Tuesday, November 19, 2013

London Underground and Overground, 2013

Deutsche Version dieses Postings

Here are a few photos from a rainy day in London.

A signal shows "clear" for an Overground train at Kensington Olympia:

Signals towards West Brompton, Kensington Olympia, 24.8.2013

And here is the train. On the left, a District Line train waits for its departure. One can see that the Overground has a third rail for providing power, whereas the Underground uses two power rails, one outside the rails and another in the center:

Underground (but overground) and Overground, Kensington Olympia, 24.8.2013

The signals on the Overground have only a single lens:

Signal VC 696 towards West Brompton, Kensington Olympia, 24.8.2013

Here is the Underground train and the end-of-track signal behind it:

Underground to High St.Kensington, District Line, Kensington Olympia, 24.8.2013

End-of-Track, District Line, Kensington Olympia, 24.8.2013

The signal towards Shepherds's Bush shows clear, but the next signal is still at stop:

Signals towards Shepherds's Bush, Kensington Olympia, 24.8.2013

And here is another train arriving:

Overground train, Kensington Olympia, 24.8.2013

Overground train, Kensington Olympia, 24.8.2013

Finally, two shots of signal NL1047 at Willesden Junction with a lighted "feather":

Signal NL1047, Willesden Junction, 24.8.2013

Signal NL1047, Willesden Junction, 24.8.2013

Monday, November 18, 2013

Three English turret clocks

Deutsche Version dieses Postings

It seems to become customary that I visit some turret clocks when on vacation. In Italy in 2012, I had seen and photographed turret clocks at Lucca and Cardoso in Tuscany (please excuse that these postings are currently only available in German).

As this blog has "... and other machines" in its title, I'll now show a few photos and videos of three English turret clocks.

In England, I climbed the clock tower at St.Albans, the church tower at South Mimms, and finally the clock tower of St. Mary’s at Oxford. Each of the clocks I saw there is interesting on its own right.

Here are a few pictures and videos from the clock tower at St.Albans. Its clock has a Denison escapement, which was invented by Edmund Beckett Denison (who later called himself Edmund Beckett and became Lord Grimthorpe). The escapement is also known as "Westminster escapement," because the famous clock in Big Ben, which was designed by Edmund Beckett, uses it. Actually, there are different versions of this escapement: Big Ben has a double three-legged Denison escapement, whereas the clock at St.Albans has a single four-legged Denison escapement:

St.Albans clock tower, 25.8.2013

St.Albans clock tower, 25.8.2013

The following picture shows the clockwork.
The pendulum and escapement are not integrated in it, but are mounted on the opposite wall. A shaft that can be seen at the top goes from the clock mechanism to the escapement. Behind the shaft, one can see the large fly brake of the striking mechanism. Originally, the clock was of course wound manually, but like almost all mechanical clocks it has been converted to automatic electric winding. Therefore, the barrel left of the center no longer carries a rope. Rather, a chain—which can been seen above the barrel—connects the driving shaft with the motor winch, whose housing can be seen at the left:

Clock, St.Albans clock tower, 25.8.2013

Here is a still image of the escapement:

Single four-legged Denison escapement, St.Albans clock tower, 25.8.2013

The following two videos show the action of the escapement:





South Mimms's turret clock has a standard Amant escapement (a type of deadbeat escapement derived from the Graham escapement; in Germany, we call it "Mannhardt escapement" after a famous Bavarian clockmaker). When we visited the clock at South Mimms, it had unfortunately been out of order for a few days, as the winding mechanism had stopped working.

