helix Does a helix ever really work?

[Harlequin]

Whenever I see a helix being proposed in a layout design my immediate reaction is, "Oh dear. Never mind. Maybe your next layout will work..."

 

But is that reaction justified? Can a helix ever work successfully?

 

What's your opinion?

My negative opinion of them is partly based on personal experience of a ~300° double-track helix on an old layout. It was about 600mm radius and rose about 150mm if I'm remembering it correctly. My Dad and I thought it was a really clever solution when we designed it but in practice it limited the trains that could actually make the climb up to the big station on the top level and contributed to the ultimate demise of the layout. I'm also put off by the dubious "solutions" to traction problems that many people resort to, such as magnetic systems, because of all the new problems that seem to come with them.

 

What's your experience?

Have you got personal experience that would help answer this question? Tales of both Triumphs and Disasters are welcome!

 

What does it take to make a helix work in practice?

I wonder if we could establish the minimum parameters of a working helix for two distinct scenarios:

• Helix Scenario A: Steam traction with 6 or 8 driven (coupled) wheels, hauling 8 bogie coaches or 24 non-bogie wagons.
• Helix Scenario B: "Modern image" traction with 4 or 8 driven wheels spread across one or two locos or power cars, hauling 8 bogie coaches or 24 non-bogie wagons.

Let's assume that we are talking about current British 4mm OO models in both cases. *Without any third party traction assistance.

To control some other variables let's say that the train should be running at 50% throttle at the bottom of the helix, that the driver can ensure there's no wheel slip in the driving wheels and the helix "works" if the train can just crawl out of the top (or better).

 

Edit: I am thinking mainly about helices within the typically restricted spaces of British layouts and as a contained sub-part of the layout rather than being wound around and through the layout.

 

Edited January 10, 2021 by Harlequin

[Corbs]

We have one on our under construction layout, which is mixed eras from 1950s steam to 1980s diesel. We were aware of the limitations before we constructed it but really wanted one 

We have done a fair bit of testing, I’ll try and dig out the results.

It’s a 5 or 6 level climb with Hornby 2nd, 3rd and 4th radius curves.

I would say that you have to have the ascending line as the outside one as otherwise you are unnecessarily making things difficult for yourself, sideways drag has so much effect on what can be towed. 

 

Modern all wheel drive diesels like the Hornby Class 50 romp away with 16 bogie coaches or more. 
Steam locos do struggle and we are looking at limiting their loads to about 4 coaches unassisted. For longer trains we are using banking engines but that was part of the objective and the fun for us.

Hornby Black 5s have terrible haulage capacity, but smaller locos like Bachmann Panniers were often quite good for their size. Duke of Gloucester was also quite strong.

[relaxinghobby]

Gradient and radius of curves are the two factors affecting length of train able to climb up it seems to me an outside observer of the world of spirals and helix.

Alternative is a giant helix with the layout climbing around the walls and the return downward run can be shorter and much steeper.

If you have the room.

Spiral climbs are often promoted as a compact solution to doubling the area of the layout, a way of getting trains up and down between levels. I think the idea comes from over in the USA where big basement layouts have the room to allow spirals with easy radius curves and genial gradients which don't tax the locos much.

Me from here will just watch any developing debate as I don't have room for anything except a short terminal to fiddle yard layout.

Hang on thinking about it I could perhaps could  get a radius one curve helix in the corner connecting several terminal baseboards. especially if the spiral can be quickly packed away ? If the trains struggle to get up they will end up on the bottom levels and just light engines on the top.

 

 

[njee20]

I think they are more suited to heavier continental models (or limited British ones). 
 

I’ve always liked the theory - great way to maximise storage space, but they do seem to massively limit the length of trains you can run. If it’s not purely the gradient you get stock being pulled off the inside edge. 

[JimFin]

1 hour ago, Harlequin said:

But is that reaction justified? Can a helix ever work successfully?

Yep - if its the right size. https://www.miniatur-wunderland.com/discover-wunderland/worlds/austria/st-wendelberg/

 

[Zomboid]

They're relatively popular in America. The modelling scene there is mostly about diesels of course, and my experience of those is that they are heavy things with a lot of pulling power. My HO Atlas RS11 with 4 powered axles will happily pull 30 (not ridiculously heavy and free running) 4 axle freight cars on the level on its own at sensible speeds and it can move 40-45 at switching speeds if I drive it carefully. Though my Bachmann Russian Decapod (5 powered axles but it's a lightweight kettle) can't shift anything like that.

