The Nottingham Society of Model and Experimental Engineers (NSMEE) is based in the Nottingham Transport Heritage Centre (NTHC) at Ruddington, five miles south of the city on the A60 to Loughborough.
Having built a large 7 1/4 “ gauge railway, automatically signalled and with a fully functional signalbox, an extension was planned. This extension incorporated a small terminal station approached by a triangular junction off the loop at the furthest point from the signalbox.
How to control the points and signals? To permit operation from the existing signalbox would involve a lot of trenching and modifications to a system that had proved very reliable over time.
We are Micromotive and our daytime vocation is industrial remote control systems, mostly for overhead cranes and industrial shunting locomotives. Our prime customer is RMS Locotec of Wakefield who has the largest operational hire fleet of industrial shunting locos. In February 2007 we introduced a new product to our portfolio: a remote control system for points in sidings and depots, though not for main line use.
Quite by chance the demonstration model of our system was being shown to interested members of the railway restorations groups during April and some of the NSMEE model engineers saw this. Two weeks later we were asked if it would be possible to control the points and signals of the extension to their 7 1/4” railway. The rest, as they say, is history. On Saturday June 2nd 2007 the first part of the control was commissioned. Two points and four signals were under remote control. The intention at present is that this part of the railway is only to be operated on the ‘one engine in steam’ principle although with our control system more than one train could be operated safely, drivers having their own remote control handset, as our full size system permits.
The original plan was to have the controls in a cabinet on the station to be operated by the guard on the train, as NSMEE did not to have enough staff to provide a full-time signalman. This would have necessitated the guard leaving the train and walking to the cabinet to change the points and signals. The radio remote control system has clear advantages over this.
The layout is shown in the diagram above. The current operating procedure is to use only the Main Line to prevent train reversals due to the triangular junction created by the branch access and departure.
Point 1 is a spring point set to the exit direction from the branch station and point 4 is currently an air/sprung point that will be changed to remote control when the ground signals gave been made and installed.
The driver currently controls points 2 and 3 and signals 11 to 14. Signals 11 and 12 indicate the platform road selected, with 13 and 14 being the starter signals.
The more astute will notice that the splitting junction signal in the photographs on the approach to the station has the dolls in reverse from that shown in the diagram! These signals, a masterpiece of model engineering by John Lopez, were constructed for this location, but plans for the station were modified between John starting and completing the construction.
I dare anybody to take a saw to that junction signal! John intends to build another with the dolls in the correct alignment in the near future. Apparently, as these things happen, his original plans of the signal were left hand divergence and he had to reverse everything.
This photograph shows the platform one somersault starting signal (13) with the junction splitter in the distance. Also shown are the track layout, points 2 and 3 in the foreground, the control panel enclosure in front of the air reservoir on the left, and two of the point operating machines.
Back to the control systems....the points mechanisms were made by John Hewitt to a design by the Colchester Model Engineers (ref: Model Engineering, January 1994), John Lopez designed and made the signal operating mechanisms which all use air cylinder actuators, and Martin Hill assisted with providing the electricity supply. The Micromotive control system for the full sized points uses hydraulic actuators, but the operating principles are the same.
The mechanism is designed to mechanically lock the points after movement with provision for automatically compensating for any gauge widening ensuring a fully closed switch; altogether a clever piece of engineering. A team effort by all the members has resulted in the branch station you can see in the photographs.
The Branch points were made to a slightly modified design from the main circuit. Copied from the full sized points at the NTHC, except that the switch rail head closes under the head of the rail, the stock rails being machined at an angle to the vertical and not joggled. This refinement was designed and made by the two aforementioned Johns.
The handset (adapted from the 'remote points handset) has ten numeric keys in addition to keys to Unlock, Lock, and command the points to move to their Normal or Reverse positions. Using an operating sequence to ensure deliberate actions by the operator and only when the points are locked which prevents the driver moving them whilst he is proceeding, can the appropriate signal be cleared.
This electronic lock is in addition to the mechanical lock provided by the point machines, and is intended to prevent inadvertent movements by accidental operation of the handset keys. Obviously if points 2 are reversed and points 3 are normal both signals 11 and 13 could be cleared, but whichever is cleared prevents the other subsequently being operated. There is currently no back interlocking, but if a point is unlocked while a signal is off, the signal immediately returns to the on position. All the electronic boards contain a safety circuit that is intrinsically safe, guaranteeing a fail-to-safe condition in the event of a system failure. This is built in to all Micromotive remote control products.
Controlling signals was not part of our original system for points, a light feather indicating the direction of the switch being the standard feature similar to conventional practice. A small amount of reprogramming meant we could use the same electronic control boards thus standardising the hardware. The solenoid valves controlling the signals are in the bottom right of the control panel, the solenoid valves for the points located in the point machines, and all circuits are 24dc.
Approaching the station junction signal the driver slows the train to give time to set the road and clear the appropriate signal. Points 2 are then set to Reverse and Locked. If point 3 is in the correct position for platform one (which they usually are) they can be Locked without Unlocking and moving the switches. Having locked both, the input pattern on the signals’ own control electronics will permit the operation of the selected signal. Obviously if the driver tries to clear a signal for an invalid route the commands are ignored and all the signals stay on. The signals revert to the on position after 45 seconds, but the driver has the facility to return any signal he has previously cleared back to the on position if required.
At present the system can handle 99 devices to be controlled but this will be increased to 999 in the near future, prior to installation of some full sized points into an industrial location. Route selection is also planned, and as this system at Ruddington is close to our works it permits the enhancement to be demonstrated. This upgrade took place on 25th August 2007.
Although there are only four possible routes using points 2 and 3, it gave us the opportunity to prove and demonstrate our enhancements. The system can handle up to 999 devices to be controlled with the ability to select 24 user determined routes each capable of operating up to 999 points. We intend to increase the number of possible routes from 24 to 104 during September 2007.
All timings, and point and signal identity codes, are contained in the ‘Dongles’, the yellow plugs at the top of each electronic board. These are programmed by the customer to personal requirements using our Windows based software so that any timings and, in the case of the signals controller any interlocking patterns can be altered to suit any changed operating conditions. At Ruddington, shunt signals are to be fitted at the station throat and will thus be controlled and interlocked simply by modifying the code in the dongle. Also if operation using the third side of the triangle come into fruition point 1 will need controlling and interlocking with additional signals.
Watch this space!
Contacts referred to in this text:
Nottingham Society of Model and Experimental Engineers www.nsmee.com
Nottingham Heritage Centre www.nthc.co.uk
The photograph (right) shows the control panel, showing (in the right hand corner) the handset which is indicating it is set for operating point 2.
John’s magnificent junction signal is shown right. All signals are removable for obvious reasons, and mounted in sockets on running days. The operating mechanism remains in the ground.
Currently, if a driver operates a set of points they remain locked for 80 seconds before reverting to the ‘available’ state for any other driver to operate. While a driver has control with his own handset, all other handsets are locked out and ignored so that there is no possibility of movement of the points from an unauthorised source. Any number of drivers can therefore have a handset but only one has control at any one time.
Remote signals - the full story