Here is the clockwork. In the center, one can see the shaft leading to the hands (with the hour hand gears at the far end). Also here, the barrels no longer contain ropes—rather, chains lead to motors on top of the clock housing that wind their own weights. The pendulum is at the back—one can see its heavy bearing frame behind the escapement. Two large air brakes can be seen at the back:

Clockwork, South Mimms, 26.8.2013

On top of the case housing the clockwork are the three winches. The two weights for the striking trains are on the right side of the clock, the weight for the clock train is apparently right below the clockwork. The picture also shows various levers redirecting wires to the bell strikers in the belfry above:

Winches and transmissions for bell wires, South Mimms, 26.8.2013

Winches and transmissions for bell wires, South Mimms, 26.8.2013

The central controlling mechanism of the clock is the escapement:

Amant escapement, South Mimms, 26.8.2013

Amant escapement, South Mimms, 26.8.2013

Here is the spring to which the pendulum is attached. On the right side, one can see the escapement wheel, whose teeth are flattened on one side. This allows them to pass by the rather thick pallets of the escapement:

Pendulum spring, South Mimms, 26.8.2013

The reduction gear for the hour hand is placed near the clock dial:

1:12 gears for minute and hour hands, South Mimms, 26.8.2013

Here are two pictures of the strike trains. At the back, one can see the air brakes necessary to control the striking.

Hour strike train, South Mimms, 26.8.2013

Half (or quarter?) hour strike train, South Mimms, 26.8.2013

The bells of the melody played are stroke by the teeth on this barrel—essentially, a small barrel organ, but with bells instead of pipes:

Bell striking barrel, South Mimms, 26.8.2013

But what had me totally confused was the missing count mechanism for the strikes. Essentially, there are two categories of striking mechanisms:
  • The older (at least 500 years old) count wheel strike trains use a single wheel that has stops after 1, then 2, then 3, etc., and finally 12 strikes. Such a "count wheel" can be seen on the picture of the old clockwork at Cardoso, and also below at St.Mary's in Oxford.
  • The more modern (less than 300 years old) rake strike trains use a toothed segment that falls against a spiral controlled by the hour wheel. A single or double toothed wheel pulls the segment back tooth by tooth, which produces the correct number of strikes. The new clockwork at Cardoso has such a strike train.
But however much I searched, I did not find one or the other mechanism in the clockwork at South Mimms. Granted, it was very dark inside, but a count wheel is usually quite large, and a rake is very easy to recognize, so I should have found one or the other.
Disappointed, I pushed my camera to the back side of the clockwork and made a last shot using the flash—and here it is: The clock does actually use a count wheel, but it is very small. On the left side of this wheel, one can see three small pins; and when one counts the teeth first between the upper and the middle pin, and then the middle and the lower pin, one finds that there are eight notches above vs. seven notches below. So this is actually a tiny count wheel! One can also see that it is driven by a "two-teethed wheel," whose teeth are actually also simple pins. Therefore, one revolution of its shaft will produce two strikes:

Count wheel, South Mimms, 26.8.2013

Finally, here is the plaque on the front of the clockwork, which tells us the installation date:

Plaque, South Mimms, 26.8.2013

A day later, we went to Oxford, where I visited the splendidly restored clock at St. Mary’s. Here is the tower—unfortunately, I forgot to take a picture of the clock dial:

St. Mary’s Clock Tower, Oxford, 27.8.2013

The clock is behind a glass cover which doubles as a board for a few general explanations. In contrast to the previous two clocks, this one has not been converted to electric winding—it must be manually wound, as at the time when it was installed!

Clockwork, St. Mary’s Clock Tower, Oxford, 27.8.2013

Clockwork, St. Mary’s Clock Tower, Oxford, 27.8.2013

Because of the glass housing, the clockwork is a little difficult to photograph. Still, here are a few pictures of important parts.

The Amant escapement is similiar to the one in South Mimms:

Amant escapement, St. Mary’s Clock Tower, Oxford, 27.8.2013

Amant escapement, St. Mary’s Clock Tower, Oxford, 27.8.2013

The hour strikes are controlled by a typical large count wheel with inside teeth. This count wheel design is at least 400 years old—it can for example be seen in the picture of the old clockwork in Cardoso (see links above). A part of the count wheel can be seen in the following picture. The other wheel is coupled with a ratchet (the corresponding saw-toothed wheel can also be seen) attached to the barrel holding the rope:

Hour strike train with count wheel, St. Mary’s Clock Tower, Oxford, 27.8.2013

The quarter-chime train can be seen here—one can recognize the chime barrel with the teeth that move the levers on the right that lead to the bells; and the count wheel with the trapezoid cuts:

Quarter-chime train, St. Mary’s Clock Tower, Oxford, 27.8.2013

In the following picture, one can see the drive train of the air brake of the quarter-chime train. One of the blades of the brake can be seen standing vertically near the wall:

Quarter-chime train, St. Mary’s Clock Tower, Oxford, 27.8.2013

That's all from this year's turret clocks!

