Why are 9Fs banned from the national network? (What's wrong with flangeless wheels?)

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alexl92

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I know that the reason a 9F can't run on NR metals at present is because of the flangless wheels on the middle axle. However, what I don't understand is why that should be the case? What's wrong with a flangeless wheel that means a loco can't run on the very track it was designed for?

Also does anyone know the reason why there are speed restrictions linked to wheel size too? I'm thinking of 48151 being limited to 50mph.

Cheers!
 
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Phil.

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48151 has driving wheels smaller than 5'. That's the reason for the restriction.
 

AM9

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... Also does anyone know the reason why there are speed restrictions linked to wheel size too? I'm thinking of 48151 being limited to 50mph.

The wheel size determines the speed that the valvegear and coupling/connecting rods cycle at. Therefore for a given speed, a small-wheeled freight loco (1435mm drivers for the LMS 2-8-0 type that you suggested), that would have similar hammer blow impact on the track as the similar tractive effort Royal Scot class locos at 72 mph with their 2057mm driving wheels. *
Given that steam locos are generally limited to 75mph maximum, 50mph for the smaller wheels would seem reasonable so as not to stress modern track that under normal use does not encounter repeated hammer blow.

* Assuming similar levels of counterbalancing, the hammer blow should be similar.
 
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alexl92

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The wheel size determines the speed that the valvegear and coupling/connecting rods cycle at. Therefore for a given speed, a small-wheeled freight loco (1435mm drivers for the LMS 2-8-0 type that you suggested), that would have similar hammer blow impact on the track as the similar tractive effort Royal Scot class locos at 72 mph with their 2057mm driving wheels. *
Given that steam locos are generally limited to 75mph maximum, 50mph for the smaller wheels would seem reasonable so as not to stress modern track that under normal use does not encounter repeated hammer blow.

* Assuming similar levels of counterbalancing, the hammer blow should be similar.

Fair enough, makes sense. Thank you!
 

markindurham

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I know that the reason a 9F can't run on NR metals at present is because of the flangless wheels on the middle axle. However, what I don't understand is why that should be the case? What's wrong with a flangeless wheel that means a loco can't run on the very track it was designed for?

Also does anyone know the reason why there are speed restrictions linked to wheel size too? I'm thinking of 48151 being limited to 50mph.

Cheers!

9Fs are barred from the national network because of the raised checkrails fitted to some point & crossing frogs these days. The flangeless drivers are wider across the tread than the flanged wheels, and there isa risk of a wheel striking the raised checkrail.
 

alexl92

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9Fs are barred from the national network because of the raised checkrails fitted to some point & crossing frogs these days. The flangeless drivers are wider across the tread than the flanged wheels, and there isa risk of a wheel striking the raised checkrail.

Fair. Thanks. Is there any realistic prospect of this restriction being lifted in the future or is two unchangeable issues (wider wheels vs distance of checkrail from track)?
 

70014IronDuke

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The wheel size determines the speed that the valvegear and coupling/connecting rods cycle at. Therefore for a given speed, a small-wheeled freight loco (1435mm drivers for the LMS 2-8-0 type that you suggested), that would have similar hammer blow impact on the track as the similar tractive effort Royal Scot class locos at 72 mph with their 2057mm driving wheels. *
Given that steam locos are generally limited to 75mph maximum, 50mph for the smaller wheels would seem reasonable so as not to stress modern track that under normal use does not encounter repeated hammer blow.

* Assuming similar levels of counterbalancing, the hammer blow should be similar.

I'm a bit surprised they are even allowed to do 50 mph, TBH. In days of yore, when 8Fs were all over the place, I thought there were only a few locos with a star above the number which were especially balanced to do 50mph for passenger trains on the Central Wales line.
I should think 95% of 8F work in those days was at 30 mph or less.
 

