Paying tribute to visionary engineer and supercar designer Bob Henderson, who died in February aged 89.
“If you accept, as I do, that the internal combustion engine will be with us for some time yet, in either reciprocating or rotary form, then it is sensible to assume that even after all of this time it can still be developed further. In my view it is only in the wide field of pressure or forced induction that any worthwhile steps can be taken, as all others will be mere hair-splitting improvements to meet the long overdue pollution regulations. These are already showing signs of producing less power for more weight, a situation which must get worse.”
“The only long term saviour will be the blown engine which can double or treble the power output for only 10-20% increase in weight, and since cost and complexity could be less than the much-vaunted fuel injection systems, which only marginally improve efficiency, this is obviously the way to go.”
These are the words of Bob Henderson in the introduction to his book, ‘Theory and practice of turbocharging and supercharging’, published in 1974. Disregarding his stated opinion on fuel injection, for he was, after all, a carburettor manufacturer, he predicted the future accurately, living long enough to see forced induction becoming near-universal by the second decade of the 21st century, and also the beginning of the end of internal combustion as a universal power source for automobiles.
Henderson was born in June 1932 to a wealthy Fife family with business interests in the rubber industry in Malaya, where he was sent in the late 1940s. There he enjoyed ownership of a new MG TC, replaced in short order by a Jaguar XK120. Either would have been beyond the reach of most people in Export or Die Britain, regardless of their means. From his teenage years, he knew that his consuming interest was mechanical engineering, starting with bicycles, and rapidly progressing to cars and aircraft.
In later years, Henderson acknowledged the understanding of his parents when he “gave up a highly-paid career in commerce to pursue his dream goal.” Recovering from a serious road accident in which he was a passenger, Henderson returned to Britain, reluctantly leaving behind his Malayan mechanics, Ah Hoi and Ah Kwan. While receiving plastic surgery, he found part-time work at Shorts Aviation through a chance acquaintance, and impressed his employers sufficiently to be offered a full-time post. In due course, he rose to the rank of Chief Engineer.
In 1956 he moved to Canada, where his expertise with both Rolls-Royce piston engines and aircraft modification and adaptation was highly valued. Automotive work started as an off-duty sideline and evolved into the establishment of successful business in Ottawa. A chance encounter with Eric Liebman of Fish Canadian Carburettors was to shape the next stage of his career. Liebman had been one of John Robert Fish’s original team when the Miracle Carburettor was being developed. He easily convinced the young Scottish engineer of its exceptional virtues to the point that Henderson described himself as “more of a missionary than an engineer”.
By the end of the 1950s, Bob Henderson had set his mind to a return to Britain. Eventually, he settled in Argyllshire, where he had enjoyed childhood family holidays in a rented castle beside Loch Awe. The Fish carburettor was to underpin his plan. He secured the rights to produce and market the carburettor in the UK and made a number of patented improvements, selling it under the Minnow-Fish name. The product was an instant success, promoted through enthusiast publications in a tuning-obsessed market.
Conventional advertising was kept to a minimum. Henderson avoided the temptation of approaching major car or component manufacturers, realising that high-volume production would very soon lead to him losing control of a profitable business. Instead, Team Minnow Fish was established, re-igniting his competition activities around the BMC Mini, which had already established itself as a motor racing phenomenon. In a pattern to be repeated later in his career, there was even a Minnow-Mini G.T. car to support the missionary work.
In typical Henderson lateral-thinking form, the car was based on the recently introduced Mini pick-up, with a new rear superstructure topped by an extended roof even longer than that of the Mini van, and a reverse –angled rear window. The aeronautical thinking reduced the drag coefficient considerably from the standard Mini’s dreadful 0.48. This delivered a top speed of 93mph and 0 to 60mph in 15.4 seconds, close to Cooper performance from an 848cc engine with a single Minnow-Fish carburettor.
By the time the 1960s were drawing to a close, Bob Henderson had found a parallel and complementary enthusiasm in experimental development of turbocharging installations. This was around the time when GM’s American production applications were abandoned, and well before BMW, Porsche and Saab had put their turbocharged cars on sale.
