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From The Production Line.
One Million Minis.
Nairn worked for BMC in the 60’s. Here is another article from his memorabilia.
The one millionth Mini, which came off the assembly line at Longbridge yesterday, looks very much like number one produced in July 1959. You might even say that the cars are as alike as two peas; but if you did, you couldn’t be more wrong. Between No.1, pictured on the left, and No. 1,000,000, there are scores of differences. Some, like Hydrolastic suspension, which was introduced last year, have been widely publicised. Others have slipped quietly into production unheralded and unsung; but they all add up to better value.
I am, of course, referring to modifications quite distinct from the specific changes made to produce variants on the original saloon model. The Mini, in case you did not know, is not the first BMC car to reach a production total of seven figures. The ever-popular post-war Morris Minor led the way; but whereas the Minor, the first Issigonis designed car to go into quantity production, took 12 ½ years (from October 1948 to January 1961), to reach the million, the Mini has done the same thing in only 5 ½ years. Both have been the subject of continuous development, but both have preserved their original characters intact. Only the details have been changed as and where improvements were possible. Production improvements are seldom of direct interest to the public since they have no bearing on usage; but they are important nonetheless because they save money and enable the maker to give customers more for their money.
Rectification of design faults, you might think, should never be necessary, and from a perfectionist point of view, you would be right. In practice no manufacturer can completely escape them with a new design. One reason is that the difference between the largely hand made prototypes and the models which subsequently flow off the production lines grows even greater as quantity production techniques improve. If this sounds odd, take the case of a simple part like a bracket which might be hand made in the prototypes but takes the form of a steel pressing in the production model. The difference is considerable, and a slight miscalculation in the material or design of the pressing might give trouble where none had existed on the prototype.
Another reason is that the public can always be trusted to think up some new form of misuse which would never occur to a trained development engineer. The old story of the spinster who pulled out the choke knob to hang her handbag on, maybe apocryphal, but it illustrates the point. Equally, no one today can forecast what the sporting types will do.
As originally conceived, the Mini was designed to provide safe, comfortable and reliable transport for four people within a minimum sized box on wheels. No one envisaged that the superb stability and cornering qualities would make it a draw for race going crowds. This sort of treatment soon showed up a design fault that was a fault only because users made it so. The road wheels were not up to it and some collapsed. The cure was simple – the use of a heavier gauge steel.
Far more wide spread were water leaks in the floor. These came about in a curious way. At the time the body shell was first designed a smaller engine giving less power was envisaged. When it was decided to increase the power it was thought wise to stiffen the structure by boxing the body sills. This produced the section shown in the left drawing, with spot welds at flanges A & B. it followed that if any water seeped in between the welds at A, it found its way into the
box section and could escape only between the welds of flange B – which it promptly did to the detriment of the floor covering. Various sealing expedients were tried, including filling the box section with polyurethane foam, but with no success.
Eventually, a complete cure was found by the simple, but costly, expedient of reshaping the floor pressing with the reinforcement applied externally instead of internally as shown in the right sketch. Now, if any water finds its way in at A, it is quite at liberty to find its way out again at C – onto the road, which is the best place for it.
You may wonder why this was not spotted at the prototype stage. The answer is simple. The weather at the time in 1959 was exceptionally dry and most of the test driving was on dry roads. It was ironic that the following winter, when the cars came into the hands of the public, was unusually wet. This wet winter also bought to light the fact that the distributor and coil were very vulnerable in heavy rain. The first expedient tried – smearing the parts affected with a silicon water repellent compound – was effected but not permanent; it needed doing every six months or so. Eventually, waterproof covers fitted to the distributor and coil and sparking plug connectors did the trick.
Another feature which gave rise to early criticism was the gear change. This was expected because the need to put the car into production with a minimum of delay made it essential to use the same gears as the A35. Not only had these been designed in the 50’s when drivers did not expect so much from synchromesh, but the synchro cones had a much harder task in the Mini owing to the additional inertia of the three gears driving the mainshaft. Not surprisingly, the synchromesh could be over ridden all too easily. The fundamental weakness remained until a completely new synchromesh of baulk-ring type was introduced in 1962.
At the same time another transmission problem was overcome. This was clutch slip, which could develop on cars which had been driven far and fast.
The primary gear which takes the drive down to the intermediate gear is mounted on a sleeve on the clutch shaft, and lubricate for this was prevented from finding its way onto the clutch lining by a seal. In the normal way, the latter was adequate, but oil in the recess behind it was at a considerable pressure owing to centrifugal force – which could reach as much as 25 lbs psi at 5,500 rpm. Only a perfect seal could stand this and when the seal deteriorated with heat and time, a burst of speed could result in oil being sprayed onto the clutch faces – a thing which usually happens after 17,000 to 22,000 miles.
After a great deal of research, a cure was found in the use of Deva metal bushes which require no lubrication and the oil feed to this point was eliminated.
The engine has proved extremely reliable, but one point which did give some trouble was the exhaust pipe, which was planned to keep costs down by serving the additional purpose of assisting in engine location. The theory was right, but neither the down pipe nor its bottom support were quite up to the job. A more robust bracket, a down pipe of heavier gauge and stiffer rubber joints in the horizontal stabilising bar cured the trouble without loss of smooth running. Additional refinement came from swapping the original 4 blade fan for, first, a 6 blade type and, later, the present 16 blade design which cut down the characteristic Mini whirr at high revs to a marked extent.
The original drum brakes have come in for some minor modifications to linings and hydraulic cylinders, stronger pull-off springs have been fitted to prevent the shoes binding. In addition, two leading shoes were adopted at the front. For the body, various detail improvements have been incorporated, such as a rubber diaphragm in place of strapping to prevent front seat cushion sag, improved window catches, better door seals and the like. In addition the heater is now of the fresh air type and the misting up troubles which occurred with the original fug-stirrer are a thing of the past.
Yet with all these improvements, and many others too numerous to mention, the Mini not only looks as it did – and as it will continue to look for many more years to come – but it still performs exactly the functions it was designed to fulfil. It does it all a little better, that’s all!
From ... MOTOR MAGAZINE. FEBRUARY 1965.
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