WHY IS THE ADO16?
Alec Issigonis, technical director of the British Motor Corporation and Charles Griffin, chief engineer, answer questions from our technical editor.
Joseph Lowrey, MOTOR: As soon as they discovered the Mini-Minor’s remarkable qualities, motorists began asking whether your unique design could also be scaled up into something larger. Is the Morris 1100 your reply to them, Alec?
Alec Issigonis: The answer to that question is that since introducing the transverse mounted engine and front wheel drive we have learnt a great deal about a new technique, and the trend towards bigger things is already visible in this new model. The similarity of this car to the Mini’s is great, but its engine already has 40% more power and is 30% larger than the one we started with.
Joseph Lowrey, MOTOR: So by now, after selling ADO15’s for three years, perhaps you know enough to design something twice as big as the original? Anyway, how long have you been at work on the ADO16 design?
Alec Issigonis: For three and a half years. About six months before a new car is ready for production we are confident about what we are doing. Six months before the public saw the ADO15, we knew its engine and architecture were sound and began to apply its lessons to a larger model. This one took us longer than the ADO15 to develop. It wasn’t so urgently needed from a commercial point of view and we were faced with problems of getting much greater refinement. In many ways, it was harder to do, in some ways also it was easier.
Joseph Lowrey, MOTOR: Such as…?
Charles Grifiin – We had more money to play with ! Not to spend on development, but to spend on building each car, so we didn’t have to simplify things quite as much.
Alec Issigonis: The bigger scale of everything makes problems easier, and there were not such fanatical requirements of space saving as in the little car.
Joseph Lowrey, MOTOR: Studying the ADO16, it looks to have some waste space ahead of the engine, whereas you built the ADO15 body to fit tightly round the works. And the smart new car doesn’t have such stark economy features as out-turned joints betweeen body panels.
Alec Issigonis: So you’ve noticed that spare space at the front? No comment – see what happens later on ! ADO16 is a refined car, not a cut price one, whereas every inch of the Mini’s 10 feet length was needed for for seating accommodation; you cannot make a shorter four seater.
Joseph Lowrey, MOTOR: Surely the BMW 600 with Isetta type front door was a four seater within a length of only 9 1/2 feet? Even if the customer thought it so strange looking that they refused to buy ! But lets talk testing – apart from your local Welsh mountains, and France, where a car was photographed and illustrated by local newspapers many months ago, where have you had your experimental cars?
Charles Griffin – Germany, Italy, Switzerland. Not outside Europe.
Alec Issigonis: I think this testing abroad is an overrated pastime. I don’t believe that a car tested in Spain or Africa is necessarily better than one not tested there. We used the European theatre, testing the suspension in southern Italy and in Norway. We have worked for six years on this Hydrolastic suspension, and as we were approaching some degree of finality we put a spurt on to finish it for the ADO16.
Charles Griffin – The handling of this long wheelbase car could not have been combined with such good ride in any other way.
Alec Issigonis: You can only use this interconnected system with all independent springing. We built about half a dozen Morris 1000’s with independent suspension all round for testing Hydrolastic. They looked normal enough; no one who saw one would know there was something new on the car. We even went to Monte Carlo in one. Six years ago, at the same time as Alex Moulton and I were developing the rubber springs for the Mini’s, we talked of practically nothing else but this coupled system which derives from it.
Joseph Lowrey, MOTOR: It is very hard to make the ADO16 bounce bodily on its four springs, but two of us standing on door sills at each side had a go, and it seems as if your spring strengths give a natural frequency of around 90 per minute – is that right?
Charles Griffin – A little higher. Equivalent to about 4 inches static deflection. The Mini has a suspension frequency of around 97, so the new suspension is very little softer in bounce – we use 6, 7, or 8 inches deflections on the big cars.
Alec Issigonis: But the very low pitch frequency, on a car which is self-stabilising thanks to the progressive rate of rubber cones, lets you share the bumps between two springs, and get a very easy ride without the roll of soft springs.
