Minimum Radius and Gradient in 009

[Gunnbrikt]

I'm interested in a bit of 009 tracking planning but was wondering what the reasonable limitation (i.e. not the absolute minimum) are for track work in comparison to 00 gauge?

 

Practically what is the tightest curve you can have for 009 which will allow most locomotives/rolling stock around reasonably?

 

What is the steepest gradient you can get away with too? 

 

Thanks in advance

 

 

[brack]

What size narrow gauge locos do you envision?

 

Industrial 040/060 like quarry Hunslet size?

 

L&b 262t/Russell sized locos for common carrier UK narrow gauge?

 

South African Railways NG15, big Indian 2'6" 284t, Sierra Leone 480, Cyprus Government Railway 484t?

 

The curve radius will be very different depending on what you choose. If you want to be reasonably confident most stuff will go round it something like 15" radius, maybe 12" at a pinch.

 

Gradients? Depends on whether the grade is on a straight or on a tight curve. Pay attention to transitions between gradient and flat - too rapid a change of gradient and you'll have potential for coupling problems.

[Nile]

The 9" radius of Peco 009 set-track suits most stock, Bachmann Baldwins are fine on it. You can go tighter with small locos and stock, 4" (10cm) is possible but best avoided.

As for gradient 1 in 10 should be possible with a short train. There are too many variables to consider for a proper answer to that one.

[Gunnbrikt]

What size narrow gauge locos do you envision?

Industrial 040/060 like quarry Hunslet size?

L&b 262t/Russell sized locos for common carrier UK narrow gauge?

South African Railways NG15, big Indian 2'6" 284t, Sierra Leone 480, Cyprus Government Railway 484t?

The curve radius will be very different depending on what you choose. If you want to be reasonably confident most stuff will go round it something like 15" radius, maybe 12" at a pinch.

Gradients? Depends on whether the grade is on a straight or on a tight curve. Pay attention to transitions between gradient and flat - too rapid a change of gradient and you'll have potential for coupling problems.

The 9" radius of Peco 009 set-track suits most stock, Bachmann Baldwins are fine on it. You can go tighter with small locos and stock, 4" (10cm) is possible but best avoided.

As for gradient 1 in 10 should be possible with a short train. There are too many variables to consider for a proper answer to that one.

Thank you both for the advice, I'll probably be going up to the L&b 262t/Russell sized locos in terms of size.

 

The gradients I was thinking would be going up a curve so guessing the gradient would need to be less severe then?

Edited November 9, 2018 by Gunnbrikt

[Stevelewis]

On a previous  layout  my Heljan 2 - 6 - 2s  would  haul 4  Peco  bogie coaches  up   1 in 25   11 radius  curved  inclines

 

The  locos  weighed 138 grammes  as  a  comparison  the  Bachmann Baldwin  weighs  around 60 grammes

[Edge]

Curved gradients need to be as shallow as possible, they represent the worst possible scenario for traction as the rolling resistance from the train increases due to the curve, the weight on the coupling effectively increases due to the gradient and the centre of gravity is 'thrown' towards the outside of the curve. So out of a six coupled driven wheelbase, you may have only three (or possibly two if the gradient is steep) of the driven wheels providing traction for a train that just got harder to pull. When you combine this with the fact that the somewhat slender prototypes of the narrow gauge world leave precious little room for ballast to assist with this traction, it is best to ease the gradient and the curve radius as much as can be managed in your available space.

Edited November 9, 2018 by Edge

[Gunnbrikt]

Thanks for the advice everyone, was really useful

[Jub45565]

It depends what prototype is being looked at. Looking around some of the Penrhyn Quarry yard curves were incredibly tight.

 

The Welsh Highland Railway (1923) was built with a 298ft minimum radius, so could look ok at 2' but would look tight below that to my eyes at least.

 

Horses for courses!

[PaulRhB]

The best test is to make a simple mock gradient on a plank and try out typical trains on it before you start building. The uncertainty comes when certain locos are lighter and struggle or others have traction tyres and walk away with anything! The Bachmann Baldwin managed 5 of the heavy Bachmann bogie wagons on a 1/24 on a friends layout but the sharpness of the curves affect it as well.

Edited November 10, 2018 by PaulRhB

[Chris Bridges]

But if you fancy something a bit ambitious magnets can help:

 

More seriously though on the level or slight gradients things like DDC Concepts Powerbase (which is what I used in the video), can help improve how much the locomotive can pull and smoothness of running.

 

Chris

[knitpick]

A quick word of warning.  You mention L&B 2-6-2T locos; the Heljan offering has a specified minimum radius of 12".  However, if you are using the Stenning kit and relevant commercial chassis then 9" radius is fine.  Other items including Egger, Joueff and Minitarins will generally manage 6" radius.

 

Not sure why Heljan went for such a large minimum radius - especially as the Peco stock is quit happy on 9" radius.

