The thread about the excavation of parts of Edinburgh’s old cable tramway system from beneath Leith Walk, what the various pieces of ironmongery were and how it all worked

This thread was originally written and published in bits and pieces between 2000 and 2022 as bits of tramway came out of the ground. It has substantially re-written here to create a coherent story.

In my previous post I covered how (and why) Edinburgh came to use cable-hauled trams in the 1880s and why Leith didn’t, and also some basics of how that system worked.

The principal of operation of a cable hauled tramway is quite simple. Between the tram tracks is a slot, in which there runs an endless loop of moving cable. The cable is powered by steam engines in a winding house, from where it runs around the system under the streets on an ingenious (and complex) series of pulley wheels. The tram car is fitted with a pair of grippers which slide into the slot; to move forward it grabs the cable with a gripper and to stop it releases the cable and applies its brakes. To move across junctions, between different cables or to pass subterranean obstructions such as pulley wheels, it can perform an elaborate ceremony whereby it grabs and releases different cables with the front or rear grippers – often with a little bit of gravity assistance.

1882 American diagram of a hypothetical cable tramway system. The winding house with its steam engines, gearing and cable drums is towards the top. The cables exit the winding house in a tunnel under the street and then head off around the system in the slot between the tracks, guided by a large system of pulleys.

Over the last few years, it has been possible to see various bits of the old cable tramway being dug out of the ground in preparation for laying the tracks of the new extension to Edinburgh’s single tram line from York Place to Ocean Terminal via Leith Walk and Constitution Street.

One of the most common finds has been sections of old tramway rail. A tramway rail differs from a railway rail in that the rail has a flat top with a groove in the middle of it for the flange of the wheel to run in; a railway rail has a domed top and the wheel flange hangs over the side. The rails were relaid when the move was made from cable traction (or in Leith’s case, horse) to electric, so none of the dug up rail sections will be from cable days.

Tram rails on Leith Walk, notice the dark line on the top which is the groove for the wheel flange to run in. © self

The next most common item that was seen during excavations were the U-shaped cast iron “chairs” that formed the supporting base of the conduit structure in which the cable ran beneath the street surface. To better understand what were are looking at (and for, underground), a cross-section of a cable tramway is helpful, I can’t find one for Edinburgh so one from San Francisco will do as the two were fairly similar. The chairs are coloured yellow, and sat on the concrete base of the conduit.

San Francisco Cable tramway cross-section. The rails are coloured green; the horizontal ties in blue; the top of the conduit structure in orange; the supporting chairs in yellow; the small cable support pulleys in pink; and the cable gripper in red.

The Edinburgh system did not use the orange cast slot shown below; it used old rails laid on top of the cast iron chairs to form the slot. Additionally it did not have the small pink cable support pulleys; it used larger, 14inch diameter pulley wheels spaced every 50 feet.

Section of an illustration of a hypothetical cable tramway system, which seems very similar to the system in use in Edinburgh. Note the cable running through the conduit and over the support pulley

The picture below shows a pile of these iron chairs dug out from beneath Leith Walk, plus sections of old rail that had been used to form the horizontal ties. Notice the chairs are caked in old concrete, as they were set into the conduit when it was being poured.

Cable conduit support chairs, September 2021 © self
Cable conduit support chairs, December 2020 © self

None of the cast iron chairs are complete; all are missing their top sections; cut and cracked off. However it was not the excavation works of 2021 that caused this, it were those of 1921! A a book kindly provided to me by Chris Wright has a photo of Hanover Street, c. 1921, on the cover. In this scene, a crowd watches workmen digging up the old cable conduit system during the switch over to electric traction (which was apparently the first use of pneumatic drills in the city). The caption explains that for ease, the workmen only removed the top section of the conduit chairs when removing them; the lower sections were left concreted into their bases. There are a couple of broken sections of chair in the pile of rubble below the boy with the cricket bat.

Edwin Catford's Edinburgh, cover
Edwin Catford’s Edinburgh, cover

The cables themselves were driven from the four winding houses at each of the tramway depots; Henderson Row, Tollcross, Portobello and Shrubhill (off Leith Walk). We see the Shrubhill winding house interior in the images below. The engines, each with two cylinders and producing 500hp, are in the foreground. They are connected to the cable system by the ropes strung between the pairs of enormous drums. The larger drums, in the back ground, were connected to the 10 foot diameter cable-driving pulleys.

Interior of Shrubhill winding house, seen from the side of the engines
Interior of Shrubhill winding house. The two wheels in the foreground are those that would drive the traction cables.

The cables were tensioned on weighted pulleys hung from the wall of the winding house, before exiting the building down a long tunnel from the winding house off Dryden Street at the northern end of the site to Leith Walk. The below photo shows the remains of one of these tunnels being demolished in the 1960s during works outside Shrubhill.

