Dewi's Trains,
Trams & Trolleys

London Trams: current collectors (ploughs)


Comments/corrections to: Dewi Williams

Some pictures on this page are from 1950, but some are modern photos of restored trams running at various museums. Most are photos that I shot, but Derek Ancona has kindly allowed the use of some of his photos to illustrate a change-pit and the changeover process.


When in the conduit mode, each tram drove a "plough" running underneath which extended into the conduit and made contact with power rails there. (Long rigid conductors are frequently known as busbars. I suppose these should be called trambars).

[My 1950 photo near New Cross]

[My East Anglia Transport Museum photo, 2004]

[My London Transport Covent Garden Museum photo, 1999]

The photos above show how the plough is carried under the body of the tram. The weight of the plough is supported on the top of the two channel-section beams that run the whole width of the body. Just above these are two insulating wedges that serve to lead the power contacts onto the power rails that run nearly the whole width. This arrangement allows the plough to slide from side to side and follow the position of the conduit between the rails (see Conduit oddities). It also allows the plough to be run in and run out at change-pits, as shown in the following diagram.

To change from plough to trolley, the driver would stop short of the change-pit and the conductor would raise the pole to the wire. Then the tram would accelerate rapidly, the plough would shoot out of the side and its momentum would carry it into the siding.


To insert a plough (to "run it in") the operator used a thing like a two-tined gardening fork. He put the tines under the support points of a plough in the siding, and pulled it out to near the point where the conduit crossed the running-rail. Then as the tram moved slowly forward (still using overhead power), he would hook the tines onto the channel-section beams and signal the driver. As the tram moved further forward (left to right in this picture), he'd walk alongside a step or two and the plough would follow the conduit under the tram. As soon as the plough was on the carrier, the operator could withdraw the fork. A few paces further, the tram could draw power from the plough and the driver would stop to allow the conductor to lower the trolley pole. The ploughman is probably the same person shown in Derek Ancona's pictures at this change-pit (see below).

London had the largest system of conduit tramways, but the centre-conduit system was also used in Washington, D.C. until the closure of that system in 1962, and in earlier times in Manhattan and in Madras, India. The monsoon flooding caused the latter system to convert to overhead wires.



This picture is from the East Anglia Transport Museum, and shows the standard plough used in London. From the top: the contacts to connect to the tram, the sticking-out pieces that rode on the channel-section beams that ran across the tram, and at the bottom, the contact "shoes" that ran on the conductor rails.


From the (U.S.) National Trolley Museum. Washington ploughs had to be plugged-in using the connectors at the top, by a man IN the change-pit.


From the London Transport museum at Acton Town: some older London ploughs, with connectors similar to the Washington ones. Such ploughs may have been used on those LCC cars that only ran on conduit, and did not have trolley poles.



This shows ploughs at the end of the siding at a change-pit. The conduit-equipped track is at the right, out of the picture, and overhead-wired track is to the left. At the left are spare ploughs that have been lifted out of the end of the conduit. Ploughs were removed when the siding filled up, which could happen if many more trams went one way than the other. In this photo, I think a stack of ploughs was made ready because it was the last day of trams on the Wimbledon line, and ploughs would be needed for all the trams being sent through the conduit-equipped area to New Cross or to be scrapped.


The change-pit operator, caught in the act of lifting a plough from the slot. Or is he lowering a plough? At any rate, it had just started to snow on January 6, 1951, eight days after Derek Ancona photographed this spot (see below). The small child in the background seems interested in the action.


Derek Ancona's photos


Class E1 car No.1783 shooting the plough into the siding at the Tooting change pit, looking towards London, i.e. looking towards the conduit-equipped area.  28 December 1950.


Class E1 car No.1810 taking up the plough at the Tooting change pit: looking towards Wimbledon,
i.e. looking into the overhead-line area. The tram is still running on overhead power until the plough picks up the conductor rails. 28 December 1950


Tooting change pit again. The weary ploughman plods his way, pulling a plough forward ready for the next car. The conductor, who is walking behind the car and who is standing almost over the conduit slot, is preparing to lower the trolley pole. 28 December 1950

[Lee Green.jpg]

Ploughman feeding plough under an E3 class car at Lee Green change-pit in 1952. The plough in the foreground has its top towards the camera. The upper light-toned band shows where the plough rubbed against the sides of the conduit. The lower band is the current-collector which picked up power from the bus-bars in the conduit. Near the top there is a section sticking out at each side: these are the supports which rode on the carrier under the tram.

My thanks to Derek Ancona for these photos.

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This page last updated on 2004-12-09.