Another promotional vehicle was presented, not only to demonstrate the benefits of forced induction, but also to mark Minnow-Fish’s permanent move to Lochgilphead(1) in 1970. The Minnow-Fish Avenger Highlander had a Rapier H120-like rear spoiler and alloy wheels for visual differentiation and extensive engine and chassis modifications. Claimed performance was a 120mph top speed, and acceleration figures of 0 to 60mph in 7.0 seconds and 0 to 100mph in under 20 seconds. Other turbocharging work included doubling the power output of the 1.5 litre Austin Maxi (that poor gearbox…), and a forced-induction Saab 99, long before the official Trollhättan item was introduced.
In 1974, ‘Theory and practice of turbocharging and supercharging’ was published. Its author claimed that its instant success resulted from there being no book on the subject published outside America, and very little knowledge in Europe on how to apply forced induction to small capacity petrol engines(2).
For better or worse, Bob Henderson’s signature dish was the extraordinary mid-engined Argyll Turbo GT. Like some mythical beast, its existence was first rumoured after sightings, until it showed its face in a road test of the first Rover V8-engined prototype. This was published in the September 1976 issue of CAR magazine, written by one Jim Dunn.
The car Dunn drove had a turbocharged Rover V8 and ZF transaxle with seating for two within the three-metre wheelbase. Dunn praised the turbocharged Rover-engined prototype’s performance, its controllability, neutral handling and unexpectedly comfortable ride, but the interior trim was described as “virtually non-existent.” A 2+2 version with a Henderson turbocharged Saab 99 powertrain was also mentioned, but there is no evidence that such a car was ever built.
After this, the Argyll car returned to obscurity for nearly seven years before re-emerging at a grand launch event at Inveraray Castle in October 1983. The news was positive. New financial backers were in place to underwrite the development costs, stated to be £250,000. A number of advance orders had been confirmed, production capacity was stated at twelve cars per year and the first customer car was being readied for delivery. A price range of £25,000 to £30,000 was quoted. At that time, a Lotus Esprit Turbo cost £18,913, a Porsche 911 Carrera £21,464 and a Ferrari 308GTB quattrovalvole £26,181.
The production car remained close in appearance to the 1976 prototype, the major change being its 2+2 seating configuration and adoption of a blueprinted and turbocharged version of the Douvrin V6 from the Renault 30, along with its own transaxle, as the standard engine. The sales brochure of the time listed an alternative 3.5 to 4.2-litre turbocharged ohv V8. No manufacturer is named, but it was clearly Rover-derived. In this specification, a ZF transaxle, also specified for the Maserati Bora and De Tomaso Pantera would be used and the rear seating omitted.
In September 1984, Motor magazine sent Richard Bremner and photographer Peter Burn to Lochgilphead to sample two production Argylls, both PRV powered, one turbocharged, the other naturally aspirated. Bremner was impressed by the dynamic competence of the chassis and the turbocharged car’s power delivery, but shocked by the chaotic and primitive workshop. The tone of the article is disparaging, making much of the conspicuously poor build quality, obvious use of other manufacturers’ parts and the square section tube chassis which he described as using “the same technology that brought the world the garden gate.”
The Turbo GT project was never going to create anxiety in Bologna or Modena, nor for that matter in Hethel or Zuffenhausen. The highest production ambition was one car a month: actual numbers are one of the things you knew not to ask Bob(3). My guess is single figures, somewhere between four and six.
Even as the 1980s drew to a close, occasional news emerged about a breakthrough; interest from a Middle Eastern distributor, and in 1989 a plan to rework the car for sale in the USA, with production planned to move to much larger premises in Glasgow’s industrial hinterland. The curtain never quite fell on the supercar project but perhaps by the end of the 1980s its creator accepted that it had served its purpose. He had achieved the car enthusiast’s dream of designing and producing his own car, imbued with his idiosyncratic ideas, and the venture had not ruined him.
I met Bob Henderson in person twice, once in the mid-1970s, and again in July 2007. The second visit was arranged at short notice, and I had some trepidation about how the passage of thirty years would have shaped the man. His writing – and he wrote well – was often trenchant and opinionated(4), suggesting ‘a good conceit of himself’, but I found him in real life to be modest, amiable and ever-enthusiastic, with a rich fund of knowledge and good stories.
I arrived at the appointed time. Bob Henderson appeared from behind his XK120, parked in the Minnow House yard. This was the car from Malaya, in his continuous ownership ever since(5).
