D7018 Special Report by Martin H. 1/11/16

Regular readers will be familiar with the considerable progress that has been made with Hymek D7018 over
the last couple of years, notably the first engine start, manufacture of a new drive shaft, static testing of the
gearbox and, most recently, running to and fro in Williton yard. So much progress has been made that we
were confident in asking the WSR for permission to take the locomotive out on the line for live gearbox
testing. The agreed date was to be Friday the 21st October 2016 as it coincided with a Steam Engineman's
course between Bishops Lydeard and Williton which meant that the signal boxes would be open, but no other
trains were running. As this date was during the Autumn Work Week, it meant we were able to exploit a
mid-week opportunity without having to specially arrange for the requisite staff to be present.

Friday morning promised to be dry and sunny, giving every indication of being comfortably warm, and getting
more so during the afternoon. Once the engine had been properly preheated we were ready to go. We had
myself and Bob C aboard to supervise the technical aspects, and we were ably assisted by a couple of good
friends from the DTG. The plan was to use the Hymek to tow Class 33 D6575 as insurance and as a load to
Bishops Lydeard. There, we would put the Hymek over the locomotive inspection pit and carry out a thorough
underframe examination before reforming the locos to tow the 33 back to Williton. If all went well with this,
then we could either use the Williton to Blue Anchor section for more testing or do another return trip to
Bishops Lydeard. The underframe exam was to identify any areas that would need to be addressed before
the loco's full return to service. The loco was running in basic form for this test in that it was operable from
either driving position, but lots of panels were missing in the cabs, there was no outer radiator grille on the
non-corridor side and we were unable to fit the engine room roof as the spring hooks were still off-site being
refurbished. Bring on the Hymek in cabriolet mode!

We departed on time from Williton and driver Paul was asked to increase speed slowly so I could check that
the gearbox operated correctly and changed gear at the right speed points. At the same time, Bob C was
able to check the engine over and make any tuning adjustments that might be needed. The first up change
happened at about 6 or 7mph, and was remarkably smooth. Paul kept the speed creeping upwards and the
second gear change occurred neatly at 21mph. We stopped briefly at Stogumber so we could repeat the
test, but by now it was evident that the control oil side of the transmission heat exchanger could not hold
against the pressure and was developing a bit of a leak. At Crowcombe we had to wait about 30 minutes for
the SEC to pass so, after making sure the cooler group fan was working, we shut the engine down for a bit.
Once we were on our way again, I asked Paul to let the locomotive coast up to line speed so I could check
that the gearbox auto-changed correctly. In theory, it should change up to top gear between 23 and 27mph
so it would be tight to achieve on a 25mph line, but we had to know. I am delighted to be able to report that
the requisite change occurred at precisely 24mph! Applying power at this point causes an immediate
down-change to whatever gear is necessary to suit the engine speed and road speed, and this also occurred

Once over the pit at Bishops Lydeard, nothing was found to give cause for concern, however the continued
oil leak made us decide to terminate testing once back at Williton. Despite valiant efforts being made to
capture the spilt oil, we still managed to lose a significant quantity. This manifested itself by the gearbox
refusing to change direction to shunt back into the depot. The directional change was initiated manually and
we drove back on to shed and shut down. Lunch was spent discussing options and replenishing the oil level,
but while doing so, Bob discovered that the bolts holding the end cap on the heat exchanger were not
properly tight, and it was only the paint trying, and failing, to hold the oil in! Five minutes attention with a
spanner and socket soon corrected that and so we decided to go for another run to Bishops Lydeard and
back to confirm it. This time the heat exchanger did not leak and the directional gear change was taking
place properly once more. The afternoon run to Bishops Lydeard and back can only be described as
uneventful, though we did enjoy the novelty of a topless Hymek! Only one other problem showed itself, and
that was an oil leak under turbocharger A on top of the engine.

This is the whole point of proper testing, to highlight any areas of weakness in a locomotive so that it can be
put right. The main purpose of this particular test was to check the operation of the gearbox under live
conditions and in this respect the testing was completely successful and so I am now declaring the gearbox
as fit for service. As I write these words, the gauges and inspection windows have now all been removed and
the proper covers have been replaced on the gearbox. The engine room roof will stay off for the moment to
allow Bob to sort out the turbo oil leak, and then we just have a lot of panels to refit and paint.

You can view a selection of short videos of the testing on the Hymek YouTube Channel at