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HOW HISTORIC IS HISTORIC?
One sees cars advertised which are claimed to be “in original condition” and cars which have been “restored to their original specification”. Just how original are these cars and the components that go to make up a restored or race prepared historic car? Let us consider various elements of the car.
Beginning at the outside; the first thing that an observer sees is the paintwork. Cars that were built in the earliest periods of motoring history would have been coach painted. This was a direct descendent of the preparation of horse drawn carriages. The paint would have been applied manually with a brush in as dust frees an atmosphere as possible. Each layer would have been carefully rubbed down before the next coat was applied. And some fifteen coats later it would be topped with a coat of varnish.
A car built from the ‘twenties onwards would have been spray painted with cellulose, Here the prepared car would have a number of coats of cellulose sprayed on in a booth which would have drying facilities built in. A number of coats would be applied with rubbing down between each of these. The paint’s immediate advantage was that it did not require a long drying time and so the space that was used in the coach painting days when cars had to stand for long periods waiting for the paint to dry were unnecessary and could be put to better use.
In the ‘seventies cellulose was displaced by the introduction of isocyanate paint, known better as “two pack” paint. As its name implies, there is a cyanide compound in the paint and its application required very careful control if the operatives are to stay healthy.
In the ‘nineties this again was displaced by water based paints which are used on all current production cars.
Were any car from the earlier periods to be restored, however, it is unlikely that they would be re-painted with the period materials. It is most likely that the modern “two-pack” paint would be used unless the restorer had facilities for the earlier processes. It is important also that the colour is to a period colour – it is doubtful whether Metalflake Purple was available in the early 1900’s.
Underneath the paintwork is the body panelling. If in aluminium, this may be of a different quality from the original. Sheet aluminium was manufactured in the UK in thicknesses expressed in the Imperial Standard Wire Gauge (S.W.G.). Now the sheets are sold by a metric thickness and so replaced panels will be to a different thickness to their originals. The United States had their own U.S. Standard Gauge for sheet metal. The comparison between the Imperial 16 SWG with a thickness of 0.064” and US standard Gauge of 16 with a thickness of 0.0625” shows a difference. Hence the repair of a vehicle from one continent being done in another will invoke differences and depart from the original specifications.
Paradoxically, some sizes of aluminium and magnesium sheet are available from the USA in Imperial sizes, so a keen restorer CAN find the right material.
Most important, though, is the method of working. The aluminium panels produced in period would have been hand hammered over formers.
Restored panels would now be prepared on a wheeling machine which gives a much better finish. They would probably be welded together using Argon Arc equipment rather than the original gas welding which required considerable skill from the operative.
If the car had steel panels, for which all of the comments on different thicknesses employed also apply, these would also have been hand hammered in the early days. With pressed out steel body panels dating from 1916, the only difference in a restored vehicle is that the panels may include welded in panels and may not be filled using lead – an alterative filler, usually cellulose, would most likely be used.
If the car had fibreglass bodywork – a racing car from the early ‘sixties perhaps, then this is also unlikely to be restored using the same techniques. Fibreglass of the early ‘sixties used a method called “chopped mat”. This comprised of layers of glass fibre which had fibres running in all directions, each layer being soaked in resin as it was laid up. The result was a thick, and by modern standards, heavy panel. Highly stressed panels would be made using woven mat and the resultant panels would be thinner and lighter.
A modern replacement panel will not use this technique and will be very much lighter and thinner (sometimes even translucent!), using woven mat of modern type and perhaps even reinforced with carbon fibre.
Beneath the bodywork is the chassis. In the case of a girder chassis which is replaced there may be differences in the dimensions of steel sections used; the originals may no longer be manufactured and a modern equivalent be used. The quality of the steel has probably improved and so the resultant chassis frame may well be lighter for the same strength.