Brick arch of the cable tunnel on the right.

These tunnels ran to large brick chambers beneath the road surface and ran off up and down Leith Walk. Each cable required two pulleys; one for it on its outbound journey and one for it returning back to the winding house. Shrubhill drove two cables, so required two sets of these pulleys in chambers below Leith Walk. The diagram below shows the State Street Cable Car power station in Chicago. The winding engines are in yellow and drive 4 sets of cables. The red and blue cables head off right and left out of the power station. The two green cables are for different lines; they travel to the start of those lines “blind” (i.e. not pulling trams), which is why they are running in between the two sets of tracks, rather than between the rails like the red and blue cables. Each cable reaches the end of its line where it turns around and comes back to the power station. Shrubhill was very similar to this but drove only two cables; one for St. Andrew Square and Leith Walk, which also served the branch to Abbeyhill, the other for the Bridges to Newington.

The Street Railway Journal, 1889

The illustration below shows a cross section of those cables coming to and from the winding house down the tunnels, running around the pulleys in their chambers and then off around the network. The chambers are brick built, with arched steel plate roofs. This is a conceptual railway, but has two driven cables, rather like Shrubhill. Notice the return pulley is inclined so as to be able to sit underneath the outward pulley.

Cables to and from the winding house and running around the large underground pulleys

The below images show the destruction of the brick walls of one of the Shrubhill pulley chambers under Leith Walk. The dark patches are not tunnels, the one on the left is a recess in the chamber walls and the other seems to be a previous collapse that had been filled in with concrete.

Leith Walk at Shrubhill, November 2020 © self
Leith Walk at Shrubhill, November 2020. Notice the cast iron chair section onwards the middle bottom of the photo © self

The image below, taken of the same overall excavation hole as those above, shows the huge steel roof section of the chamber – the frame is almost identical to drawings of one for the terminal pulley of one of the Henderson Row cables. There is a supporting structure of steel I-beams that would have sat on the brick walls and foundations, and the metal sheet sections forming the roof on which the road surface lay. The large pulleys that directed the cables in and out of the tunnels to the winding house sat directly below this.

Shrubhill cable chamber roof structure, November 2020 © self

These chambers, and others around the system (particularly where there were junctions) were manned to make sure the cable was running properly. Children were in the habit of tying a can to a piece of string, then dropping the loose end into the slot in the road, where it would catch the cable and be dragged off up the road creating an amusing racket. If there was any snag or derailment of the cable, they would phone back to the powerhouse, who would disengage the cable until it could be reset or re-spliced, or the offending item untangled from it.

The excavations here also uncovered the structure of the railway tunnel under Leith Walk, where the North British Railway passed beneath. This was incredibly close to the surface (as a result of the tunnel being built after the road surface, and the Town Council refusing to allow the road level to be raised where it passed overhead); the outer skin of the tunnel is about only 30cm or a foot below the surface. Indeed, a special system had to be devised here to support the new tramway as there was not enough space to fit the standard concrete track slab. You will notice a large trough in the tunnel structure here. This, I think, is where the cable for North Bridge to Newington ran, as it was not used for traction purposes here and is described as “running blind” as far as Picardy Place, where it came in to use to go up Leith Street.

Leith Walk railway tunnel, May 2021 © self

The shallowness of this tunnel totally precludes the urban myths of any tunnels under the road running up Leith Walk towards Elm Row from Shrubhill. Those tunnels are actually a single passageway, just large enough for a man to walk up, that ran under the pavement from Mcdonald Road up to Picardy Place, which was to carry the first electricity cables into the city from the McDonald Road Power Station.

When Edinburgh moved to replace its entire horse-drawn tramway with the cable system across the city, for various reasons Leith declined. Up until the last minute, it had been hoped and assumed that a compromise could be reached and that Leith would join; but it declined to do so. The Shrubhill winding house had a third winding drum for a cable round the Leith rails, but it was never used. Instead, the cable ran from the winding house at Shrubhill, turned left down the hill to the municipal boundary at Pilrig Street, and then ran back up the hill towards Edinburgh again. This meant that passengers had to change onto a Leith tram to proceed any further north (and vice versa). This 24 year inconvenience became known as the Pilrig Muddle. In the below photo, an Edinburgh cable car loads its passengers at the terminus of the line at Pilrig Street. In the background, the electric cars of the Leith system wait for the exchange of passengers heading the other way. exactly where this pit is.