Sunday, November 17, 2013

Nene Valley Railway - signals, rodding, tracks

Deutsche Version dieses Postings

After I had inspected that ground frame (and Joel had screwed tight the cover of the locking bed), I went around the station a little bit. Here are somewhat random pictures from Nene Valley Railway's Wansford station.

Hand points, Wansford (NVR), 22.8.2013

Here are a few demonstration pieces of rail fastenings, but also a joint connecting two different types of rail:

Old chairs for light rails, Wansford (NVR), 22.8.2013

Even older rail chairs, Wansford (NVR), 22.8.2013

Old rail chair, Wansford (NVR), 22.8.2013

Going from chair (bullhead) rail to vignoles (flat-bottom) rail, Wansford (NVR), 22.8.2013

The inner starters towards Peterborough are somersault signals—I did not wait for any of them to be cleared:

Somersault signals and signal box, Wansford (NVR), 22.8.2013

Cranks at signal bridge, Wansford (NVR), 22.8.2013

Somersault stop signal, Wansford (NVR), 22.8.2013

Somersault shunt signal, Wansford (NVR), 22.8.2013

Somersault signals, Wansford (NVR), 22.8.2013

The gates of the level crossing need locks—here is the rodding of one of them:

Gate lock, Wansford (NVR), 22.8.2013

And here is a sequence of pictures showing various signal-related parts between the signal box and the advanced starter towards Peterborough:

Wires and point rodding, Wansford (NVR), 22.8.2013

Signal wire deflection wheels, Wansford (NVR), 22.8.2013

Signal wire deflection wheels, Wansford (NVR), 22.8.2013

Point and gate rodding, Wansford (NVR), 22.8.2013

The brick base of the signal box is not rectangular, but has one corner cut off at the side where a small river flows:

Signal box and station, Wansford (NVR), 22.8.2013

Signal box, Wansford (NVR), 22.8.2013

Here are the signal wires and the point (or gate?) rodding leaving the signal box:

Wires and rodding leaving signal box, Wansford (NVR), 22.8.2013

On the line to Peterborough, one encounters at first points no.26, where the loop track diverges from the main track. Because trains travel over these points in facing direction, they are heavily interlocked: Not only is there a facing point lock (which, when not engaged, does not allow the home signal levers to be pulled in the interlocking frame), but additionally the lie of the point blades is checked directly by the signal wires:

Wire detector and facing point lock, Wansford (NVR), 22.8.2013

Wire detector and facing point lock, Wansford (NVR), 22.8.2013

A bit farther, the points to a storage track have been disconnected from the interlocking and are now clamped. The facing point lock is however still in place:

Disconnected facing point lock (left blade is clamped), Wansford (NVR), 22.8.2013

A bit farther, the rod between the two disconnected points is compensated for temperature changes with this horizontal compensator:

Horizontal compensator, Wansford (NVR), 22.8.2013

Usually, signal wires are deflected with wheels. The following wire leading to the down advance starter, however, uses a crank that is commonly used for rodding:

Using a crank instead of a wheel for signal wire deflection, Wansford (NVR), 22.8.2013

The storage area contains a few ground frames—this seems to be common with English heritage railways:

Four unused ground frames, Wansford (NVR), 22.8.2013

An operational and a non-operational shunt signal, Wansford (NVR), 22.8.2013

Finally here are the farthest signals I visited:

Inner home signals, Wansford (NVR), 22.8.2013

Down advance starter, Wansford (NVR), 22.8.2013

And that's all from the NVR!