The 9F 2-10-0

There's a piece by J.M. Jarvis out there on the internet (borrowed from the SLS Journal I think), in which he describes the balancing of the 9Fs. He quotes a hammer blow of 1.564 tons at 5rps (300rpm or 53.5mph), against an axle load ranging from 15.15 to 15.9 tons. Since the 9Fs had the unusual feature of the reciprocating balance being done on a whole engine basis, rather than per cylinder (Jarvis says this was directly inspired by the lack of reciprocating balance on the Bulleids), we can say that the hammer blow is approximately one tenth of the axle load at that speed. Hammer blow will be proportional to rotational speed squared, so the speed at which a 9F completely unloads its coupled axles is 53mph x 10^0.5, or 169mph.

Conversely, the Royal Scots had reciprocating balance on a per cylinder basis, leading to a wheel hammer blow of 4.25 tons at 360rpm (also sourced from Jarvis). Given an individual wheel load of 10tons 7 cwt (from the weight diagram), it'll unload each wheel completely at 562 rpm, or 135mph, so actually considerably slower than the 9F. Isn't maths fun?

Edit to add: For the obvious comparison of the Britannias, the figures are wheel hammer blow 2.12 tons at 300rpm, which with an estimated axle load of 20.5 tons gives an unloading speed of 145mph.

 

Dame Vera Lynn worked fine on the Grosmont to Pickering section so I can't see that a 9F to Whitby would be very different.

 

So did 92214 and 92220 on the NYMR . The curves into Whitby ar a bit tighter though. Having said that 92220 has been to Whitby in times past.
No raised check rails between Grosmont & Whitby, either.

 

In addition to this question, I think a supplementary one would be were too many different classes of Standards designed? Was it necessary to have the class 4 4-6-0 as well as the 2-6-0? ie the 75xxx and 76xxx? also what was the purpose of the class 3 2-6-0, the 77xxx? only a small number of these were built, surely a few more 75xxx 4-6-0s would have covered all three?

The 78xxx class 2s were really just a continuation of the LMS Ivatt class 2s, as were the class 2 2-6-2 tanks.

Obviously, at the time it wasn't known that steam would be eliminated as quickly as it was, otherwise, surely all steam construction would have ceased much earlier and some pre group types given a life extension overhaul to squeeze a few more years out of them before being directly replaced by diesels

 

Weren't the 77xxx's meant for routes that wouldn't allow use of the 75 and 76xxx's and wasn't part of the 77xxx order cancelled? The last 5 weren't built for some reason?

 

I would suspect yes, but I think weight limits had a lot to do with it. Possibly also why there was so little standardisation.

 

I wonder as well whether, in a nationalised industry, there was a political expedient in making sure that not only construction, but also design work, was shared around the country regionally - hence the 80xxx being designed at Brighton; the 82xxx designed at Swindon and the 84xxx designed at Derby?

Tom

 

Probably, yes. There were other instances of locos that should probably never have been built. I always think the GWR 9400 class panniers area good example, a large order was placed, with outside builders, just before nationalisation. Their axle loading was too heavy for them to do the same job as the 5700s as they were in the red category, which restricted their use.

Was the order placed with outside builders to make it more difficult to cancel? and to lumber BR with something they wouldn't want as the GWR did not want the amalgamation?

 

But the axle loading did give the 9400s extra braking power to permit them to do the same job as umpteen red route Welsh 0-6-2Ts that were scheduled for withdrawal over the time the 94s were being built. It seems to me that they should be looked at as a cheaper alternative to building more 5600 [0-6-2Ts], not an expensive alternative to 5700s.

 

If

If you'd ever been on one, John, you'd not think it odd at all. I spent many "happy" hours on WD 600 "Gordon," which would be joyously attempting to shake itself to pieces at 25mph. The effects were very noticeable in the first coach.

 

Isn't balancing one of those areas where there is no perfect solution though, only compromises (at least for a two cylinder design)? So you can balance the reciprocal fore-and-aft motion, but only at the expense of more hammer blow. Or, stated the other way, you can reduce hammer blow but it will tend to make the fore-and-aft imbalance more extreme, which manifests as a surging that can be felt in the train. I suspect (but don't know) that in the case of the Austerity 2-10-0s, they were designed for use at low speed on very light and poor-quality track that may have been quickly relaid after bomb damage. So minimising hammer blow would be desirable, even at the expense of being rough fore-and-aft. That would not matter much for freight (no thoughts then of using them on passenger turns!) and the damage they would be doing themselves was hardly a concern for a design aimed at a relatively short lifetime. Whereas the 9F was presumably designed with better quality p/way in mind, and therefore increased hammer blow was a price worth paying for a smoother ride at speed.

The 56xx seems to fit a similar mould - rough at speed, but no doubt well suited to slow speeds around collieries with poor quality track. Just don't use them on your posh dining train!

Tom

 

I heard that part of the problem with WD 2-8-0s (and, presumably the 2-10-0 as well) was the lack of a spring loaded draw bar between the loco and tender. Lees shed, at Oldham, modified two by fitting a spring draw bar, and these were supposedly better.

 

It was according to Gordon's driver back in April 1966 when it went mainline from Woking to the LMR taking over from a couple of Maunsell 2-6-0s. Does anyone else remember it? We had a trip round the Longmoor system behind an Austerity 0-6-0ST, I think a duplicate train was run the following week

 

Just a note on the use of the word ' Standard' as applied to the BR standards.
At inception the designs we're to conform to two Standard loading Gauges that had been arrived at suitable for nearly all or most of the whole rail network. and apart from trying to use a limited number of boiler making tools and using common controls and fittings the degree of commonality of major components between the Standard designs is not especially great, nothing like the degree of commonality in say Churchwards scheme. The 9F Being the classic example.
although the boiler is an odd combo of Britannia and Clan diameters very little of a 9F is common to any other 'Standard...

 

There was indeed a "political" requirement not to continue building more of the practical unashamedly Ivatt types, so they just disguised them a bit and called them "Standards".. There were only really four new designs; the three Pacifics and the 9Fs.

 

Hate to disagree - but since the 5MT was a product of the Doncaster drawing office, and clearly with its 6ft 2in wheels and outside, three bar walschaerts valve gear, this surely was more of a Chimera of two previous 4-6-0 locomotive classes - the Black Fives and the Thompson B1 - than a standard locomotive class based on one specific design? So it too should be considered more of a new design - the 5th in that list.

 

I refer you to my post 32, been there and done it, got the T shirt and the scars

 

You're right, the Class 5 was a mongrel. Riddles decided that 6'2" would be the largest wheel size, probably noting what the A2s and Bulleid's Pacifics could do. Therefore using 6'0" wheels as on the Black 5 made no sense. The LNER variant of Walschaert's was adopted as the better type but the boiler / firebox followed Stanier's practice.