Class 37 or Class 55? Bachmann Bogies
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Entry posted by Silver Sidelines
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I am now the proud owner of two BR Green Bachmann Class 37s.
Two Bachmann Class 37s produced around 2004
According to Mick Parker’s splendid new Class 37 web site https://www.class37.co.uk/fleet.aspx?strnumber=37676 my D6707 was outshopped in 1961 and spent its early life allocated to March. D6826 was a later design without gangway end doors and was outshopped in 1963. It was first allocated to Cardiff Canton. Although outside of my layout period it was reported as being based in the north east of England between 1966 and 1969.
Two Bachmann Class 37s, note the blue BR WR route availability symbol on D6826
These Bachmann models date from 2004. They were unused and would have been ‘resting’ in their packing for around 15 years. Not surprisingly when placed on the track they were rather reluctant to move.
In one case the motor was dead. There was an oily residue in the packaging and I surmised that the brushes might be gummed to the commutator. I dropped one of the bogies and turned one end of the motor by hand. I was lucky, with power from the track the motor stuttered back into life.
Early Bachmann Chassis - Class 55 top Class 37 bottom
The early Bachmann Class 37s are similar internally to the larger Class 55 Deltics and as such are easily dismantled. Both Class 37s were taken completely apart, excess oil removed where it shouldn’t have been and fresh oil applied to the dried up motor bearings. I even had to prise out one of the motors to tighten the fixing screws for the plastic cradle. These screws must have been loose when the model left the factory.
Back together and performance was much improved. However I thought both engines had a wobble. I would swap some wheels (and gears if needed).
Bachmann Class 37 bogie (L) with Bachmann Class 55 bogie (R) NB Different designs of steps
Bachmann Class 37 bogie (L) with Bachmann Class 55 bogie (R) NB Finer profile leading wheels at the right of the picture
My last two Blog Posts have been concerned with Bachmann Deltics. I have become very familiar with the Deltic bogies highlighting how the leading wheels have a smaller profile to assist with negotiating ‘train set’ curves. Comparing my early Class 37 and early two axle driven Deltic bogies I had decided that with the exception of the front wheel profiles, the Class 37 and Class 55 bogies were identical.
What about the prototype? I would dig out my copy of ‘British Railways Main-Line Diesels’ by RS Carter from 1963. Quoting from RS Carter ”The traction motors (Class 37) are identical and interchangeable with the traction motors fitted to the production “Deltics”. The bogies, too, are generally similar to those on the “Deltics”.”
The Deltics were rated at 100mph whilst the Class 37s were only rated for 90mph. From memory the speed rating was linked to construction, some bogies being welded whilst others had ‘cast’ parts I can also remember reading when the Deltics were withdrawn that their higher speed rated bogies were given to Class 37s, and this included those Deltics sold into preservation.
I had some spare Bachmann Class 55 bogies so I would swap wheel sets around between the different classes. How wrong can you be! The Deltic wheel sets went into the Class 37 bogies no bother and the wobbles disappeared. However all was not well with the replacement centre driven wheel in the Class 55 bogie which no longer sat evenly on the track. I only have dividers and a steel rule for measuring but my check showed that the wheels in the Bachmann Class 55 two driven axle bogies were 14mm diameter whilst the wheels from the Class 37 were 14.5mm (the same as some spares that I had for a Class 24). I checked a couple of other old Bachmann Deltics and they were all fitted with the smaller diameter bogie wheels – so yet another ‘trick’ to ease the Bachmann model round over tight radius curves?
In the absence of ‘one’ outside to measure I have had another look in my copy of ‘British Railways Main-Line Diesels’ by RS Carter published 1963. I also visited the Scale Four Societies CLAG web site and Wikipedia. I have summarised my findings below. More details are presented as an Appendix at the end of this Post.
Being the owner of a 1973 MGB I am well aware of differences between present day and past specifications. The Class 37 and Class 55 locomotives are even older than my MG so it is not surprising that there are differences of opinion. I would say that the evidence confirms that the Class 37 and Class 55 used the same wheels, with a diameter in the range 3’7” to 3’-9”. I would also say that the wheels used on the BachmannClass 55 Deltics are a touch undersize.
For completeness I have posted a video on YouTube showing my two overhauled Class 37s running with correct sized wheels. I am well pleased.
Appendix
Wheel Size Data
Firstly two extracts from RS Carters book from 1963. The 4.3” wheel diameter for the Class 55 Deltic seems erroneous. The drawings were made to be 3.5mm to the foot to fit the printed page. The erroneous dimension might have been added as an afterthought and the value would be correct for a drawing scale of 3mm to the foot.
Class 37 dimensions from 'British Railways Main-Line Diesels' RS Carter 1963
Class 55 dimensions from 'British Railways Main-Line Diesels' RS Carter 1963
Secondly an extract from the Scalefour Society website. Interesting to see the foot note rejecting a size of 3’ 9” for the Class 37 wheels.
Comparison dimensions for Class 37 and Class 55 from the Scalefour Society
Finally some extracts from Wikipedia:
Comparison dimensions for Class 37 and Class 55 from Wikipedia
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