Froude Engineering Ltd., Dynamometer Specialists

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Measuring power by old-established principles and modern electronics

Gregory’s bank in Worcestershire is home for one British business that, like so many in the competitions world, is a widely accepted international authority in its sphere. Surrounded by the kind of factories attracted to the now ubiquitous modern estate, Froude Engineering employs 475 people, has a turnover of approximately £10 million a year and makes most of that sum from the production of what is claimed to be the World’s widest range of dynamometers.

They do make the electricity or hydro-electric principle power testers that are popular in the American market, but by far the majority of their dynamometers are based on hydraulic principles that were established (for this purpose) nearly 100 years ago.

It was actually in the 1870s, when the British Admiralty wanted to discover the amount of power that the then new-fangled marine engines were giving at their output shafts, that scientist William Froude was asked to come up with a solution.

His answer, and one that lies at the heart of all Froude hydraulic machines today, albeit with some very sophisticated control systems in the high-speed applications we will discuss, involved feeding water to a shaft-mounted and vaned rotor and stator. As the shaft turned, powered by the output of the test power plant, the amount of torque transmitted could be read by means of a load-sensitive torque arm: the water provided the medium against which the turning vanes dissipated their energy. Today’s big improvements concern the speed at which that water can be diverted and the long term automatic test programmes that can be applied.

In fact they have got to the stage where they could supply a pioneer with equipment to develop a competition engine entirely on the test bed. As one company engineer told me — “We can now put in virtually everything on a programme and length is no object. We can allow for wind resistance, tyre drag, sudden acceleration and deceleration and number of corners and acceleration modes … we could even build in a complete baulking back-marker every 10 laps or so!”

Most people, including many of those within the company, refer to the company still as Heenan and Froude, but the official title for most of the dynamometers is that simply of Froude Engineering. The Heenan name is still used for equipment used to check the output of aero engines but otherwise is not officially used: the company itself is part of the Redman Heenan Group, which is quoted on the Stock Exchange.

It was early in 1974 that the company was split into four specialist divisions, and the Froude name applied to the manufacturers of dynamometers. The Froude name was honoured in 1976 with the Queen’s Award to Industry conferred upon the company for “Technological Achievement”. Richard Froude and Hammersley Heenan, who founded the company in 1881 after Richard had taken over his father’s dynamometer designs, would certainly have been gratified at the progress made!

From a competition viewpoint what was known as the Heenan and Froude G-range had provided brake horsepower testing facilities for some of the leading Formula One names for some considerable time before the company set out to design a high-speed dynamometer specifically for the competition engine.

Thus, in the mid-sixties, emerged the G490 model. At the time the demand for accurate power output testing was growing from two sources.

Both were Ford-lined, though indirectly. For the GT40 programme Ford, through American preparation specialists Holman and Moody, wanted to develop the GT40 and subsequently J-series cars with the aid of 7-litre V8-power.

In Europe 3-litre Formula One started to push the interest in machines that would not only register high outputs (a capability the Worcester firm already had through their marine history) but also register those figures at high r.p.m. The 490 was, and still is, the success story amongst such dynamometers. Even today when the F and 209-types offer more sophisticated control and other features, many prefer to stay with the 490 and modify its control systems.

Bored? The point was that the 490 could absorb a remarkable 14,000 r.p.m., and more horsepower than the then-new 3-litre Grand Prix racing engines could provide. The 14,000 r.p.m. figure was no accident, that was the r.p.m. specified by Ferrari at the start of the formula!

Early customers for the 490 included Cosworth Engineering (of course) who had such a bed in full use in 1966, but they were preceded by BRM at Bourne. Though that Lincolnshire enterprise is now demoted to forays within Britain, Froude were rightly proud of their association back in the sixties when their V12 engines were beginning to make the Froude dynamometer work for a living.

Development of both the 490 and the 7-litre Ford V8 went almost hand-in hand. The big American engines could apply torque very quickly on demand, and the 490 was made to measure just such sudden increases in power.

