U class Versus N class 2-6-0,what's the difference?

There's a copy of the sectional appendix for the Ilfracombe line in Nicholas and Reeve that gives (in BR days):

Braunton to Mortehoe & Woolacombe (which was about 3 miles of 1 in 40)
- U class = 150 tons
- N class = 200 tons

Ilfracombe to Mortehoe & Woolacombe (which was a bit over 2 miles of 1 in 36)
- U class = 150 tons
- N class = 150 tons

I'll leave @Steve to work out the equivalents on the NYMR! Those gradients were long enough that they put a premium on both tractive effort (to start a train) and sustained steaming rate (to keep it moving). I think it was fairly rare for trains to get much above 15mph anywhere on the run from Ilfracombe to Mortehoe; the allowance was I think 11 minutes.

Tom

 

to complete the picture, here's an Irish version.

 

Steve - I was fireman on 31806's first train on the Moors andwhat an interesting trip it was. We took 7 LNER teaks loading to about 240 tons. With an unknown engine and a cold start we tried to keep the water up at the expense of steam. On the approach to Bridge 30 we were down to 125lbs and things looked pretty grim, but with enough water in the boiler we knocked off the feed and she started to rally. There is a video on You Tube (by acw71000 I think) of us plodding round the Darnholme curve which shows just how close we were to not making it. But by this time we were back to 145 lbs and I put the feed back on just after the up distant by which time we were back to 165lbs. All credit to Dave Jackson who managed to keep her going. We were clearly on the limit of the boiler capacity for the work we were doing, but it recovered impressively once the demand was reduced. We took 7 Mk 1s up on the second trip and did somewhat better. It was still a plod but never got below 145 lbs this time. The engine was now warmed up and was fired by Jack, the Swanage fireman who had joined us at Pickering. It was one of those days that was educational - you could say character building - to say the least. And that is what makes this lark so much fun!

On the issue of load limits 240 tons was the U/U1 class limit on the S&D between Bath and Evercreech Jc. Trials were carried out with both types in 1954 but not deemed a success, probably for the same reason as discussed in this thread.

 

I agree that seven is overload and six would be much better Depending on your point of view, the NYMR overloads most locos. Limit for a Black 5/B1 unassisted in BR days was five. However, the timings were quicker in those days.

 

I was on that first run - it certainly seemed a bit hairy from the front coach!

Acw71000's video is the run in question starts at 12 minutes.

 

So was I. Never mind 1 in 49, its actually 1 in 42/3 on that curve.

 

Saved by the brake ejector eh Peter?

 

Thanks for that - very interesting. Everything I've ever been on from Ashford has been pretty free-steaming, and the U boat is no exception as you found by how it recovered, but even a free-steaming engine is eventually going to struggle if the demands are very high.

Out of interest, how long (in time) is it between Grosmont and the Goathland, and how much of that is against the collar?

Tom

 

Tom - Grosmont to Goathland is 3.5miles of which there is at least 3 miles of continous grade averaging 1 in 49. As Steve says it does fluctuates a bit, but none of this is to any advantage. The booked running time is 15 minutes. You ought to come and sample it sometime - I think you might enjoy it! I am sure that Steve would sort something out for you, him being a man of far greater influence in these matters than me.

I too have a real soft spot for the Us and Ns as I remember them at Redhill at the very end of steam on the Central Section. Hopefully we will one day have a visit from the N once that is up and running

Peter

 

Torgormaig beat me to this as I had connection problems but, having found the file, here is a theoretical graph of time against distance for the climb. It shows a required theoretical speed of 15.5 mph for the journey between them, once out of station limits. The 20 mph slack has now gone but it makes no difference to this. In practice, with 7 mk.1's, you can usually get up to 17-18 mph before you hit the 1 in 49 and keep it there with a class 4 or 5, subject to your fireman and rail conditions. If you don't get there before the steep grade it can be hard to get the speed up once your climbing The curves tend to drag you down and you accelerate slightly on the straights. The Std Cl.4's are better than the Cl.5's as they don't weigh as much and have virtually the same T.E. The tanks really do have an advantage over the tender locos in this respect.
.

 

Thanks Peter - might have to take you up on that (to my embarrassment it's been just over 6 years since we last went to the NYMR, just before our oldest was born).

The N is definitely high on my wish list as well. Amazing to think for such a modern design that it will be 100 years old next year! There's only a decade in build date between a Wainwright C and a Maunsell N, but a lifetime in conception...

Tom

 

Slightly off the thread but the video suggests strongly that the ideal machine for 25 mph running on a steeply graded tourist railway is an o-8-0. Total adhesion and low in the wheel. This is one such railway that genuinely can justify big machinery.

Paul H

 

that video settles it...NYMR on my list for this summer!

 

In that case, wouldn't it be nice to have a new build Z Class?

 

Slightly off the thread but the video suggests strongly that the ideal machine for 25 mph running on a steeply graded tourist railway is an o-8-0. Total adhesion and low in the wheel. This is one such railway that genuinely can justify big machinery.

You would think so, but NELPG have been hinting at taking 63395 away from the NYMR because of excessive tyre wear. Hopefully the realignment and relaying currently taking place at one of the worst spots, Kingthorpe Curve, will allay some of these concerns.

 

Don't think it is a simple as that - the permanent way people for example will almost certainly prefer a locomotive with a leading truck / bogie as being kinder on the track and reducing wear and tear. In any case, how many 0-8-0s have been preserved? I can only think of three, one of which is indeed based on the NYMR. So even if such a loco were the absolute optimum, insufficient of them exist!

Tom

 

A new build Z class would provide a good case study in why locomotive top trumps needs to consist of more than simple comparison of tractive effort! They were a very clever design, typical Maunsell in how they made use of other pre-existing bits, but by design they had a high TE but low sustained steaming rate - probably not ideal for the Moors.

Tom

 

Without breaking any confidences, 2016 looks like being an interesting year on the NYMR, motive power-wise, and might become more interesting still, , depending on what happens on the main line. The NER of course had its own 8-coupled shunter, the massive Wordsell T1 4-8-0, but it's another example of a purpose-built shunter, with a relatively small boiler - I'd love to see one though!

 

Yes in this sort of use it would pull but is unlikely to have sustained steaming capacity (unlike a certain replica express locomotive being made rather to the south of the NYMR which is unlikely to pull very effectively on a wet rail but will produce more steam than can be utilised sensibly)

Just go back to the video where the freight loco. is seen romping away whilst the passenger types, at least when single headed, struggle. It does not have to be an 0-8-0 for there are plenty of 2-8-0s, 2-8-0Ts and even 2-8-2Ts with suitable small wheels. Alternatively just leave off the pesky buffet car and save umpteen tons.

Paul H

 

It seems to me that 2 of the most suitable engines for the NYMR are both seemingly not wanted, i mean the S160 2-8-0 and the MOS 2-10-0 both have the haulage power, plenty of driving wheels to put that power down and enough boiler capacity to keep up with demand .