david.hill64

Great photo. What sort of tender is that, and what colour is it?

Roger Ford has an interesting analysis showing that cost cutting cannot restore railway finances, you have to go for revenue growth. Long distance leisure travel has more than recovered post Covid - only commuting is in the doldrums. Yet DfT seems to be hell bent on making life uncomfortable for passengers. Short formations, poorer onboard services. They may yet be the death of rail.

Thank you. So essentially the object controller is divorced from the interlocking module. I think I probably knew that at one time but it's over 20 years since I was involved with main line practice. But I do remember now reference to track side modules. More recently on all of the MRT signalling projects that I have been involved with, there are a number of solid state interlocking centres spread around the system, located within 1km of the objects they control. Because MRT stations are close together it is convenient to do it this way. Edit to make clear that the interlockings are modern!

I am not disputing this as I don't have recent experience on main line signalling, but on metros it is usual to have a single central control centre (usually with a separately located back-up which may or may not be a hot standby). The interlockings though are distributed, mostly because there is a practical limit to the length of cabling between a switch machine and its object controller, which is part of the interlocking. If the cable is too long the voltage drop is such that the current needed to throw the switch is likely to fry the controller. I would be interested to understand how this problem is overcome on main lines especially as we move to fewer larger control centres. On the systems I dealt with the cycle time of an interlocking controller was just over half a second, so it would take over a second from receiving a command to acting on it and then sending proof back that the command had been successfully implemented.

Mike, Are you sure that was the conclusion? The issue with 14X and 15X not activating track circuits is usually ascribed to the superior wheel-rail interaction characteristics of these vehicles compared to the DMU's they replaced. The later designs lost much less energy at the wheel-rail interface than the older designs: hence lower wheel wear/ lower rail wear and better ride. The downside is that if you are not scrubbing the muck off the rail head you run the risk of not shunting the track circuits as the resistance is too high. David

You're absolutely right: nothing like Hunslet!

When TPWS was being introduced the ROSCOs were eager that this should be seen as a Network change as it would mean that Railtrack would have to pickup the bill for T&RS as well as infrastructure. Railtrack argued that with such schemes 'costs shall lie where they fall'. Good to see that Network Rail have agreed that ETCS is a Network change and are funding trial fitments on things with grandfather rights.

So no chance of the Middleton's engine being used to shunt the yard as occasionally happened...........

In the late 70's the Middleton Railway in Leeds decided that crew competence needed to be assessed by an outside agent, so arranged one weekend for a Holbeck traction inspector to assess all of the drivers. The loco assigned for duty that day was the Borrows well tank which had a number of idiosyncrasies and was left hand drive unlike the rest of the steam fleet at that time. I had never driven it before and passed comment to that effect when I got into the cab. 'Doesn't matter, son, they're all the same' was the reply! (I passed). I remember an example of one of the first arrivals of a pair of 20's in Gloucester in the very early 70's. They had arrived from the north and were immediately sent back. Unfortunately the crew didn't know the road quite as well as they thought and misread a main line signal as applying to them in the loop adjacent to the site of Barnwood shed. A pair of 20's light engine then proceeded to demolish the buffer stops at the end of the trap siding and finish, IIRC, at least an engine and a half length past the stops, wheel deep in ballast and halfway down the embankment. I think my first sight of a 20 in Gloucester.

The only issue I have with it is can the countries afford their new infrastructure? As you say the biggest beneficiary will be China and they get others to pay for it.

Not on the same scale, but in the mid-60's Gloucester used to gain a surplus of locos from the north. It was usual on Sundays to see convoys of light engines - 4 or 5 at a time - steaming back to Birmingham.

True I think for SR stock, but unless things have changed it wasn't true for class 313. When I was at Eversholt we wanted to fit a bus cable to these to overcome some of the problems with gapping on the North London Lines, but couldn't get the safety case approved at the time. Something to do with the problems with old DC track circuits on AC lines IIRC. David

The Wiki entry on Railway Air Brakes has a reasonable explanation of the workings of the Triple Valve. David

Further to The Stationmaster's explanation about driving with the vacuum brake, the other reason for adopting this style for traditional stock with cast iron brake blocks acting on the wheels is that the friction coefficient between then iron block and the wheel rises rapidly as speed drops to zero. Although the force acting on the block is constant, the braking force will rise rapidly. This results in a significant jerk as the train stops, likely sufficient to cause problems for standing passengers. Stopping on a 'rising brake' overcomes this problem.