I had also landed at an opportune moment. The Minnow House dynamometer was being re-calibrated, necessitating an extended tea and biscuits break for Bob and his much younger assistants. Conversation was easy and wide ranging; Jaguar XK engines and British Leyland’s deleterious influence on the marque(6), the notion that there is no engine yet made which cannot be improved, the error of modern turbocharging practice which majors on the volume of the charge. Bob maintained that the quality of charge is more important. Also discussed were life in colonial Malaya, the possibility of re-starting Minnow Fish carburettor production on a small scale, and the enormities of Scottish Enterprise, a regional body controlling public funding of grants and loans to businesses(7).
I was able to inspect a resting Argyll in the workshop, and take stock of its inventive features, such as the rear view optical trough, and the aerodynamically refined louvred headlight covers which avoided the need for headlamp washers and wipers .
Even in 2007, when Bob was in his mid-seventies, the possibility of making a few more cars was not ruled out. There were stocks of parts at Minnow House, including complete chassis and some ZF 5DS-25 transaxles. It’s doubtful that this renaissance ever happened but, according to a Scottish Field article in June 2019, the Minnow House business was functioning much as I found it in 2007, providing maintenance, restoration and engineering services to a loyal group of customers.
The Argyll Turbo GT venture is sometimes characterised as vainglorious. Certainly the commercial ambition was in vain but, for me, it did have a glorious quality in its audacity and the unadulterated expression of its creator’s ideas. It is but a small part of Bob Henderson’s lifetime contribution to the progress, understanding, and enjoyment of the automobile, and particularly the engines which power it. For all of this, he deserves to be fondly remembered.
Robert MacLaren Henderson. Engineer, pilot, racing driver, inventor, author, car manufacturer. June 1932 – February 2022.
(1) An attractive small town on an inlet adjoining Loch Fyne. The gateway to Knapdale and the Crinan Canal. Although the locale is only 90 miles from the centre of Glasgow, it feels like a totally different world.
(2) LJK Setright arrived at the party a little later, with his ‘Turbocharging and supercharging for maximum power and torque’ first published in October 1976.
(3) The other was the origin of Turbo GT components. Richard Bremner noted “Henderson is irritated by people who try to spot their origins.” I think I got away with recognising the Granada front subframe in the workshop.
(4) Henderson considered fuel injection to be over-rated, likewise Italian stylists. He also deeply disliked low-profile tyres.
(5) Bob took some pride in claiming to have seized the crown for longest XK120 ownership from Alan Clark. The politician and historian procured his car a little earlier, in 1948 when he was a student at Oxford, but his tenure was cut short by his death in 1999.
(6) Lord Stokes was a particular bête noire. Bob considered any Jaguar engines with the Leyland logo in their castings to be “ruined.”
(7) In the 1983 launch publicity material, it was noted that “Astonishingly, the entire project has been privately financed, and has been neither aided nor funded by the Highlands and Islands Development Board, or any other government agency to date.”
Reference sources:
Theory and practice of turbocharging and supercharging. Bob Henderson. Speed Sport Publications June 1974.
Car magazine, September 1976
The Oban Times, 27th October 1983
Motor magazine, 1st September 1984
The Scottish Field, June 2019
Driven To Write 
Thanks for that Robertas. How curious that someone tried to make an object as complex as a motor car so fare from the traditional centres of industry associated with that activity. This bit is curious: “Bob maintained that the quality of charge is more important.” Is that the mix? The temperature? Engineers don´t usually talk about quality but quantities.
From my reading, temperature is the issue. Measurement of Volumetric Efficiency (VE) does not take account of the loss of charge density as a result of heat inevitably added by the process of going through a pump. The faster the pump turns, the greater the heat added. In the 1974 book, Henderson has a table which shows the best thermal efficiency being achieved at 2000-3000rpm and dropping sharply after 4000rpm.
In the 1984 Bremner article there’s a quotation: “other manufacturers do not understand the way in which a turbocharger works. It should be regarded as a centrifuge rather than a pump if its advantages are to be realised”. There’s no further elaboration, but it suggests to me maintaining charge density is more important than straightforward – and more easily measured – air volume.