 

I imagine a helix would work fine so long as it's designed properly and with realistic expectations about what can manage a tightly curved incline.

[melmoth]

1 hour ago, Corbs said:

 

I would say that you have to have the ascending line as the outside one as otherwise you are unnecessarily making things difficult for yourself, sideways drag has so much effect on what can be towed. 

 

 

It's a pretty good principle for any double track rise as the increased length of run lessens the gradient relative to the inside track.

[melmoth]

42 minutes ago, relaxinghobby said:

 

Alternative is a giant helix with the layout climbing around the walls and the return downward run can be shorter and much steeper.

If you have the room.

Spiral climbs are often promoted as a compact solution to doubling the area of the layout, a way of getting trains up and down between levels. I think the idea comes from over in the USA where big basement layouts have the room to allow spirals with easy radius curves and genial gradients which don't tax the locos much.

 

 

There was an article in Model Railway Constructor in the late 70s/early 80s discussing the idea of a spiral around  the sides of a room, and it suggested the original idea was an American one. Unfortunately I can't remember the size of room it suggested, but the aim was to gain 18" on each circuit and the layout was assumed to be end-to-end.

[t-b-g]

Short answer! Yes!

 

 

Edit to add that I didn't build it but it was a layout I used to have great fun operating built by a good friend. Sadly, the friend and the layout are no longer around.

Edited June 6, 2020 by t-b-g

[Enterprisingwestern]

 

At the end of the day it's all down to physics.

Gravity pulls the coaches backwards and friction at the wheel/rail interface increases as the radius decreases, so the priority is to lessen these unavoidable circumstances.

As large a radius as possible and wheels with pinpoint bearings running in brass top hats will minimise problems, depending on space and finances available.

It's down to damage limitation and overcoming nature.

 

Mike.

[34theletterbetweenB&D]

49 minutes ago, relaxinghobby said:

...If you have the room...

That's the answer to the question right there. as some posts already acknowledge. It's not a restricted space solution, but an 'expander' for already generous size spaces.

 

2 hours ago, Harlequin said:

What does it take to make a helix work in practice?

...

To control some other variables let's say that the train should be running at 50% throttle at the bottom of the helix, that the driver can ensure there's no wheel slip in the driving wheels and the helix "works" if the train can just crawl out of the top (or better).

Allow me to suggest that better specifications are: 

that the loco can restart the train with the whole of it standing on the helix ascending,

that the loco can stop the moving train with it wholly on the helix descending.

Just because a steam model can do one, doesn't mean it can do both. Centre motor both bogies driven types, you only need to test the ascending restart capability, because they have a degree of stability which RTR rigid chassis steam models do not possess.

 

There's no substitute for testing the proposed gradients with the loco and stock combinations that will have to work if the layout is to be a success. Having seen the 'wrap around the room' helix on North American layouts I was sold on the idea long ago, if only I had the space. With the space now available, I have put all the gradient on the straight track, left the end curves flat. That was the best option for the steam models: had the operation been all centre motor both bogies driven traction there could have been gradients on the curves too.

[Harlequin]

I was thinking mainly about helices within the typically restricted spaces of British layouts and as a contained sub-part of the layout rather than being wound around and through the layout. I should have said that in the OP.

 

Obviously there's some maths and basic physics involved here but I have the feeling that many builders don't think about those things and just go ahead and build something that fits in their space before finding out whether it works.

 

30 minutes ago, t-b-g said:

Short answer! Yes!

 

Edit to add that I didn't build it but it was a layout I used to have great fun operating built by a good friend. Sadly, the friend and the layout are no longer around.

 

Thanks @t-b-g. That wonderful photos says something interesting: it may be that only a small increase in radius makes a big difference to the feasibility of a helix because it will have a big effect on the gradient. I think that particular helix looks like about 3ft radius. Does that sound about right?

 

@34theletterbetweenB&D I'm very open to changing the parameters. Why do you think it's important to allow for stopping and restarting on the helix? That would seem to make the test more difficult to achieve.

 

 

[melmoth]

I hope this is useful and fairly self-explanatory. A complete circle gives 3" of rise, which must be about minimum for clearance in 4mm scale.

