helix Does a helix ever really work?

[St Enodoc]

9 hours ago, GWR-fan said:

Possibly a slightly greater gradient on the straight track could be used,  reducing the gradient needed in the incline to account for additional friction in the helix.

The gradient in the helix is governed solely by the radius and vertical clearance between turns. A gradient on the approach would only have the effect of reducing the number of turns.

[AndyID]

Has anyone ever tried an automated switchback as an alternative?

[Grouse101]

Reading this with interest. Designing a new layout for a larger space. I want a significant amount of staging for 8ft+ trains. I'm considering a helix to allow staging below the boards, but I've had bad experiences with gradients before. I can get the gradient down to 1.1% by running three loops around part of the layout which drops the staging down by 50cm, but it involves 90m of track (double track), of which I think only 7m could be incorporated into the scenic layout which seems crazy.

[Alan Kettlewell]

A glimpse backstage at Miniatur Wunderland in Hamburg .. 

 

[RobinofLoxley]

13 hours ago, Grouse101 said:

Reading this with interest. Designing a new layout for a larger space. I want a significant amount of staging for 8ft+ trains. I'm considering a helix to allow staging below the boards, but I've had bad experiences with gradients before. I can get the gradient down to 1.1% by running three loops around part of the layout which drops the staging down by 50cm, but it involves 90m of track (double track), of which I think only 7m could be incorporated into the scenic layout which seems crazy.

I see that the Helix has two uses on a layout. One is to gain significant height in a situation where the alternative is metres and metres of steady incline, basically the helix length unravelled to straight. The other is a prestige project as in 'Look what I can build' as in Miniatur Wonderland.

[fulton]

Something else to consider, test your locos going DOWN a gradient, I had the experience on my old garage layout that some locos "hunted" terribly going down a 2% gradient, due to slack in their drive trains, maybe thrust washers would have helped but I just relegated those locos to the flat sections, this was all HO American diesels.

[Dr Gerbil-Fritters]

1 hour ago, RobinofLoxley said:

I see that the Helix has two uses on a layout. One is to gain significant height in a situation where the alternative is metres and metres of steady incline, basically the helix length unravelled to straight. The other is a prestige project as in 'Look what I can build' as in Miniatur Wonderland.

 

That's a bit unkind   MW need to gain height too.  I doubt anybody builds a helix just because they can!  Also, it's off-scene, so hardly 'look what I can build'....  

[NIK]

33 minutes ago, fulton said:

Something else to consider, test your locos going DOWN a gradient, I had the experience on my old garage layout that some locos "hunted" terribly going down a 2% gradient, due to slack in their drive trains, maybe thrust washers would have helped but I just relegated those locos to the flat sections, this was all HO American diesels.

Hi,

 

Just out of interest was that on DC or DCC?.

 

I ask because I'm working on an experimental gradient and curve predictor, plus I'm hoping to add a steep gradient on a curve to a hidden section on a club DCC layout*.

 

*The gradient will be mainly used in the down direction but could be used uphill by suitable trains.

Powerbase will be fitted in case it proves useful.

 

Regards

 

Nick

[Dr Gerbil-Fritters]

7 minutes ago, NIK said:

Just out of interest was that on DC or DCC?.

 

In my experience the control system doesn't make any difference - it's caused by slop in the mechanical drive systems in many model locomotives.

 

Powerbase and Bullfrog poop are not going to make any significant difference either - see Charlie's experiences on Chadwick.  Sometimes, physics is just physics.

[fulton]

Was DCC, I agree it was caused by slop in the drive train, I also found one loco, a Kato GP35, had no play what so ever to allow for any change in gradient, derailed every time on the transition from level to grade, another loco relegated to level sections. 

[Corbs]

I noticed there was some conversation and scepticism about bankers and helices somewhere (probably) so thought I would repost this.

 

The 2-8-4T struggled with the whole train on its own, but with the 0-6-0T banking they were both fine.

 

Key point: both locos are RC (here he goes again....) so no track connectivity loss leading to sudden lurches. The lead engine is running flat out on 3.7v and the banker slightly slower. A bit of wheelslip but I think I got it under control...

 

Similarly, our HST set now has two powered locos (one with a metal cab) and has absolutely no issue with a full length train.

 

 

[Colin_McLeod]

7 hours ago, Alan Kettlewell said:

A glimpse backstage at Miniatur Wunderland in Hamburg .. 

 

 

What is the radius and gradient on this one?.

