jim.snowdon

Didcot to Oxford was a classic example of half-baked thinking. Fine for the passenger services, but strategically a dead end. What was really required, and may yet come to pass through the drive for decarbonisation, was electrification Basingstoke - Reading and Didcot - Coventry and/or Birminham. Southampton - Birmingham is a significant freight route and whilst it has gaps in it, the diesel fuelled 66s and 70s will rule the roost as operators do not want to waste time and effort swapping from diesel to electric traction and vice versa en route. Britain's railways are far behind the rest of Europe in electrification as a result of passenger dominated thinking.

Virtually all modern electric stock is capable of dual voltage operation, essentially because the control equipment operates on DC. The GWR's 387s are even equipped with shoegear, normally strapped up, and did some of their early testing on the Brighton Line. The problem is not engineering the AC/DC changeover, but managing the differences between an AC system that has earthed running rails and a DC system where the rails are intentionally not earthed, as well as the issues affecting the signalling equipment, although that problem is disappearing with the general adoption of axle counters in place of track circuits.

Correct, as far as the negative rail bonding is concerned, but the Watford DC Lines are still only 650V on account of the limitations of 1972 tube stock, which cannot cope with 750V (and was never designed to, unlike some later LU stocks).

The notes with the original picture state blue, with yellow gangway covers, although they appear to be absolutely filthy.

Looking for other dmu related matters turned up this example via wikipedia - taken in 1967 by Hugh Llewelyn - a class 128 parcels unit plus an ex-116 DMS converted for parcels use with three GUVs in tow on the way in to Paddington.

Back in the late 1980s, the LURS, by way of the late Bob Greenaway, with some assistance from myself, saved considerable quantities of working drawings for the pre-war stocks from the drawing office archive when it was cleared out. The museum had first pick, but they were generally only interested in the large GA drawings and not the detail stuff that is often more useful. Where this collection now resides I don't know, but it might be worth asking.

True, but I wonder if there were greater plans for 'main line' dmus that never came to fruition. Were the 126, then 123 and 124 fleets the start of a wider plan for the conversion of longer distance main line services to multiple unit operation, a change that eventually happened with the HST fleet and the later Voyager fleets. The 124s, as the last of the first generation dmus were a whole step ahead of anything that had gone before, bar the 123 sets , being designed to be flexible in their makeup, all the way to 12 car trains.

The 123 and 124 sets did have retractable buffers and pullman gangways within the sets - https://www.rmweb.co.uk/topic/129641-class-124-dmu-trans-pennine-bogies-4mm-source/ , unlike the later EMU sets for the Southern Region.

The important part is that those Inter-City units, ie the 124 & 126 sets, were built on the premise that they were full train sets - they would not be run in multiple with another complete set so the drawgear at the outer ends was provided only for shunting, dead movements and recoveries. The oddity was providing buckeyes on the outer ends of the 124s, but that may have been considered as a convenience when moving odd vehicles around in the depots given that the rest of the vehicles in the sets were buckeye coupled. In the end, they lost them, so it can't have been that much of a convenience.

Remember, the Metropolitan was not part of the Yerkes Underground Electric Railways empire. It was thoroughly independent, with its own works and design offices at Neasden. The miniature (half-size) buckeye came in with the 1904 electric stock and they stuck with it for all electric stock except the the 1931 MV stock and the sets made up from converted Bogie stock. Even the 1922 electric locomotives had facilities for carrying the buckeye couplers, although there is no record of their having actually been fitted. Standardisation only arrived with the adoption of the Wedgelock coupler by London Underground for all new stock after the 1935 tube stock, except for the Q38 stock, which had Ward couplers in order to work with the rest of the Q stock family.

Until it meets a curve. Been there, done that and had to fetch a locomotive to shift it, and it was an empty bogie wagon with roller bearings.

It can be interpreted both ways. Compared to coal wagons, there were not many of these wagons, but there were quite a modest number of owners. And either way, pictures of them in use are about as common as hen's teeth, if that much.

Agreed, but that is just one picture and we don't know what happened next. Quicklime is not only stuff that you want to keep dry, but kept away from people, especially those not directly involved. There was a reason for all those peak roofed lime wagons, but a chronic lack of evidence as to how they were used. The same is true of the covered salt wagons and it is purely by chance that I discovered a piece of cine footage that showed some with the doors open that confirmed that they carried bagged salt. Our problem is that freight operations and the movement of goods on the railways was so much less interesting to photographers than the thing at the front of the train. As a ps., quicklime can come in two forms - in lumps, which is as it comes out of the kiln, and as powdered or ground form. The former is relatively innocuous, in as much as it probably isn't that dusty, but you wouldn't want to handle it with bare hands. You still don't want to get it wet. As a powder, it is obviously rather more hazardous, but is easier to handle in bagged form.

The difficulty with a thread like this is defining what is meant by 'lime'. There's limestone - calcium carbonate - which is used for all manner of purposes, ranging from construction, through iron smelting to agriculture, where its prime purpose is as a means of improving acid soils by raising the pH value. Limestone is pretty inert, so can be transported loose, in bulk, with no real need for protection. Then, there is Slaked Lime - calcium hydroxide - which is used for such purposes as making lime mortar, papermaking, agriculture (where it is more effective than Calcium Carbonate). Again, it is relatively inert, and can be transported in bulk with no real requirements for protection, although as an aqueous solution it can cause chemical burns, being quite alkaline. Lastly, there is Quicklime - Calcium Oxide - made by heating limestone in a kiln. This is not nice stuff and has to be kept dry, or it will convert into Calcium Hydroxide, generating a lot of heat in the process. Deduction would suggest that it was for the carriage of quicklime, presumably in bagged form, that the various peak-roofed lime wagons were built. Apart from its use in making lime mortar (once slaked), quicklime is also used in the steel making process for removing Silicon, Aluminium and Iron oxides as slag.

