West Somerset Railway General Discussion

Springs.

Breakage of springs will depend upon 3 basic factors: -

• Design of locomotive suspension.
• Quality of track, especially twist and dropped joints. The latter being a real spring killer.
• Quality of spring manufacture/repair.

On the WSR in the 1990's the PW gang did a tremendous amount of excellent work on establishing a good "line and top" to the PW, part of which was the eradication of dropped joints. As a result of this the loco dept managed to get the rate of spring failures down to 1 spring every 10,000 miles of locomotive operation, or about 5 springs a year. In the mid 2000's management of PW dept changed and PW maintenance followed practices applicable to national "Group Standards" where quite bad dropped joints are acceptable on lines operated at lower speeds. As a result spring failures started to rise again and loco dept had to find another way of partially overcoming the problem. In conjunction with 3 other railways we did some work with a spring manufacturer so that we could understand their manufacturing problems and they could better understand our application and operating problems. The outcome of this was a revised specification of manufacture which included; adoption of some more modern processes, better quality control, reduction of stress raisers. For our part we realised that trying to repair a spring was a waste of time/money, manufacture of an all new was more cost effective in service. Because of this we contained the problem but failure rate did rise to about 1 spring every 6,000 miles.

I do not know which spring had broken on 53809 but I would be surprised if it was a driving/coupled spring, more likely a pony or tender spring. 53808 throughout its 120,000 miles of operation on the WSR has only broken 2 driving/coupled springs as far as I can remember, but many pony and tender springs. This is probably due to the 4 driving axles being compensated suspension and being able to ride over the dropped joints easily without significant deflection of the spring. Pony springs were a particular problem so we redesigned the pony springing with new springs that supported the same load but with a softer rate of deflection, the individual leaves being less stressed in service. A side effect of being softer was that the spring was able to lower the axle box/wheel into a dropped joint without significantly reducing the vehicle load on the wheel. It had been the original design that if the axle box dropped about 1" in the horns the spring load reduced by about 80%.

Andy.

 

Hi Ian , I'm not disagreeing with you but is it possible to overload a tender with coal and water . I would have thought the cubic capacity would stop any overloading in weight , just thinking .

Paul . K

 

With water yes, but you could easily add an extra ton or so of coal just by "heaping it up" a bit - it'll be burned down soon enough anyway. There's also a variation depending on how full the boiler is: the difference in loco weight on a loco like a Manor is probably about a ton depending whether the boiler is at half glass or full.

The old railway companies had defined conditions of height of water in the glass, pressure (which is proxy for temperature and hence density of the water in the boiler), coal on the grate etc. in order to take weights in comparable conditions. Even so, taking weights seemed to be a bit of a fraught science. There's an interesting set of weights given by Langridge about the attempts to find a weight for the "Clan" pacifics. Crewe only had five weighing tables to weigh a six axle design, so could only do it by moving the loco back and forth, such that the whole loco wasn't being weighed simultaneously. The weights taken at Gorton were somewhat different. My experience on a heritage line is that you can only weigh one wheel at a time, which makes things even more difficult. Effectively you are just trying to make sure everything is within tolerance and in particular, that there isn't a big variation left and right on the same axle. (Even BR didn't necessarily get that to work: looking at the figures in Langridge of a sample weighing of 72001, there is 1/2ton difference between left and right leading driving wheel (right hand heavier) and the same again on the trailing driving wheels, but this time left hand heavier.

Tom

 

Out of curiosity how much water is in a boiler, it would be interesting to compare the ratio of water in the boiler to water in the tank/tender

 

Quoting Langridge again, he gives estimated weights for what became the Britannias - as such, these are maybe not quite what the final figures were, but would be broadly accurate for the purposes of comparison.

Water in boiler (cold, 1 inch in glass)*: 8t 3cwt 3q

Coal on grate: 1t 1cwt

To put that 8 tons of water in context, 5000 gallons of water in a large tender is a bit over 22 tons.