[peach james]

5 hours ago, Dr Gerbil-Fritters said:

 

In my experience the control system doesn't make any difference - it's caused by slop in the mechanical drive systems in many model locomotives.

 

Powerbase and Bullfrog poop are not going to make any significant difference either - see Charlie's experiences on Chadwick.  Sometimes, physics is just physics.

For the hunting issue, this is true- because what is happening is the motor is being over-run by the grade, and is trying to be turned by the weight of the train pushing the loco.  If there is slop in the geartrain, then it will hunt as the motor alternatively slows down and speeds up.  The problem with DCC making it worse will be due to feedback on the motor exactly as explained upthread.

Powerbase and Bullfrog snot won't help in this case, or at least not much.  They both will work in a normal helix, as they are increasing the adhesive factor- one by providing increased downforce (Powerbase) and bullfrog snot by changing the co efficient of friction.   In the model engineering world, there is a wide aversion to using Aluminum wheels, in part because of the reduction of co efficient of friction. 

The logic of the experiment ^ (of putting locos on top of one another) probably has more to do with the slightly different CoF's of different wheels than anything else- that the profile can make quite a difference as to the CoF due to trapping of crud.  (the infamous "wrong type of snow" and "leaves on track" problems...)  The issues with 4-6-0 vs 4-6-2's are also well documented- the same thing goes for 4 cylinder locos vs 2 cylinder locos in real life- a 4 cylinder loco is going to be more surefooted than a 2 cylinder loco of the exact same weights.  (and an electric even better...).   

All of this to say, that if your helix is made at a minimum radius, you are going to have problems with it !  

Spiral Video by Peach James, on Flickr

Rest assured, he's not _still_ in the middle !  (he's also 15 years old now !)

[NIK]

Hi,

 

While doing some tractive effort tests on OO locos that there was tiny amount of oil being deposited on the inner edge of the rail. I put some talc on those edges and the tractive effort went up considerably. I did look into what different colour talcs were available to see if any matched ballast. However I think the main source of the oil was the bearings on my rolling road and since I find it so handy I may either live with the oil or get one of those wheel cleaning track pads.

 

Regards

 

Nick

[AndyID]

12 hours ago, peach james said:

For the hunting issue, this is true- because what is happening is the motor is being over-run by the grade, and is trying to be turned by the weight of the train pushing the loco.  If there is slop in the geartrain, then it will hunt as the motor alternatively slows down and speeds up.  The problem with DCC making it worse will be due to feedback on the motor exactly as explained upthread.

Powerbase and Bullfrog snot won't help in this case, or at least not much.  They both will work in a normal helix, as they are increasing the adhesive factor- one by providing increased downforce (Powerbase) and bullfrog snot by changing the co efficient of friction.   In the model engineering world, there is a wide aversion to using Aluminum wheels, in part because of the reduction of co efficient of friction. 

The logic of the experiment ^ (of putting locos on top of one another) probably has more to do with the slightly different CoF's of different wheels than anything else- that the profile can make quite a difference as to the CoF due to trapping of crud.  (the infamous "wrong type of snow" and "leaves on track" problems...)  The issues with 4-6-0 vs 4-6-2's are also well documented- the same thing goes for 4 cylinder locos vs 2 cylinder locos in real life- a 4 cylinder loco is going to be more surefooted than a 2 cylinder loco of the exact same weights.  (and an electric even better...).   

All of this to say, that if your helix is made at a minimum radius, you are going to have problems with it !  

Spiral Video by Peach James, on Flickr

Rest assured, he's not _still_ in the middle !  (he's also 15 years old now !)

 

That's a nice demonstration of how a "helix" doesn't have to be circular. If you have the room you can ease the gradient by splitting the helix in two and add straight inclines.

 

Another way to ease the gradient might be to make the the helix more like an old type woodscrew where the radius continuously changes. That means that you don't have to achieve the unit vertical clearance in a single turn, but might take a lot of space too

 

EDIT: I think I know now why the woodscrew helix idea is baloney but I'll leave it up there for entertainment.

Edited January 21, 2021 by AndyID

[Dr Gerbil-Fritters]

Charlie's posted some fascinating insights into the continuing Helix Saga

 

 

So add another 'desirable' to the list of Helix Commandments:

 

My radius shall be generous

My grade shall be shallow

My grade shall be consistent and accurate

 

Fascinating stuff.  I only have the one grade on my layout, and that's enough trouble on its own.  Kudos to the helix builders of the world!

