Discussion in 'Railway Operations M.I.C' started by Eightpot, Jun 4, 2012.
Thanks, I thought that was the case.
Buckeye fitted vehicles, as generally used by the LNER, SR & BR for corridor vehicles, had 'Pullman' gangways, which had a buffing face and came together when coupled. The LMS and, I think, the GWR used British Standard gangways, which needed to be brought together and connected. I also think that the first generation DMU's, which had conventional buffers and screw-coupled drawgear, also had British Standard gangways.
The old BR General Appendix required the gangways to be locked out of use if the emergency screw coupling was used but not on ex LNER vehicles for some reason that I'm not too clear about. The LNER vehicles had a different form of emergency screw coupling, though.
With regard to Instanter couplings, the General Appendix allowed one Instanter fitted vehicle to be attached to passenger trains, provided that an adjacent vehicle screw coupling was used wherever possible.
Thinking in terms of ex BR Mk. i coaches, in the event of a 'Buckeye' coupling failure and the emergency screw coupling used surely this means that the buffers would have to be extended also and the accompanying 'saddles' fitted on. In this condition wouldn't the coaches actually be further apart resulting in a gap between the corridor connections, which would presumably mean that the end doors would have to be locked?
Since posting the above I have been able to physically check and the result is that there would be about a 6" gap between the corridor connections.
Just resurrecting this thread, I have spotted a very recent video of a heritage railway using an instanter dropped over both the loco hook and the coach hook to couple a loco to a service passenger train. Bet that gives an interesting ride unless handled very carefully!
I am new to this forum but have been guard on two heritage railways. I cant believe a heritage railway would use an instanter on coaching stock unless they had no other choice. As has been alluded to instanters even when short leave a gap between the buffers. Screw couplings hold the buffers together but you can occasionaly get snaches. I hate to think what the ride would be like, especially on starting. Those of us who have worked unfitted freight know all about snaches at starting.0 to 5 to 10 mph in the length of a three link chain for the guard.
There was a query why LNER stock does not need doors locking. The answer is that LNER emergency couplings are shorter allowing the ganways to meet
The reasons are many, firstly, a buckeye or Screw shackle will remain tight so the whole train starts away as a block, where as an instsanter has a certain amount of slack, so upon starting, there can be a huge amount of backlash in the coupling, on goods trains this is controlled by the guard using the handbrake on the van to assist with controlling the train, and therefore the instanter should remain tight.
Secondly, as an instanter cannot be fully tightened, and if both vehicles have long buffers you won't even get the instanter into the short position, it is a lot easier for the couplings to part, which is why instanter and three links can be uncoupled with a shunting pole.
As Threelink Dave pointed out, the reason ex-LNER stock can run with the Emergency shackle in use and the corridors open, is because the emergency shackle has got a shorter link on one end so the coupling can be tightened sufficient that the corridor ends come together.
My understanding is that Buckeyes were used where possible because in the case of high-speed derailments they tended to keep coaches in line and upright, which drastically increased the odds of survival. However, it's still good practice in preservation because there is far less snatching with buckeye couplings than screw couplings.
I was always taught that after Buckeye couplings, it was screw, then instanter, then three-link. This is partly to ensure a smoother ride, although couplings are more likely to break when snatching occurs - so the tighter the coupling, the less snatching and the less likely that a coupling will fail.
If an emergency shackle is being used, I would always lock off the internal corridor end doors, because the gangways may separate enough for unwary passengers to trap fingers or similar - although I'm not sure it's in the rule book. Whether the guard could still gain access would of course depend on whether you locked them with the French Pin/bolt as well. However, access isn't a big problem - we run suburban coaches and don't worry about it with those - in the event of a fire, once the train had stopped I suspect people wouldn't wait for the guard to appear before getting off the train!
I was always told that a true emergency screw coupling is easily recognisable because the links are both the same length (on a normal coupling one end will be secured behind the drawhook and therefore necessarily longer). However, many railways will use any screw coupling as an emergency coupling (especially for shunting), so that may not always be true.
Hope this helps
You cannot use a screw coupling on a vehicle fitted with Alliance couplers because they are incompatible.
Dont know where you got your info from. The UK buckeye is a drop head version hung from a standard draw hook. . To couple buckeye to buckeye the head is lifted and buffers shortened. To couple to a screw fitted loco head down and buffers extended by use of the saddles. see the pics
Quoted from British Railways General Appendix To Working Timetable BR 29944 June 1981
"Coupling and uncoupling of vehicles "
3.1 "Vehicles fitted with instanter couplings may be attached to trains conveying passengers provided they are separated by screw - coupled vehicles and the screw couplings of the adjacent vehicles are used."
You are confusing Buckeyes used on Pullman gangways in your photograph with "Alliance" Buckeyes that are used on class 253/254 trains. The latter are not drop head and have no side buffers.
Quoted from British Railways General Appendix To Working Timetable BR 29944 June 1981
When a vehicle fitted with a BR screw coupling is to be coupled to a vehicle with an instanter coupling, the screw coupling must be used. This instruction does not apply to class 9 trains (unfitted) on which any coupling may be used, provided that when an instanter coupling is used, it is placed in the LONG position."
What you say is quite correct.
I believe "Alliance" simply refers to the foundry in the US which originally made them so has nothing to do with class 253/254 per se.
I agree that there are a number of multiple units which dont have side buffers 4CEP /BEP 4CIG/BIG 4VEP and those you mention which dont have side buffers on intermediate vehicles. The couplers are however compatible, at least for emergency purposes. So if you need to tow a HST spare coach around you can use loco hauled stock as barier vehicles.
The only reason you would put buckeye conected vehicles together with a screw is because the buckeye had failed in service.. You would not go into service in that condition, at least not on a well run railway
No argument there, I was just quoting from the general appendix which uses the name "Alliance" to differentiate between the fixed and the drop head coupler.
With reference to the point about the buffers being in the long position so the corridor ends not being together, this is not entirely true, Our Gresley brake van (and I presume others as well) has two emergency couplings, one standard one, for coupling to screw coupled vehicles and one with a short link, to couple two buckeyed vehicles allowing the buffers to remain in the short position and bring the gangway ends together.
I have noticed that some of the ballast trains I see around Westbury are air braked but have instanter couplings. I had thought they would have been screw coupled with buffers together I can only guess it is so that the loco can "pick up" the train gradually.
There are a suprisingly high number of freight and balast vehicles which are air braked and instanter fitted. Whilst now being disposed all the HAA coal wagons were instanter fitted. Will have to make a mental notr to self to document those I see
As regards picking up the train gradually, did you see the RAIB report a few years back of a train divided near St Pancras? Part of the reason was given as the front of train being instanter fitted 51 tonne wagons moving off gradually , then the jerk as the rear portion of 102tonne screw coupled wagons tried to move all in one lump.
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