Model Railway Forum banner
1 - 8 of 8 Posts

·
Just another modeller
Joined
·
9,983 Posts
Discussion Starter · #1 ·
Hi all

We have several "new modellers" asking layout questions so I thought I'd write a few words on how to make a good job of creating a gradient on the layout, and show a simple tool I make in 5 minutes to keep things consistent. All notes are written with 3.5mm~4mm scale (HO/OO) in mind but the basics apply in all scales and gauges. Experienced modellers *Please note*. I know that a shallower gradient is ideal always BUY many modellers still want the variety of different levels without having the luxury of a large layout, so I am targeting info to the smaller layout which has less choice!

First a little about gradients.

Its tempting to make an up and over on a small layout or add a second level without really thinking about how steep it will be or how well the loco's will cope with it. Nickel silver rail and NS wheels as used on many of our loco's are actually quite slippery however, so its important that we match the gradient to the type of trains we want to pull and the types of loco's we will use.

So - the first thing to understand is that the steeper the gradient, the less wagons or coaches can be used in the average train.

Limits: You CAN go steeper of course but ideally please regard 3% or 1 in 33 as the steepest gradient that can be used without putting severe load limits on loco's. Always, shallower gradients are better, so plan VERY carefully for them.

Clearances: For HO/OO, a "track over track via a bridge" separation of 75mm is a good rule of thumb to aim for, as we have to allow for the thickness of roadbed or bridges as well as the "on track height" of any loco's. If you want to run any overhead electric locomotives, even if you will not use real overhead wire, you will have to allow a wee bit more to clear the pantographs.

for a second level that will allow storage, you really need at the very least 125mm clearance. This allows for the thickness of the top board, the bracing of the top board and a tiny bit for hands to get to rolling stock on the lower level.

Ideally more "headroom" - ie: a clearance of 150mm or more track to track should be the aim of course.

Please note if there is no room for a fully braced top board, then lots of "props" spaced say 200mm / 250mm (max) apart will also do the job. Don''t skimp on them though!!

Keeping it at a gentle rate: The best way to do this is to "split" the gradient, so one track rises as the other goes downwards. If you do this you can get twice the separation in the same distance, or even better, halve the steepness to get the separation you need! If you can only go "up" then make sure you start it early as you can so it can be as shallow as possible.

Start it gently! A gradient should start at zero and slowly build to the chosen angle/rate of ascent/descent. Sharp transitions will guarantee derailments and problems with running. Be SURE you make it a smooth transition and TEST it with your longest rigid frame loco's and rolling stock.

Because of transitions, it takes MORE length than a simple calculation tells you! The start and end of a gradient will "transition" from Zero to the chosen rate of ascent/descent. The minimum smooth transition will be LONGER for a steep gradient than for a shallow one. Acknowledging the fact that most layouts will be small-ish, allow 33cm at BOTH top and bottom for the transitions. To keep it smooth try to NOT have rail joints on transitions and similarly, for (I think) obvious reasons, avoid any turnouts/pointwork on the transition areas please.

For the 33cm allowed each end, assume only 1/2 the rise of the main segment of the gradient.

Example. You want to rise a total of 10cm at a rise rate of 1 cm in each 33cm (This is also called a 3% gradient).

Allow 1/2 of a CM for 2 lots of 33cm (the transitions) so... 66cm takes you up 1.0cm
allow 1cm per 33cm for the rest which will be 9.0cm. 9x33 = 297cm
add them both together and you will have a total length of gradient needed of 297 + 66 = 363cm! That's 3.63 metres or a full 33cm MORE than you probably thought it might take!

Avoid sharp curves on gradients if you can: a curve has a lot of friction, and a curve on a gradient is a VERY tough thing for a loco that has a heavy train. Accepting that you will have to use say second radius sometimes, be aware in your planning for operations that if you are using steep-ish gradients, then this will reduce the load the average loco can pull up the grade by about 20% compared to the same grade on a straight bit of track. (so if it could pull 5 coaches up a 1 in 33 grade on straight track, it will probably only be able to manage 4 on a curve of the same steepeness).

Avoid "Humps" in gradients - keep them smooth: The best way to do this is use the simple tool I have drawn in the diagramme attached to this post.

Have a realistic "reason" for the gradient... Avoid simple "Up and downs": They always look toylike and are quite hard to treat well scenically. If it must just go up and down then at least try to hide some of it in a tunnel or behind buildings!