[Grouse101]

Glad Charlie's fixed it. Has given me a bit more confidence to give it a go, especially since I can easily get the gradient to 1.5% by using straight sections between each half of the helix.

[Corbs]

We ended up lowering our segments to the minimum possible (height of Mk.1 coach plus human hand height for re-railing).

 

As an aside, Bachmann 57xx Pannier (non-split chassis) was amazing. Hornby Black 5 was abysmal.

[Sir TophamHatt]

I really don't like them.

I think they look big, bulky and ugly.

 

I understand their uses but if you have the space for one (or two!), you should have the space to fit a slope to get on and off any storage yard.

 

My layout isn't huge and I rarely leave any locos / trains on it.  I'm happy to take them off after a short running session as for me, the beauty is in the building not the running so much.

 

If I had the layout I wanted (it would be bigger than I have now but not huge), then there would be plenty of storage sidings and places I could drive trains to stable rather than some underground cave that looks more like a freight depot that you can't see.  Much more exciting having to drive to a part of the layout and stable rather than watching it slowly rise up an unrealistic circle of track, round and round... drive me round the bend!

[RJS1977]

I think use of a helix very much depends on the location it's in.  It doesn't really matter if they're ugly as most of the time they're used off-scene (Khan's for example was inside a mountain), and I'd query the argument that if you've got room for a helix, you've got room for a gradient - a 'normal' gradient requires a considerable amount of length, which gets longer the more height you need to gain. OTOH a helix requires a much shorter length, more width, and takes the same footprint for any height.

[Chimer]

25 minutes ago, Sir TophamHatt said:

If I had the layout I wanted (it would be bigger than I have now but not huge), then there would be plenty of storage sidings and places I could drive trains to stable rather than some underground cave that looks more like a freight depot that you can't see.  Much more exciting having to drive to a part of the layout and stable rather than watching it slowly rise up an unrealistic circle of track, round and round... drive me round the bend!

 

I tend to agree in theory, but MPDs, carriage sidings and goods yards require so much space if they're to look OK, especially if you want to pay attention to favourite RMWeb issues such as only trailing access, room for horses to turn carts, proper facilities and flows through depots etc, and have to straighten out your envisioned sweeping curves to fit in a turnout every couple of feet.  Whereas an underground cave .....

[mdvle]

1 hour ago, Sir TophamHatt said:

I really don't like them.

I think they look big, bulky and ugly.

 

I understand their uses but if you have the space for one (or two!), you should have the space to fit a slope to get on and off any storage yard.

 

Not really.

 

The advantage of a helix is that once you make the decision to have one you are no longer constrained in vertical distance, which in turn can mean the other level can be at a convenient height for access.  Want your storage yard to have 30" of headroom to allow easy access in case of a derailment or other problem - helix is easy, slope becomes a big problem.

 

But even if you are willing to sacrifice easy access to the storage yard so the vertical distance is minimal, where to you put the slope?  One option would be to put it at the front of the layout so it becomes part of the scenery, but for most people that destroys the illusion they are trying to create.  Put it at the back of the layout and you then run into access problems in the case of trouble, made all the worse if you have done scenery and aren't running a bare wood layout.

 

And that is without getting into the unavoidable fact that slopes also take up a lot of space or require extreme gradients that can (for many) cause operational problems.

 

1 hour ago, Sir TophamHatt said:

My layout isn't huge and I rarely leave any locos / trains on it.  I'm happy to take them off after a short running session as for me, the beauty is in the building not the running so much.

 

In which case you have no need for a storage yard, so neither possible solution is an issue for you.

 

1 hour ago, Sir TophamHatt said:

If I had the layout I wanted (it would be bigger than I have now but not huge), then there would be plenty of storage sidings and places I could drive trains to stable rather than some underground cave that looks more like a freight depot that you can't see.  Much more exciting having to drive to a part of the layout and stable rather than watching it slowly rise up an unrealistic circle of track, round and round... drive me round the bend!

 

If what you want in a layout can be achieved entirely in the visible area, then great, but again these sort of solutions aren't appropriate for how you want your layout.

 

But if you want to attempt to create the real railway - and have anything other than branch line terminus / small goods yard / mpd where a small fiddle yard for 2 or 3 short trains is enough - then you are looking at having 10 or more full length trains for passing through your scene.  And at that point the hidden storage sidings become a necessity.