 

[34theletterbetweenB&D]

1 minute ago, Harlequin said:

 

@34theletterbetweenB&D I'm very open to changing the parameters. Why do you think it's important to allow for stopping and restarting on the helix? That would seem to make the test more difficult to achieve.

It is more stringent, but this is my 'complete reliability' requirement. It doesn't matter where the train is on the layout, it will go when given power and stop if required to. If the trains won't restart aqscending the helix for example, then you need an operating discipline in place to prevent any train being stopped while ascending, to avoid manual intervention.

 

And these are much simpler tests than the subjective 50% power, no wheelslip, crawls off the top. Go / No Go, no subjectivity. (Can you see my background in QA showing?)

[Darius43]

They have their place and their limitations as have been excellently described in the previous posts.  A double track helix has been incorporated into the layout that my friend and I are building.  Some locos handle it with ease hauling a train, others less so.  A full length Hornby HST will manage it up and down on both the inside and outside tracks.

 

 

 

 

Cheers

 

Darius

[gordon s]

I started to look at a helix in the early ET days, but eventually went for a round the room spiral. The maths are quite simple. A rise of 70mm plus a 12mm trackbed means 82mm and at a 1:100 gradient you will need 8200mm run.

 

Put that into the usual Pi calculation for the circumference/radius of a circle and you have a radius of 1305mm and diameter of 2610mm. Once you add the possibility of double track and the trackbed, you're heading towards a 3m circle. Even at 1:100 the additional drag of the curve and the gradient is no guarantee that steam loco's will haul a 7/8 coach train up the helix.

 

It certainly needs some careful planning and a fair amount of space.

[Vistisen]

2 hours ago, JimFin said:

Yep - if its the right size. https://www.miniatur-wunderland.com/discover-wunderland/worlds/austria/st-wendelberg/

 

If you have not visited this place. Then you really should as soon as the pandemic is over( assuming you don't need a visa after Brexit) They really should just open it as a center for self isolation. 14. days is about right.  By then you should have had time to make a prioritised list of the bits to examine closely on the full visit later on!

[JDW]

In terms of it being an idea from America, some mentioned that US models tend to be heavier and more powerful, but I would imagine that it also helps that many US trains are headed by two, three, four locos, which would massively increase the power available for climbing. 

 

Personally it's something I'd avoid on a personal layout, as it feels like the trains would spend more time going round and round in circles and getting to/through/from the fiddle yard than actually on the layout. I can see the advantage at places like Miniatur Wunderland, though, where it's more a "show" than something to be played with. It does seem like a lot of extra expense and effort is required, adding various solutions to stock and track to get them up and down but as ever, its horses for courses. What works for one won't work for another.

[stewartingram]

A change of direction here, literally! Although I expect there would probably be no overall space advantage, what about a zig-zag railway to gain height? Just to add that I've done no calculations on this, It just crossed my mind whilst reading this thread.

 

Stewart

[t-b-g]

30 minutes ago, Harlequin said:

I was thinking mainly about helices within the typically restricted spaces of British layouts and as a contained sub-part of the layout rather than being wound around and through the layout. I should have said that in the OP.

 

Obviously there's some maths and basic physics involved here but I have the feeling that many builders don't think about those things and just go ahead and build something that fits in their space before finding out whether it works.

 

 

Thanks @t-b-g. That wonderful photos says something interesting: it may be that only a small increase in radius makes a big difference to the feasibility of a helix because it will have a big effect on the gradient. I think that particular helix looks like about 3ft radius. Does that sound about right?

 

@34theletterbetweenB&D I'm very open to changing the parameters. Why do you think it's important to allow for stopping and restarting on the helix? That would seem to make the test more difficult to achieve.

 

 

 

Hello Harlequin,

 

You are spot on with the radius. The chap who designed the layout was a maths genius, no other word for it. He worked out all the gradients to perfection. It was all about creating the minimum possible headroom from one level to the next.  The smaller the headroom, the smaller radius you can use to get from one height to the next  On that layout, a train running from one end to the other at a scale 60mph took 16 minutes, yet the room was only about 20ft x 12ft.

[t-b-g]

5 minutes ago, JDW said:

In terms of it being an idea from America, some mentioned that US models tend to be heavier and more powerful, but I would imagine that it also helps that many US trains are headed by two, three, four locos, which would massively increase the power available for climbing. 