Joseph Lowrey, MOTOR: The Citroen 2CV, which pioneered interconnected front and rear springs, could give a wonderful ride, but just occasionally awkward conditions would make it imitate a ship on a rough sea. I’ve spent quite a lot of the past week failing to catch out your suspension on awkward bumps, and I’m wondering why I failed.
Alec Issigonis: The ADO16 is damped, whereas the 2CV has inertia dampers on the hubs which act only to limit wheel patter, plus only a trace of friction damping. Our suspension is much stiffer, and though we don’t make any great claims for its being super comfortable, our compromise has let us put what we think is a very good system into a cheap car. We were not trying to build a DS19; this car is a compromise.
Joseph Lowrey, MOTOR: A very successful compromise too – the big Citroen is not really an all rounder, whereas your new car is. I followed a Mini out of London this morning, driving the ADO16, and only the lively movement of the car in front told me what a jolly rough road I was covering, yet on M1 the new car felt beautifully solid.
Alec Issigonis: Our interconnection is not mechanical like the 2CV, but through two pipes. We made the pipes unnecessarily big in bore, to give ourselves room to manoevre, and there is a little washer in each with a small hole controlling speed of flow, so we get a firmer ride at speed than around town. With a lot of water-alcohol fluid in the system, we don’t have high temperatures causing damper fade, nor are we worried by viscosity changes. We do not feel that we have put the emphasis on comfort ; we have erred on the side of making the car safe, making it swervable in an emergency.
Joseph Lowrey, MOTOR: Although you designed the Mini Minor as a cheap and simple car, much more expensive variants of the design have now been added to the range. Will Hydrolastic suspension find a place on some of the ADO15’s?
Alec Issigonis: We don’t feel this would be a commercial proposition, partly on cost and partly because it affects so many other parts of the car also. It is a suspension system which, unlike accessories, has to be built into the car itself.
Joseph Lowrey, MOTOR: Since you have put this more refined rubber springing system on ADO16, you must think the rubber springs on ADO15 have justified themselves in comparison with steel?
Alec Issigonis: Certainly from the reliability point of view. The primary creep condition on the Mini was more than we thought, but only the public can really find this sort of thing out for us. Now the really interesting thing with this new suspension is that we have eliminated primary creep almost entirely. If you take a Mini spring and ‘scrag’ it by stressing it on a machine, as you would on a steel spring, the rubber will slowly recover before you put the spring on the car, so you must still set the suspension high and let it settle towards its desired level in a few weeks of use. On the new suspension we found the most exciting thing; when the car is going down the assembly line we pressurize the hydraulic system to about twice what supports the car, lifting it hard up against the rebound stops for a period, then, when the car gets on its wheels, the hydraulic system is let down to its normal 205 lb. pressure and sealed. The springs immediately carry their normal load and creep is thus virtually eliminated.
Joseph Lowrey, MOTOR: Nowadays most cars have anti-roll bars at the front to make them understeer, but you have to make the anti-roll bar at the back of ADO16. Is this because you have got so much weight on the driven front wheels that you could have too much understeer?
Charles Griffin – Alec has been pushing us for responsiveness, for ‘swervability’.
Alec Issigonis: It’s like flavouring a dish after it has been cooked. You add salt and pepper to your taste, and everyone’s taste is different, but you can vary the flavour without the food being frightful or lethal. Look at the racing boys, you’ll find they all have an armful of anti-roll bars to try in practice, and no two drivers, and no two drivers choose the same combination. Do you like our choice?
Joseph Lowrey, MOTOR: Almost, but for my taste the steering response is just a shade to eager. I’ve had it on the MIRA proving ground where there are corners with plenty of spare ‘elbow room’ to see what happens if you are silly, and nothing happened ; but on the road, if you want to tuck in quickly after overtaking someone and have not to much elbow room as you finish your swerve, sometimes there was just that doubt in my mind about straightening out precisely on my intended line. We were advised to run the front tyres at 28 lb. pressure and the back ones at 24 lb., whereas a 2 lb. smaller differential gives the steering my ideal amount of ‘pepper.’
