Motoring in the 1930's
Part 2B The Cars (continued) Gearboxes were usually three speed, although some were four, especially on the more up-market cars. In the early thirties many had gears with no synchromesh, these required the driver to synchronise the appropriate engine speed with the road speed in order to get a smooth change and that involved using the clutch twice on each change down, or ‘double declutching’. This procedure required a certain level of skill that not all drivers acquired. The noise of gear changes could sometimes make you wince as you heard the grinding of metal, not surprisingly this type of gearbox had the name ‘crash box’. Synchromesh was widely adopted during the thirties but it was mostly limited to the top two gears. Some of the more expensive cars had a free-wheel, Rover and Triumph for example, the free-wheel could be engaged or disengaged at will. The free-wheel offered opportunity for some fuel saving whilst free wheeling, and the ability to select a different gear in advance of requirement. With synchromesh these gear changes could be clutchless. Many drivers were not too keen on the free wheel because of the consequential loss of engine braking. Epicyclic gears were used in some cars, most famously in the Model T Ford of course, their use in the thirties was generally associated with a fluid flywheel in place of the clutch, notably in Daimler and Lanchester cars. They were generally associated with a pre-selective gearbox that enabled the driver to select his next gear before actually engaging that gear by operating a pedal. This type of arrangement was widely adopted for buses and was the fore-runner of the automatic box.
Rigid axles mounted on leaf springs of the semi-elliptic or quarter elliptic type were almost universal on British cars. These ‘cart springs’ offered a cheap and simple, if not very precise, means of locating the axles but they were far from ideal. They are still widely used on commercial vehicles where their shortcomings are of less concern. The rigid axles increased the potential for a pitching motion and their weight contributed more to the unsprung weight, with detrimental effects on the ride quality. Many cars used friction dampers in association with leaf springs. Whilst these crude suspensions were very inferior to those of modern independently sprung cars their shortcomings were less apparent because of the lower speeds in use.
Steering was usually through a steering box. ‘Worm and peg’ and ‘recirculating ball’ were the most favoured mechanisms. These steering boxes were less precise than the rack and pinion method now widely used, they also tended to wear, leading to increasing amounts of play. Power steering was unheard of in British cars leading to a requirement for large diameter steering wheels and low gearing that required several turns of the wheel from lock to lock. When driving it was usually necessary to make constant minor adjustments to the direction of the vehicle because of play in the system. The effect of steering and suspension geometry on the handling of the vehicle was less well understood also, making for more difficulty in maintaining the desired course. Swivel pins (or king pins) were supported in plain bushes that were exposed to the elements. Nearly all steering and suspension moving joints required very regular greasing. This was very demanding and often not done as frequently as it should have been with the result that water and dirt would get to the bearing surfaces leading to rapid wear and excessive play. This all went to make the car less pleasant to drive, more noisy, more difficult to control and potentially more dangerous.
By the thirties brakes were almost universally drums on each wheel with internally expanding brake shoes lined with an asbestos based compound. Later in the thirties two leading shoes were widely adopted for the front brakes such that the rotational movement of the wheel helped to increase the braking force applied by both shoes. The means of transferring the force applied to the brake pedal to the brake shoes differed, by far the best method was to use hydraulic pressure, as on all modern cars, Morris were the first of the large scale manufacturers to adopt this method, but others used mechanical systems employing rods or cables. All worked well when properly adjusted and maintained, but this was often not the case, leading to uneven distribution of the braking on the four wheels with consequent effect on the steering. The friction generated by the brake lining material reduced at high temperatures, frequent use of the brakes, as on the descent of a long hill, would cause the brakes to overheat and the braking capability to fade. The absence of any testing resulted in many cars on the roads with badly maintained or worn brakes. With hindsight it is difficult to understand why the disc brake did not appear until the 1950s (not until the 60s was it fitted to popular makes) when its advantages now seem to be so obvious. (I believe it was the aircraft industry that were the first to develop and employ disc brakes, except that many bicycles had been employing the same principle for years.)
Most British manufacturers tended to favour 12volt electrical systems, although some used 6volt, especially on the smaller Austins and Morris. The Americans favoured 6volt, despite the heavy starting demands of their large engines, and they adopted the same policy for Fords in the UK. The starter current on a 6volt system could be as high as 200amps or more, twice as much as that for a 12volt system. Coil ignition with the contact breaker integral in the distributor had become established as the preferred method and was almost universal by the late thirties, this method persisted through to the 1970s. It was reliable but that too required regular maintenance, badly adjusted or dirty contact breakers were the most common cause of difficult engine starting. Needless to say there were no petrol engines with fuel injection, metering of the fuel was by means of a carburettor with a hand controlled ‘choke’ for mixture enrichment during starting, getting this mixture right was rather ‘hit and miss’ which could also impair starting. The sound of a starter grinding away until the battery was exhausted was common place. Dynamos rather than alternators were used to charge the batteries. Dynamos necessitated an automatic cut-out, to prevent the reversal of current from the battery to the dynamo when the dynamo voltage output fell below that of the battery, together with a voltage regulator to limit the charging volltage. These units tended to break down occasionally. It is more difficult to manufacture low cost dynamos to withstand high rotational speeds, the centrifugal forces can cause the commutator to disintegrate. In order to avoid excessive dynamo speeds at high engine speeds the belt drives were chosen with appropriate pulley diameters and the result was that at low engine speed the electrical output from the dynamo was also low. This was a potential problem when driving in heavy traffic because the battery could be run down when there was a requirement for lights and perhaps windscreen wipers. The introduction of additional equipment such as radios (and heaters and de-misters on post-war cars) exacerbated the problem. (It was not until further advances in electrical engineering that the mechanically robust alternators were able to be used). Car radios did appear in the 1930s, they used thermionic valves of course and were heavy and made heavy demands on the battery. Insulation on the wires was mostly rubber, not plastic, the rubber tended to deteriorate with age, especially when situated in a hot region under the bonnet. The combination of crumbling insulation and high electrical currents, especially with 6volt batteries, presented a greater fire risk and car fires were more common despite the protection provided by fuses. Overall electrical systems were very very much simpler than on a modern car. On most cars there was only a requirement for lights, a horn and an ignition system, with the associated battery and charging equipment. Some cars had indicators in the form of ‘trafficators’, these were electrically operated mechanical arms that were raised on either side of the car, the arm containing a bulb for night time visibility. They were pathetic in comparison with modern flashing indicators, they were notoriously unreliable and, when they did work, they were easily missed by other drivers.
Despite the many shortcomings of these cars compared to present day models, properly maintained they were capable of reliable and relatively safe service over many thousands of miles. Ron Watts