Crossing SG track with NG track

[Dave Cooper]

Hi All

To go with my new (single road) engine shed, I'd like it to be dual purpose -  ie SG and NG.

In order to achieve this, the NG line has to cross the SG line but not in any conventional geometric angle (it may need to be on a curve for instance).

I'm planning to cut slots in the SG rails for the flangeways and, then, use bridging wire under the baseboard for electrical connections. This is, primarily, to avoid having to build dual-gauge point work etc.

Am I likely to run into any shorting problems across the tracks ? Operationally, I tend to only power one line at a time, but, sometimes am joined by a second operator.

I think I can arrange things so that both NG rails only have to cross one SG rail before running down the middle of the SG track and into the shed. SG track is Peco code 75 '00', NG is Peco code 80 'N'.

Thanks for any assistance /pro's and con's etc.
Dave

[JulienW]

It's probably not a good idea for the NG track to be on a curve through the crossing and you may be heading for trouble unless you have a short straight on both lines through the crossing.

Electrically I'd be tempted to make the crossing so that the 4 corners are isolated from one another - so gapping the running rails - and making the check rails within the 'diamond' with something non-conductive like plastic strip on its edge or angle. The four 'poles' of the crossing can then be switched for either standard or narrow gauge, but I'm afraid that I can't work out if that can be done simply with a single double pole, double throw switch or if it needs something more complex (two switches working in tandem?).

Re-reading your post also suggest you are thinking of 'gauntleted track' with 4 rails - NG within the SG - as you mention the "NG rails crossing one SG rail". That might be a bit difficult to arrange with the somewhat over scale Peco rail (though may be possible with a finer rail section), though if you used a 3rail system (one running rail common to both gauges) then this is available commercially from Europe (Tillig?), and one can buy plain 16.5/9 mm gauges (HO/HOe) and point work including where the gauges separate (or merge, depending on which way you are running).

[Tom Haythornthwaite]

I need to jump in and remark that I found that Peco rolling stock could not run through the Tilig bifurcation point.  When departing the dual gauge track the Peco flanges would hit the sharp end of the fixed point rail.

I have an equivalent requirement - for a dual-gauge bridge - and will be watching this thread with interest...

[Hobby]

What on earth is a bifurcation point?

Peco's flanges must be bad, then I saw a dual gauge layout using Tillig track a few years ago and it seemed fine, but all the stock was continental.

[Dave Cooper]

Thanks for the replies all.

It seemed like quite a simple idea - there could be hidden snags though as you say. I think a diagram of the requirement may help to visualise it.

I'll see if I can knock something up in MS Paint. (Not much in the way of CAD skills at present !). 

[Dave Cooper]

Here's the general idea : (looks like a '4-frog' set-up maybe ?)...

[JulienW]

Here's the general idea : (looks like a '4-frog' set-up maybe ?)...

That helps Dave.

A bit of terminology here - the 'frog' is also (more correctly?) known as a 'common crossing'.  Getting the NG rails in between the SG ones needs two. The set up will also need check rails (rails just inside the gauge that guide the flanges).

As to the electrical set up I'd think of it as '½ a crossing', so I'd gap the SG rail between the NG rails (to prevent the NG track current shorting) and the NG rails before the frogs into the dual gauge section. It might also be worth gapping the SG rail opposite the gap in the crossing and arranging the section switching through a double pole double throw switch so that one way energises the SG, the other powers the NG (meaning that you can't have both 'live' at the same time), and if the switch is also 'centre off' then it will also isolate both sets of rails.

[Dave Cooper]

Thanks Julian

That gives me a bit of encouragement to start experimenting.

I have a DPDT /Centre-off switch in stock that I bought for the rope-worked incline. As this is now planned to be under Arduino control, I can 'borrow' the switch for the shed testing.

I've not worked out how best to do the check rails yet. I probably need to order some more track and some track gauges. Will the mix between code 75 and code 80 trip me up ? I may be able to lower the '80' to match the '75' in height ?

