31 May 2016

Blackpool Tower - Highs and Lows

Blackpool Tower is Lancashire's answer to, and was inspired by, the Eiffel Tower. It was designed by Lancashire architects James Maxwell and Charles Tuke. Heenan and Froude of Worcester, structural engineers, both supplied and built the tower proper. Architects draw, engineers build.

Unlike its Parisian cousin, Blackpool Tower is not free-standing. Its base is surrounded by a monumental building that occupies 54,400 square feet, constructed from more than five million Accrington bricks. The tower proper is formed of 2,493 tons of steel and 93 tons of cast iron, hydraulically riveted together.

The foundation stone was laid in September 1891, and the tower opened in May 1894. 518 feet tall, the tower was inadequately painted during its early years. As a consequence between 1921 and 1924 all the steel-work had to be replaced.

The tower closed during WWII, and the crow's-nest was removed in 1940 to allow for the installation of a radar array, the station known as RAF Tower. Normal service resumed in 1946. The two hydraulic lifts were replaced in 1956-57 by electrically-driven ones. They were replaced again in 1991, and carry one up 315 feet.

A walk-on glass floor to the sea-facing side of the enclosed observation deck, over 380 feet up, was installed in 1998. Two open decks above this are accessible by means of stairways. Not accessible to the public are the 563 steps from the top of the brick building to the tower top, used by the maintenance teams, which coat the tower in nine tons of paint each time it's repainted.

Sadly, it is impossible to simply ascend the tower to appreciate the engineering. The only way up is to purchase an extortionately-priced 'experience', involving endless schmaltz and a pointless '4D' cinema show. These can both be bypassed if one insists, but the queues, disorganisation, bored staff pushing gift shop tat, and rip-off entry fee cannot. The tower is Grade I listed, and deserves much better.

15 May 2016

Rochefort Transporter Bridge

Frenchman Ferdinand Arnodin, with Spaniard Alberto de Palacio, was the patentee holder for the first transporter bridge design brought to realisation, just outside of Bilbao, Spain. Five transporter bridges were built in France, more than in any other country: at Brest (relocated from Bizerta, Tunisia), Marseille, Nantes, Rochefort, and Rouen; with a sixth commenced at Bordeaux but never completed. All were designed by Arnodin. Only the Rochefort bridge remains to France.

Crossing the Charente River, construction of the 700 ton all-steel Rochefort Transporter Bridge commenced in March 1898 and was completed in July 1900. The towers, marked with Arnodin's name on each of the 16 shoes, stand 217 feet high, and the bridge has an overall length of 574 feet, with a main span of 459 feet. The boom is 26 feet wide and 164 feet above water level. The suspension cables terminate in massive anchorages (below).

The gondola, 46 feet long and 38 feet wide, was originally moved under steam power, with electric motors taking over in 1927. It could carry 14 tons - either nine horse-drawn carriages plus 50 pedestrians, or 200 pedestrians alone. The crossing took four minutes. The boom was rebuilt in 1933-34, when the gondola was uprated to carry 26 tons. The boom was dynamited in 1944.

The bridge was abandoned in February 1967 upon opening of a nearby vertical lift bridge, itself demolished in 1991 after opening of the Martrou viaduct road bridge (in background of first photo). Funds were put aside in 1975 for the bridge's demolition, but it was declared an historic monument in April 1976, and refurbished between 1990 and 1994.

The bridge is normally open in the summer months for use by pedestrians and cyclists. At the time of writing it has been closed for a predicted three year period, to replace the boom with one constructed more closely in accord with Arnodin's original design, at an estimated cost of £15.2 million. There is a good museum on the Échillais (Martrou) side of the river.