Interview with Dave Allen 24/4/2008

Dave worked at BAC between  1958 and 1964.

He served a 5 year apprenticeship with the BAC at Filton Technical College and within the company’s 12 departments on airframe and general products. After work experience and Drawing Office tuition he progressed to become a Technical Illustrator in the Technical Publications department working on sales, operating and maintenance manuals between 1958 and 1964. He has run his Type  406 for many years. 


SC – So you’re telling us about the first  Lotus Elites– the Lotus Elite body shell contract that Bristol Aeroplane Company plastics division had in September 1959.

DA – Yes. And they undertook the manufacturing of the tooling and the production, and there were roughly 32 mouldings to make up the whole shell, it was mainly twin skinned throughout.

SC – That was quite high technology for glass fibre.

DA – It certainly was. It was the first monocoque car.totally constructed from glass fibre. And Colin Chapman pioneered the design both in epoxy resins and in polyester resin, the doors, bonnets and bootlids were epoxy resin and the rest was polyester.

SC – What’s the difference?

DA – Cost. Well, the epoxy resin is less brittle.   It gives a better engineering strength and it has higher qualities i.e. that’s why it was fully utilised on the Mosquito and other aircraft in bonding wood to metal in the aircraft industry.

SC – So Colin Chapman benefited from the aircraft industry technology?  Straight from the Mosquito into the Lotus.

DA – Yes. He was an ex-De Havilland graduate apprentice, both he and Mike Costin, and Frank Costin, Mike’s brother … the aerodynamicist, worked with Chapman all the way through until he eventually left and teamed up with his partner in   Cosworth, Keith Duckworth, who also worked for Chapman at the time, that’s how they met.

SC – Cosworth was  Mike Costin and Keith Duckworth.

DA –They both worked together working for Colin Chapman and they were red hot on engine development and power output, and the Elite, Graham Warner’s Elite, was prepared by them and was one of their early projects to get far higher performance from the Coventry Climax FWE engine, the 1216 c.c.,  and they were very successful.

SC – It was a fire pump engine wasn’t it, originally?

DA – It was a fire pump engine made by Coventry Climax in Coventry, all alloy, very light, very big main crank journals diameter, really chunky, it was designed to start and give maximum power and performance right away to pump water for fire pump delivery to the fire service.

SC – It had to run flat out from cold.

DA – Yes. And they were in a tubular carrier, two loops and they were totally independent, they had their own fuel tank and pump, the Coventry Climax fire pump unit.   It was a single overhead cam wedge shaped combustion chamber engine which was extremely light and big hearted. It won many, many competition races, for instance in the Lotus Elevens at Le Mans they won in 1957, fifty-one years ago, winning the 1100cc class and the index of performance. Quite an outstanding engine, and the Lotus Elites won their class at Le Mans six years running. So it was an outstanding car in competition in the hands of people like Jim Clark and Ian Walkerand others, they proved extremely effective. So the pictures I’ve got here are sixteen of the views of the tooling and the production of the various moulds being moulded and offered up in the jigs and bonded together, so that eventually the complete bonded twin-skinned shell proved …

SC – Each skin had to be made separately and bonded together.

DA – Yes. Separate moulds, bonded together in a clamp mould, which you can see from the photographs. That’s the mould of the base and then there was the inner and outer, both roof and upper and lower sections, three major mouldings.

SC – That must have given this quite simple and elegant shape terrific stiffness and torsion and rigidity.

DA – Absolutely. Yes. Extremely light and extremely strong. 300  lbs. devoid of accessories.

SC – Because when you say fibreglass car you think of something that’s flexible and shakes.

DA – Yes. No, the rigidity was quite amazing, and because it’s all compound curves and the aerodynamic form of it, it’s as smooth underneath as it is elsewhere, the only thing projecting was the exhaust pipe and the differential. The differentials have the draught to  cool the oil.

SC – You said there was an issue with the differential mounting.