My understanding of the early application of knuckle couplers by the Southern to some of the 3-SUB units is that they were fitted without buffing plates, in the same way as they are fitted to US freight cars. The problem was that they were susceptible to becoming disengaged due to vertical motion in traffic. Assuming that they were the same 3/4 scale version of the AAR coupler that everyone else, bar the Metropolitan, used in Britain, the smaller vertical depth of the coupler would not help in this regard. (The Metropolitan used a 1/2 size version.) As far as I am aware, those 3-SUBs and the 1938 LMS Wirral line stock were the only occasions in pre-1970s era British practice when these couplers were not used with a buffing plate. The relevance of that is that the friction between the buffing plates provides a degree of coupling between the adjoining vehicles, reducing the relative motion between them. BR successfully introduced buckeye couplers with low height buffing plates with the 1951 EPB stock on the Southern. The need for buffing plates with knuckle couplers only finally disppeared with the arrival of the Tightlock coupler, which is locked vertically once coupled, not least because it is a proper autocoupler.

Something that has long puzzled me is why the Southern, having adopted Buckeye couplers and Pullman gangways for its locomotive hauled stock reverted to side buffers and screw couplings on its electric stock, particularly the through gangwayed stock built for the Portsmouth electrification (the 4CORs etc).

And by the Metropolitan Railway, who used them on all of their electric stock, with a few exceptions, starting in 1904.

Signal bounce is down to a combination of how fast the pull on the wire is released, ie how hard the signal arm hits its end stop, and how flexible the signal post is. The faster the arm is allowed to return to its on position dictates how much kinetic energy it has when it hits its end stop. That energy has to go somewhere (see Newton's laws on the conservation of momentum, etc), and the only place for it to go is in bending the post (as the least stiff part of the whole signal structure/mounting). The post is elastic and behaves like a spring, so as it recovers it passes the energy back to the arm, which then bounces away from its end stop. Gravity then repeats the whole process. Bounce on timber posts will generally be less than on steel posts, as the timber also damps out the motion.

A fascinating thread, all six pages of it. A few additional snippets - - The Metropolitan Railway had a fleet of 18 cattle wagons, 12 of which were built to the essentially standard length of 18', and 6 that were 22' long (over headstocks) that had been converted from redundant rail wagons. That probably made them the largest cattle wagons ever used on British railways, and they came with partitions that could be set in one of four positions - S, M, L & XL? They were all built in the era when the use of lime wash was normal, but unlike any others that I have come across, the Met painted the lower parts of the outsides white, I guess so that the inevitable spillage of the lime wash didn't look so untidy. - related to the use of screw couplings on cattle wagons, whether fitted or not, was a Board of Trade requirement that loaded livestock wagons should always be marshalled next to the engine so as to minimise the longitudinal shocks encountered in transit. Screw couplings obviously allowed the buffers to be drawn up tight. - my understanding is that wagons conveying horses were, in accordance with BoT regulations, sheeted so as not to cause the animals distress. That went out the window to an extent during the First War, when the needs of the considerable horse traffic required for the Army in France caused, at least on the Great Western, high sided goods wagons to be used for this traffic. Rings were added to their outsides so that the animals could be tethered, but that was about it.

It is not uncommon to see reports of AC electric trains routed into sections that have been blocked to electric traction due to being isolated. The question I always ask when one of these is how the signaller is supposed to know whether the train description on his panel is electric or not, especially in these days of not only bi-mode stock but operators who diagram both electric and diesel units on the same services on different days. It's very rare in DC areas, but then anything with a train description that isn't 1, 2 or 5 is almost certainly not going to be electric.

The most significant part of the SNCF electrification was not the voltage, but the frequency. Until the mercury arc rectifier had been made robust and reliable enough to function on a moving vehicle and thus enable the use of DC traction motors AC electrification had been limited to low frequencies - 16 2/3Hz in Europe and 25 Hz in the USA. These are low enough to allow series motors to be used on AC without the eddy current and inductive losses reaching intolerable levels. Those low frequencies are still the norm in the Germanic countries and Sweden, and bring with them the need to create a separate high voltage grid network just for the railways, with the attendant cost and complication of low frequency generation and/or frequency converters. The significance of the French project was in taking power directly from the national 50Hz supply without the complications of frequency changing or parallel low frequency supply networks. Raising the voltage from the Germanic 15kV to 25kV simply reduced the weight of the catenary system and increased the distance between supply points. Apart from reducing the number of costly supply points, this makes it easier to find places to tap into the national grid at high voltages - Network Rail currently takes in supplies from the 400kV grid network where it can as this not only provides a higher level of power security but minimises the unbalancing effects of large and fluctuating single phase loads on the three-phase power supply network. Equally, having longer electrical sections increases the number of trains in section and flattens out the power demand simply through the law of averages.

Even now, there is an unhealthy element of 'not invented here' about Britain's railways and their engineering.

Exactly as was done when the up lines slipped at Berrylands back in the 1970s.

No one can ever say that what you have modelled is wrong, as the fitting of such modifications was undertaken on an 'as available' basis, usually determined by such random factors as when it was shopped for mechanical or boiler condition. Railway companies did not ordain that a particular modification was to be undertaken on locomotives x, y and z, only that a specified number of locomotives of a particular class were to be modified, possibly with a caveat as to expected remaining life.

Supposedly as an anti-trespass measure, but as the graffiti amply illustrates, about as much use as a chocolate fireguard in preventing trespass by those determined to gain access to the track. If anything, an incentive for them to do so by making it more of a challenge to be conquered.