middle of the composite crank to a power shaft beneath, and the drive gears for the overhead camshafts were buried in the middle of the engine also. Despite this, and double the number of cylinders, the flat-16 was only an inch longer than the FVVMV V8 and barely 10-151b heavier, principally due to the need for twin eight-cylinder Lucas ignition systems. Offsetting these slight disadvantages were a much lower centre of gravity and the hoped-for power hike.

Before settling on this configuration, Hassan and his team had also considered a 135-degree vee layout, and even an inverted vee, but both were rejected.

The vee configuration had too high a CoG, while the inverted vee made packaging the exhausts almost impossible.

Frustratingly for all involved, on its first trip to the dyno in late 1964, the flat-16 broke while warming up. The problem was traced to a low-rpm quillshaft resonance which was overcome by beefing up the shaft and ruling that the engine never be run below 4000rpm. Still, precious weeks were lost before it was back on test. This time it held together, but fluffier, even longer, delays were caused by recurring valve-spring problems. With these and a few other issues finally attended to, the flat-16 engine produced 209bhp at 12,000rpm - nothing to be ashamed of, but crucially no better than the MkVII V8, which in 1965 generated a rousing 213bhp at 10,500rpm.

Hassan knew the shortfall lay in unexpectedly high parasitic losses which, given time, could have been identified and reduced one by one. But by now they were deep into 1965 and Clark already had a iron grip on the title. The decision to halt development was disappointing but inevitable.

Thus Hassan's notable career as one of Britain's finest racing engine designers came, despite the Clark/Lotus triumph, to an unfulfilled conclusion.

Next season he would be preoccupied with a V12 not for screaming around racetracks but for wafting Jaguar road cars along on a tidal wave of refined power.