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Section 3 - History

Hymek Locomotives

The Hymek story started in 1958 when a consortium of companies was formed under the name of Beyer Peacock (Hymek) Limited.  The main partners were Beyer Peacock, Bristol Siddley Engines and J Stone.  Beyer Peacock has some small experience of locomotive building having won an order for the construction of under-frames for Brush locomotive works.   Strange to think that the Brush locomotives were eventually to replace the Hymeks not yet built!  Additionally they were already engaged to provide components to British Railways workshops at Sheldon for inclusion into shunting locomotives.

The Hymek very nearly never happened.  While the 1955 modernisation plan included Type 4 Warship Locomotives and Type 2 D6300 Locomotives there was no equivalent Type 3 hydraulic locomotive.    It was to fill this gap that the consortium had been formed and the design of the Type 3 Hymek Locomotive featured a 16 cylinder Maybach MD870 capable of supplying up to 1920 HP.  This was connected to a Mekydro K18U hydraulic transmission.

In June 1959 the British Transport Commission placed an order for 45 Hymek locomotives and so the story entered a new phase – construction.

The construction of the Warship and Western class locomotives involved a stretched skin production method necessary to help control the weight problems of those designs.  With only a single engine and transmission there were no such problems with the Hymek design so conventional construction methods were employed.

The Maybach MD870 engine was a larger version of the MD655 unit employed in pairs in the Western class locomotives.  In a Hymek they were fitted with four intercoolers and two turbochargers.    The power output was de-rated to 1740 HP at 1500 rpm so as to match the specification for the Type 3 locomotives.

Final assembly was at Beyer Peacock’s works at Gorton (Manchester).  Engines were assembles at the Bristol Siddley plant at Ansty (Coventry).  Both J Stone Limited (Deptford) and Mekydro in Germany assembled hydraulic transmissions.

The Hymek bodywork was, as already stated, of traditional construction.  Longitudinal girders formed the main load bearing members while lighter angle sections were used for mounting smaller components and for the framing for the bodywork.  The bodywork was formed from lightweight sheets, as there was no load bearing on these panels.  The cab roofs were moulded fibreglass panels.

The bogies used were the well-trusted Commonwealth type but fitted with 45-inch diameter wheels, larger than for the other hydraulic locomotive classes.

These construction methods allowed the locomotives to be produced with a finished weight of 75 tons, which was an ideal weight for a Type 3 locomotive.

Even before the first locomotive was delivered the British Transport Commission was so confident with the design concept that they placed an order for a further 50 locomotives.  Thus, in July 1960, ten months before delivery of the prototype, the order was increased to a total of 95 locomotives.  One last batch of 6 was ordered in December 1961 bringing the total order to 101 locomotives – the final tally.

16th May 1961 was a red-letter day in the history of the Hymek locomotives.  D7000 was handed over to the Western region at Paddington station, two months ahead of schedule.

Sadly the last Hymek was not delivered until February 1964, twelve months behind schedule, due to problems at the Gorton assembly plant in Manchester.

Differences between locomotives in the class were minimal.

The first three had air-horns under the buffer beam while the rest of the class had them relocated to the centre of the cab roof.  The first three were later modified to match.

D7000 – D7044 were fitted with Stone-Vapor train heating boilers.  Brakes were Knorr straight air type with Laycock-Knorr compressors.  These were built to Diagram DH/3100/1

D7045 – D7100 were fitted with Spanner Mk 3a train heating boilers and Westinghouse air brakes and compressors. These were built to Diagram DH/3100/2

Lickey “Banker” Modifications

I had always believed that Hymeks D7021 - D7025 had first gear permanently locked out to prevent transmission hunting between gears whilst banking at 20 - 30 mph, which was transmission changeover speed.  This now appears to be incorrect.

I have  been contacted by Darryl Lucas who worked as a fireman / secondman at Bromsgrove from  1962 to 1973.   Darryl has advised me of several interesting facts relating to the use of Hymeks on the Lickey.

First gear was only locked out when necessary (very lightly loaded trains for example).  The bankers were given a load indication by Gloucester Panel Box so the crew could determine if it was necessary to lock out first gear.  To lock out first gear on a heavy train would result in high transmission temperature.  That would cause the engine to return to tickover which would result in the train stalling on the bank.  Often when working Hymeks in multiple only one locomotive would have first gear locked out.  This was achieved by means of a changeover switch on the main control panel in "A" or No 1 end.   For this reason if a "strange" locomotive was used and found to be facing the wrong way it was taken to the triangle at Worcester and turned as required to get the "A" end facing north (up the bank).

The locomotives used on the bank were not restricted to the pool D7021 - D7025 and Darryl has records of using 83 different Hymeks on the bank on different occasions.

Hymek Liveries

D7000 was delivered overall brunswick green and without yellow cab front.

The same livery was originally planned for all Hymeks but the livery on all later locomotives when new was brunswick green with a light green relief band along the lower body side.  Cab windows were white and cab fronts were yellow.