The F-type and 209 ranges were developed with the aid of the giant 27-litre Rolls-Royce Meteor engine, an unsupercharged offspring of the legendary Merlin that produces some 600 b.h.p.

Because the Meteor revs to only 2,500-3,000 r.p.m., Froude used their usual gearing up process to produce the number of r.p.m. needed in their specialist application. In both cases a Sherman tank 5-speed gearbox and a 4-to-1 final drive arrangement of pulleys provides up to 12,000 r.p.m. on a regular basis, with a pulley change required beyond.

Others to use the 490’s talents included all those Cosworth DFV engine preparation specialists we mentioned recently … Swindon Racing Engines, Hesketh, John Judd, Alan Smith, Euroracing, et al. Broadspeed had such a unit when they were developing the Escort RS1700 BDA (and subsequently the Jaguar V12); Weslake adapted their G-type equipment for its new role and the Americans really took it to the heart of their tuning enterprises. Holman and Moody had in excess of 20 units all sold now, we think even Richard Petty Enterprises at the centre of the conservative stock racing world in Carolina had the Froude equipment. So did Offenhauser and Penske: at one time it was thought that there were over 25 Froude G490s just in the Los Angeles area, serving an enormous variety of needs.

So far as Froude are concerned the 490 is obsolete … however, the racing car business just seems to refuse to let it die! In Europe both Ferrari and Porsche bought such units, quite a triumph in face of opposition from Schenk and other West German manufacturers.

Since the 490 the Froude people have produced the F-type and the 209.

The F-type turned out to be something of a halfway house, really produced with automatic testing programmes in mind. This kind of thing becomes paramount when carrying out any kind of durability programme, or emission control work which depends on extensive engine running and therefore demands staff attention if it is not automated.

It was this machine that won the Queen’s Award, for it featured a new butterfly control valve which allows full work-loading of the shaft in milliseconds and the improved control offered by electronics instead of manual throttles and so on.

From a control-panel viewpoint the difference was immediate because there was a digital presentation of numbers instead of a large conventional tachometer. “That way nobody can query a reading,” one engineer told me, “whereas two men will give you two readings for the old-type of tachometer: this way there is no argument!”

However there was a limiting factor to the F-type, and that was of r.p.m. John Nicholson’s prototype installation was constantly working right tip against the limits of 10,000 r.p.m. continuous or 11,000 r.p.m. for five minutes.

From that experience was born the 209, fathered by former Rolls-Royce and Broadspeed engineer Barry Dukes, plus Froude’s own engineering man Don Lavis. The big improvement was the use of  £400  angular bearing sets from the aircraft component supply industry and sealing them for lubrication life with the Isoflex-branded grease produced by Kluber of Munich.

These changes allowed a safe 16,000 r.p.m. and the first customers were Ferrari. The 209 represents some £12,000 to a customer. For this sum he has a machine that is more compact than those before, plus a full range of electronic aids that have been developed in association with GEC during the past 18 months. The machine is the workings of a dynamometer, rated capable of absorbing up to 800 officially, which will probably take care of current Ferrari F1 development for a while…

The Froude works are not particularly interesting in themselves, but the people who work there producing such sophisticated electronics to complement such an old-established principle were fascinating to talk to. When sales manager Edward Denley talks of selling to the Chinese, Russians and virtually every other country in the World one realises what a wide-ranging business this can be … and how successfully it has capitalised on Froude’s basic expertise.

For the future we can look forward to far cheaper general purpose dynamometers (though they look unlikely to rejoin the rolling road market they once explored with Crypton) and ever more advanced electronic control systems. Even now an operator is not strictly necessary in some cases. However, it does look as though it will be some time before the electronic control systems that allow one to preset an engine’s running cycle become generally accepted in the competition world, even though Leyland already have one Froude layout that incorporates 56 dynamometers, seven “slave” computers and one master to analyse all the results. — JW

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