The 9F 2-10-0

Yes but it was not intended they would be able to go so fast and it was eventually decided it was potentially unsafe. The margin of safety on the rodwork of a steam loco is in any case relatively small - Mallard's rods didn't buckle at 126 but they might well have done at 150, and the rapid hammer blow from a two-cylinder loco would be highly undesirable as well. Blue Peter's motion disintegrated at an estimated 140mph with wheels only 6 inches smaller than Mallard's.

I've seen the calculation somewhere, I don't have it to hand, but a 9F at 90 was felt to be getting too close to the safety limit for rotational speed.

 

With regard to hammer blow, is the converse a potential issue, in other words, at very high rotational speeds, the wheels might actually part company with the track?

I realise this might be well known, and possibly even a contribution to the hammer blow, after all, to hit something with a hammer it is necessary to lift it first but presumably in more normal situations, the weight of the loco would prevent it.

 

In essence yes. If you have an axle with a nominal axle load of W, then over a whole revolution, the average force it exerts on the track will be W - that has to be true, since the combined axle loads support the weight of the vehicle - if they didn't, it would rise or sink until they did balance. Therefore, if for part of a wheel revolution the downwards force on the rail is greater than W then it must be true that for part of the revolution, the force is less than W. There is therefore a cyclic variation in force on the rail, which is what hammer blow is. That cyclic variation increases as a function of wheel rpm. So there will come a speed at which the minimum has declined so much as to be negative, i.e. an upward force, that will tend to lift the wheel off the rail.

I believe (might be wrong) that that was measured with 8Fs allowed to run fast on a rolling road, and as a consequence, some were re-balanced; those retaining the original balancing being restricted to a relatively low speed.

Tom

 

Whatever the potential speed of a 9F was/is the obvious question is what sort of speed might have been require for the majority of services in steam days.

I suggest that in many cases the answer is probably rather low

 

9Fs were designed to do 50mph and everything above that was a surprise bonus (although the designers would have known jolly well that they would exceed specification). As I said in the "flange" thread smaller wheels, shorter stroke and shorter wheelbase might have been interesting. The odd thing is that I never heard of anyone trying to get an Austerity 2-10-0 anywhere near the 9F's speeds.

 

Had they tried that with a WD the thing would have shaken itself to bits long before it reached such speeds. I had a footplate ride on one at Wakefield in 1966, the ride was frightening enough at 30mph.

 

Clearly Riddles learned something between 1943 and 1954!

 

Don't forget the WDs were built under wartime conditions and did everything they were designed for. They were not built to last, really a sort of pound shop version of the LMS 8F.

 

Tom, the LMS test was on a Black Five on oiled rails. Its speed over the ground was less than 10 mph but the wheels were rotating at the equivalent of, from memory, 104 mph. The driving wheels lifted 2.4 inches clear of the rails. A 9F at 90 has the same rotational speed as an A4 at 120 mph.

John, The WDs did everything that they were designed to do but what that was involved moving trains at low speeds: they were notorious for the heavy shuffling between engine and tender above 25 mph due to the lack of balance of the reciprocating masses. Speeds above 30 - 35 mph became untenable.

I hate to be the only pickled onion in the fruit salad here but the 9Fs were not universally popular with crews. They were ahead of their time. They would have been ideal on fully fitted block workings - say Freightliners - running at 60, perhaps 75, mph. Instead they usually worked the same turns as WDs, 8Fs, 28XXs and 01s, 02s, etc. On these trains most men preferred the smaller engines: the 9F offered no advantages but a lot of difficulties. They were too big and long in most yards and if the train involved dropping off and picking up, the driver would have a hard time with the notoriously stiff reverser. By the time the trains it was best suited for had arrived, so had the diesels, so they rarely got the opportunity to shine, at least on goods traffic. And yes, I know about the Tyne Dock - Consetts and Shotwicks on the Wirral.

 

They were well liked on the Birmingham -Carlisle fitteds, provided it wasn't a stoker fitted one coaled with unsuitable coal, however it has been said that the job could be worked pretty well by a Black 5, with lower coal consumption.

