Route availabilty/Curves

John Tremelling · September 28, 2012, 04:21:45 PM

Good afternoon all,

Is there a publication which readers may know of to include such information as route availabilty and minimum radius curves for prototypes, or is it simply a matter of tedios individual research? I am not a rivet counter, but do wish to be near prototypical, something which we can do in N.

Thanks,

John T

painbrook · September 28, 2012, 08:00:09 PM

I'm probably wrong but I've found that there needs a lot of compromise, one glaring thing alone comes to mind, that is couplings, far to big and clumsy. Cheers john.

John Tremelling · September 28, 2012, 09:05:24 PM

I was born to compromise, after all I am married, just looking for a mental start line for a possible new setup.

John T

edwin_m · September 28, 2012, 10:40:18 PM

Route availability is in the Platform 5 books I think. If you're thinking steam era then the reprints of Ian Allan ABCs may help.

Minimum curve is not an issue on the main line, I don't think there is anything that is barred anywhere on a running line due to excessive curvature. Much tighter curves exist in yards etc and here the minimum radii of individual locos and rolling stock are more significant. IIRC one design of modern container wagon has a minimum of 80m and I think the Mk3 coach is 5 chains or about 100m. The curves on most N gauge layouts would cause catastrophic derailments if their radius and speed was scaled up by a factor of 148.

Sprintex · September 28, 2012, 10:48:34 PM

Quote from: edwin_m on September 28, 2012, 10:40:18 PM
and I think the Mk3 coach is 5 chains or about 100m.

Which equates to a 65cm (or 25.5") radius in N

Paul

mr magnolia · September 28, 2012, 11:00:26 PM

at work we often look at 'what if' development scenarios for vacant sites, and umpteen years of looking at historic maps for railway lines and stuff has led me to think that 100m is a generic minimum real life radius for goods traffic siding accesses. No idea about main lines though.
100m is about 675mm radius in N, and thats for a wheel squealingly tight siding. (oops - just as paul says above)

Sprintex · September 28, 2012, 11:31:08 PM

And further to this I have just estimated the curve from Hitchin Junction onto the Cambridge branch to be of approx 250m radius (that's 162.5cm or 64"in N), this curve has a 40mph speed limit AND a check rail

Paul

tim-pelican · September 28, 2012, 11:36:48 PM

Hmm... N-gauge garden railways, anyone?

John Tremelling · September 29, 2012, 08:35:51 AM

Thanks for your various calculations. I have made some from current and vintage OS maps, but was wondering if anyone had so much free time as to do a study and publish more extensive data. As Edwin says, various Ian Allen books must be the best source.

I think that Z Gauge in the garden must be the answer?

John T

edwin_m · September 29, 2012, 09:05:05 AM

Fortunately in N it is often possible to hide the tightest curves off-scene, leaving nice gentle flowing ones in the visible areas.

John Tremelling · September 29, 2012, 09:27:59 AM

I wish to run prototype length close coupled trains Edwin, thus not necessarily an option.

John T

Newportnobby · September 29, 2012, 01:37:53 PM

Not so long ago we were due to get 'Tornado' at the Ribble Steam Railway.
Unfortunately no one checked the radius of some of the curves in the docks area and she was pulled out at short notice 'cos she couldn't get round them

EtchedPixels · September 29, 2012, 01:50:36 PM

Quote from: John Tremelling on September 29, 2012, 09:27:59 AM
I wish to run prototype length close coupled trains Edwin, thus not necessarily an option.

John T

Z won't help you there at all. The trick with close coupling and off scene curves is to use stock with couplers that change position and spacing on curves (or fit ones that do). Quite a bit of the new stock does this so you can tighten it right down and it'll still do 12" curves happily.

It's also partly a question of model railways as art. What looks acceptable and reality are not quite the same thing.

Alan

John Tremelling · September 30, 2012, 09:06:15 AM

Thanks Alan, my comment on Z was in jest, my failing eyesight batrely copes with N.

I do know that modelling consists of creating an illusion, but in order to create such an illusion I need to know what I am trying to allude to.

John T

dodger · September 30, 2012, 09:08:44 AM

Platform 5 and Ian Allan books only give route availabilty for locomotives. For rolling stock a quick rule of thumb is to work out using axleload.

There used to be 10 grades of route availabilty, RA1 to RA10, but a quick search has only revealed four. The current maximum axles loads are:
RA3 16.5 Tonnes
RA5 19 Tonnes
RA8 22.8 Tonnes
RA10 25.4 Tonnes

The original RA1 had a maximum axleload of 13 tons. Not all vehicles have equal weight on all axles, e.g. multiple unit power cars with only one powered bogie or and engine at one end and the heavy end could put the vehicle in a higher RA category. Frieght stock will often have a different route availability for empty or loaded conditions.

Route availability does not depend entirely on axle loads but also takes into account of bogie wheelbase and bogie centres as the have an effect on bridge loading, usually the weakest point on a route.

From memory the minimum curve radius for mainlines is 200 metres, but all mainline curves of less than 300 metres require a check rail and will be subject to a speed restriction.

Roger