Gradients and Helixes in TT

[ateshci]

The models of bogie diesels are better pullers in general than those of steamers. This is because the rigid wheelbase is short and the bogies can flex under the chassis. This results in an uninterrupted tread-railhead contact taking full advantage of the available body-weight. Steamers, on the other hand, have a rather long rigid wheelbase without flexing capability. Our scale allows not easily for ( expensive as well ) flexichas designs in Mike Sharman's style, the only commercially available model I know of is Tillig's V36(236) model of an 0-6-0 side-rod diesel(!) loco. In general, the larger the wheel diameter, the more it is prone to slipping. That's why some models come with tender-drives -rather short wheelbase, small diameter, and you can pack in some weight, too. The loco is just a freewheeling dummy and lightweight.

Some people in the UK have overcome the gradient problem of their two-tier layouts by installing a vertical train-lift. 

[Silver Fox 17]

Don't forget that BR steam locos did not always pull up gradients easily some slowed and struggled and in a few places a banker was used on the rear and in other locations added at the front to double head.  There were a few places on BR with climbs like 1:100 which is 1% which is a lot less than the 2% you are talking here and that was hard for BR locos.

A 2% incline is like the 1:49 on the NYMR near Beckhole and that is hard going with 6 coaches on.

[Skelton Junction]

In hindsight, I’d not have used a 3% and tried to accommodate 2% at both sides but that would have included more R4 curves on the incline so somewhat self defeating. The branch doing the same distance one way at 2% is more agreeable I’m thinking. 

[Rallymatt]

To relate to the real railway, the infamous Tyne Dock to Consett line was the steepest locomotive worked line on the BR Network, just near me the grade started to ramp up to 1.8% (1in55) and West of Stanley 2.8% (1in35) ore trains of 9 40 tonne bogie hoppers were hauled by modified 9fs, very powerful and superb traction; to get up the grades they needed a second one as a banker! Real locos could also use sanding to aid traction. 
Southern has always been popular with modellers because of its short expresses, powerful locos and half length trains. That was primarily due to the steep climbs and tight bends that nature forced on the railway. 
It’s rare that a model loco actually lacks ‘power or torque’ its weight that’s missing; a real A4 weighs approximately 105 tonnes, scaled down that would be 875g, our models are 152g. I appreciate the loads are less but the effect on tractive effort is notable. 
Always worth setting realistic goals for our model railways especially with gradients 😁

Edited March 26 by Rallymatt
Lazy finger

[ateshci]

@Rallymatt
May I nitpick? As the weight is proportional to volume, and that is to be divided by 120³, the situation is even worse: 105(metric) tons scale down to 61g under the assumption that material density stays the same! Alas friction doesn't scale down accordingly, so we have to use crutches to pull scale-size trains or go uphill.

[Tim-1330659]

My helix will be 1st Radius, two loops not going to buy a kit I like the idea of building it myself.  I will be in the wagon yard up the top. Working on the 2 deg seems to fit in nicely with heights and clearances.

[Yelrow]

i built  all mine. used threaded rod, and nuts.

[ntpntpntp]

36 minutes ago, Tim-1330659 said:

My helix will be 1st Radius, two loops not going to buy a kit I like the idea of building it myself.  I will be in the wagon yard up the top. Working on the 2 deg seems to fit in nicely with heights and clearances.

What height are you climbing for each revolution?
I would imagine the bare minimum is 45mm (doesn't allow for any pantograph locos).   My calculations using R1 (267mm) curves makes that roughly 2.5% gradient, not only is that steep for a straight gradient and locos with no tyres but on such a tight radius as well that's a lot of drag.   Good luck but I would have serious doubts!

[Rallymatt]

1 hour ago, ateshci said:

@Rallymatt
May I nitpick?

Of course you may 😁 It was only intended as a very basic example of how our model equivalents quite literally have an uphill battle to match the performance of the real thing. The motors are actually, in most cases the saving grace. 👍

[Too Tall]

1 hour ago, Tim-1330659 said:

My helix will be 1st Radius, two loops not going to buy a kit I like the idea of building it myself.  I will be in the wagon yard up the top. Working on the 2 deg seems to fit in nicely with heights and clearances.

Yep, I think any helix needs minimum R3 and even then, as I noted originally, its pretty steep. If you have much heavier 00 steam locos struggling on a R4 helix as has been seen on YT, TT isn't going to be any better !

I think if I want a 2 tier layout, it may need to be separate upper and lower levels

[ateshci]

There was a UK website describing the 'Valdovia Rwy' ( now defunct ) and the builder used two of these in line, driven by an electric motor and carrying a roughly 6' long track ( it was 00 ) to have his trains travel from one tier to another. When talking TT, a 1m long bridge takes the same space in length as a reasonable helix with 45cm radius to keep the 2% per turn would do without the depth requirement. Taken the costs for material, I don't think there's much of a difference

Edited March 26 by ateshci

[Too Tall]

You know, it gets more confusing 😆

Scissor jacks ... not really the point for me, I was after trains running themselves up (or down) an incline.

I downloaded some SCARM plans of multilevel layouts to see what had been done by others, and they are crazy ! HO layouts with near 5% inclines ( I think mostly American), how the heck does that work 🤔

back to the drawing board (or SCARM screen in my case) !

I don't like being defeated, but I might have to accept defeat on this 🤣

 

 

Edited March 28 by Too Tall

[Postman On The Rails]

The club magazines isssue 2 & 4 i think have a flyover at 4.5% What I have based mine on, but yet to build.

Edited March 28 by Postman On The Rails

[Too Tall]

Success (in planning at least) ! I managed to get a quite nicely sized 00 layout with a 2 track passenger upper layer, and a single track goods line that traverses upper and lower layers, with a gnat's leg below 2% gradient up and down, the upper layer being 100mm higher (I would only need to rise 65-70mm for TT).

I am now working on being able to get both passenger lines to be able to get on and off the goods line, not that I think I would have need, but if I can, the option is always a bonus ! My brain has been struggling to plan in 3 dimensions so its been slow going 😄

I haven't yet decided if my second layout is going to be in TT or 00, but if I get an 00 plan down, designing a similar one for TT will be a lot easier than the other way round !

Likely it won't be started until next year as I want to finish Millbrook off first, and I have to sell all my slot cars, as its their track I am losing to make room. 😜

Still it's never too early to start planning 😊