Literally the central feature of our Roundhouse. Its purpose was to turn engines around and to enable a small building to house many engines that could all be accessed individually.
The full Monty!
The page wouldn't be complete without a film of a full rotation. Just in case you were wondering, it takes about 3 min 48 sec with a light load.
Dale at the controls, having a well earned rest!
The film is taken alongside Harry, our little diesel shunter, and shows a typical working day in the Roundhouse.
An list of the locomotives we see as we pass by is shown below.
The turntable is demonstrated on open days, only by electrical power however!
The need to turn locomotives
Steam locomotives fall broadly into two categories. Those with tenders and those without. Smaller tank engines that have their coal and water supplied built into the single chassis can run equally well forward or backwards, although open cabs on a rainy days made things very unpleasant for the driving crews. Locomotive with tenders have a very definite front and back. In most cases these locomotives had speed restrictions imposed when driving tender first to prevent the lighter tender derailing. The drivers view was also severely restricted.
Turning these locomotives with tenders could have been done in a number of ways. With plenty of land available in America they developed systems called "wye's". As their name suggests the locomotives could pull into one leg of the the wye and reverse out of the other leg, thus turning the engine. This was also quite useful for turning whole trains where the end observation car also needed repositioning.
In England we call them "triangles". If you look closely at an aerial shot of the Barrow Hill area a similar arrangement can be traced.
A system used by some small gauge railways is to have the engine drop off its coaches then perform a "balloon" loop, continuing to drive forwards around the loop untill it points in the other direction. This system can be seen on the Scarborough light railway. Not seen on standard gauge because of the sheer size of the turning circle needed.
The system adopted most widely was the turntable. This allowed the locomotive to turn in its own length, thus using the minimum of space for the task. The turntable also offered a second advantage in that many tracks could lead off it enabling the engines to stand on short individual tracks for storage. This made them more readily available rather than being lost in a long siding of engine storage.
Disused Railway Wye, USA
Turntable at Polmadie, c 1950
The reason is really quite simple
Modern Diesel and Electric locomotives have driving cabs at both ends, there isn't a 'front' or 'back'. For a goods train to travel in either direction the engine only has to use a passing loop to reposition itself at the head of the train. The driver then controls the locomotive from the forward facing cab.
Passenger trains are now formed from a train 'set'. This is where there is an engine, and a driving position, at each end of the train. The train never has to turn round. This feature is used in all terminus stations and indeed on some branch line operation where the train changes direction mid route. A local example of this is seen when travelling from Sheffield to Bridlington where the train performs this manover at Hull.
Why don't we see many turntables today?
With a locomotive balanced in the centre of the turntable the combined weight to turn is well in excess of 100 tons. Moving this amount of weight was originally achieved by connecting the vacuum brake system of the steam locomotive to a cylinder mechanism which drove the turntable. This system was very effective and lasted into the days of diesel power. The change came when Class 56's were introduces to the shed. These had no vacuum brakes and a different system had to be used. An electrical system was brought in which is still used today.
On the turntable are still some of the original devices needed to turn the table by hand. This was necessary when a locomotive needed to be collected from one of the roads. The empty table was pushed into position by using the long bar, normally seen today in the lowered position.
Turning by hand
Dale and Mick regretting being around when the turntable was being filmed.
We have another hand system now to turn the table when the electrical system fails. A little easier then pushing but not an easy job by any stretch of the imagination.
Dale again drew the short straw. What a star!
The film was shot in December 2014. In order, we pass the following locomotives;
XXX, 41708, Midland Compound, Butler Henderson, XXX, Prairie, Blue Peter, Baby Deltic, Tornado's tender
Class 56. xxx, xxx,
Tricks of the trade - Dave Darwin remembers
The turntable has been replaced twice since the Roundhouse was first built. The present structure is 54ft 8 1/2 inches in diameter and was constructed by Cowans of Sheldon in 1931. It was installed here in 1962 by a team from Gorton Locomotive Works near Manchester.
Around the turntable are 24 'roads' or 'pits'. The longest of these is 75ft 8 inches and the shortest 51ft.
Each road is numbered and some had names for simple identification purposes during the steam era.
Number 3 was the 'Boiler washers pit', backing onto the boiler washers cabin.
Number 9 was the 'Sand hole pit', backing onto the sand drying oven.
Number 15 was known as the 'Stores pit'
Number 18 was called the 'Short pit'
Number 21 was called the 'Legs pit', stradding the Sheerlegs
Number 20 was termed the 'Fitters Corner pit'
Often the roads were referred to as 'next to', as in 'next to the Legs pit'
The road leading outside towards the overflow car park was called the 'Garden road'. This was from the days where a decorative rockery was maintained by some of the employees.