Gradients going down

[DavidBird]

I've looked around here and other places for information on gradients. The best answer is that a 1 in 50 (2%) gradient seems to be accepted as the steepest for reasonable train lengths that a wide variety of locos can cope with.

 

But what about going down?

 

The latest version of my planned layout, with storage sidings/reverse loop at a lower level has the track leaving the visible area, going steeply down to the storage level, into a fan of 2 or 3 storage sidings, round the reverse loop and gradually up on the 1 in 50 back past the storage sidings to re-emerge on the visible top level.

 

Whats the steepest down gradient I can use?

 

Does it just depend on what the vertical curve radius is, if so whats the minimum I can get away with for that?

 

Also what do others think about how much space needs to be left between the two levels to allow for access? I was thinking of about 25cm, as that is the highest position available for a shelf in the kitchen unit. I know this would need at least 12.5 metres of 1 in 50 to climb back up, hence the idea of dropping down as quickly as possible.

[kipford]

I consider there can be no one correct answer for this. I have dropped to 1 in 30, using 3 coach trains and a pacific, without problem on my sons old layout. The actual value to use will depend on a number of variables. As you say the radius of the curve makes a huge difference due the drag on the wheels increasing from a straight incline. How many coaches/wagons you want to haul along with the tractive effort of the loco will also effect things, use of weighted locos, traction tyres (argh) etc.

 

I do find modern DMU/EMU stock eat gradients for breakfast though.

 

As appears to be central to the design of your layout, may I make the suggestion that you actually make up a test incline and trial out various scenarios with the intended stock. It although it may cost a little extra in time and money, its better than finding out its all gone to rats when you run the first train.

 

Regards

 

Dave

[Allegheny1600]

Hi there,

From what you say, it looks to me as though you could go very steep indeed! However the prime limiting factor must be the transition from level to gradient - too sharp and your longer stock will bottom out at the apogee and possibly bogie stock will come off at the perigee. Depending on your coupling system, you may also have trouble with these - Kadees for example do not take kindly to sudden changes in gradient!

Bearing these criteria in mind, i do not see why you couldn't go to a grade of 45%!!!! (1 in 2!) although for that kind of grade, the transitions would be rather long!

HTH,

John E.

[DavidBird]

Thanks

 

Seems as if I'll have to do some testing here, to find out what transition into the gradient I can get away with.

Problems seem to be

Long coaches bottoming out - Hornby Mk3/Mk4s in particular

Long rigid wheelbase stock eg Hornby 8F/Bachmann 9F and also possibly rigid all-wheel-drive bogied diesels (Bachmann Deltic) "rotating" on the centre axle only

 

A test rig is called for - and its not going to be as simple as a piece of track on a plank with blocks under one end!

[HLT 0109]

Thanks

 

Seems as if I'll have to do some testing here, to find out what transition into the gradient I can get away with.

Problems seem to be

Long coaches bottoming out - Hornby Mk3/Mk4s in particular

Long rigid wheelbase stock eg Hornby 8F/Bachmann 9F and also possibly rigid all-wheel-drive bogied diesels (Bachmann Deltic) "rotating" on the centre axle only

 

A test rig is called for - and its not going to be as simple as a piece of track on a plank with blocks under one end!

 

David, I have been watching this thread to see what came up as I have contributed at length to an earlier one on inclines - I confess I see no difference between the requirements of inclines and declines. I have built only one layout so cannot claim extensive experience but my gradient was an afterthought so had to fit what was already done. I have a gradient of 1:20 at the bottom increasing to 1:15 at the top over a total length of 25 feet and have just modified the top transition in order to eliminate an "S" bend immediately before a standard point. It was your reference to a Bachmann 9F that prompted me to join the discussion because it is that loco that caused me the most trouble. It was not the steepness of the gradient (although it affects the amount of rolling stock that can be handled) but the transition. The problem was that the front pony wheels lifted when the transition was too abrupt and often lead the driving wheels off too. In reverse, the 9F tender would also lift off the rails because of the inflexible coupling to the loco. This was aggravated by the "S" bend which has now gone (and the standard point which has been replaced with an express point) but I also took the opportunity to make the tranisition more even. The top transition takes place over a distance of two feet on a bend of about a 4th radius and the 9F now handles the gradient perfectly. Do take care also to avoid tilting the track sideways within the transition.

 

Just an aside - my Hornby Railroad A4 looses traction altogether on the 1:15 if it has any coaches attached and is pulled back to the bottom! However, my Bachmann diesels (classes 25, 37 47 and 55) all pull five coaches up the full incline without difficulty (and take them back again) whilst my Bachmann 3-coach 108 does struggle a bit. I call my incline "Struggleup".

 

Harold.

[DavidBird]

Thanks, Harold

 

Thats given me a bit more to think about.

