Detector Fitting

 Tuesday 29th March

A bit more work to do on the new crossover at Toddington today. The connections to the points (14) and their  FPL (nearest the station) have not been made yet and are clipped for the road from platform 1 to the main line south. 

Our main objective today was to fit the detection unit for this point

Firstly, a concrete base is prepared using wooden shuttering:

The detector has four securing bolts (note the blue nuts) which have had a short bar welded on to the head. We then lifted the unit into position and sank the bolts into the wet concrete. We will tighten the nuts  next week when the concrete has set.

There is a slotted bar which passes through the centre of the unit (aligned with and parallel to the signal wire seen on top). The signal wire which connects to the adjacent ground signal now has to be cut and attached to each end of the bar.

Only if the slots in the three bars connected to the point blades and FPL coincide with the slot in the detector can the signal be operated. This next picture gives a better view of the arrangement

The FPL in the centre of the photo is not yet connected to the angle crank (on the 3rd sleeper to the right). To ensure that there is no relative movement between them and to prevent misalignment, the sleepers are strapped together with a steel strap on both sides:

And finally a bit of ground signal refreshment. Replacement of the two discs on the unit by the bracket signal - beautifully hand painted by Malcolm W!

Despite the weather - raining heavily in the morning - we achieved our objectives and the concrete escaped the downpour!

Curly

Motorised Points 22

 In a previous post Curly alluded to work being done on Motor Point 22 at Toddington.  Here is a bit more detail of what goes on with a motorised set of points.

On the GWR we now exclusively use Alstom HW point machines.  These are a fairly simple and robust machine and were (still are) in wholesale use over the national network.  The photo below shows the machine fitted to Points 22.

The machine sits on two timbers and is bolted through them.  The 'business end' of the machine is bolted through the sole or gauge plate (along with the rail chairs that hold the toes of the point switches) and this ensures that none of those can move relative to the other, thus keeping the toe of the points at the correct gauge and the machine at the same distance from them.  The machine is connected to the points by four bars:  The first and heaviest is the drive bar, this links the drive stretcher of the points to the drive portion of the machine and this is the first part that we set up.  The machine has a throw of about 150mm which is not adjustable, the points would normally have movement of 105mm to 110mm between the two positions.  In order to couple these two movements together we use an item called a basket, which is a block through which the drive bar goes.  On the Drive Bar, either side of the Basket, is a drive nut and lock nut, these are adjusted tight for each position of the points, allowing the drive bar an amount of free movement before picking up the points and moving them.  This is the first job in setting up the machine and is achieved by hand winding the machine between the two positions until the blades have been set correctly.  The second bar connects the Lock Stretcher (a bar which connects the toes of both blades together) to the facing point lock within the machine.  The purpose of this stretcher and bar is to lock the points safely in one or other of the correct positions and this is the next part that we set up.

When the machine is operated from one points position to another a clever set of cranks and gears (unfortunately hidden beneath covers in the photo above) take the machine through three distinct stages: 1: disengage locking bolt, 2: move drive rod, 3: re-engage locking bolt.  The locking bolt is hidden (as is so much in these machines) under the contact block in the above photo.  It is removed and inserted into a slide which is connected to the locking bar from the points locking stretcher and as previously mentioned is the main safety device to hold the points correctly in either position.  This is adjusted to be only just clear when the points are fully over in each direction (there is a go/no go gauge which is slipped between to point blade and stock rail to set the tolerance).  This process is again done by hand winding the machine back and forth until the adjustment is correct.

Finally we have the two detector bars.  These are independently connected to each point blade toe and are a backup check to prove that the blade toes are in the correct positions (should the lock stretcher break or become detached at either end).  These detector rods are connected to two more slides in the machine which are underneath the contact block.  The astute of you will probably guess that the position of the closed blade on a point is very important, with little room for error, whereas there is far more tolerance in the open blade (just needs to be open enough not to foul the backs of the train's wheels) and this is the case with some slots in the slides connected to these bars.  For the position where the bar concerned with the slide has its blade closed there is a very accurate cut out in the slide, and we adjust the bar to position this correctly.  For when the blade associated with that bar is open, there is a big wide cut out which does not need further adjustment.

