Helix Query

[Newmodeller96]

I have always wanted to add a lower level fiddle yard to my design. I have been doing some work with dimensions in my loft space and have come up with the following design. I don’t have the ability to have a double track helix which is a shame however I can fit 2 x 3rd radius helix one each side of the layout. I would then design a fiddle yard with a line that can swap trains from the UP to the Down side of the fiddle yard. I plan on having the fiddle yard only about 8 - 10 inches lower than the main layout as space is of a premium still.

 

My thought is that with the double slips at the top of each helix means that i could technically move a train off of each line to each helix however on second thoughts i don’t think there is need for this as I do want to run them as UP & Down lines so the trains would only need to run off the helixes in 1 direction. 

 

Looking forward to some constructive advice about these. 

 

 

 

[ITG]

I too am exploring helices, and have a thread running.

what I can’t tell from your plan is where the entrance / exit roads are from each helix, other than the connecting lines between each helix. 
can you provide more info please? As it is the only way on/off looks to be onto the other helix?

Ian

[RobinofLoxley]

Whatever else is going on, remember the helix has got to descend at an incline that is feasible, say 2%. You are only showing a single curved track at top left before expecting the track to pass under the sidings. A helix is going to need all of the circle to descend before it can pass under other tracks. So I cant see your proposal as being remotely feasible I'm afraid.

[Newmodeller96]

Thanks @RobinofLoxley I realised this today while having a play. I have had a bit of a play and think that I have come up with a better option. I hope this helps with the issue of getting lines below the main layout. 

 

 

[Michael Hodgson]

My first concern with with this design is the ability to get into the corners for maintenance, especially the upper one.

I am assuming your access to the layout is a loft hatch into the operating well at the right.

The baseboards are not excessively wide, but the overhang of the helix effectively widens them and will prevent you from getting access even to the edge of the baseboard in those corners !

Or do you also have access to the left hand end?

[ITG]

The lower helix appears to connect to the double track mainline running above it. The link via the slip is probably some 400 mm away (using the 839mm as a reference). If that’s correct, to drop, say, a minimum of 70mm in 400mm gives  a gradient of something like 1 in 6. Impossible.

The other helix calculations seem similar.

 

And I still ask, where’s the exit on each helix?

Ian

[RobinofLoxley]

Although you havnt posted the full track plan, it looks as though you have quite a reasonable space barring obstructions that as I know too well are very common in lofts. In which case you may be able to factor in an incline to a lower level. The problem then is always turning any train that has gone down the incline, as a return loop needs the same space as a Helix more or less. You could read the recent thread by ITG to see the debate.

[Michael Hodgson]

What is confusing us is the entry/exit to the helices - I don't know how many turns you are proposing (not many for a fairly small height difference, but the number is nevertheless important for gradient calculation).  It's usually a number like 3 1/2, the half turn being to exit in the direction you want to end up going, which usually isn't the same way as where you went in.

[RobinofLoxley]

13 minutes ago, Michael Hodgson said:

What is confusing us is the entry/exit to the helices - I don't know how many turns you are proposing (not many for a fairly small height difference, but the number is nevertheless important for gradient calculation).  It's usually a number like 3 1/2, the half turn being to exit in the direction you want to end up going, which usually isn't the same way as where you went in.

True but a bit academic when the inidcated positions arent usable anyway

[Newmodeller96]

Ok thank you all for your comments. I guess the fundamental is that this won’t work. Here is a full image of my layout. Ignore the helix at the left I took a screenshot while I was playing around. The lift entrance is to the right of the layout and the 2 lines at that end are removable to allow access. Any help with a better position for a helix would be much appreciated. 
 

I’m pretty flexible with where it can go. I currently haven’t laid any track on the lower edge of the layout so can remodel to make that work. 

[john new]

Charlie, on YouTube has a good video on his helix - search for Chadwick Parkway. 
 

There is a lot of central dead space, I suggest doing what Charlie did and move the spirals (or reverse loops) to half way down one side.  Reason = you can then get into that area from both sides needing a reach length only equivalent to slightly more than the radius, where you have it now needs a stretch over the diameter + n to get into the back corners. Not practical for retrieving a derailment or for doing any scenics in that area.

 

Edited January 20, 2023 by john new
Added an extra note

[RobinofLoxley]

Can I just check that you are modelling 00 and ask what era, diesel/electric or steam? It affects whether a lower level definitely needs a return loop.

[Newmodeller96]

@RobinofLoxley sorry I should have said. I am in 00 so was hoping to use a single 3rd radius helix. I will be modelling late NSE to modern southeastern stock so mainly EMUs and DMUs which is why I hadn’t added a return loop into my equations. Hope this helps. H

[Harlequin]

Ideally, you need to keep the helix clear of all other tracks so that each wind of the helix only needs vertcial clearance to itself, and isn't forced to be steeper to clear other tracks.

 

You have a good location to do that (subject to there being some way to reach the back of it) in the bottom left hand corner, where the space beside the chimney breast is otherwise very difficult to use in the layout.

 

Maybe something like this:

[RobinofLoxley]

Yes it does, because a lower level storage area can be a set of dead-end sidings which is much easier to locate. Doesnt even need a headshunt unless you might have some freight, something using a loco. Say you need a 9-inch descent (22cm) at an average of 2%, of that 22cm only 7cm is required for clearance of the overhead track plus baseboard (ignoring supports which is a bigggg factor) which is 3.5 linear M of track, one long side plus a bit. The implication is that the descent would require two sides, plus the second long side for the sidings.