 

 

The top transition takes place over a distance of two feet on a bend of about a 4th radius and the 9F now handles the gradient perfectly. Do take care also to avoid tilting the track sideways within the transition.

Just to be clear, is the top transition 2 feet horizontal distance from the end of the 1 in 15 to the start of the level? If so, then that seems to be a reasonable amount. On my layout this would be the start of the descending section and I think I could use a sharper transition from the gradient back to the level

 

Also, thinking about it, any curve on a gradient is twisted. The outer rail is longer than the inner rail, so must have a shallower gradient. Any straight track with differing gradients on each rail would obviously be twisted, so curves are also twisted.

 

Just an aside - my Hornby Railroad A4 looses traction altogether on the 1:15 if it has any coaches attached and is pulled back to the bottom! However, my Bachmann diesels (classes 25, 37 47 and 55) all pull five coaches up the full incline without difficulty (and take them back again) whilst my Bachmann 3-coach 108 does struggle a bit. I call my incline "Struggleup".

 

Harold.

Seems to confirm the general view from elsewhere that 1 in 30 is the absolute max gradient for reliable climbing with a variety of stock

[Nickinwestwales]

David:-Hi there, I will start off with the good old received wisdom....In this instance the late & lamented C.J.F :-One of his `out & back` plans gives a recommended 1:30 going down & 1:40 back up,which,if memory serves was for 4 coach trains of 60`s vintage (with all that that implies in terms of axle friction ) and whitemetal kit built locos.

On my own layout,the `big bank ` is 12 ` at 1:40-most of the big steamers ( M/N,B/B ,9F,Duch,King ) will take 6 up without gypping-although the `little bank`-a further 8` at 1:60 through S bends at the other end of the midway station is a great leveller...........The C.N / O.N.R Diesels, working in pairs,will walk an N.M.R.A weighted 20 car train up without hesitation-but I put that down to 8 wheel drives & lots of lead weight.

 

But enough of that-you are talking about down the hill-My best advice is:- precise carpentry-As noted above ,a smooth transition-if possible make a single smooth run off from your high point to the centre and then reverse the (vertical ) curve to the lowest point -worth spending some time calculating the exact required height of each support,This way you may well be able to pack in a steeper gradient than might be expected....Just remember to post notices that drivers of loose coupled freights need to stop to pin down brakes.....

 

As a footnote,from the prototype for everything dept,a line locally ( The old Fishguard & North Pembs.) ran at a 1:29 gradient from the junction west of Clynderwyn up to Rosebush then down at 1:40 to the Jn at Letterston-incoming ballast trains for the harbour construction were limited to 4 wagons.......

 

ATB

Nick

[HLT 0109]

 

Just to be clear, is the top transition 2 feet horizontal distance from the end of the 1 in 15 to the start of the level? If so, then that seems to be a reasonable amount. On my layout this would be the start of the descending section and I think I could use a sharper transition from the gradient back to the level

 

Also, thinking about it, any curve on a gradient is twisted. The outer rail is longer than the inner rail, so must have a shallower gradient. Any straight track with differing gradients on each rail would obviously be twisted, so curves are also twisted.

 

 

Seems to confirm the general view from elsewhere that 1 in 30 is the absolute max gradient for reliable climbing with a variety of stock

 

David,

 

I confirm that the 2 feet is as you describe but I would advise against a sharper transition. If I had had room I would have used a gentler transition. However, if you use a 1:30 gradient, the transition will take only half the space of mine at the same intensity.

 

I am not sure about your reasoning/conclusion on curves and twisting but it is very difficult to avoid canting the track around a curve on an incline and this readily leads to derailment if there is insufficient room to level it up again before the end of the transition. If your transition is on a curve, the longer the transition the better, I think!

 

I hope this helps.

 

Harold.

[DavidBird]

A bit of basic trigonometry has given a value of just about 9 metres as vertical curve radius in Harold's 1 in 15 to level transition.

 

Using that radius in a S-shaped (+ve transition/-ve transition, no constant gradient) gives a distance of just over 3 metres to drop 30cm, and a steepest gradient (momentarily, at the change from +ve to -ve v/curve) of 18% or 1 in 5.5

 

How does this sound?

 

As Nick in West Wales says

My best advice is:- precise carpentry-

...

-worth spending some time calculating the exact required height of each support,

...

This seems to be the way to go.

[HLT 0109]

A bit of basic trigonometry has given a value of just about 9 metres as vertical curve radius in Harold's 1 in 15 to level transition.

 

Using that radius in a S-shaped (+ve transition/-ve transition, no constant gradient) gives a distance of just over 3 metres to drop 30cm, and a steepest gradient (momentarily, at the change from +ve to -ve v/curve) of 18% or 1 in 5.5

 

How does this sound?

 

As Nick in West Wales says

 

This seems to be the way to go.