Deltic1

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In the latest Network Rail Group Standard (GO/RT3440) published June 2007, steam locos hauling passenger trains are normally limited to a maximum speed of 60mph, except for a few locos with driving wheels of 6ft 2in diameter or larger which are approved for 75 mph running. Locos with driving wheels below 5ft 8in diameter are normally limited to 50mph, and those below 5ft in diameter are normally limited to 35mph. (A few locos such as 9466, 48151 and 76079 have derogations allowing them to run faster than these new limits). Lower speed limits normally apply when running light engine or with a single coach. Tender locos travelling in reverse are normally limited to 35mph, but may be towed in reverse at speeds up to 60mph.

- From UK steam - http://www.uksteam.info/tours/locos.htm
 

Cowley

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I remember reading that 9Fs could reach quite a speed if they were standing in for a failure and when pushed. I'm sure I read somewhere that speeds of 90 mph had been known on occasion.
 

AM9

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I remember reading that 9Fs could reach quite a speed if they were standing in for a failure and when pushed. I'm sure I read somewhere that speeds of 90 mph had been known on occasion.

Now that's impressive as in drive train terms it's the equivalent of Mallard doing 120mph!
 

Cowley

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Now that's impressive as in drive train terms it's the equivalent of Mallard doing 120mph!

Indeed. I just looked it up and it's even on Wikipedia, if I knew how to link it I would but I'm doing this on the phone. It says that one replaced an LNER pacific between Grantham and Kings Cross and was recorded by an enthusiast twice exceeding 90 mph.
That must have been pretty exciting!
 

Bletchleyite

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Fair. Thanks. Is there any realistic prospect of this restriction being lifted in the future or is two unchangeable issues (wider wheels vs distance of checkrail from track)?

Would it not be easier to fit replacement wheels to one steam locomotive rather than modify points across the network?
 

Monty

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Would it not be easier to fit replacement wheels to one steam locomotive rather than modify points across the network?

It would heavily restrict where the 9F could go, it has a long fixed wheelbase and the reason it had a flangeless centre driving wheels (in fact wheelsets either side of the centre driving wheels had a reduced flange compared the outer most sets) in the first place was so it could go around curves. ;)
 
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Bletchleyite

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It would heavily restricted where the 9F could go, it has a long fixed wheelbase and the reason it had a flangeless centre driving wheels (in fact wheelsets either side of the centre driving wheels had a reduced flange compared the outer most sets) in the first place was so it could go around curves. ;)

Ah I see, thanks.
 

markindurham

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Fair. Thanks. Is there any realistic prospect of this restriction being lifted in the future or is two unchangeable issues (wider wheels vs distance of checkrail from track)?

No problem :) Will it be lifted? I very much doubt it. The one glimmer of hope would be something like the Esk Valley, where there are no raised checkrails, but would an owner go for the full main line electronics fit just to run Whitby-Battersby? This topic has been discussed in depth elsewhere (Nat Pres for one) on several occasions, btw.
 
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It would heavily restrict where the 9F could go, it has a long fixed wheelbase and the reason it had a flangeless centre driving wheels (in fact wheelsets either side of the centre driving wheels had a reduced flange compared the outer most sets) in the first place was so it could go around curves. ;)

out of interest - what is the 'tightest' radius they can negotiate in their in service form and what would the tightest curve be if all wheels were flanged ???
 

70014IronDuke

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I remember reading that 9Fs could reach quite a speed if they were standing in for a failure and when pushed. I'm sure I read somewhere that speeds of 90 mph had been known on occasion.

The story went something like this: Some time in the latter part of the 50s, a respected train recorder (a la Ian Allan mags) was on an up ECML express which had an ailing train loco. (I forget whether it was steam or diesel.)

The loco was taken off at, I think, Doncaster (which had an allocation of 9Fs) and the train restarted, picking up time from thereon with some 90 mph running. The logger had not left the train at Donny, and, from the back, assumed the loco was an A1 or other regular pacific.

It was only on arrival at KX and walking past that he realised it was a 9F on the front.

