Ancient Monuments

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Dorothea Quarry Beam Engine

A Scheduled Monument in Llanllyfni, Gwynedd

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Latitude: 53.0542 / 53°3'15"N

Longitude: -4.2435 / 4°14'36"W

OS Eastings: 249730

OS Northings: 353122

OS Grid: SH497531

Mapcode National: GBR 5K.CMMX

Mapcode Global: WH43T.SHHG

Entry Name: Dorothea Quarry Beam Engine

Scheduled Date:

Source: Cadw

Source ID: 2440

Cadw Legacy ID: CN165

Schedule Class: Industrial

Category: Engine house

Period: Post Medieval/Modern

County: Gwynedd

Community: Llanllyfni

Built-Up Area: Talysarn

Traditional County: Caernarfonshire


The Dorothea Quarry pumping installation formerly used for removing water from the quarry. It consists of a tall pump house with a date stone of 1904 within which is a Cornish beam engine, a boiler house complete with boilers, an open fuel hopper with ramp to enable the tipping of fuel into it and a building said to house an electric pump, which replaced the beam engine for pumping. Near the head of the pump shaft is a large pulley wheel attached to some timbers, which once stood atop a pair of tall shear legs in front of the SW elevation, the remains of a windlass.

The engine was the last Cornish Beam Engine to be installed from new anywhere in the world (Gwyn, 2015) and is also the youngest engine still in its original setting (Osment, 2016).

The engine was built by Holman Bros of Cambourne, Cornwall in 1904 and is installed in a slate built house 25ft by 19ft 3in internally; the front wall carrying the beam is 5ft 9in thick, all the others are 2ft 6in. The wrought iron beam is about 34ft long; engine-end 18ft 3in from bearing centres. The beam is 6ft deep at the centre and about 3ft at each end. The single cylinder has a stroke of 10ft and a bore of 5ft 8in; cylinder height 14ft 8in. It operated a boiler pressure of 38lb per sq in and its normal working rate was 5 strokes per minute, which could be increased to a rate of 9. The bucket was 7ft long and the pumping shaft 460ft deep.

The following information comes from the Industrial Steam Preservation Group –

Built 1904. Stopped working 1952 owing to the boilers being condemned but did work in 1956 when the electric pumps failed. It is a conventional Cornish pumping engine. Beam: about 30 ft long; weighs about 11 tons. Worked normally at 5 strokes per minute, the maximum rate being 9 per minute. The beam of wrought iron is a very unusual feature. Inside stroke 10 ft, outside stroke 9 ft, giving one lift of the pumps (7ft bucket) at a depth of 460 ft. Cylinder: 10 ft by 68 inches. (Fairly small engine). Worked at 38 psi. Boilers: 2. Fittings by Mather and Platt, possibly/probably the boiler shells also. Lancashire type. The chimney is a recent affair. (At least it seems so). Slate in lower parts but concrete above. The boiler house roof was very derelict when we started work on the engine in March 1968. Some half of it had collapsed with the ravages of time, vandals and the elements and we subsequently demolished the remainder of the roof, removing also the vast quantities of roof, rubbish and herbage which had collected on the boilers.

Notable features. 1. Wrought iron beam 2. Only two beam engines were built after it. (In 1911 and 1919). 3. Only beam engine (still) in a quarry. 4. Only engine complete with boilers, headgear and winch. The latter is believed to be off a ship and is almost entirely of non-ferrous metal. No doubt it would be of interest to a naval historian in that it may be from one of the old dreadnoughts.

5. Almost certainly the engine is steamable given new boilers. It is complete and with only a minor amount of mechanical work, mainly with the Husbands’ Safety Gear, it could work. 6. The house is complete and is weatherproof. We have done a fair amount of work on the inside walls ie. rendering. Also we have painted half of the beam itself, most of the woodwork on the outside, and also some of the metalwork.

The engine was built by Holman Bros of Cambourne, Cornwall. However, there is a plate on the side of the cylinder lagging attributing the design and erection to N Trestrail, Engineer, of Redruth, Cornwall. Possibly this applies to the cylinder only.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw

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