What is so special about Sydney Single Deckers?
Sydney's Single Deck Electrics have a history like no other in the world. Our suburban train system was developed from a large, existing steam based network of heavy rail vehicles. It also came
at a time when electric traction technology was rapidly changing throughout the world and new products emerged almost daily.
The one single reason why Sydney's Single Deck Suburbans served our city for so long was due to the extensive "commonsense" attitude applied to our network by the Australian engineers who shaped it.
Extensive studies into overseas networks were undertaken before designs on Sydney's rolling stock were finalised. The design of Sydney's cars was a unique blend between the need for an American style "New York" system, where maximum passenger capacity and minimum loading times were essential, and the existing "English" steam based suburban system with traditional carriages and longitudinal seats.
The result was an extremely practical car which held around 70 seated passengers, allowed ample room for standees, featured large sliding doors for fast entry and exit, a long lasting steel construction, and a look which transcends many different design periods.
It's no wonder that these cars look as natural in the Sydney landscape of the 1990s when they were withdrawn, as they did in the 1920s. Very few rolling stock designs worldwide can share such a claim.
Above: Driving Trailer D4009 on Set F31A in the early '60s. This is an example of the many vehicles that originally were steam hauled, and then converted to Electric operation in the 1920s. The cars were also widened, which in reality amounted to almost a total rebuild.
Just as unique is the design of the electrical technology which drives the cars forward, and has carried some carriages over three million kilometres in their lifetime, exceeding the distance to the moon and back. Perhaps the most striking difference between Sydney single deckers and other electric rolling stock is the "two motors" legacy. A single motor and trailer combination has only two 360HP (200kW) motors on the motor car, both placed on one bogie. This led to a very fine engineering line between the amount of power available and the amount of traction which could be gained from only four wheels lifting 85 tonnes of steel plus passengers up the steep 1 in 30 grades which exist on the network.
Without adoption of the "two motor" scheme Sydney may not have had electric trains at all, because the cost would have been so prohibitive to equip the trains in any other way. The amount saved exceeded 200,000 pounds, equating to tens of millions of today's dollars. To understand the reason, we must go way back to the time before electric trains began in Sydney.
At that time, an extensive network of steam hauled suburban trains already operated using a variety of wooden bodied rolling stock, including a fleet of 101 motor cars built in 1921 to a standard which would allow later conversion to electric. These existing cars were already equipped with expensive trailer bogies (the steel "cradle" assembly which supports the wheels under each carriage end). By adopting a two motor approach, the engineers were able to manufacture only 101 new bogies for the first 101 motor cars, because the existing trailer bogies could be left underneath the other end. To add to this, the 101 trailer bogies displaced by the conversion of these cars were immediately re-used on the first 101 new motor cars built. The savings were so immense that the two motor option was adopted; however there
were a few problems.
Before 1926, only 750 volt traction motors had been built. The need for only two motors meant that Sydney's cars required very high powered 1500 volt motors. At the time they were introduced, Sydney's electric trains featured the most modern and advanced electrical traction technology anywhere in the world, the very first motors in history to utilise 1500 volts directly across a single motor. These motors were amongst the first to employ manufacturing methods now considered "essential" in modern electrical design.
Above: Another early photo of a Driving Trailer, this time D4257, a Tulloch vehicle built during World War 2.
But the Australian innovation didn't stop there. The switchgear controlling the motors was of a revolutionary, modular electro - pneumatic design. An eight car single deck train accelerating from Wynyard over the Harbour Bridge consumes more than one million watts of power. In 1926 this was astronomical, amounting to 250kW per car - more than most electric locomotives in manufacture at the time. Sydney's electric motor cars carried 70 passengers as well as the motors, switchgear and equipment! It's a small wonder these cars had little trouble keeping 1990s timetables alongside modern Trains, long after stock of similar vintage around the world had since been shunted to that carriage shed in the sky.
The Sydney single deckers were originally designed to use cast iron brake shoes. During the 1950s, it was discovered that these shoes wore down too quickly, and left dust everywhere. They were replaced by a newer (and far more reliable) "Composite" brake shoe, giving the trains that classic, distinctive "Sydney Train" smell which dominates the underground network to this day.
Unfortunately it was found that the new shoes also "polished" the driving wheels and caused more problems with the already limited traction ability of the single deck two motor cars. This has led to the classic "Single decker wheelslip" which often turns many rail fans crazier than their counterparts at the drag strip raceways, and makes a single decker trip in wet weather a truly memorable experience for any traction fan. Sydney’s Single Deckers are a full sensory experience!
Yet another innovation introduced in Sydney's' electrics was the Electro Pneumatic brake, or "EP" as it is known. This refinement of the well established Westinghouse system included a special electric magnet valve (called an "EP Holding valve") which "Holds" the air in the brake cylinder of each carriage. This allows a much smoother braking cycle without the "bunching" effect experienced with conventional Westinghouse brakes. It also allows the driver to "hold" the brakes on full at a station without the need to apply handbrakes.
Later this system was refined into the "EP Application" system used on the "W" and "U" sets where it is possible to electrically apply the brakes on each car without discharging air from the brake pipe. This was again further refined with the introduction of "Westcode" brakes to the double deck power cars and finally the regenerative braking used in modern Trains, which return otherwise wasted energy back to the overhead wire.
Above: C3040 stands at Carlingford station in the early '60s as part of a 2 car train operating the Carlingford line. This is a good example of the original wooden bodied "Bradfield" motor cars towards the end of their operating life.