All locomotives were fitted with cast aluminium cab side numbers.  In later years the “D” was painted out on many locomotives and although they were designated “Class 35” under the TOPS scheme they never lasted long enough to ever carry that number sequence.

Later livery modifications saw the introduction of a chromatic blue livery with small yellow cab fronts.  Initially D7004, D7007 and D7051 carried blue all over, including the cab window surrounds.  This was later modified to incorporate white cab window surrounds.

The last livery carried was British Rail corporate blue with all yellow cab fronts and yellow window surrounds.

Some locomotives never acquired these later liveries being condemned while still in their shabby green paint work.  D7054 was noted scrapped in tired green livery still with small yellow cab fronts.

 Operating Difficulties

Towards the end of 1961 the first major operational problems were noted.  The engines ran too hot.  Coolant temperatures were excessive and additionally the hydraulic transmissions were prone to failure on initial starting from rest.

To help identify the exact causes the class were modified in two ways

Type A modifications

Odd numbered locomotives up to D7075 had their engines further de-rated to 1350 HP.

Type B modifications

Even numbered locomotives up to D7078 had first gear locked out of use.

These controlled experiments proved most useful in proving that the two faults were related.  The root cause was a problem within the transmission control equipment that was failing to change gear at the required engine speeds.  This in turn caused the excessive engine speeds that resulted in the overheating also experienced.  All Hymek locomotives already delivered were modified with improved transmission controls and the fleet was back in full service by the end of 1963.  All new locomotives were built with the modified controls included. 

The Hymek locomotives were now set for an extended period of (relatively) trouble free operation.  They were allocated to depots mainly in London, Bristol and South Wales

Apart from the occasional loss of coolant into the cylinders the Maybach MD870 engines were relatively trouble free.  8000 – 10000 hours between major overhauls was quite normal.

The Mekydro hydraulic transmissions were however a little more fragile.  Major operational problems included multiple clutch failures, converter failure, stripped gear teeth and metal in filters.  As time passed the rate of transmission failures was such that there were no more spares available.  This resulted in British railways “borrowing” transmissions from Hymek locomotives with other faults.

This situation was exaggerated by the failure of Beyer Peacock as a business in July 1966.

The next phase of the Hymek story was about to start – withdrawal. 

Hymeks – The Final Years

The lack of spare parts, the drive towards standardisation and the corporate “dislike” for diesel hydraulic locomotives were all to play their part in the inevitable decision to dispense with Hymek locomotives. The first two locomotives D7006 and D7081 were withdrawn in September 1971.

By the end of 1971 several of the class had been withdrawn.    The 1972 Ian Allan Combined Volume excludes D7002, D7006, D7058, D7059, D7060, D7062, D7063, D7064, D7067, D7069, D7072, D7078, D7079, D7081 and D7083 as withdrawn.

The next 15 months saw regular withdrawals and by December 1972 80 Hymek locomotives had been taken out of service leaving an operational fleet of just 21 Hymeks.

The 1973 Ian Allan Combined Volume lists the survivors as D7000, D7001, D7009, D7011, D7016, D7017, D7018, D7022, D7023, D7026, D7028, D7029, D7030, D7031, D7032, D7044, D7055, D7075, D7076, D7089 and D7093.

In January 1973 these 21 Hymek survivors were based at Old Oak Common (14) and Bristol Bath Road (7).

Against all odds ten Hymeks survived to see out 1973.  The 1974 Ian Allan Combined Volume lists them as D7000, D7001, D7016, D7017, D7018, D7022, D7026, D7028, D7029 and D7093.  The other interesting note in this Combined Volume is that only Hymeks, Westerns and the solitary 1200 Falcon remain outside the TOPS numbering scheme.

The Hymeks survival was due to the replacement locomotives, Class 31 Brush Type 2, failing at a rate even greater than the Hymeks had managed.  Hymek withdrawals were put on hold while the Brush problem was investigated and ultimately resolved.  You may recall that Beyer Peacock had been engaged to construct the under frames for these Brush built locomotives BEFORE construction of Hymek locomotives commenced.

British Railways had planned to see off their last Hymek locomotives for some time and an enthusiast rail tour was organised and run by them on 22nd September 1973.  This farewell rail tour behind D7001 and D7028 proved to be somewhat premature.  D7028 managed to survive until January 1975, an amazing 16-month stay of execution.

However the Hymeks were far from finished and to the amazement of all only four Hymeks were withdrawn during the whole of 1974 leaving six still in service at the start of 1975.

In January 1975 the Hymeks still in service were D7011, D7017, D7018, D7022, D7028 and D7029.

Sadly Hymeks were now doomed.  Withdrawal came quickly; January D7028, February D7029 and the remaining four did not survive March.

The story of the Hymek was entering the last phase – Preservation

Worcester Locomotive Society                  South Devon Railway