helix Does a helix ever really work?

[ecgtheow]

Another contributor has probably already suggested it, but I would recommend testing the locos you intend to use on the layout with different loads on a small section say one turn of the maximum radius helix you can fit on your layout before committing to a helix. What I have suggested is quite easy to using blocks of wood of different sizes as you can easily move them around to see what gradient your trains will climb or start on. I have done this twice: once about 20 years ago on a layout of Wassen on the Gotthard line that I was building for my young son with 3 helices of 22“ radius (using Maerklin set track rather than flexitrack) in a room 17' X 14'. The steam locos were Maerklin & most had no problem with the longest passenger & goods trains planned to run on the layout so all the helices were completed, but then I accepted that my young son had almost zero interest in model railways & we moved house shortly afterwards anyway. More recently I have been building a much smaller 009 layout of of the Darjeeling & Himalaya Railway & found that a Backwoods Miniatures Class B 0-4-0 tank could only pull 2 brass DHR bogie coaches up a 12“ helix, but 3 if I increased the radius to 14“. I hope that helps.

 

William

[Chimer]

On 14/11/2020 at 14:16, imt said:

Yes but what was it FOR?  Apart from showing off that is - lots of consisted locos and wagons.  But it all goes in one way and comes out the same way. 

 

Same reason America went to the moon - to prove it could be done?

[scottystitch]

Just now, Chimer said:

 

Same reason America went to the moon - to prove it could be done?

Not because it was easy, because it was hard?...

[Peter749]

On 12/11/2020 at 19:23, class26 said:

 

Try White Rose, their Helix is well made and works.

 

I got the Proses version which comes as a kit and it very well built from Laser Cut MDF

 

Peter

[ELTEL]

Check out on YouTube “ Chadwick Model Raiway” as Charlie has done either two or three recent in depth videos on a Helix 

 

Definitely worth a watch.

 

Terry 

[Dr Gerbil-Fritters]

On 14/11/2020 at 14:16, imt said:

Yes but what was it FOR?  

 

I think it was for fun.  You remember, that thing we all used to have with our toy trains until we discovered model railways. 

 

[Largechris]

Just for information, Charlie has posted a helix testing update on Chadwick. The Powerbase isn’t totally convincing tbh. But I think his main conclusion is that the helix works with his stock (2% gradient). 
I think the original premise of this thread was that helixes were not a good idea - there’s an awful lot of variables though. I’d say they clearly can be made to work, if you have the space and appropriate stock. A 2% gradient is not ridiculous for prototype gradients in any case. 

[Corbs]

I wouldn't have thought anything using modern diesel or electric models (all wheel drive and huge cast chassis) would need a powerbase.

[gordon s]

Just watched the video on Chadwick which was interesting, but perhaps misleading as the gradients were much steeper than he suggests. A 2.83% grade is not 1:50 but 1:35 and 3.2% is 1:31 not 1:39 as stated.

 

This may go some way to explaining the lack of haulage from steam locos. Diesels with their higher weight and multi driven axles will always perform better. My personal view is a minimum of 1:50 for steam locos, although I would prefer to see 1:100 if you want to run full length trains.

[hayfield]

7 minutes ago, gordon s said:

Just watched the video on Chadwick which was interesting, but perhaps misleading as the gradients were much steeper than he suggests. A 2.83% grade is not 1:50 but 1:35 and 3.2% is 1:31 not 1:39 as stated.

 

This may go some way to explaining the lack of haulage from steam locos. Diesels with their higher weight and multi driven axles will always perform better. My personal view is a minimum of 1:50 for steam locos, although I would prefer to see 1:100 if you want to run full length trains.

 

To achieve this presumably the radius of the curves have to be larger ?

[ikcdab]

11 minutes ago, gordon s said:

Just watched the video on Chadwick which was interesting, but perhaps misleading as the gradients were much steeper than he suggests. A 2.83% grade is not 1:50 but 1:35 and 3.2% is 1:31 not 1:39 as stated.

