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jim.snowdon

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  1. Which is why on engineering drawings all dimensions are sometimes quoted in millimetres, even though numerically they may run to six digits. No decimal point is required, anything finer than 1mm being lost in the tolerances. Jim
  2. Although I am sure they were found other purposes, as far as I am aware the only purpose that the holes (whether three, four or more) served was to reduce the weight of the wheels. That said, it remains a puzzle that the 3' 7" wheels used on coaching stock, NPCS and locomotives only had two very small holes, presumably for lifting eyes to be attached. Jim
  3. But LMS/Ivatt experiments, and although BR did build some standard locos with Caprotti valvegear, they came quite a bit later in the whole process, BR having chosen straightforward Walschaerts gear as standard. Jim
  4. It boils down to how far had it run, which translates into tread and flange wear. Wheelsets would be slated for turning if they had exceeded the limits for hollow wear of the tread, flange depth and flange angle. In the pre-modern era, wheels were a standard profile, agreed between the railways and the RCH, that eventually became what we now know as the BR P1 profile. Failing the go/no-go gauges for the tread and flange meant that the wheelset had to come out for turning, and would be replaced by whatever was available. Whether it was three-hole, split spoke or solid spoke mattered not so long
  5. A typical arrangement on a proper tramway (Metrolink is a bit of a hybrid) would be for only the incoming facing point (which selects where the tram goes) to be motorised. The remaining three would be simply spring points as the routes out of the platforms are all unique. Correct, and when I was talking to audiences about the signalling on Croydon Tramlink, I would usually introduce the subject by saying that there is only one safety-critical element, the driver. Everything else is line of sight. Metrolink is a bit of a hybrid as it is line of sight operation in the
  6. There were. They aren't common, but there are photographs. Volume 3 of Bill Hudson's private Owner Wagons has one belonging to Abbot's of Birmingham (plate 67) and I have a feeling that there is another one buried somewhere in the four volumes (not least as I modelled on in 7mm scale). Apart from the fixed coke raves, they look a little odd because the extra foot is in the centre section, so the door has a wider than usual gap between it and the washer plates for the middle body knees. It is also worth remembering that these drawings are not so much authorised designs to be followe
  7. Yes, but they would be coke wagons (of the non-convertible type). The 1923 issue RCH drawings include both 16' 6" and 17' 6" underframes because, apart from the coke wagons, they also cover merchandise wagons, and then there are the other underframes for the 20T wagons and the tank wagons. I have a nearly complete set of the RCH drawings in scanned form dating back to the 1907 series and a few from the 1904 set (which are mostly tank wagons). Individual drawings are emailable if required. Jim
  8. A similar practice was common on the Southern Railway/Region for the simple reason that it reduced the number of lever movements that had to be made when setting routes through double junctions, particularly those with a high number of trains using each route, as could be comon in the London area. With the 'up' and 'down' points set normal in opposing directions, only one of them needed to be moved for any movement. Jim
  9. They were also used on daytime London (Euston) - Edinburgh (Waverley) services around this time. Jim
  10. The issues with their ride would have been a consequence of the bogie and suspension design, not the design of the underframe. As it is, I have a strong suspicion that the bodies, which were all steel, were substantially integral with the bodies, in which case they could not have simply been changed. Doing something about the bogies was probably feasible, but uneconomic. Jim
  11. The entire underframe on the BR vans was full of concrete from one end to the other, although there may have been a bit extra at the ends. The same is true of most other railway's goods brake vans, although frequently the added weight was in the form of iron scrap and swarf from machining. I have seen it said that the riding qualities of the Southern Railway vans were not exactly ideal at higher speeds (hence the birth of their bogie brake vans). Something else to bear in mind is that the mechanics of what made rolling stock ride well were only barely understood back then, even more so when th
  12. I believe one of their redeeming features for such use was the size of the verandahs - you could stow quite a lot of equipment there in without it getting in the way. The same was also true for the ex-GW vans. Jim
  13. It appears to be a standard BR 20T brake. It isn't an SR 25T van, nor any of the SECR pattern vans, nor can it be any of the LMS or GW types, not least as it has end platforms. Jim
  14. Referring to Volume 4 of An Illustrated History of Southern Wagons, the clue lies in their official Southern Railway designation of 'Bogie goods brake vans, express service'. They were created in the early 1930s specifically to work with the Southern's fast fitted goods trains, for which the standard 4-wheeled vans were not considered suitable, partly due to their riding qualities at high speeds and partly due to the perceived difficulties of fitting vacuum brake equipment to them. Whether any turned up on the Southern's ballast trains from Meldon has to be a moot point. The bogie hopper wagon
  15. It only seems fair to point out that the Royal Scots were designed by North British rather than Derby. Jim
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