A couple of points to add: In respect of question 2: Trains that were fitted with a vacuum brake were able to have the brake application continually variable between off, full service and back to off. Early adaptations of the air brake relied on something called the triple valve to control the supply of air pressure to the brake cylinders from the reservoir on every vehicle. It is an essential characteristic of the triple valve that although you can demand increasing levels of brake application, once applied you must make a full release before reapplying. On more modern applications the triple valve has been replaced by a distributor. The distributor is fully proportional on both application and release. Moreover, on passenger stock it is linked to a load weighing valve in the suspension which then adjusts the brake cylinder air pressure according to both demand and vehicle weight. This keeps the brake force on every vehicle in a train the same to prevent longitudinal dynamic shocks. In respect of question 1: The vacuum brake is relatively slow to act. If you consider activities like coupling up to a train, having more precise control of the brakes is obviously desirable, even if early engines often lacked loco brakes. A direct steam brake is much quicker acting. On air braked locos, including steam locos, a direct air brake provides a relatively lightweight controllable option. Many years ago I had a cab ride on a Taiwan Railways loco hauled passenger train where triple valves were in use on the vehicles. On making a train brake application, the driver immediately dumped the brake on the loco and then as the train came to a halt applied the direct air brake. This caused the stock to gently buffer up to the loco, so that on starting the engine had the advantage of getting the first vehicles rolling before taking the whole train weight.

Alstom has developed the AGV - a distributed power TGV - complete with articulated bogies, but as far as I know the only customer has been in Italy. They are reported to be working on a double deck variant. SNCF of course partly own the design rights to the TGV having paid for its development prior to the EU banning such nonsense and there might still be commercial advantages to SNCF in maintaining the procurement of traditional TGV designs. Or of course it is entirely possible that SNCF will understand, as BR did, that if you want an intercity train longer than about 5 coaches, you are much better off with power car(s) and trailers..........

Ken, We now pack threaded crankpin bushes with these kits to help overcome the clearance issues. Regards David

Traction return currents in electrified areas pass along rails and will seek the path of least resistance. If this happens to be from one rail to another via the wheelset and bogie frame of a passing DMU it will do so. Fitting brushes to prevent electrical damage to bearings is good practice.

Two issues here: First: there are no applicable standards relating to Stress Corrosion Cracking in rail vehicles. I expect one will be developed. Second: there is a Technical Standard for Interoperability and supporting Euronorms relating to fatigue loading of rolling stock components. These standards are mandatory and it is illegal (at least until, and if, the relevant EU legislation is removed from UK law) to specify any stricter (or more lax) requirement. Unfortunately it appears that vehicles running on UK track are likely to experience higher loadings than the standard mandates. When assessing vehicle compliance, the Notified Body responsible for certification can only confirm compliance with the standard. Having said that, Hitachi were provided with sufficient information on track geometry for them to have worked out that mere compliance with the standard was likely to be insufficient to prevent fatigue. They could have designed according to the likely actual loads and then submitted for assessment evidence that the vehicles complied with the standard.

Not quite. Alloys are combinations of metals which form a common crystal structure. The structure forms on solidification by grains growing from nuclei in the melt. Eventually these grains meet up so there is a boundary between grains of different orientation. The grains themselves have similar chemical composition and do not act as electrolytic cells in the same way as you get, for example by mixing aluminium and steel components in the same vehicle. The grain boundaries are a source of weakness in the alloys and in certain materials (eg aluminium alloys) are prone to rupture in the presence of a corrosive medium and stress. Metallurgists make a lot of effort to negate the effects of the grain boundaries and various mechanical working, heat treatments and added elements can be effective at improving strength depending on the base alloy. In certain critical applications - eg aero engines - parts are grown as a single crystal to ensure that there are no grain boundary effects.

Also check for photos of BRR stock: several of these vehicles were used to make up brake force in test trains after they were displaced from the E-G services.

Agreed, but you might want to add noise mitigation. You will remember Roger Gawthorpe - head of aerodynamics at BRR- who once told me that one term in the equation for noise generation was raised to the ninth power of velocity and above 200mph it becomes significant. The other issue is of course maintenance, especially of the OHL and energy consumption.

I am sure that I read that there was also a demarcation problem: electrical equipment could not be serviced by mechanical fitters. I wonder how many steam sheds had a large contingent of electrical fitters?

Ken, Take care with the smokebox. The wrapper is just the right size and if the smokebox is formed larger than it need be, the wrapper will be a bit short. I have had customers caught out by this. Dave

We have decided that the range of GWR centenary coaches and super saloons is not a good fit with the rest of our range and we are seeking to sell these on to another supplier. If these are not bought we will take orders for a final run of kits to be produced early 2022. Please let us know if you either want to acquire the range or wish to reserve for the final run. Thank you. David railwaycitytrains@btinternet.com