I seriously doubt that manufacturers like Porsche or Saab did not understand the working principles of turbochargers.
It was long known because it is a basic fact of engine physics that the relevant factor is not the volume but the weight of the mixture that is put into the engine by suction or by pressure. The problem was that there was no way to measure it until air mass meters (with a platinum wire that’s heated up and cooled by the air) became available and replaced air flow meters (with a movable flap measuring the air stream) or pressure sensors.
Only when you are able to precisely measure the mass of the mixture are you able to go at the limits of the engine – and that is what is done today with compression ratios that would have been unthinkable not too long ago and with power outputs consistently in the region of 100 PS per litre and more that would have been pure racing engine territory not too long ago. Air mass meters and knock sensors are key factors for going to the limits of the engine.
The effect that thermal efficiency ist best at 2.000 rpm and drops at higher revs is a matter of engine setup.
A small turbo will deliver little pressure but can be run with a higher geometric compression ratio, giving good mid range efficiency but not much support at higher revs. Most modern turbo charged engines are set up this way but need precise air metering to avoid pinging and small turbos that react quickly to changes of load.
Going for a large turbo will need lower geometric compression ratios with bad mid range efficiency but has room for high pressure at high revs giving good power in the upper regions of the engine range. Think BMW 2002 turbo or early three litre Porsche 930 turbo with their ‘open throttle – nothing – bang’ engine characteristics.
Engineers who work with steam turbines use “quality” to refer to the proportion of condensed water droplets in their steam. It is (somewhat ironically, I suppose), in fact quantified—100% quality refers to pure steam with no condensate. I’m guessing Bob was referring (loosely) to the atomization/uniformity of fuel in the charge, in much the same way.
But of course car manufacturers were well aware of the importance of this characteristic of the charge; this is why (very ironically, with respect to Bob) everyone (besides Maserati) quickly concluded that turbocharging and carburetors were a silly combination and that the potential of forced induction could only be fully realized with fuel injection!
A few words about the Comecon Car / RGW Auto project.
It all started after the “fraternal aid” of the Warsaw Pact countries to Czechoslovakia in 1968. However, a few years earlier the East Germans had already shown interest in four-stroke Škoda engines in their cars. There was no longer any interest in their two-stroke engines in the West. But Škoda had no interest. It was a competitor
After the Second World War, the East Germans produced BMW cars at the former BMW factory in Eisenach, which was renamed EMW after legal disputes and the blue field in the emblem was changed to red. However, they did not continue development. With the new bodywork on the original chassis frame, they produced several thousand Sachsenring P 240 six-cylinder cars from 1956 onwards, which they intended to produce in large series as cars for the Eastern Bloc state authorities. However, the eight-cylinder Tatra 603 with a self-supporting body beat them to the punch.
All mass-produced East German IFA F8 and IFA F9 passenger cars were based on the pre-war DKW design with two-stroke engines. The later IFA Wartburg and IFA Trabant models received new bodies, but still on the adopted chassis frame with two-stroke engines.
The Wartburg did develop a four-cylinder four-stroke flathead boxer engine, but instead of producing them, it invested in the military.
After the RGW Auto project ended, the East Germans were looking for a replacement for the two-stroke engines. They considered installing a Dacia engine, but eventually bought an old, low-cost Volkswagen engine production line from their compatriots in West Germany. And they started making four-stroke Wartburg and Trabant cars.
Trabant was never body-on-frame.
Trabant was duroplast plastic body on the space-frame.
Of course CAR magazine failed to report that they asked Bob Henderson to advertise in the magazine. When he declined to do so the article that eventually appeared damned him and his cars with faint praise.
Interesting fact: the journos drove a Porsche 911 up to Bob’s premises to do the interview and then road test one of his Argylls. They scared themselves a few times in the Porsche (narrow, wet, bumpy roads with lots of tightening off-camber corners). The Argyll behaved itself in the conditions. It handled well, rode well and was not disturbed by the poor quality of the road surfaces. Hard for them to deny that it really did have an excellent chassis and that the handling was of a very high order.