The fun starts soon !
Dave

[duttonbay]

I've not worked out how best to do the check rails yet. I probably need to order some more track and some track gauges. Will the mix between code 75 and code 80 trip me up ? I may be able to lower the '80' to match the '75' in height ?

I would use the same sized rail for the four-rail section. As JulienW said, the issue might be the width of the base of the rail. With centrered dual gauge the inside running surfaces are 3.75mm apart, so check whether it can be fitted in with either of your two rail sections.

Just as an aside, I would think that having the SG of a smaller rail size to the NG might be a bit unusual, but 5-thou is two-tenths of bugger all (actually 0.13mm) so your joining section could well be aligned vertically with a bit of judicious filing of the code 80, or packing the code 75 with a 5-thou section of styrene. Convert to whatever rail you choose a short distance before the two crossings.

The shallow angle you have drawn might also result in difficulties with the K-crossing. With the long gaps in the flangeways there, it is likely to be very hard to support the wheel across the gap.

[Hobby]

I don't understand why you are over complicating it. In real life they are much more likely to just use one common rail for both SG and NG, that simplifies it, you only have one crossing and (in real life) would be cheaper. There's no logic which would make that set up the preferred option as only one loco, SG or NG can use it at one time. If you needed a pit it would simply go between the NG rails but would simply be used for maintenance, emptying clinker would be done outside the shed.

[Tom Haythornthwaite]

In my opinion four rails is less complicated than three.

Here's the Tillig "solution": 

.

(I'd mention its type but that didn't go down too well earlier.)  The Standard Gauge rail between the Narrow Gauge rails needs to come to come to a sharp end (I'm trying to avoid using the word 'point') and my experience with Tillig indicates that this has to be be made to work with the desired rolling stock.

[Hobby]

Oddly the JHMD uses a single blade where they branch off the SG mainline. But that's probably for safety rather than anything else, the speed limit is about 60mph at that point so you don't want derailments!

[JulienW]

Having had a bit more thinking time on this like Hobby I can't help thinking that 4 rails in the engine shed seems to be a lot of effort, both in terms of prototype and model, for no real reason I can think of (other than the aesthetics or symmetry and the satisfaction of doing something difficult and getting it to work).

As Hobby has pointed out in the real world there would be extra cost involved in laying 4 rails as opposed to 3, and if there is to be an inspection pit in the shed then the percentage cost goes up even more as the SG rails could be supported on the sides of the pit and the NG rails will need a girder under them, and a 4 rail setup needs 2 girders. Any smoke ventilation can be made to accommodate the 'off centre' NG locos with wider collection trough similarly set off centre, though if the shed relies on a ventilated clerestory then it will not matter as any smoke / steam will find its own way out.

Personally, being a fan of the easiest option were possible I'd go for the Tillig (or similar) 3-rail track as it's ready to lay and should work (or be fairly easy to make work) as opposed to something hand built that might or might not work, with the resultant dissatisfaction if (when?) it doesn't...

Even if you do go down the hand built route 3 rails will be easier to lay then 4, and probably easier to wire up too.

[Dave Cooper]

Thanks for the photos and extra thoughts folks.

Yes, on reflection, 3 rails in the shed makes a lot of sense. (I was really thinking of electrical simplicity with 4). I also think a 'crossing' would be easier to make than a dual gauge turnout - for me anyway !

A few measurements on the layout lead me to think there could be space problems....if so, a dual gauge turntable just outside the shed maybe the answer - perhaps...

Will come back to you when I've got some space /dimensions in mind.

[Dave Cooper]

A different solution giving a fuller illustration of this part of the diorama. The NG line would probably need very tight radii, new gauge, loco and stock. It would cross the SG line at about 50 degrees or so.

As I was measuring up, I couldn't help thinking that a dual-gauge 'slip' would be handy at the first point position !