Support gradients really well: Use more supports than you will use for flat track - say every 200mm as a target! you CAN use thin trackbed but be careful of material choice. two layers securely glued together will always be stronger than one layer of the same thickness! (example: two layers of 3mm MDF or customwood glued firmly together will be stronger and less likely to warp than one layer of 6mm thick material)

Using the "Tool": Place it on the trackbed that forms the rise. Put the level on the tool. When the level has the bubble centred, you are at precisely the right gradient angle!

I hope the above is clear, and helps your planning - please don't hesitate to ask if you have questions.

Regards

Richard Johnson
 

·
Registered
Joined
·
5,592 Posts
In effect Richard you have created what Toolmakers call a Sine bar, should the overal length between the two contact points be 5" as I recall then you can simply look up the sine of the degree, as it's nearly 40 odd years since I used one, I'm a bit rusty but
:Wikipedia Sine Bar will relay the concept.
 

·
DT
Joined
·
4,794 Posts
Very good info thanks.

I have a couple of gradients on my layout. I learnt the hard way how to do it. The first one I built looked great, but didn't work as it was too steep and on a curve. I now have an up ramp that is about 1:40 and over 6 meters long.



See here for more photos.

I have a dedicated down ramp that is much steeper, but it is hidden and will only be used to bring trains down to the yards from the mainlines. I have thoroughly tested the ramps with all sorts of combinations of trains, locos and loads and I'm now very happy with them.
 

·
Premium Member
Joined
·
2,837 Posts
There is a lot of useful advice there Richard, although I would like to add a rider to one of your points. You can get away with a lot less than 150mm between levels with two provisos.

Firstly you can use aluminium angle or hardwood to brace the upper level which need only be about 15 to 20mm thick. Alternatively you could use ordinary softwood bracing but with arches cut into it where tracks will actually be underneath so that it is only 20mm thick at a few places.

Secondly you could make the top section removable if you need to deal with derailments underneath. I built both of these into a small looped figure-of-eight layout at a previous house and managed to get the top level only about 90mm above the lower one. Of course it is not so easy to disguise the different levels with a tunnel mouth.

Hope that might be of use to someone. Cheers, Robert.
 

·
Just another modeller
Joined
·
9,983 Posts
Discussion Starter · #5 ·
QUOTE (Makemineadouble @ 14 Dec 2007, 16:48) <{POST_SNAPBACK}>In effect Richard you have created what Toolmakers call a Sine bar, should the overal length between the two contact points be 5" as I recall then you can simply look up the sine of the degree, as it's nearly 40 odd years since I used one, I'm a bit rusty but
:Wikipedia Sine Bar will relay the concept.


***I used to hate those B*** books full of tables in school - thank god for calculators!

Thanks very much for the reference to it though, while I was sure it wasn't necessarily a new idea (few things ever are) its simple to build and use and now, with your reference to a history for it in "the real world", a bit more interesting too :).

I had no idea it had a precedent in toolmaking.

Richard
 

·
Just another modeller
Joined
·
9,983 Posts
Discussion Starter · #6 ·
QUOTE (Robert Stokes @ 14 Dec 2007, 18:55) <{POST_SNAPBACK}>There is a lot of useful advice there Richard, although I would like to add a rider to one of your points. You can get away with a lot less than 150mm between levels with two provisos.

Firstly you can use aluminium angle or hardwood to brace the upper level which need only be about 15 to 20mm thick. Alternatively you could use ordinary softwood bracing but with arches cut into it where tracks will actually be underneath so that it is only 20mm thick at a few places.

Secondly you could make the top section removable if you need to deal with derailments underneath. I built both of these into a small looped figure-of-eight layout at a previous house and managed to get the top level only about 90mm above the lower one. Of course it is not so easy to disguise the different levels with a tunnel mouth.

Hope that might be of use to someone. Cheers, Robert.

*** Good points Robert. totally agree.
The "removeable" comment is important too - thanks for mentioning it as I shouldn't have left it out!

Richard
 

·
In depth idiot
Joined
·
7,678 Posts
Good summary, but I would add one precautionary rider: do not trust the floor level to be a true horizontal. I got caught by this, blithely constructing my first real 'off the floor' layout in my teens. What was planned as a 1 in 40, summed with the floor gradient of roughly 1 in 100 to make a 1 in 30. Which was just too much for the train lengths I wanted, and required considerable reconstruction to correct. Probably less of a problem now with laser levels and all the rest: forty-odd years ago all I had was my dad's 10 inch spirit level...
 

·
Registered
Joined
·
296 Posts
Thanks for the advice
- Are there any good examples of multi-level layouts on-line that one could take a look at?
 
1 - 8 of 8 Posts
Top