When a tubular chassis is considered, replacement tubes added currently may well not be to the same standard. Chassis frames made in the UK would have used tube which was to Imperial standards – tubing which was dimensioned in inches representing its outside diameter and with a wall thickness denoted by the Standard Wire Gauge (S.W.G). Thus a typical chassis member might be made up of tubing which is 1 inch outside diameter with a wall thickness of 16 S.W.G. (about 0.064” or 1.625mm). With metrication in the UK steel industry, all that happened was that manufacturers of steel tube metricated their existing dimensions and 1” 16 S.W.G tubing became 25mm tubing with a wall thickness of 1.625mm. A British chassis repaired in the UK would therefore probably have replacement tubes of the same dimensions as the originals. However, if that same chassis were repaired in Europe or the USA then the repair might not use tubing of the original dimensions and the chassis would not be as it was.
There are various aspects of the engine which may have changed from original. Re-working the cylinder head to accept un-leaded petrol will certainly have changed from original. Cast iron heads will have had valve seat inserts put in to protect them from valve seat recession. Aluminium cylinder heads have always had valve seat inserts.
Petrol which included Tetra Ethyl Lead, included as an “anti knock” agent – the protection of the valve seats was a by product - went on the market, in the UK, in 1929. Hence all engines before this would have run on un-leaded petrol, but the need to protect older engines from valve seat recession which unleaded petrol promotes is acknowledged. Due to the much reduced mileage of vehicles in the early part of the twentieth century would mean that valve seat recession was probably not considered a problem.
The valves currently used may be of better material than the originals. Similarly, the pistons may have been changed to those of a better alloy – or even aluminium for cast iron. On racing cars the pistons will probably be forged rather than cast. Certainly the piston rings will be manufactured to closer tolerances and the bore will have been honed to tighter tolerances than the originals, resulting in an engine with better (and more consistent) compression.
If the car is a model with sporting pretensions, then it is possible that the con rods will have been changed for more modern performance enhanced versions. It is likely that the crankshaft is also not the original but one made by a number of specialists who make it of better steel and to finer limits, thus enabling it to withstand the increased performance that old engines are expected to develop. The new crankshaft may be machined from a single billet of steel rather than be the forged unit used in period. It is also possible that the new crankshaft will have been manufactured to use modern shell bearings instead of the original white metal. This is discounting the advances that may have been made in camshaft profiles and timing.
Spark plugs will be different in that modern copper cored plugs have better heat ranges that earlier examples. The insulation on plugs is better than in earlier times when mica was used as the insulator which is replaced by porcelain. The plug leads would have been copper in period but are likely to be carbon cored cable now, partly to prevent electronic radiation. Very early ignition systems are likely to have been replaced many years ago. It is the exception that still runs hot tube ignition. Many cars, which used trembler coils, or low tension ignition, will have been modified to magneto, or coil and breaker points.
Some later cars may well have acquired electronic ignition and it may well not be appropriate for the period of the car. Transistor assisted ignition, where the points merely switch the transistor to activate the coil were available from about 1959. The next progression was to magnetically coupled ignition where the points were dispensed with, which came in about 1962. Light coupled electronic ignition was introduced in 1967 and capacitive ignition in 1969. thus even cars built in the ‘sixties when electronic ignition was introduced, may well have a system incompatible with the period.
Carburettors are often changed, sometimes by replacing the unit with a later version of the model and sometimes, particularly on competition cars, by a different unit entirely. Even carburettors purporting to be the same model may well be later die cast models rather than the sand cast originals. In racing cars some liberties may be taken by using carburettors of a type that was around in the period but which were not used on that model.
The clutch may have been originally a leather covered cone clutch. This unit may well have been changed, perhaps shortly after the car’s manufacture by a plate clutch. This in turn may have been replaced by a modern plate clutch with different spring arrangements. But even so it is unlikely that the friction material is as it was then. With the removal of asbestos from general use, particularly in Europe, other friction materials have been substituted. One that is used is carbon fibre based – certainly not a period material. Some competition cars have multi-plate competition clutches fitted which owe much to modern technology and are certainly not of the period.
The gearbox may be fitted with re-manufactured gear trains which are machined to closer tolerances that the originals and may even have a different tooth profile – some early cars used an hypocycloid tooth profile but may now use involute profile teeth, which give quieter running. On some production cars used for racing alternative gears with straight cut teeth, manufactured by modern competition car specialists, in place of the more normal production helical gears may be fitted.