The WR also used Evening Star on passenger duties on the main line, i think it hauled The Red Dragon on occasion. AFAIK, that was not a sharply timed express (despite being billed as the main up 'business express') - nonetheless, it would have required 70-75 mph running i should think. The LMR also used them on summer reliefs/holiday specials.

Some combination of the ECML run and the WR usage supposedly stirred the BRB to issue an order to ban 9Fs on passenger duties, or at least to put a restriction (70 mph?) on their use. Perhaps someone else can confirm the details.

The WR/SR also used 9Fs on the S&D, of course, but I doubt they could get above 55 mph on that road.
 

Flying Phil

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In the current issue (#168) of "Main Line" the GCR magazine, is an article by Tony Cooke, where he says 9Fs were used sometimes on summer express passenger work and on 29th July 1958 he saw No 92164 in Leicester GCR shed with the "Master Cutler" headboard and he wondered if it was that incident which prompted concern about express speeds being too much for the small wheeled 9Fs.
 
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furnessvale

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Would it not be easier to fit replacement wheels to one steam locomotive rather than modify points across the network?

In the real world I doubt either will happen.

A fully flanged 9f would punish the wheelsets and track.

Changing all raised check rails to accommodate the occasional steam loco is obviously not on, especially as raised check rails are already in place for a reason.

I have no idea if it would be possible to identify a route or routes free of raised check rails that a 9f could use. Again, I have no idea if a 9f could negotiate raised check rails on the straight, rather than using the turnout, which "may" ease the situation.
 
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Townsend Hook

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While it would be nice to see a 9F on the main line there is pretty much zero chance of it happening, with the exception of maybe a derogation for Battersby-Whitby (might be a possibility for the NYMR's WD 2-10-0 'Dame Vera Lynn' when that is eventually overhauled) the closest you'll get is 92214 on the Great Central.
 

ainsworth74

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This is probably a silly idea but why can't the flangeless wheel be made narrow so it wouldn't catch on the pointwork?
 

edwin_m

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This is probably a silly idea but why can't the flangeless wheel be made narrow so it wouldn't catch on the pointwork?

They would probably then drop off the inside or outside of the rail on curves, and derail themselves when returning to the straight.
 
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Is the 9F a flawed locomotive design?!

arguably a 5 rigid axles with large(ish) diameter wheels is going to be an issue , even more so on a railway that has for the past 50 years been designed around everything being bogied or pacer - style none bogie stock
 

alexl92

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Is the 9F a flawed locomotive design?!

A heavy freight locomotive capable of starting a 2000ton stone train and equally capable of hauling express trains comfortably at 75mph in place of a pacific? In my humble opinion, definitely not flawed!
 

Townsend Hook

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They would probably then drop off the inside or outside of the rail on curves, and derail themselves when returning to the straight.

As I understand it the issue is not that the wheel is particularly wider than a flanged wheel, but that it will move further laterally across the railhead from the running edge, increasing the chance of contacting a raised flangeway.
 

CarltonA

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I may be wrong here but is it not the tyres on the centre wheels which are flangeless rather than the wheels themselves? Dislodging a tyre on a check rail or through narrower wheels falling off the rail would be disastrous I imagine.
 

Townsend Hook

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I may be wrong here but is it not the tyres on the centre wheels which are flangeless rather than the wheels themselves? Dislodging a tyre on a check rail or through narrower wheels falling off the rail would be disastrous I imagine.

The tyres certainly will be flange less, whether the wheel design is significantly different I don't know. Certainly the tyres must still be securely fastened, or BR and its predecessors wouldn't have bothered with flangeless centre drivers.
 

Monty

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A heavy freight locomotive capable of starting a 2000ton stone train and equally capable of hauling express trains comfortably at 75mph in place of a pacific? In my humble opinion, definitely not flawed!

The 9F was probably one of the best ever steam locomotive designs used in this country.
 
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