 

If you used a Helix, it would need 3 turns to get 22cm drop, although 2 turns might be enough, but it would have to sit in the open space, or if you tucked it into one of the alcoves, change the layout quite a lot (as @Harlequin has just shown while I was typing)

[Michael Hodgson]

There is dead space in the corner at the left hand side - is it possible to convert those corners to an access point for rerailing etc, via duck under* etc ? 

 

As it's a loft, there may not be enough space to get in and stand up because of slope of roof etc.  John New's point about the central space is partly valid, but I assume it's only the central area where there's headroom to stand up?  All the same, you've got a very large operating well/ visitor space, which I would be seekimg to use to put more track, whilst retaining access to the edges.  I agree that a helix half way down gives much easier access to its far side; Charlie's rounded corners to the bit of the baseboard protruding into the operating well aren't easy to construct but make a big difference.  Removing the helix you said to ignore in your latest plan leaves a lot of unused space in that bottom corner, where I would be aimimg to lay some sidings or whatever - but only in the parts that you can reach!  Narrowing the middle section at the left hand end (chimney breast?) and providing curved or triangular baseboards for the roundy roundy track might allow you to maintain access further into those corners.

 

If you've already built the baseboards, you may now feel it undesirable to change it and do more joinery, but building the baseboard before deciding to track plan is putting the cart before the horse.  But as you haven't yet laid the track, more joinery may be your best option.

 

* not great if you're elderly and less flexible !

[Newmodeller96]

13 minutes ago, Harlequin said:

Ideally, you need to keep the helix clear of all other tracks so that each wind of the helix only needs vertcial clearance to itself, and isn't forced to be steeper to clear other tracks.

 

You have a good location to do that (subject to there being some way to reach the back of it) in the bottom left hand corner, where the space beside the chimney breast is otherwise very difficult to use in the layout.

 

Maybe something like this:

Hi @Harlequin thank you for this. The only question I have is what are the 2 other lines coming away from the helix for? Would this be a long ramp back up/down so that I don’t need the second helix? 
 

@Michael Hodgson unfortunately I have quite a big slope on the roof so that corner that is unused isn’t able to be accessed standing up so I was planning on it being scenic/hidden below a hillside hence the helix below. 
 

the reason for the large centre is as you say because that is the only area I can “stand up” in and I actually can’t stand up properly anywhere which is annoying but I can overcome it. 
 

luckily I am 26 so don’t mind crawling around so much. I built the baseboard around the original design I had and have then changed some major parts since then so that is why they are already constructed. I will stick another post below with some pictures of the loft space for people to see so it might be easier to see where they layout is going. 
 

thank you for the ideas so far! 

[Harlequin]

12 minutes ago, Newmodeller96 said:

Hi @Harlequin thank you for this. The only question I have is what are the 2 other lines coming away from the helix for? Would this be a long ramp back up/down so that I don’t need the second helix? 

 

Those are the mainlines through the station realigned so that they miss the helix.

 

[Newmodeller96]

5 minutes ago, Harlequin said:

 

Those are the mainlines through the station realigned so that they miss the helix.

 

Ah ok. So open the back of the board up totally to allow the helix to sit there? 

[Harlequin]

Combining what @RobinofLoxley and @Michael Hodgson have said this morning, I think there's a better solution. Something like this:

 

The operating well size and shape is almost the same as the original plan. The station remains more or less as it was, just some minor tweaking might be needed - no major re-alignment.

 

The fiddle yard line descends behind the station (the station baseboard would need to be offset from the wall slightly). It then curves around, still descending and feeds a fan of sidings under the station. If you're lucky you might not need an entire helix at all but if you do, just add as many turns as needed to get to the required level.

 

BTW: It's a bad idea to permanently cover a helix with scenery. The only access to clean the track and fix derailments is then very awkward from underneath.

 

Edited January 20, 2023 by Harlequin

[Newmodeller96]

14 minutes ago, Harlequin said:

Combining what @RobinofLoxley and @Michael Hodgson have said this morning, I think there's a better solution. Something like this:

 

The operating well size and shape is almost the same as the original plan. The station remains more or less as it was, just some minor tweaking might be needed - no major re-alignment.

 

The fiddle yard line descends behind the station (the station baseboard would need to be offset from the wall slightly). It then curves around, still descending and feeds a fan of sidings under the station. If you're lucky you might not need an entire helix at all but if you do, just add as many turns as needed to get to the required level.

 

BTW: It's a bad idea to permanently cover a helix with scenery. The only access to clean the track and fix derailments is then very awkward from underneath.

 

@Harlequin thank you so much. I think

you have hit the nail on the head here! I guess I kind of ignored the other end of the layout but that seems to be the perfect option to get the helix run low enough! 
 

I will definitely keep in mind the option of uncovering the help and maybe the 2 tracks going above the helix will be on their own board just enough to hold the tracks above it. Then I can see as much as possible. 
 

thanks H 

[RobinofLoxley]

Also, it cant be ruled out, but on the basis of what Harlequin has drawn, the descent might be enough by itself to get sufficient separation. The fiddle yard junction can also move back to the opposite long side, creating even further distance for descent.

[john new]

18 minutes ago, RobinofLoxley said:

Also, it cant be ruled out, but on the basis of what Harlequin has drawn, the descent might be enough by itself to get sufficient separation. The fiddle yard junction can also move back to the opposite long side, creating even further distance for descent.

And more importantly the return run for ascending trains. 

[john new]

The fiddle yard has a double slip in a critical location - two Ys toe to toe does the same job with better options for any future maintenance needs and simplified wiring issues.

[Newmodeller96]

16 minutes ago, john new said:

The fiddle yard has a double slip in a critical location - two Ys toe to toe does the same job with better options for any future maintenance needs and simplified wiring issues.

I’m not sure where the double slip in the fiddle yard you are mention is?