The Pilrig Muddle © Edinburgh City Libraries
The Pilrig Muddle © Edinburgh City Libraries

There was another one of these awkward interchanges on the network, at Joppa, which I like to call the Joppa Jumble. Here the cable line from Portobello met Musselburgh’s electric system and again a change had to be made for through travel. But this was at least at the network end, not the middle of a principal route, and traffic here was much lighter

lothian - musselburgh tram 9 joppa terminus
The “Joppa Jumble”, with the Musselburgh electric car in the foreground advertising Heinz Baked Beans. Embedded from the Flickr of John Law

The terminus of the cable car lines was always on a short, single line siding of track on a slight incline. If the terminus was a downhill incline; the car would disengage from the cable and run by gravity into the siding, where it would pick up the cable running back the other way with its other gripper. The process was reversed for an uphill terminus; it ran into the siding on the cable, and ran out of it by gravity to the return cable. This was required as the cable could not be gripped where the it ran around the huge terminal pulley to change direction. This is shown by the diagram below, where the terminal pulley is in blue, inclined so as to fit below the street surface. The cable (red and white dashed line) is guided to and from it by the orange pulleys.

Terminus of the Edinburgh Northern tramway from Henderson Row.

Much excitement erupted at the Pilrig Muddle in August 2021 when unexpectedly (considering this shoul dhave been discovered way back during the first round of tram works), an almost completely intact terminal pulley chamber was uncovered, with not one but two huge pulleys, each totally complete and in remarkable condition. Both were still sitting on their original bearings, just as they had been left almost exactly 100 years before when they were covered up and forgotten about!

Side view of the Pilrig terminal pulley chamber and pulleys © self
Side view of the Pilrig terminal pulley chamber and pulleys © self
One of the terminal pulleys, approximately 8 feet in diameter. Photo Credit: ACamerunner / @aljaroo1874

The Pilrig Muddle pulleys are unusual for two reasons. Firstly, they are mounted vertically, usually they were horizontal. Secondly, they are back to back, which makes little sense for the terminus of the line. I suspect they are vertical as the street is narrower here, so there was less room to fit them in horizontally. And I think there are two back to back in anticipation of the cable being extended down Leith Walk into that burgh (which of course never happened). The red pulley on the right would have returned the Edinburgh red cable back up Leith Walk to Shrubhill. The blue one on the left would have returned the blue Leith Walk cable back down to the Foot of the Walk. If the cable had been extended to Leith, at Pilrig trams coming uphill from Leith would have swapped from the blue to the red cable here as they crossed the civic boundary. Because Leith was never added to the cable system, if I am correct the blue pulley would therefore never have been used.

Side view of the Pilrig terminal pulley chamber and pulleys © self

The below animation shows how a car would have swapped cables here. A car travels with its front gripper engaging the cable. As it approaches the end of the cable, it is released before the gripper gets dragged into the pulley. To move onto the next cable it can either use its momentum (known as a “fly shunt”), can use gravity if it is running down hill, or it can push itself off the cable onto the next one by using its rear gripper. When the front gripper is over the next cable, it can be re-enaged and the car sets off again. This was a laborious (and potentially hazardous) process, so by design a cable car network keeps junctions and switching between cables to a minimum.

Swapping cables © self

If you look closely to the left of the archaeologist squatting on the ground peering into the chamber you can see the conduits for electrical wires on the wall along with a box. This is either for electric lighting or the communication telephone.

Electrics in the Pilrig pulley chamber © self

Pilrig was not “de-muddled” until 1922 after the amalgamation of the Burgh of Leith and its Tramway into that of the City of Edinburgh. Edinburgh quickly decided to adopt the electric system of Leith and rapidly converted one to the other. The picture below shows the Muddle being converted. A cable car has reached the terminus at Pilrig Street and is about to return back up the hill. You can see the slot between the tracks for the cable. The tracks on the right are being relaid for the electric trams and a new junction to connect down the Leith Corporation tracks on Pilrig Street is being incorporated. The centre poles for the overhead wires are already in place. I suspect the reason that the Pilrig pulley chamber was left in such good condition, with its pulleys still in situ, was the speed with which the switchover was made. There was no time to demolish the chamber, remove its pulleys and infill it. The new tracks were simply built over it and connected together one night to allow for running of the electric trams the next day.

De-muddling the muddle, 1922 at Pilrig Street looking up Leith Walk.

When Leith Corporation rebuilt its horse tramway for electric traction in 1904-1905, it constructed a large new depot on Leith Walk. This later became the Leith Depot of Edinburgh Corporation Tramways. Sadly the depot structure was demolished for no good reason about 4 years ago now, but the depot office building remains. During excavations at the rear of this, the brick outlines of inspection pits appeared, where the running gear could have been checked and maintained without having to lift the tram body off of it. The tram rails would have run along the top of these walls, see the lower picture for an example.

Inspection Pits at Leith Depot. These were only ever for electric cars © self
Interior of Leith Depot, pre-1920. © Edinburgh City Libraries

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