As soon as the cars entered traffic, the argument over the four motors alternative continued, however it wasn't until 1955 that the technology was updated using four motors per power car - in the "W" and "U" Sets. The "U" Sets were designed for inter-urban use and featured an early form of regenerative braking.
Regenerative braking on NSW suburban cars did not become a technical reality until the double deckers of the 1980s when the introduction of Silicon thyristor controls and computers could take over the complex operations required.
Not to be outdone, the "four motor camp" continued and was finally addressed in the late '60s with the commencement of the "7000" programme, where existing two motor cars were converted to four motors. Heading this development was car C7500, known as "Moss's Rocket", named after the electrical engineer who supervised the project - Geoff Moss - who now assists "Historic Electric Traction" in the restoration and maintenance of the historical Sydney electric car fleet.
Above: Preserved set W3 stands at Rhodes Platform during the inaugural HET "commissioning" trip in November 1999. The "W" sets, built in 1955, were the first design to break with the standards set in the 1920s, and are incompatible electrically with earlier stock. They were the first electric trains on the system with four motors per power car.
The ultimate aim of the project was to produce enough "four motor" cars to place one or two in each eight car set - an aim which was reached in the early 1980s and contributed significantly to the retention of the cars in traffic until 1992. It also enabled the formation of the six "M" sets which consisted of a mix between single deck standard motor cars and double deck trailers, which played a crucial role in the 1980s timetables.
Another important change which occurred in the 1970s was the progressive disabling of the "weak field" notch (sort of like an overdrive speed) in the single deck cars. This was due to a parts shortage. By the '70s, the old 1920 vintage switchgear was becoming difficult to maintain, and there were insufficient switch units to allow all the cars to be maintained.
The removal of weak fields required four less switch modules per car, and the second hand switches made available were then reconditioned and re-used in lieu of new ones being purchased. Unfortunately this resulted in a lower maximum speed, however as more modern rolling stock replaced the single deckers, they were generally relegated to "all stops" runs which rarely reached 80kph anyway.
Despite the constraints practiced in the '70s, it was still apparent in the mid '80s that there would not be enough switch modules (called "Unit switches") to maintain the fleet in operating condition while new rolling stock was built. So tenders were sought to supply "brand new" unit switches which could be intermixed with the old in as much that a mixture of both types in the network would not cause an operational problem. As a result the underfloor electrics of the cars were "upgraded" for the first time since 1926 with both Mitsubishi (Japan) and Brown Boveri (Germany) answering the tender and supplying equipment between 1985 and 1990.
In 1986 the technically ambitious Tangara project was announced with a long development program. It became clear that as a result, it would be necessary for the single deckers to "last just a little bit longer" until the Tangaras began to replace them in 1989 / 1990. So a "rebuild" program for single deck power cars began with work carried out by many different contractors. As each car was "rebuilt", it was equipped with the modern "Mitsubishi" switchgear and the motors reconditioned, although the weak field option remained inoperable. The modern switches are wired and operate exactly the same as their 1926 design counterparts.
As a result, most power cars still operating in 1992 were in very good electrical condition when they were finally retired. Many rail fans are quick to suggest that the Tangaras spelt the death of the Sydney single deckers but in actual fact the Tangar as development was indirectly responsible for the restoration of the last fleet of old cars, and it is this single fact which has permitted the vintage carriages to be retained in tours operation today. Whilst critical high energy components have been upgraded, most of the other components in these cars still date back to 1926 technology.
Above: The first "interurban" stock, built in 1955, used the same electrical equipment underneath as the "W" cars pictured above. These trains quickly became known as "U Boats" with their "U" target and their tendency to "float" (or is if fly?) down the track. They incredibly lasted until 1997 in regular service, despite being perhaps the least maintained of all in the network, having never been rebuilt or in some cases overhauled since 1955. This legacy means that restoring some of them to tours service is a major job.
Above: A typical No. 2 switchgroup rebuilt to use the Japanese "Mitsubishi" electro - pneumatic switches in the 1980s. While much newer, they work on the same principle as the old "Metropolitan Vickers" equipments and use the same electrical designs.
The Sydney Electrification scheme pioneered many aspects which have made the current Sydney system possible. These include an excellent double colour light automatic signalling system employing train stops. This ensures a level of safety which does not exist outside the suburban area even when very high train densities exist. Another important aspect was the increase in width of rolling stock in 1926 by adopting a new "loading gauge" for the suburban area of 10'6".
This increased the seating capacity to a 3 + 2 arrangement which remains in today's modern rolling stock.
The wisdom of retiring the "single deckers" in 1992 will be debated for many years to come, especially as the city suffered an acute shortage of rolling stock for operation of new lines such as the Airport link and the 2000 Sydney Olympics events.
Perhaps if instead of rebuilding the cars to 1926 condition the cars had been rebuilt with modern automatic doors and air conditioning the Single Deckers may have seen yet another era in regular services. Of course now it's too late.
Regardless of the outcome of these debates, a healthy selection of these unique trains will remain operational and carrying passengers well into the next century in Sydney---
Thanks to the efforts of dedicated enthusiasts.
Left: The single important safety device which has given Sydney's suburban electrics their incredible safety record since the 1920s. This is not new technology! The "Brake trip valve" simply activates the brakes in the event that any train passes a signal at "stop". This system at present does not extend past the metropolitan area.