9F why does not having a flange on the centre wheels stop it being mainlined

If this has been asked before sorry I have searched but came up with nothing.
Why do 9F's not having a flange on the centre wheels stop it being mainlined?

 

IIRC it has been discussed before. Briefly, checkrails, in many places throughout the network have been raised above the level of the running rails. By having the centre drivers of 10-coupled engines flangeless that wheelset could ride across the railhead and allow the loco to negotiate sharper curves than otherwise. Where the checkrails are higher the flangeless wheel could ride up onto the head of the checkrail leading to a derailment. Hope this answers your question. Ray.

Sorry Pete - replies 'crossed'.

 

If we are really desperate to see a 9f main line one could always....
put a flange on the middle tyre , decouple the rear driver and allow it a bit more play ?
Take the tyre of the middle wheel completely take the springs right up and have here riding on the outer 8 wheels ! still only 20 t per axle
or you could... eh whats that? ER...... I'll get me coat.

 

I believe that the figure was 1/4". It might not sound a lot but hit that at speed and you will know about it.

 

Images of Polar express on Frozen lake ' spring ' to mind

 

Would it be feasible for a wealthy body to commission analysis of the affected routes? Or is the type of infrastructure so common place so as to be unavoidable even on a restricted basis?
The question above would provoke an interesting answer. One would have thought with modern techniques it ought to be possible to model the theoretical problem.
Could a heritage line be used to carry out research and analysis using the type of track work said to be of concern?
A couple of 9Fs would not be short of mainline work. Could one be used on the WH extension for example?

 

I believe it followed derailments at Glasgw Central with derailments of 1Co-Co1 bogies of Class 40 / 45 / 46 when checks were made of locomotives with longer frames and the 9Fs came under scrutiny because of their length; the identification of the flangeless drivers only made their situation worse as the problem of flangeless wheels and check rail height was only then identified and the class was banned totally from the main line whilst the diesel 1Co-Co1 classes were simply restricted.

 

A bit like the time a member of Western Region management saw Evening Star at Paddington. Immediate ban from express passenger work. Reason ?

 

Is D345 currently restricted and if so could a 9F have the same rules?

 

I think it's a bit more than that, certainly in practice. I've just measured a raised check-rail and the difference is just over 3/4", though some of this is due to wear on the running rail. Because check-rails are usually on curves, running-rail wear is more pronounced, whilst there is no wear on the top of the check-rail.
Raised check-rails are not a new thing, which probably explains why 9Fs were banned from several parts of BR even in steam days.

 

I know that 9Fs had problems on one or two lines, but that was because of curves. Wrexham to Brymbo is a good example. They had restrictions in many sidings, as well.

 

I'll have to check some old Sectional Appendices, but I think that they were not allowed, or at least were restricted, on much of the GE, except March-Temple Mills. I certainly never saw them except on that line and the connections to the Tilbury line. I know that they were not allowed on the Liverpool St.-Colchester main line and understood that that was due to the track layout at the London end, which was a bit complicated, but not particularly curved.

 

Remember that the tyres on the middle wheelset are wider than on the other wheels too, hence more chance of hitting the raised checkrails.

As for 9Fs being banned from express passenger service, wasn't that due to 'management' getting concerned about piston speeds? This is why NR limits speeds based on driving wheel diameter these days...

 

Not for long, though.

 

I came across the "express ban" story along time ago, I think it was in a book by E.S. Cox. Someone tried a 9F on express passenger duties and it did very well, so it became a regular thing until an article appeared in Railway Magazine entitled "Ninety with a Nine". At this management started worrying about the stresses on the coupling rods at that level of RPM and whether one of these might break at such speed, and what they would say to the Railway Inspectorate if it did.

Tim