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

Check rails are on the inside of curves, so the flangeless wheel would move away from the check rail. It is only the wing rail at the vee of a turnout that might be struck by the flangless wheel, as the only situation when the centre wheels move towards the wing/check rail is when the loco is on the curve of a turnout. Those high flanges on the one piece vees look the most likely to be the problem items.

 

Interesting that they've reverted to LMS type slidebar/ crosshead. (got fed up with all the broken piston rings ... oh yeah its only a model)

Heres someone elses worthy attempt.
https://www.google.com/search?q=br+...943-2-8-2-after-a-couple-of-weeks%2F;1024;768

 

Interesting ... These things were regularly timed in the high seventies mph (possibly as high as 80mph), with 4'6" wheels and 3'6" track gauge!

https://www.flickr.com/photos/jamessquared/8590986469/in/set-72157633093482314/lightbox/

(The same calculation as above would suggest they should be limited to the high fifties!)

Tom

 

Is it too late to ask A1/ST to build instead of replicating the P2. The WSR has already created a "might have been" by creating 9351 so another "might have been" could prove a winner in the main line stakes.

 

Yes.

 

The above seems a somewhat simplistic calculation, as does the one used for mainline limits. What are the actual engineering factors?
Loads on the motion will be related to wheel rpm and piston stroke, both rotary and reciprocal, and hammer blow and the like wheel rpm and diameter, but what are the actual sums? My maths is a bit nominal to calculate piston rod acceleration without a spreadsheet and a textbook...

 

So perhaps the one after next could be a 2-8-2 Britannia 9F hybrid and it might have a 3 cyl. Caprotti front end similar to 71000 and the boiler could be designed using 5AT thermodynamic principles.

 

Best of luck getting the enthusiast mass to contribute to that... History seems to show that if it is not a traditional machine of a type already run on the UK rail network the support is primarily vocal. Think anything from a builder from outside of the UK or pioneering work such as the 5AT and see how difficult it is to raise money for such a project.
Getting slightly back on topic I understand that it was the raising by 1/4" of the check rails that sparked the debate. I do not know what the maximum was in the days the 9F was in active service.

 

I think the BRB were just guessing and used wheel diameter as a handy figure to match what they thought was right for that sort of loco. Since pacifics could do 120mph or more, i e 1.5 times the figure based on wheel diameter, it seems that 90mph plus would be a reasonable max for the 9f, track speed limits not withstanding. On the other hand, a proper calculation based on piston speeds, weight of components, etc, might prove both 9f and pacifics were running too fast

 

Agreed. Recreating the past is just that. Whilst the technically minded will be interested in what ifs and further development of the steam loco, neither really ticks the nostalgia button for the majority of enthusiasts.

 

Not really: pacifics - 0ne anyway - did 120 mph but that was hardly a daily affair. The nominal allowed speeds for steam engines was 90 mph, but since few were fitted with speedometers, the driver could always claim ignorance, as could the drivers of the 9Fs.

 

You can find in the annals the following Hints...
- Brits would have been better as 3 cylinder Machines ( Bond)
- Caprotti gear would have been adopted more widely if further standards had been built ( Bond/ cox/ riddles)
- 2-8-2 ( brit/ 9f hybrid) with 5ft 6 inch drivers would have been able to run everything except the heaviest and/or fastest trains with consistently higher average traffic speeds(Riddles, though this was to be a 2 cylinder caprotti machine)

As long as there is mainline steam here and a potential lottery win who knows.
The 5AT /ASTT People could certainly suggest any number of worthwhile improvements, but would more than likely prefer a development of Walshaerts and Piston valves to Caprotti.

Cheaper / more objectionable to adapt the back end of a 9F, but the supply of available 9F's is now very limited...

 

The absence of a flange can't be a problem in itself. If a flangeless wheel would hit something, a flange projecting further down would certainly do so. And I commented in another thread that the centre drivers on a Class 9 are only slightly wider then the other drivers. If, nevertheless, that extra width were the problem they could be replaced by thinner wheels. So the only remaining real problem is that the flangeless wheels can be significantly offset from the rails.

That seems logical. If it is correct, then check rails on curves on plain track are irrelevant.

At those places, how far would the centre driving wheel be offset from the centre line of the rail? Would it be far enough to hit anything?

 

Depends on the radius of the curve (obviously).

As an example, on a six chain curve, and using 21 feet 8 inches, which I believe is the coupled wheelbase of a 9F, the segment height (or offset) at the position of the centre axle would be 1.78 inches. I'm not an expert on track, but I'm sure that would put the inside of the centre wheel pretty close to the check (wing?) rail.

Thanks for this thread, I had also wondered why 9Fs are banned.

 

Just to show what potential a 9F does have on the mainline and that one has run on the mainline in the preservation era (although a long time ago)..
Courtesy of a very interesting website.. http://locoperformance.tripod.com/edition11/92220oxf80.htm
I would loved to have been on that tour!!

 

Looks like some blind eyes were turned that day as that run was in the 60 mph era.

 

Hey, thanks for that link. It has the Waverley Railtour on it from 1965. I was on that tour, what a great day. Still fresh in my memory to this day.

 

can i throw my tu'penny worth in here please!

i dont think the 9Fs had flangeless middle driving wheelsets because of check rails. i thought it was to avoid wear on the flanges and friction on 'ordinary' curves which didnt need checkrails?

i stand to be corrected please!

cheers,
julian

 

Yes, but haven't we established that the problem (insofar as it is a real one) is on pointwork, not on curved plain track? What would be the sharpest radius, and therefore the largest offset, at a turnout?

I think that is correct. On a curve with a checkrail, as pointed out above, the flangeless wheel would move away from the check rail.

 

The one on the inside of the curve would move away; the one the outside of the curve would move in towards it and probably run against it. The check rail was there to prevent the flange of the outside wheel from moving further to the inside, and the flangeless middle wheels were the same width as the flanged ones, so contact - or riding over the top - would be very likely.