Charles Griffin – Actually, the roll bar encastrements on the production cars have come out unexpectedly firm, and we are going to take a few thou off the roll bar diameter soon to get back to our chosen result. I wanted 26 as the front tyre pressure but I batled with Dunlop over it and lost. The rear anti-roll bar has helped reduce front tyre wear. We have done a lot with this car in the course of its development to get neutral steer, like a bike !
Joseph Lowrey, MOTOR: Whilst you are doing this development to make a new car handle precisely as it should, what testing can you do to make sure that the finished article will be trouble free?
Alec Issigonis: It’s difficult to see how new models can be tested without a great element of artificiality. For instance, I can only test a car properly if I am using it for such errands as going to buy cigarettes, something unconnected with the car which I then treat as transport. But if you use a prototype like this and all your customers see it, they are liable to jump to conclusions and stop buying existing cars long before the new model is ready to be sold. I take such a serious view of this problem, which worries other manufacturers just as much as it does us, that I sometimes even wonder if we would be better off if we didn’t test prototypes at all !
Joseph Lowrey, MOTOR: I couldn’t agree more about everyday usage being an invaluble form of testing, and the cars which we try out are used for all sorts of errands and calls as well as being tested to a deliberate programme – we learn just as much from living with them as we do from taking them to the MIRA track.
Alec Issigonis: Of course one excludes specific testing from any such idea, but a great many tests such as finding out the strengths of particular parts are done as well or better on a rig, rather than on a road. But nobody has ever discovered how to test prototype or pre-production cars in such a way that there will be no fresh bothers when the first customers get their cars. Around the factories, you’ll find quite a lot of people who wait until they hear that production of a new model is going to start, and then buy one of the old models because they reckon it should have reached as close to complete reliability as it ever can.
Charles Griffin – The teething troubles of the Mini were really remarkably few for such a new car. A 1% production problem stops the assembly line, yet how can you be sure of discovering on prototypes a problem which will arise on 1% of the cars you build? Perhaps we should hire charwomen to do our test driving for us !
Joseph Lowrey, MOTOR: A Peugeot engineer told me that the first 500 examples of any new model were sold to their suppliers, maybe to non-technical folk who supply such stuff as cloth for the seats but they are in regular touch with the factory.
Alec Issigonis: What a wise little firm. A new model is never a real success when the engine and every single other part are new ; some big parts of a new model must be inherited from previous models if a good car is to be made. If everything is completely new, the development problem is to big and the result is not good. This applies to the engine in particular. The ADO16 power unit is within the general framework of ADO15, but in making it bigger we have added a stiffer crankshaft with a vibration damper. Front suspension architecture is the same too, it has the same ball joints, but with bigger and more dished wheels we now have centre point steering.
Joseph Lowrey, MOTOR: The front wheel drive is more evident than on a Mini if you take your foot off the accelerator when cornering.
Alec Issigonis: This is a punchier motor. The Cooper is the same compared with the original Mini – there is more slip angle on the tyres due to the extra power, so you notice more when this is cut.
Joseph Lowrey, MOTOR: And if you use braced tread tyres?
Alec Issigonis: They are great fun. The self aligning torque is reduced. When we designed this car there were 10 inch, 11 inch and 13 inch wheels and tyres available, but 12 inch was the odd man out, so a special size had to be made when we insisted on it.
Joseph Lowrey, MOTOR: You have chosen disc brakes for the front of this new Morris, though some people have found that very small sizes of disc brake suffer rather quick pad wear, as an offset to their fade resistance. Have 12 inch wheels helped here?
Charles Griffin – They do give more development space.
Alec Issigonis: At the moment disc brakes are fashionable ; the thing to have. I was not particularly in favour of them, but the management suggested our having disc brakes, even though it was a more expensive thing to do. The ADO16 has more braking relative to its size than the Mini.