 

Personally it's something I'd avoid on a personal layout, as it feels like the trains would spend more time going round and round in circles and getting to/through/from the fiddle yard than actually on the layout. I can see the advantage at places like Miniatur Wunderland, though, where it's more a "show" than something to be played with. It does seem like a lot of extra expense and effort is required, adding various solutions to stock and track to get them up and down but as ever, its horses for courses. What works for one won't work for another.

 

Having worked the layout shown, I disagree that it doesn't work well on a home layout. That layout was worked to clocks, timetables and block instruments. The 4 to 6 minute delay from a train leaving one station to arriving at the next gave you a bit of time to do some shunting, or to clear stock out of a platform for the next one to arrive. Operators used to work two, three or sometimes 4 stations, so it was intense and very challenging. It was one of my top two layouts I have ever had the opportunity to operate, being a very close second behind Buckingham.

 

I fully accept that this style of operating is not for everyone but if you do enjoy it, that was the layout to do it on! 

[Zomboid]

43 minutes ago, JDW said:

In terms of it being an idea from America, some mentioned that US models tend to be heavier and more powerful, but I would imagine that it also helps that many US trains are headed by two, three, four locos, which would massively increase the power available for climbing

In reality yes, though not necessarily in model form. Some lash ups have multiple powered locos, but unpowered dummy locos are available too (probably more commonly used before DCC).

 

Frankly my RS11 at least can pull the kinds of loads where I'd be starting to get concerned about the couplings if I used two of them, though I've no idea if I'd be right to do so. Properly fitted Kadees would probably be fine, but some of the cheap plastic knockoffs you can get...

Edited June 6, 2020 by Zomboid

[t-b-g]

One aspect of the layout I have illustrated is that part of the timetable included loading limits for various locos. So if a 6 coach train had to go up the spiral, it might have a smaller, less powerful loco. A 10 coach one needed the most powerful. If it so happened that all the most powerful ones were out when a 10 carriage train needed to go out, or one had failed, then double heading was arranged or a banker was used.

 

There was also a single track branch that went between the top two levels plus tracks that went round the back of the spiral but didn't go on it. So you could glance up from you operating and there would be trains going all over the place.

Edited June 6, 2020 by t-b-g

[Harlequin]

2 minutes ago, t-b-g said:

One aspect of the layout I have illustrated is that part of the timetable included loading limits for various locos. So if a 6 coach train had to go up the spiral, it might have a smaller, less powerful loco. A 10 coach one needed the most powerful. If it so happened that all the most powerful ones were out when a 10 carriage train needed to go out, or one had failed, then double heading was arranged or a banker was used.

 

There was also a single track branch that went between the top two levels plus tracks that went round the back of the spiral but didn't go on it. So you could glance up from you operating and there would be trains going all over the place.

Was this layout ever published anywhere? Might there be some info about it on the web?

 

[The Stationmaster]

56 minutes ago, gordon s said:

I started to look at a helix in the early ET days, but eventually went for a round the room spiral. The maths are quite simple. A rise of 70mm plus a 12mm trackbed means 82mm and at a 1:100 gradient you will need 8200mm run.

 

Put that into the usual Pi calculation for the circumference/radius of a circle and you have a radius of 1305mm and diameter of 2610mm. Once you add the possibility of double track and the trackbed, you're heading towards a 3m circle. Even at 1:100 the additional drag of the curve and the gradient is no guarantee that steam loco's will haul a 7/8 coach train up the helix.

 

It certainly needs some careful planning and a fair amount of space.

I'm not into such precise maths as Gordon but I did do a lot of calculations about including one to allow train to use hidden sidings under the scenicked area of a proposed layout.   In order to get useable gradients for r-t-r steam outline locos I very quickly realised that I was heading towards something like the sort of numbers mentioned by Gordon and in a room c.17ft x 11ft that  just would not work especailly if I went for a helix at each end of the room .

 

The key thing here is look at the sort of space I was going to put the layout into - pretty large by normal British standards.  I even got hold of a 'Model Railroader' booklet on helix design and construction and began to carefully check dimensions on US layouts using a helix and they were generally coming out at 6ft diameter or larger on layouts which were either wholly diesel worked or used more expensive, and heavier, versions of steam models.  My conclusion is that in British conditions a helix is not suitable for steam age layouts and needs a lot of space, for a large diameter,ion order to be consistently successful even with diesel outline models.