GNER contracted EWSR to provide strategic rescue
services for its HST fleet operating out of London. The Class 67
locomotive was selected for the job because it is a high-speed diesel
locomotive. However, the Class 67 has a combination coupler that does
not interface with the coupler carried on the HST. So, ESG were asked to
design, test and deliver a suitable adapter to connect the two
Due to the restricted side clearance of the draw hook
on the swinghead autocoupler, the current adapter (that fits a standard
locomotive drawhook) did not fit. Initial design ideas investigated
ways of modifying this adapter but were quickly replaced with one that
interfaced with the knuckle coupler of the Class 66/67. Drawings were
created on AutoCAD, and stresses calculated using MathCAD software. The
main design restraints were; ensuring the component withstands the rated
strength without any permanent set; is of low weight (for
man-handling); ease of installation and manufacture; and low cost.
Material selection formed a vital part in this process, and a high-alloy
aluminium was finally selected.
There was some initial testing of a lightly modified
drawhook adapter, as currently used on the HST, but this proved to be
fiddly to fit and, more importantly, was unstable in buff. It was clear
that the best solution was to interface with the autocoupler on the
66/67 and a prototype was made and subject to controlled field testing
using an HST trainset and a Class 67 (checking installation/fit, low
speed curving, static pull etc). the couple was then subject to
destructive proof testing on a tensile rig.
The coupler performed very well in
all tests and met the proof tensile test requirement, it eventually
failed when subject to an offset (5°) tensile load just above the rated
A second prototype
was made and subject to more realistic field testing, hauling an HST set
down the East Coast Main Line to London and back. During the test the
loco speed and traction amps were monitored to ensure the coupler
received the full tractive effort of the locomotive. After the test
critical dimensions were rechecked to ensure there was no permanent set.
The test was also an opportunity to gauge the opinion of ground staff
into the ease of fit and installation of the adapter coupler.
Although, the coupler met the test criteria, it was
decided to strengthen the component around the area of failure (the
second pin joint) and the material section was increased around this
The coupler was fitted with more
robust locating chains and supplied with short extension hoses,
following experience gained on test and the wishes of GNER ground staff.
Surface finish and chamfering details were added to the drawing, to improve the look and handleability of the coupler.
ESG managed the production of over 20 adapter
couplers, fitted safety labels, attached ancillary components and made
up the extension hoses, so that a complete and final kit could be
presented to the client. Spare parts and maintenance information (such
as NDT) were also developed and supplied as part of the contract. ESG
also managed the delivery and transportation logistics to ensure the
client was supplied where and when agreed.
- Selection of materials to meet stringent strength and weight (man-handling) requirements
- Full technical support for design and production units
- Extensive testing in laboratory and on full HST sets out on the track
- Comprehensive 'one-stop shop' solution for the client
- Design compliant to latest Railway Group Standards and legislative regulations
- Design to meet stringent cost and turn around timescales
- Material selection
- In-field and rig testing
- Project Management
- Client liaison
- Risk assessment
- Technical documentation (spares and maintenance)