 

This may go some way to explaining the lack of haulage from steam locos. Diesels with their higher weight and multi driven axles will always perform better. My personal view is a minimum of 1:50 for steam locos, although I would prefer to see 1:100 if you want to run full length trains.

I also watched Charlie's video with interest. It's important to factor in the friction from the tight curves. A 1 in 30 on a curve is a far more difficult proposition than a 1 in 30 on the straight.

[Harlequin]

12 minutes ago, hayfield said:

 

To achieve this presumably the radius of the curves have to be larger ?

Yes, Gordon set out the maths above:

 

This is really the core issue with helices, which others have already touched on in this topic: To achieve the gradients required to make them work reliably, without resorting to the powerbase solution, they have to be physically large and that is often impractical in the space that most UK-based modellers have available. And as Gordon and others have pointed out, an arguably neater solution is a "round the room" level change ramp that is combined into the general layout design.

 

Edited December 5, 2020 by Harlequin

[scottystitch]

On 05/12/2020 at 09:50, Harlequin said:

Yes, Gordon set out the maths above:

 

This is really the core issue with helices, which others have already touched on in this topic: To achieve the gradients required to make them work reliably, without resorting to the powerbase solution, they have to be physically large and that is often impractical in the space that most UK-based modellers have available. And as Gordon and others have pointed out, an arguably neater solution is a "round the room" level change ramp that is combined into the general layout design.

 

But that is still a helix, isn't it (admittedly only if it makes at least one complete revolution) just less compact than the ones being discussed up until now...

 

Best

Scott.

[Alan Kettlewell]

Here's a couple of short (poor quality) videos of my H0 layout showing several helices.  It's a U shaped layout with three sets of helices to take trains between three different levels.  The radii and gradients were carefully planned using some basic maths and spreadsheets, the smallest helices mainly used Peco radius 2 and 3 set-track curves - set-track is much preferable over flexi-track for these curves.  One end of the layout features a helix built above another helix - then it was all buried in a mountain - it was good fun working it all out and building it.

 

As for capability of trains - well the continental H0 diesel and electric locos would easily handle 10 or more coaches up there, but the steam locos were far less capable and could only pull 5 or 6 coaches up at best.  But given the restriction on steam locos it all works flawlessly.  For double track helices, where possible I designed it so the rising gradient was on the outside ie on the largest radius. 

 

The first video shows early testing during the construction so the helices can be seen.  The second video is from when the large helix at the end was covered with mountainous scenery     

 

 

 

There's a link to the layout thread below but I should add that I've discontinued building it now in favour of working on a new 0 gauge layout.

 

Cheers ... Alan

 

[Alan Kettlewell]

Here's another with some movement on the big helix captured ..

 

 

Edited December 17, 2020 by Alan Kettlewell

[Alan Kettlewell]

Helices ...

 

[AndyID]

On 05/12/2020 at 01:28, gordon s said:

 

This may go some way to explaining the lack of haulage from steam locos. Diesels with their higher weight and multi driven axles will always perform better. My personal view is a minimum of 1:50 for steam locos, although I would prefer to see 1:100 if you want to run full length trains.

 

It's the weight carried on the driven wheels that matters. An 0-4-0 of a given weight will haul just as effectively as a 2-8-0 or an AWD BO-BO of the same weight.

[DCB]

On 06/01/2021 at 17:44, AndyID said:

 

It's the weight carried on the driven wheels that matters. An 0-4-0 of a given weight will haul just as effectively as a 2-8-0 or an AWD BO-BO of the same weight.

To test the theory see what two similar locos will haul double headed, then tape one on top of the other and see if the combo still pulls the same train. To be absolutely fair swap the top and lower locos over.  I will be doing the test this evening

[AndyID]

44 minutes ago, DavidCBroad said:

To test the theory see what two similar locos will haul double headed, then tape one on top of the other and see if the combo still pulls the same train. To be absolutely fair swap the top and lower locos over.  I will be doing the test this evening

 

You can certainly do that but everything else being equal (surface lubrication etc, etc.) the contact area does not make the slightest bit of difference. It's simply the force produced by the weight that determines the friction.