Having now set up all four bars correctly we come to the clever bit with the contacts.  The contact block has a set of contacts down each side and in the middle a rocking contact mechanism.  This mechanism sits on two sets of rollers, one down each side, and is held down by a strong spring.  When the locking block is correctly inserted and the detector slides are correctly aligned then all the rollers on one side of the contact mechanism are presented with cut outs below them, and the mechanism rocks to one side, thus making those contacts.  These contacts control three main things, motor power, clutch power and detection of position.  The detection contacts operate relays under the signal box, showing the position of the points and releasing signals which may be cleared when the points are set in that direction.  The motor and clutch contacts control the operation of the machine from one position to the other.  Correct detection of the opposite points position causes the contact mechanism to rock to the opposite side and operate the opposite set of contacts.

Once the machine is correctly set up then the winding handle can be removed and the machine operated electrically.  The winding handle inserts through three aligned holes in plates attached to the machine body, the inserting of the handle and aligning of these holes operates a switch which disconnects the power to the motor.  This is a safety mechanism to prevent injury to the operator.  The switch is reset by pressing a release button after the handle has been removed.

I hope the above isn't too wordy and gives a rough idea of how one of these machines work.  We've re-installed three of these post the winter works.

Neil C.

Joint Venture

 I took advantage of the nice weather on Monday to fix a wet/noisy cable joint which had been causing problems with the Gotherington internal phone extension.  Nowadays we try to buy and install cables in the correct length to span between cabinets, so that the joints are well above ground, in the dry and only occur where cable access is required.  However, in the old days we often acquired second hand cable in varying lengths and this needed jointing far more frequently.  My predecessor on the S&T electrics side was fond of joining cables in what he called 'Trough Joints' (a crimped joint in a drainpipe inside a length of S&T trough) or a 'Coffin Joint' (a crimped joint in a brick box on the ground with a lid of some sort).  Whilst these joints served a purpose they suffered from rodents nesting in them (and eating the cable grease and insulation) and water ingress.  This inevitably led to cable failures and noisy phone lines.  I have gradually been removing these joints, either by cable replacement or repair.  The cable from Far Stanley Cabinet to Gotherington Box was one of the last he installed and that had a coffin joint just short of Gotherington platform.  The inevitable rodent damage had occurred and the phone line to the Gotherington Box internal phone had gone low impedance to ground, tripping the exchange.  This joint is just a straight joint in a 10 pair grease filled cable, nothing joins or leaves the cable here, so I decided to try an experiment.  I cut the rather moth eaten ends off both cables, cleaned off the grease, remade the joint with new crimps and then 'potted' it in a standard mains resin joint case (see photo).  This joint is now sealed for life and is rodent and moisture proof.  Let's hope it does the job.  The Gotherington phone line is certainly back to normal. 

Now that the joint has set I have dropped it back into the brick coffin and replaced the metal lid.

Neil C.

A Lot of Finishing Off To Do

 Tuesday 8th March

Off once again to Toddington to continue with all the re-connections associated with the new pointwork south of the station.

Firstly the replacement of the signal wire stakes. These are hammered into the ballast and then firmed up with a bit of concrete. Eight of these to do.

Malcolm W spent most of the day re-jointing signal wires - of which there are many - we estimated that about 50 joints are required. He ended up with some fairly rough and sore fingers.

I may have described these joints in a past blog but here is a quick teminder. The wire is threaded through a thimble and cut off leaving about six inches protruding.  Each of the seven strands of wire is then teased out and then sequentially wound round the entry wire. This gives a very reliable joint which will not give . 

Malcolm's knees also taking a pounding, not the best position for doing this!

Because the new pointwork is now in a different position most of the concrete blocks  supporting the angle cranks have to be moved - so some more serious ballast digging to get them in the right position

And for the angle crank across to the points

This will need a bit of  cutting of point rodding to connect up but after a bit of block adjustment this should be OK.

One of the problems with unbolting  these fasteners which have been buried in these blocks for years is that you have to get a spanner inside a limited space  underneath to stop them from turning when you are trying to undo the nut on top. So the four blue nuts you can see holding the two bars here have  a welded strip on the bolt head underneath to prevent it turning.  

And unless you have a large enough clearance round the block,  ballast  keeps falling in to impede  access!

Neil C has been finishing off the wiring of the motor point and associated  connections at the north end of Toddington  station.

No photos I'm afraid but I am reliably informed that the motor point which was removed from Winchcombe adjacent to the embankment works (now completed) has now been put back and re-connected. Just a few more signal wire stakes to replace once the remainder of the contractors  access road adjacent to the track has been levelled. 

So fingers crossed for the weekend!!

Curly

PS  I have recently visited relations in Lancaster and have been made aware of an interesting project that is being launched later this year. This is a major investment planned for Morecambe to build a similar site comparable to the Eden Project in Cornwall called Eden Project North (could be part of the government's levelling agenda??)

Worth a look on www.edenproject.com