 

Interesting calculations! I drop about 140mm in 3m, including the top transition; does this suggest a momentary steepest gradient of about 1:12? If so, then there is something wrong - my maximum gradient is 1:15. Running yesterday, my class 37 pulled six coaches up the incline (just!) with lots of wheelspin. Going downhill, the loco wheels can be heard to skid, although they do not lose traction - ie I can still stop the train. Usually I would pull four coaches at a time uphill. Undoubtedly, Nick's advice is sound - I wish my carpentry skills were so.

 

Harold.

[34theletterbetweenB&D]

a steepest gradient (momentarily, at the change from +ve to -ve v/curve) of 18% or 1 in 5.5

 

How does this sound? ...

Crash, bang, wallop!

 

Any metal tyred loco will be on the slide when the gradient goes much steeper than 1 in 15 on nickel silver track. So it will accelerate through the steepest section under gravity, then slow down on the shallower gradients lower down as traction is regained. Any sort of length of train, (especially of 4W wagons) will bunch up as the loco slows, and as more fast moving vehicles on the steepest section pile in from behind...

 

Transitions on straight track in OO, a good rule is a rate of 1 in 100 or easier, for the simple reason that the flanges are roughly 1mm deep, and the longest rigid wheelbase will be something like a 9F approaching 100mm long. Some attention may well be required to ensure enough free travel in pitch in bogies and vehicle couplings, particularly loco to tender. That rate will transition to a 1 in 20 in under 400mm, and that's about as steep as you want to go descending, as the loco will then be able to hold the following train at constant speed.

 

Gradients on curves, as you have realised inevitably have a 'wind'. Best kept very gentle (under 1 in 100) if reliable running is a priority, and avoided altogether if possible

[250BOB]

Gradients eh...?

 

I run 6 coach passenger trains...00 guage, and about 20 wagon freights........I first started with 1:48 gradients, which diesels mostly cope with....but it was a nightmare for most steam locos, I then reduce the gradients to 1:75 ish, and the problem is much better, although some steam locos need some severe amounts of weight adding still.

 

DO SOME TESTS IF YOU CAN...!!!!!

 

Bob

 

Check out this link to my thread on gradients the old RMweb site

http://www.rmweb.co.uk/forum/viewtopic.php?f=5&t=35936&p=552563#p552563

[Nickinwestwales]

Gentlemen all-first,thank you for acknowledging my contribution (warm fuzzy glow time...) second:-carpentry-It really isn`t that difficult,I dont know why people are so scared of it-

1st-draw out what you want on an old envelope

2nd -do it again on an A4 sheet (this is called a plan view)

3rd- get a beer from the fridge

4th-draw another sketch,but from the front and to one side (I think this is called 3rd angle isometric projection-but then again it might just be scribbling............)

5th-another beer-poss. some nibbles......

6th-Draw it out on the biggest paper you can find ( A1 for choice )

 

Now you should have a good idea of how it should look...so...open the toolbox-the only tool you need just now is the tape measure-remember to add the depth of roadbed to your calculations...and the most important rule of all:-measure twice,cut once-when in doubt,cut to the right of the line and shave a bit off rather than the other way around-at worst you have some useful kindling and start again.......We are not looking for the quick fix here-NASA didn`t put men on the moon by pointing in more or less the right direction and pressing the big red button

 

enough-

 

As a last thought,have you considered the American approach-the helix...???

 

ATB

 

Nick

[DavidBird]

Thanks Nick, points 3 & 5 sound especially useful

 

I'd considered a helix, but dismissed it because of the overall diameter projecting out into the room. But I may be able to be combine it with a end-of-dogbone type of reverse loop.

 

I need a bigger envelope...

[PWSlack]

I've looked around here and other places for information on gradients. The best answer is that a 1 in 50 (2%) gradient seems to be accepted as the steepest for reasonable train lengths that a wide variety of locos can cope with.

 

But what about going down?

 

The latest version of my planned layout, with storage sidings/reverse loop at a lower level has the track leaving the visible area, going steeply down to the storage level, into a fan of 2 or 3 storage sidings, round the reverse loop and gradually up on the 1 in 50 back past the storage sidings to re-emerge on the visible top level.

 

Whats the steepest down gradient I can use?

 

Does it just depend on what the vertical curve radius is, if so whats the minimum I can get away with for that?

 

Also what do others think about how much space needs to be left between the two levels to allow for access? I was thinking of about 25cm, as that is the highest position available for a shelf in the kitchen unit. I know this would need at least 12.5 metres of 1 in 50 to climb back up, hence the idea of dropping down as quickly as possible.

 

The vertical curve at the bottom is of interest. A recent test with an HO NYC 4-6-4 suggests it will pick its driving wheels up and sit on its bogies if this radius is much under 3 feet.

 

What couplings are in use? The Peco/Hornby Dublo side-operating coupler is immune to gradient changes, as is the Alex Jackson and the 3-link.