 

Trust me. If locomotive engineers could have got away with making ever heavier 0-4-0's they would have but the civil engineers made them distribute the load over more wheels so they would not wreck the track.

 

I was fortunate enough to have a really great Physics teacher who taught us that our intuition was quite wrong.

[DCB]

The test was done, 2 X Gaiety Panniers on Hornby Dublo chassis double heading pulled 48 Hornby Dublo wagons and a brake van around the layout and struggled over the top of the 1 in 100 grade.   Placing one on top of the other resulted in less wheel slip but the loco stalled until a more powerful controller was hooked up at which point the haulage was almost identical, swapping locos made no difference.  However the Bachmann WD with sprung axles pulls more than the ROD of similar weight but no sprung axles. All good fun.  No other loco we have could match the haulage of one Pannier on top of the other...  Wrenn 8F, WC, Triang 9F included.

 

hss_333e_class_t9.pdf

Edited January 11, 2021 by DavidCBroad

[AndyID]

39 minutes ago, DavidCBroad said:

The test was done, 2 X Gaiety Panniers on Hornby Dublo chassis double heading pulled 48 Hornby Dublo wagons and a brake van around the layout and struggled over the top of the 1 in 100 grade.   Placing one on top of the other resulted in less wheel slip but the loco stalled until a more powerful controller was hooked up at which point the haulage was almost identical, swapping locos made no difference.  However the Bachmann WD with sprung axles pulls more than the ROD of similar weight but no sprung axles. All good fun.  No other loco we have could match the haulage of one Pannier on top of the other...  Wrenn 8F, WC, Triang 9F included.

 

hss_333e_class_t9.pdf 4.1 MB · 4 downloads

 

A very clever experiment. Well done that man!

 

Assuming they put almost the same weight on their drivers I suspect the difference between the ROD and the WD might have more to do with slight differences in the surfaces of the driver's treads than anything. Suspension definitely improves current collection but according to the laws of friction it has no effect on adhesion though that might seem quite counter-intuitive.

 

Sort of related to that full-size 4-6-0's tended to be more "sure footed" than 4-6-2's. When starting a train locos tend to transfer a fair bit of weight to the rear. With a 4-6-2 that transfers some weight from the drivers to the trailing truck. Of course that's not usually a problem with OO.

[Harlequin]

I see Charlie at Chadwick Model Railway is finding out about helices the hard way.

He has tried magnets and bullsnot and now he’s going to reduce the pitch and thus the gradient.

 

[johndon]

17 minutes ago, Harlequin said:

I see Charlie at Chadwick Model Railway is finding out about helices the hard way.

He has tried magnets and bullsnot and now he’s going to reduce the pitch and thus the gradient.

 

 

I'm sure he'll get there in the end but, so far, his videos haven't been a great advert for a helix...

 

[GWR-fan]

Several points to consider:

a) simply because a prototype loco will haul a given weight up a 2% gradient does not infer that a scale model will perform the same.  The prototype discovered that doubleheading or banking was a solution to traction issues.

b) the radius of a model helix is not going to represent the prototype so frictional losses need to be accounted for.

c) when approaching a helix I notice that it seems that everyone enters the helix from a flat surface.  If there is a straight section before the helix then why not reduce the incline of the helix by having a gradient on the section prior the helix.  Any height gain on straight track before the helix would require less gradient on the helix for the same overall height gain.  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.

[Dr Gerbil-Fritters]

Does a helix ever really work?

 

Yes, they always work but they'll work better if you can achieve two crucial criteria.  Shallow grade, and generous radius.  As the grade increases, and the radius decreases they'll very quickly work less well.  I'm guessing that most helices that don't work because they are being used in the wrong way for the wrong reasons.  They are not a space saving dodge, for example.

 

This guy has no problem with his helix - but the grade is shallow and the radius is generous.   His layout is superb, but that's a bonus!    

 

 

Having watched the pertinent Chadwick videos, I have to say that a 'just over 2% rise' on a 19 and 22 inch curve was never going to work.

Edited January 19, 2021 by Dr Gerbil-Fritters