The prop shaft in early cars used fabric universal joints to accommodate the movement of the shaft. These are sometimes changed to Hooke’s joints. The fashion for using rubber doughnuts on drive shafts to dispense with the need for sliding splines and to provide the universal joints, prevalent on some performance cars of the ‘sixties, may well have been replaced by Hooke jointed, splined shafts.
There is little that can be done to the differential unit, although some may have substituted a hypoid axle in place of a straight cut crown wheel and pinion. Some competition cars may acquire a limited slip unit where none was specified, or available, in period. Where a limited slip differential was fitted, the type may have been changed to one of the more progressive types in place of the cruder cam and pawl system.
There is usually little done to the suspension, but on some competition cars nylon bushes may be substituted for the original Silentbloc rubber bushes. On some competition cars uniball joints are sometimes added in places that they were not employed in period. Different shock absorbers are sometimes put on to a car and in later cars better telescopic shock absorbers are sometimes fitted. On some competition cars the substitution of out of period aluminium bodied and/or gas filled shock absorbers for the original oil filled units is sometimes done. Also on some competition cars the suspension is a favourite area for development and spring rates are likely to be changed from the original specification. In extreme cases, suspension pick up points may even be moved and non period anti roll bars added to achieve better handling.
Wheels are usually original but often cars of the ‘sixties with wire wheels have had the number of spokes augmented. Most cars of that period which had wire wheels were furnished with 48 spokes. If the car is used for competition it will probably now have wheels with 72 spokes. Period or non-period aftermarket alloy wheels are sometimes added to cars of the ‘fifties, ‘sixties and ‘seventies.
The braking system may have been changed. Often cable or rod operated mechanical brakes are converted to hydraulic operation. This was sometimes done only a few years after the car was new; an eighty year old car may well have been so equipped for fifty years. The hydraulics are sometimes converted to a dual master cylinder system, ostensibly for safety reasons. When this is done it requires a balance bar between the two master cylinders and allows the balance of the braking effort between front and back to be adjusted.
When a model had an option for disc brakes, this is often added out of period. Sometimes later ventilated discs are substituted and on some competition cars up rated competition discs are fitted. Similarly disc brake callipers are often changed. When the originals are no longer available, later proprietary units are often used. There are some reproduction callipers of the ‘sixties now made which are often used on competition cars.
Brake linings and pads are subject to the problems of asbestos no longer being used and they will consist of modern friction materials.
The electrical equipment on the car may be out of period. If the car has been re-wired, modern plastic covered cable may have been used in preference to the fabric covered; vulcanised India-rubber insulated original specification cable. The dynamo may have been changed for an alternator, which, if the car was built before 1960 is unlikely to be to an original specification. It is possible that the headlights have been converted to sealed beam units and may use halogen bulbs. If the car was originally built with oil or acetylene lighting, this may have been converted to electric lighting a few years after it was built.
The tyres on the car are unlikely to be to the original specification. Cars built in the early part of the twentieth century would have been equipped with high pressure beaded edge tyres made from a canvas or cotton carcase topped with real rubber. The replacement, even though it has the appearance of the originals, will be on a nylon carcase and use synthetic rubber. An original from the early nineteen-hundreds would have had a mileage expectancy of 1500 to 2000 miles. The replacement will last considerably longer. The extra mileage is in part due to the changed road conditions in the century that has passed. In the early nineteen hundreds the car would have been running on unsealed roads strewn with nails from the many horses and horse drawn traffic which abounded at that time. Today the car will run on sealed, smooth roads and punctures, from nails or any other source, are a rarity.
On racing cars, the car may be required to run on specific period racing tyres which will be made on nylon in place of the original cotton carcase and use a synthetic rubber compound for the tread which dates some ten years after the period that the cars were running, thus giving considerable gain in performance.
And so, the historic car requires considerable diligence and skill for it to have been maintained in its original specification. It is difficult to find the old skills necessary to reproduce parts as bad as they were; which is motive enough for changes to have been made. In addition, in these days of product liability, manufacturers are reluctant to provide components to the relatively low standard of the past, since when it fails it will be judged on current standards of reliability and the producer may find himself liable.
One also has to examine the ethical position: is it better to restore the car with some incorrect parts and have it running or to leave the uncompleted car in an inoperable state because of the unavailability of a single original component?