So to look at it another way, if in the course of a duty you completely emptied a tender, it would be equivalent to filling and completely evaporating the boiler water about three times over.

Obviously the figures for other engines will vary a bit: a Britannia is a relatively large engine.

(*) That's probably equivalent to the water somewhere over half full when at working pressure

Tom

 

Another approach to cure dropped joints is to eliminate them. Slightly controversial but if you replace bullhead with welded flat bottom the joints simply dont exist. Between stations no one on the train can see the difference and whilst the tum te tum has gone you end up not noticing. Keep the bullhead for public and station areas and you get the best of both worlds

 

Many thanks for that Jamessquared , I imagine from the horses mouth so to speak .I understand the designed weight limits but surely there is some in built tolerances for the occasions when the coal is heaped up . I did see a L.M.S educational film where they showed an express chasing through a country station with lumps of coal falling on the platform just missing a porter , with a warning in a crystal cut voice " that's what happens when you don't take care ".

 

I imagine also once the initial work is done the maintenance would be reduced hence freeing the PW guys to get on with other works .

 

You don't have to go for flat bottom rail as I understand it - you can weld joints in any track. When doing so, usual practice is to weld 1 or 3 out of every 3 joints to reduce the number of joints that need maintaining.

Steven

 

Indeed, there are tolerances. Tenders must be quite interesting vehicles to design, because they have to have suspension that can cope with a very large variation in weight through the course of a day's duty. For example, a 6,000 gallon / 5 ton three axle tender behind a Merchant Navy will have a variation in over 10 tons per axle between fully loaded and empty, but the springs have to be able to cope with that variation and still function correctly.

Quite so: ensuring that the coal is correctly trimmed is one of the listed duties of a fireman in the BR Black Book, and no doubt is included in the training given to loco crew on all heritage railways.

Tom

 

Thank you Steven , this is what happens when armchair railway persons start hypothesising .

 

Would you please explain your comment?

Yes you can weld bullhead, KESR were doing this in 80s on the Wittersham Rd - Northiam section.

The SVR are relaying sections out in the country with welded flat bottom so not a hypothetical issue

 

Jamessquared , I know on HGV lorries things aren't quite the same but to deal with the varying loads they have 2 sets of leaf springs . The rear axle sits on one set of springs , when the load increases and the chassis sinks with the weight then the second set of springs come into play .

 

Happily threelinkdave , I was inferring that I really don't know what I am talking about . Apologies if you thought anything else .

 

But we've just seen this thread at its best: exchanges that are interesting and informative (especially for laymen like myself). Keep it coming.

BK

 

Pleased to report 53809 returned to service this afternoon, hauling 1530 MD-BL.

 

I was concerned that threelinkdave might feel slighted by my comment , so will keep quiet about rails .

 

My understanding is that 53808 will now be out for a few days.
To answer Ann C-B's point, we normally have a "spare" loco available in the summer, so 3 in steam and one on washout for a total of 4 plus one extra, but this year it seem that we've had a spate of loco failures so that has created a little pressure. If we had springs for 44422 then we'd be fine (well hopefully) and be able to cope with the odd mechanical.
It is of great credit to the Minehead shed staff that when we arrived on shed yesterday with a failed injector on 7820 due to a blown gasket they were able to fix it during the turnaround time otherwise the loco would have been a failure for the afternoon working.

 

What is the current fleet? 6960, 44422, 53808 and 53809 plus 7820 - do I recall correctly that a second Manor will also be visiting?

Thanks

Steven

 

7822 Foxcote which is still at the K&ESR where it was failed in May .

" It was very soon discovered that the new valves were problematic, however this was attributed to them “bedding in”, however 7822 was failed completely on 13th May by KESR and officials from FMS. The valves were subsequently removed to show unprecedented wear and were transported back to Llangollen for assessment and ongoing attention, which is the subject of ongoing discussions between the Trustees of FMS and LR.
It is hoped that 7822 can return to action very soon after subsequent repairs (for and extended stay at KESR), followed by a further period of hire at West Somerset Railway."