DA – Yes, they had problems with the structure of the four mounts and they were breaking away with very severe clutch acceleration use, competition starts, and Bristols reinforced this. But all of the Bristol shells had their own Bristol red manufacturers’ plate on the bulkhead, you can always tell a Bristol shell by it having this, and they were made to a better standard than the others, which were made by Maximar mouldings.  Anybody who’s buying one always wants to focus in and get a Bristol shell.

SC – But they were made in other places as well, other manufacturers made them?

DA – Lotus had another production plant of their own contracted out to Maximar Mouldings Ltd.

SC – How many were made, do you know?

DA –   They had an order for about 850 and I think they made some extra ones as well. But they were completely bonded together, rubbed down, finished, painted, and assembled with their windscreens and suspension and sub-frame, lights etc. As shown in the figures those are the shells being loaded up on a transporter to go to Lotus’s for having all the wheels and engines installed, and the hydraulics.

SC – And a terrific little shape …

DA – Oh it’s beautiful.

SC – … when you consider it led into the Elan and the Elan Plus 2.…

DA – And the other subsequent Lotuses. But Frank Costin had a lot of input on its aerodynamic shape for efficiency.

SC – Was it designed in a wind tunnel? Bristol’s Car Division had their own 1/10 scale one which they used for many of their models.

DA – No, it wasn’t. Frank Costin used provens design principles from his racing experience gained on his previous Lotus models, Mk 8, Mk 9, and Mk eleven.

SC –Just on the  back of an envelope, like a lot of Lotus stuff.

DA Yes.  Initial concepts, then they applied science and maths.


SC – You were saying about the standards that the Bristol Aircraft Company in 1959 worked to, and that they were very jealous about protecting their reputation.

DA – They were. They wanted the integrity of the car and its structure to be reliable because it was such a new venture, nobody else had gone down this path of making a complete GRP shell, monocoque shell to withstand all the stresses.

SC – This was the first of its kind.

DA –. It was revolutionary. But the key thing was that the main weight of the engine and gearbox was in its own small sub-frame and the front suspension was bolted to it, so the body wasn’t a stressed member as such in all the direct weights, the engine and the suspension were a unit. And this frame was bonded into the structure with long strips to spread the load into the shell each side of the prop shaft tunnel.

A – Just strips of metal?

DA – Yes, it was a steel welded triangular frame, space frame. This coped with all the immediate high load stresses and then pick-up points called bobbins were moulded into the fibre glass structure and then items of suspension, trailing arms, were bolted into them with fore and aft thrust locations.

SC – Fibre glass is quite an unforgiving material for the workforce, do you know of any problems with dermatitis and so on?

DA – The dust and sharp irritation of glass fibres in the skin, eyes and so forth are not to be tolerated. In modern day fibre glass production units they have all enveloping ventilated suits and masks and head gear.… and also very efficient dust extraction plant.

SC – But these guys have just got overalls on …

DA – Yes, they just went out there with a file …

SC – Just with their sleeves rolled up, yes.

DA – and dressed the areas down, which today wouldn’t meet Health and Safety rules.

SC – A friend of mine made racing yachts in Bristol and he had such difficulty with this, he had a very skilled workforce who were terrific at doing it, but he had to use different materials eventually because there wasn’t a way out of the dermatitis.

SC – So that’s an example of aircraft technology coming straight over to car production.

DA – Absolutely, yes.

SC – From the Bristol Aircraft Company, being made to the high standards and a very radical and successful design.

DA – Yes. At the time the Bristol Aeroplane plastics division were making fuel tanks and drop tanks for the aircraft industry. I worked on them when I was an apprentice, they were made of Durestos. It was asbestos fibres mixed with resins, and it was sort of a grey pink colour.

“Durestos”, obviously dure for duration and durability and -estos from asbestos.   The fuel tanks were moulded in Durestos with all of the appropriate metal mountings and pressure take-offs and hangers etc.