Joseph Lowrey, MOTOR: Continental designers of front wheel driven cars have often used beam axles to couple the undriven rear wheels, presumably to get the handling characteristics they want. You prefer I.R.S. and I’m curious as to why.
Alec Issigonis: We did consider using a rigid axle, but in the end just didn’t. There were practical considerations, and it did not make such an elegant little unit.
Joseph Lowrey, MOTOR: The synchromesh in the ADO16 works incomparably better than on ADO15, but why no synchromesh on bottom gear?
Alec Issigonis: I don’t like synchromesh on bottom gear. I find that it is difficult to get into gear with it.
Joseph Lowrey, MOTOR: But your biggest Austins have synchromesh on bottom gear?
Alec Issigonis: Yes, and I don’t like them. I have driven most of the small continental cars which have synchromesh on bottom gear, and found engaging bottom when the car was stationary was almost impossible.
Joseph Lowrey, MOTOR: The new car has a wheelbase 13.5 inches longer than the ADO15, yet its turning circle is hardly any bigger ; what have you done to the constant velocity joints?
Alec Issigonis: It’s a matter of margins of safety. When you put a new joint into a design, you tend to give it a few degrees less movement in case of variations in production, but after three years we know more than we did when designing the Mini. Wider track on the ADO16 means that its drive shafts are longer and so the suspension movement uses up less of the available angularity, leaving more for the steering. More lock on the Mini would have meant wider front wheel arches restricting the footroom too.
Joseph Lowrey, MOTOR: This is not a seasonable question, but people who live in cold countries sometimes claim that pre-engaged starter pinions are preferable to Bendix drives because they don’t get thrown out of mesh when the engine kicks but doesn’t quite start. As one British designer, can you say why we seem to be the odd country out?
Alec Issigonis: If you use a car in very cold conditions, our starters are excellent – we do have our cold chambers to test them in, you know. It is a matter of using the right lubricant in winter, and the Canadians know better than to lubricate their engines with treacle. We sell a lot of cars there and have had no complaints. Some very small engines may need pre-engaged starters, but for us it would be stupid to use them when there are much simpler ways of getting the result.
Joseph Lowrey, MOTOR: To fit winding windows into a car which is almost as wide inside as out, you have used curved glass, so the man who breaks a window in Timbuktu will have to get a BMC spare instead of having some glass cut locally. Remembering how a little firm in Rochdale makes a sloping window of flat glass drop into a hollowed out sports coupe door, I wonder if curved glass was necessary.
Alec Issigonis: The curved windows were not used as a styling gimmick ; they are a practical measure. We overlooked the spares problem, because we had to. We were pre-occupied with getting more room, and gained about 1.25 inch of elbow room on each side. With sloping windows of flat glass, the body would have become wider at its base, and we dislike the modern styling trend of designing thick, bulbous doors. If you sell a car on a styling gimmick, sooner or later the fashion changes, but if you are selling a design based on sound engineering it will last much longer. I think the countries economy must be considered and that we must design cars that will last a long time : this country just cannot afford ‘planned obsolescence’ on American lines.
Charles Griffin – And the public cannot afford to buy transport which is merely fashionable, and will be quickly dated.
Alec Issigonis: If you don’t sell fancy styling there need be nothing to get out of date. I give the ADO16 ten years, and the Mini too. Of course, a design is always being developed ; just compare the original Morris Minor with the Minor 1000 as we are building it today.
Joseph Lowrey, MOTOR: As a final question, if I take one of these charming little cars to France, and fill the Hydrolastic system with Scotch for the outward journey but drain and re-fill with V.S.O.P Cognac for the return, how many pints of each can I smuggle?
Alec Issigonis: Moulding some diamonds into the rubber springs might be a more profitable way of getting into prison ! Just now don’t you think fully duty paid pints all round might be safer?
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