Bob’s autobiography is well worth a read. There were to be two parts to it. Part one was finished and published. I fear part two may never see publication (I hope I am incorrect with this forecast). Did you know Bob was involved in gathering intelligence prior to the Malayan Emergency? His work was vital. He was lucky to survive his time of stealthy observation and intelligence gathering work deep in the jungle, all on his own and at great personal risk. He had a more adventurous career than James Bond- but what he achieved was real, not just make-believe from a novel.
It is a pity he has passed. The world needs people of spirit, passion, honour, integrity, principle and bravery just like him more than ever. And yes, he was a good engineer.
Robertas, thank you for remembering him.
Bob was concerned about the quality of the fuel/air mixture. Gasoline is liquid at room temperature. When it is introduced into the inlet manifold of an engine a spray of droplets is created- some larger than others. Also some of the gasoline is immediately vapourised and some is not. So we have a complex mix, with some vapour and some droplets of various sizes entering the engine along with the air. Hence some of the inlet mixture may be rich while other portions lean. Some of the gasoline droplets may plate out on the manifold or port walls and then form rivulets which eventually dribble into one cylinder or perhaps another. Notice also that droplets of gasoline are heavier than the gas (air) they are introduced into. Any bends to negotiate or changes in direction can encourage the droplets to plate out or wet out the surfaces they are adjacent to (ports or manifolds or valves or cylinder walls or piston crowns). This is concerning in carburettored engines. It is concerning in suck through or blow through turbo engines. It is also a problem which can exist in injected engines (although not to quite the same extent) and it needs attention to minimise its negative effects.
A poorer quality mixture will negatively affect combustion. Consider a flame front advancing into a mixture of inconsistent areas of rich and lean, as well as trying to vapourise droplets of gasoline so the gasoline they contain can be mixed with air, ignite and burn- remember, wet fuel does not burn. Also think about vapourising large droplets of fuel. This can end up with regions immediately surrounding the droplet being very rich compared to regions a distance away (which may be overly lean). Compare that with the smaller droplets. Add to all this the bulk mixture motion (swirl, tumble and all that) as well as local mixture motion, well, you get the idea.
When Bob said he was worried about quality, he really did mean quality.
Thanks for that reply. I can imagine fluid dynamics are at play here and they are famously hard to deal with. What we can´t quantify we must qualify, I suppose.
Very interesting. Gasoline is liquid at room temperature. When it is introduced into the inlet manifold of an engine a spray of droplets is created- some larger than others. Also some of the gasoline is immediately vapourised and some is not.
I don’t know much about it, but is it the same in a really warm engine with a hot intake manifold and hot valves?
Thanks
It’s the same in a hot engine, simply because the fluid fuel is sucked from a nozzle.
The only way to prevent this is using a surface carburettor like in the first years of the automobile. These had a reservoir of fuel heated from below (mostly by the exhaust), creating real fuel vapour that was sucked away by air drawn over the surface. Every bump in the road set up the mixture and the jetted carburettor was a big progress.
It is interesting that dealing with LPG there are injection systems that either inject a gas vapour, or inject the LPG still in liquid form – the latter is supposed to provide a cooling benefit during the liquid to gas evaporation
Intrigued by the reference to the Fish carburettor, and the suggestion that Henderson deliberately avoided high volume production. I assumed at the time that if it was as good as it was made out to be, a major manufacturer would be using it. The only drawback I can see now, looking online, is that synchronising a pair of them was extremely challenging – in single carb set-ups they were very effective.
Thanks for this article, I’d heard of the Argyll GT but not about the man and story behind it. Definitely one I’ll have to come back to when not on my phone to appreciate fully.
One observation is that the location wasn’t the car’s biggest obstacle to success, but all power to Mr Henderson for having a go!
His must have been a fascinating life.
Electing to use a R30 V6
was, most probably, due to the convenience of its transaxle for mid-mounted application such as the Argyll. Yet, something tells me that Henderson
could have been also fascinated by the PRV V6’s wide “nest”
(being a 90°),
which makes it extremely convenient for overcharged applications
(less sharp turns in the intake tracts = less chance of mixture falling out of homogenity, more space for proper plenum/port volume matching, etc.etc.).
Thank you for a splendid article
& hommage.
I worked with Bob Henderson at his workshop in Hackbridge when he raced mini’s It was a pleasure to be part of the manufacture of an iconic Carburettor.
Very sad I haven’t been able visit him before he passed. There were lots of fond memories He will be missed