SC – Moulded like the body you mentioned on the Lotus…

DA – Yes, that’s right, and all made to Ministry spec and tankage for the volume of fuel that they carried. And they made them for Hawker Hunters, Seahawks, Canberras, the whole range of British and foreign aircraft, American Sabres, F86 Sabres.  It was one of their big money spinners.

SC – Yes. But they were able to spin-off those kind of skills into just this little project.

DA – Oh yes. Well the Bristol Aircraft plastic division also made the nose cones for the ground to air missile Bristol Bloodhound, and the nose cone and radar domes for the Bristol Britannia  and others.

DA – The Bloodhound, was just made in a separate part of the missiles division.  Yes, they were always in the background beavering away on various projects. Of course it was all secret  – and controversial.

TSR 2 used Bristol engines, two Olympus engines, Bristol Olympus, because in those days the engine division became Bristol Siddeley and it was all Bristol Siddeley before Rolls took it over and the whole Patchway complex was all Bristol Siddeley. And they also did the Ramjets as well, and there was a Ramjet development division which had a huge test facility. They injected water to dampen down the heat of the thrust of these Ramjets on test, because the Ramjet was used on the Bloodhound missile. The missile was accelerated up to 150 miles an hour on solid rockets and then the Ramjet came in and continued on its path by Ramjet thrust.

SC – So once it had got a critical speed the Ramjet could fire?

DA – Yes, the Ram compression effect. As you know with all these engines, induction compression, power and exhaust is all done purely on flow instead of containing it in a cylinder .


Bristol Aircraft  plastics division, also made a small motorcraft which I’ve got a picture of amongst my old photos.  They were quite diverse in their applications, their projects.

SC – Was this GRP , what was it made of?

DA –The Alpha Boat was all GRP and the small cruiser they made. And some of their other pipe work was various other types of polypropylene etc.

MW Vincent Motorcycles, of which I’m a fan, developed around the same time the first fully enclosed motorcycle in fibre glass, the Black Knight. I believe Bristols made the front hydraulic forks which are aluminium alloy, they called them Girdraulics because they looked like girder forks.

DA – Yes, you’re correct. The Girder Forks were made to very, very high tolerances, close tolerances, interference fits, and not many people at the time had the machinery and the expertise to be able to manufacture these, and batch production of them was given to the Bristol Aeroplane Company to make and that was one of the things that they used to do for Vincent.

SC I wondered why the elegantly  streamlined, black stove enamelled front forks on my Vncent were stamped BAC. Now I know.

MW One of the features was that they had the same casting for the left and the right fork, they had the numbers of the parts cast into the mould,  but then when they came to actually allocate the left or right they just ground off the appropriate side.

DA – Yes, this was probably done quite a lot in industry, if truth be known. But Bristol Cars had very little to do with fibre glass all the way through. I think the only fibre glass parts that I can recall came in on the 412 and later models.

SC – So when did they do the Aston Martin shells?


DA – Aston Martins at the time were trying to make as many as they could to up their production because of demand, and the chasses were sent to Filton with the aluminium pressings, and our metal workers fitted the whole car, fitted all the panels and panel beat all of the edges around the Superleggera  construction. It was made just like a Bristol, finished, and they used to put a special tool in the headlight aperture in the front wing to get all the flange form and alignment right, it was all totally hand worked and hand finished.


SC – But at that time the British aircraft industry was starting to shrink.

DA – Yes. Because of the vast amounts of money that were needed to invest into new projects, single companies were unable to finance certain standards so there was quite a   reduction. Hence with the birth of   the Concorde project, we had to go in with it with France because of the huge expenditure and the cost of all the design and testing and research and development that was necessary to make it all happen. And an awful lot of that was done at Filton of course, they made one at Toulouse and one at Filton, the 001 and the 002. And the good old Concorde served well for thirty years’ service, and even in the end its downfall was due to debris on an airfield dropped by a French aircraft.