River Wissey Lovell Fuller

AN INTERESTING DAY OUT (For some perhaps)

October 2006

Ron gives us a vivid description of the joys of the Prickwillow Engine Museum

Prickwillow Engine Museum

Most people living in this area have some awareness of the historical background to the drainage of the fens. Those early drainage schemes relied on gravity to move the water along the drainage channels. As the peat-like soil dried out, however, it shrank so that the level of the land fell and it proved necessary to build banks on the sides of the channels then lift the water from the land into the channels. In the 18th century wind mills provided the only practical means of providing the power to do the lifting. Needless to say, at times of light winds they had a problem.

In the 19th century the arrival of steam power finally solved the problem. In the early days lifting was achieved by the simple means of scoop buckets on a rotating wheel, the extent of the lift being determined by the diameter of the wheel. A fairly typical installation of an early steam engine was at Prickwillow, which is situated on the River Lark where the road from Mildenhall to Ely crosses the river. It was a beam engine driving a scoop wheel of 10 metres (33ft6ins) diameter, installed in 1831. It drained about 2500 hectares. A second steam engine was installed in a new engine house in 1880 driving a churn pump (an axial flow pump comprising an impeller at the bottom of a vertical pipe).

In 1897 the first engine was replaced by a 300 horsepower compound steam engine driving a centrifugal pump, the whole set built by W H Allen, this was used in conjunction with the second steam engine. By 1920 the continuing shrinkage of the land meant that the second steam engine's churn pump could no longer provide enough lift. Diesel engines were now on the scene and a five cylinder Mirrlees diesel engine driving a centrifugal pump replaced the second steam engine set. The Mirrlees formed the main power unit at Prickwillow until 1958. Following the installation of electric pumps the Mirrlees continued on standby until 1981.

In 1983 the 'Prickwillow Engine Trust' was formed to preserve the engine in the engine house. Later two large Allen engines from Ten Mile Bank were donated to the Trust and, with the aid of a grant, the building was extended and a museum created.

The Mirrlees engine is quite a monster of 195 litres with 5 cylinders, it must be more than 16 ft long and 10 ft high. It produces, what is by modern standards, a rather meagre 250 horsepower, but this it does at only 250 rpm. (some modern engines can produce 100 horsepower/litre but they do this at much higher speeds and have a shorter life). In a car covering 100,000 miles the total engine running time would be of the order of 2500 hrs, it is estimated that the Mirrlees operated for 44,000 hours before it was taken out of service and it is still in good working order.

The Mirrlees is the centrepiece of the museum but it is only one of nine or ten engines of varying size, including the old Allen compound steam engine. One of the Allen diesel engines is a 4 cylinder supercharged two stroke of 124 litres developing 400 horsepower, the other is a three cylinder unit of no less than 238 litres and 340 horsepower. Most of the engines are technically interesting in one way or another. On engine running days most engines are run, including the Mirrlees. The day of our visit was not a programmed 'running day' but we were fortunate that the engineer present had decided to run the Mirrlees. The starting procedure was interesting, two of the five cylinders were fed with compressed air to turn the engine over, once rotating fuel was admitted to the other three cylinders, when they were firing regularly the compressed air supply to the first two cylinders was turned off and those two cylinder fired up. The fuel system was very different to modern diesels, using compressed air at 800 psi to blast the fuel into the cylinders.

Without doubt the museum will have the greatest appeal to those with an interest in engines but even those with no knowledge of engines will find the information, artefacts and photographs relating to drainage of the fens interesting and will be impressed with the size and appearance of some of the engines. Prickwillow is a quiet village and there are views of the river and the fens from within the museum. There is a cafe with a large window area where you can get a tea, coffee or soft drink and a (very light) snack. The Prickwillow Engine Museum is well worth a visit.

Ron Watts

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