Going back to the earlier point about a 2-8-2 freight loco, Cox in "BR Standard Steam Locomotives" makes the point that after the war there was no immediate need for a 2-8-2 freight loco ( with 4ft 8inch drivers) because of the large number of LMS and WD 2-8-0's available, and Riddles was looking for higher running speeds than 4ft 8 inch wheels could provide. Riddles also felt that for a freight loco adhesion was important, ie ten drivers over eight drivers. So once it was proved that 5 foot diameter wheels could be used and clear the ashpan, and stay within the L2 loading gauge, then a 2-10-0 it was to be.

46118

 

I had the pleasure of foot plating 2-10-0 WD Gordon from York to Sheffield in 1975, the ride was interesting at 50/55 mph! The engine and tender were banging together, no need to bring the coal to the front of the tender it was mostly in the cab! What was interesting was that opening or closing the regulator would disturb the banging motion for a short while, as soon as it returned the driver either opened or closed the regulator and as if by magic the banging would cease again.
This was the return trip from S&D 150 double headed with 43106.

 

John Powell described it as 'suicide coal'. It worked its way off the shovelling plate, along the cab floor and piled up under the firehole doors, waiting to be tipped in!

 

Agree with all that, though they did good work on the ECML and the GCR as well - but again, they were on faster fitted goods and block trains (and of course the famous Windcutters , probably the fastest unfitted trains in the country). In some cases they took over from V2's which were then released for passenger work.

They got taken off the Whitemoor - Temple Mills runs as being too big and unwieldy - o1's could do the job perfectly well as speeds were lower than the ECML. The WR didn't want them at all, they wanted more 28xx's , which makes it somewhat ironic that they got the final batch including Evening Star.

Nevertheless I believe the design turned out well, was certainly more versatile than , say, more WD 2-10-0's would have been and , surely, at the time, more suitable that the 2-8-2 which would have been even less at home on the typical work the 9F's got. Building the 2-8-2's instead of the Clan's, well, that might have been a good move.

 

Weren't the 9Fs later subjected to a speed limit due to excessive valve and piston wear as a consequence of the small wheel size and consequent high piston speed ? Certainly this was the reason quoted for taking Evening Star off the Cardiff Canton Britannia turns on London expresses after only a few weeks use.

 

That was indeed the case but drivers had been getting up to 90mph to make up time because the locomotives would do it. These days, if only we could overcome the flangeless problem, they could do 60mph on the main line (I know that 8Fs have a 50mph limit) without ever slipping and take 15 coaches over Shap without a box on the back.

 

Totally agree 9Fs would be incredibly useful steam charter locos especially on secondary routes. There ought to be some means of working out route availability and reasonable restrictions if NR could be paid to carry out the assessment. Surely not beyond the pocket of at least one owner?

 

Your statement shows up a lack of appreciation of the reasons why the 9Fs are banned from the national network.

For avoidance of doubt this is purely due to the wheel / rail interface through points fitted with raised check rails found in the majority of pointwork these days - regardless of whether you define the line as 'primary', 'secondary', etc.

To determine whether it was safe for a 9F every single piece of pointwork in the the proposed route - including depots sidings, lines it might get diverted onto as the result of things running out of sync, etc would have to be checked beforehand. It also assumes that no track replacement work takes place between the train being planned and it being run.

You should also take note that this issue was present even back in the 1950s - a recent post somewhere showed up a genuine 1950s BR (E) publication which had plenty of restrictions on the use of 9Fs clearly shown - all of which related to pointwork, curves, etc rather than axle loadings

 

Stand corrected for a gross over simplification. It remains regrettable however.
WRT your comments about historical restrictions is it the case that the type of trackwork is more prevalent thereby extending what were location specific prohibitions to apply network wide? Or does that level of detail not exist so blanket restriction?

 

The scenario that begs askance would be something like the esk valley line. IF it just so happened that the track layout contained nothing that a 9f would come to grief on then a dispensation might be asked for, though ii suspect in reality that's not a great stretch of line ffor long wheelbase locos.