A bit of background and history into these classic machines.
Most were built at Vulcan foundry in the early 1960's they were designated type 3,type 5 being the most powerfull.They have a 12csvt English Electric diesel engine coupled to a main generator,they also had an auxillary genny coupled to the main gen.They ran with this set up till the 1980's when they went through a life extension programme.This consisted of being fitted with GEC electrical and Brush equipment.An alternator replaced the main generator.This required two starter motors to start the diesel as previously the main gen was used to motor the diesel to start it.
These sub class locos were given extra weight bring it from as new 109 ton to over 120 ton.This improved traction.
The early class 37's were fitted with a steam heat generator to provide heat for coaching stock,these were fuelled by diesel.Water was drawn from an underslung tank next to the fuel tank.We started removing the steam generators in the 1970's.Concrete blocks were put into the space the boilers were to keep the correct weight.The water tank was connected to the fuel tank and used as a second fuel tank.holding 1750 gallons in total in two tanks
During the loco refurbishment in the 1980's ,some 37's were equiped with a train heating generator.This supplied power for air con and heat to the coaching stock.These were designated 37 /4. the othere, 37/ 4'5.6 7 and 8 were the refurbished locos 37 /0 were the as built ones.307 were built.
Then six 37's were selected as a test bed for new engines. 37 901 to 904 had 6 cyl Mirrlees and 37 905,37906 had 6 cyl Ruston.Both had same power output.They were nicknamed by us "slugs" as they took longer to get moving than the other 37's
I was involved with these locos in the late 1980's.We had reps form the engine makers working with us to make improvements as we went.Very interesting time.The Mirrlees had engine problems such as coolant leaks and head valve gear.The Rustons were very good.
Then BR chose the 8 cyl version Mirrlees engine to power their new locos,the class 60's
A major problem to both Mirrlees and Ruston were the silencer boxes,these were big as a mini. The required constant welding repairs.
I put forward an idea to our depot engineer to do away with the boxes therefore the locos will be more reliable.We tried it out on one loco.We made a stack from the turbo outlet straight out.No silencer.To our surprise,it was not that much louder.All six locos got this treatment.
Some of the re engined locos are now in preservation and hav a distinctive bark
Martyn