[BernardTPM]

A quick word of warning.  You mention L&B 2-6-2T locos; the Heljan offering has a specified minimum radius of 12".  However, if you are using the Stenning kit and relevant commercial chassis then 9" radius is fine.

Not sure why Heljan went for such a large minimum radius -

Part of the reason would probably be the outside frames; the old Minitrix chassis recommended for the Stenning kit has no such authentic niceties below footplate level.

[Nile]

It will negotiate 9" curves, but there is no guarantee it will do so 100% of the time while pulling a train, hence the caution by Heljan. It's a long loco and those pony trucks are at their limits on such tight curves. Peco set-track was never meant for such big locos, but smaller ones like Minitrains.

[knitpick]

It will negotiate 9" curves, but there is no guarantee it will do so 100% of the time while pulling a train, hence the caution by Heljan. It's a long loco and those pony trucks are at their limits on such tight curves. Peco set-track was never meant for such big locos, but smaller ones like Minitrains.

 

Interesting - mine wouldn't - but then I was using N gauge 9" radius Peco set-track rather than 009 set-track.  [009 set-track wasn't available back then.]  I didn't expect there to be any difference.  Then again, it may depend on the actual Heljan model one bought?

[Bob S]

Greetings from California!  New member of this forum.

 

I’ve been Modelling in OO UK and ON30 for a while now, and have recently started an OO9 micro layout.  It’ll be on a 2’ by 3’ board, with a track elevation of at least 6”.  I’ve been doing some grade and clearance tests to confirm the viability of my plan.  I’ve run a MinitrainS Gmeinder and a Bachmann Rheneas, and both easily handle a 5% grade on a 9” radius curve pulling 7 minitrains shorty rolling stock. Coaches and vans will be heavier, but that’s the restrictions real railways had to deal with!

 

I now come to my question for you good folks.  Is there an accepted OO9 clearance standard for tunnels and bridges?  In the US, height is 2 3/8” and width is 1 3/4” .  Trying it on my test track, it looked much larger than necessary.  Particularly, if I can make the height less, I can reduce the grade to 4%.  I note that Bachmann sells an OO9 tunnel portal.  If anyone has one, what might it’s dimensions be?

 

So guys, thanks in advance for any advice you can share.

[Bob S]

Oops guys, I’ve found my answers embedded in other threads; whatever fits!  I’ll go for that, but any opinions would still be appreciated.

[PaulRhB]

Bob, it’s another depends answer! Loading gauges vary enormously. Quarry lines might just clear the dimensions of a cabless little 0.4.0 and others like the Leek and Manifold has to clear a standard gauge tank wagon on a transporter. The Festiniog has a very tight loading gauge so while the FR locos can run all the way to Caernarfon, on the connected Welsh Highland, the WHR Garratts can’t get past Boston Lodge on the FR. The replica Lyd L&B has special rounded corners to its cab roof to get it within the FR loading gauge. 

Lines like the Talyllyn and Lynton & Barnstaple also had pretty tight clearances to their stock but which would preclude stock from 2’ 6” lines (eg Welshpool & Llanfair) but comfortably take the majority of 2ft gauge stock.  

In many ways it’s best to get drawings of the biggest stock you intend having and work the gauge out to cover that, allowing for overhang on corners  

[Bob S]

Thanks Paul.  Interestingly, in the US there are NMRA clearance standards.  For narrow gauge, it recommends a standard “classical” clearance, meaning 1800’s like the 4-4-0 American, etc.  This would accommodate the nearly full size rolling stock.  

 

However, I’ll be Festinog and Talyllyn type right of way, and the NMRA clearances are way too huge!  So, custom dimensions it is.  Thanks!

[BernardTPM]

The Festiniog was particularly limited by its horse and gravity worked origins, with tight clearances as a result and minimal headroom. For my own project I adopted the structure gauge of the NWNGR which was designed for locomotive operation from the outset, though with an added twist of a underheight bridge built over the line by the Cambrian Railways (both lines would have been built about the same time, mid-late 1860s).

[Hobby]

On 07/06/2019 at 14:28, Bob S said:

Thanks Paul.  Interestingly, in the US there are NMRA clearance standards.  

 

Sounds like the NMRA trying to be all things to all men... They obviously don't understand narrow gauge!!

 

As Paul says it depends on what the real line was designed to carry. A mine railway could have minimum clearances, especially if it was a drift mine and the railway came out from the mine itself... On the other hand a narrow gauge railway that had to transport SG stock on transporter wagons or bogies would be a lot, lot bigger. Some places such as Saxony in Germany had a deal of standardisation, especially stock in their case, but even then the minimum radii was different with some lines having curves too tight for the newer locos!

 

Best bet is to decide on your prototype and that will govern the loading gauge!

[PaulRhB]

The NMRA standard is for US lines and they think mainly in terms of Colorado, as the Maine 2 footers will tell you  

There’s classic for the 4-4-0’s etc then there’s the K37’s