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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 Peacocks 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.
D7045
D7100 were fitted with Spanner Mk 3a train heating boilers and Westinghouse air
brakes and compressors.
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.
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.
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