Irish Railway Record Society
Nenagh
Commuter Service Signalling
A commuter service between Nenagh and
Limerick was reintroduced on 1 September 2008 after an absence of 45 years. The
Monday – Friday service provides a rail option to commuters living in the
Nenagh, Birdhill and Castleconnell hinterlands and working in Limerick City and
its environs. The evening service departs Limerick at 17:45 serving
Castleconnell, Birdhill and arrives at Nenagh at 18:40, subsequently departing
for a return service to Limerick at 18:45. Nenagh is a ‘mid section’ station
in the Roscrea / Birdhill Electric Train Staff (ETS) section. It was necessary
to make changes to the Train Signalling Regulations to allow a train to return
to the same end it entered without proceeding through the entire section. These
changes did not require any technical alterations to signalling equipment.
The timetabling arrangements for the
morning service require that the train depart Nenagh at 07:55 and arrive in
Limerick in time for commuters to reach places of employment by 09:00. It is
also required to provide a connection from the Nenagh branch into the 07:35
Limerick-Dublin at Ballybrophy in order to reach Dublin by 10:00. Neither
service could be altered by much without compromising these requirements.
Thus the timetable required that both
trains occupy the Roscrea / Birdhill (Kilmastulla) ETS section at the same time,
something not normally possible. Services are provided by 2700-class railcars.
The best timetabling option is to run a 4-piece railcar to Nenagh, split it into
2 x 2-piece railcars with the front set proceeding onto Ballybrophy and the rear
set returning to Limerick as the commuter service. Several options were
explored, which would permit this method of operation.
One option was to extend the area
controlled by Birdhill to include Nenagh. Another option was to re-open Nenagh
cabin as a Block Post. Both these options were considered too expensive for the
anticipated revenue return on the line.
A third option considered was to make
use of the siding at Nenagh currently designated a ‘mid-section’ siding
operated from a ground frame. The Roscrea / Birdhill ETS is used to gain access
to and from the siding. One possibility reviewed was to split the Ballybrophy
train at Nenagh, put two railcars into the siding and allow the Ballybrophy
train to proceed, and when it was clear of the section at Roscrea, the commuter
train could be allowed out of the siding and proceed to Birdhill. The delay to
the Ballybrophy train would be such that it either missed the connection at
Ballybrophy or have to run much earlier from Limerick. This was unacceptable.
A fourth option was to run the commuter
train to Nenagh early in the morning so that it could be locked into the siding
before the Ballybrophy train left Birdhill thus eliminating the delay to the
Ballybrophy train. However, in both options 3 and 4, the Ballybrophy train would
not clear the section in time to allow a 07:55 commuter departure from Nenagh,
in fact the earliest departure would be about 08:30 allowing for time to release
the ETS and operate the ground frame points.
Around this time I had a flashback to
the time when the IRRS resided at the old station in Drumcondra. As part of the
collection there, the signal cabin frame from Beauparc on the Drogheda /
Oldcastle line was installed on a raised platform on the ground floor just
inside the entrance door. It was in working order and I spent numerous Wednesday
nights exploring the cabin and its workings. Several items of railway signalling
equipment, not necessarily from Beauparc, were also displayed in the cabin. One
of these was a ‘Banking Staff Apparatus’. This allowed a banking engine to
assist a goods train in a single line section and return to the originating
station while the train continued through the section as normal. The apparatus
was simple. A section staff was obtained as usual. It was then placed into the
apparatus and this released a Banking Staff. The section staff was then
withdrawn from the apparatus. The section staff was given to the driver of the
leading engine of the train and the banking staff to the driver of the banking
engine at the rear of the train.
The removal of the banking staff from
its apparatus disabled the Electric Train Staff system so that no staff could be
released from either end of the section until the banking staff had been
returned to the apparatus.
This system seemed to provide an
economical and feasible solution to the problem of splitting a train at Nenagh.
Some preliminary investigation was carried out, which consisted of contacting P.
N. O’Brien one lunch time to find out what happened to the banking staff
apparatus. That evening when I arrived at the IRRS premises at Heuston, the
apparatus was in the Currivan Room available for inspection. While it provided
much needed information, (including the fact that I had not dreamed it up!), it
was unsuitable for use in connection with the Nenagh commuter service. It was
designed for use with the large type ETS, none of which remain in regular use.
In addition once the banking staff was out, bell communication between both ends
of the section appeared to be disabled. (A pencilled inscription on the
‘wall’ side of the apparatus indicated that it came from Drogheda South
cabin, the junction for the line through Beauparc.)
Over the past number of years, a type
of interlocking system using mechanical keys and locks has been in use on
signalled level crossings. The system under the brand name Fortress Interlocks
is designed for use in places such as factories where, for example, a key
allowing access to an enclosure containing machinery, must be removed from an
electric control box which in turn isolates the machinery electrically to
prevent it operating. The key is trapped in the cage door until the cage is
closed and locked thus ensuring that the machinery cannot operate while someone
is within the cage. Similar systems also prevent access to rooms containing high
voltage switchgear unless the electricity supply is cut off first.
Discussions with the suppliers elicited
the fact that locks using electric solenoids were available and that such a lock
could be used to provide an interlocking system between a banking staff and an
ordinary staff. It also allowed some additional features to be provided
improving on the original system.
The system devised for use by the
Nenagh commuter service consists of an electric lock containing a key attached
to an inscribed plate, a second lock which operates as a switch (see photo 1), a
set of indicator lamps and four Roscrea / Birdhill section staffs with keys
attached. The electric lock has a number of electric switches enclosed within
it. The inscribed plate and attached key is called the ‘Nenagh to Birdhill One
Direction Token’. When the One Direction Token key is locked into the electric
lock, switches in the lock mechanism close and operate a relay which is wired
into the ETS system. When in this state the ETS works normally. The four ET
staffs are locked into the Roscrea / Birdhill ETS instrument in Birdhill. The
ETS hand generator associated with the Roscrea / Birdhill section has been
changed to one which generates alternating current (AC) as well as direct
current (DC).
The remainder of this article appears in IRRS Journal number 168, published February 2009.
Copyright © 2009 by Irish
Railway Record Society Limited
Revised: January 04, 2016
.