If...

The grade is constant through the, then there isn't any difference that I've ever noticed by having switches on grades many times, not only on my current layout, but almost all of the past layouts.

Fret thou not.

Andre

Watch for the vertical curve.

Like Andre, I’ve had no trouble with turnouts on a grade but the transition from grade to flat beyond will be important to keep gentle. Going up and toward flat can cause couple mismatch if not done well and the back of the train may decide to leave the party. Turnouts just add an other level of mischief for runaways. 

keep it "flat" on the 2% grade

and it shouldn't be a problem......DaveB

Seconding Neil's caution

G'day EW, all,

You will be OK if you keep the whole turnout on a constant grade. See below

This is about as tight as you can have a turnout on a grade with transitions and not bend the turnout.

I also wouldn't recommend trying to pull a grade transition immediately after a turnout on the diverge route. It is a whole lot easier getting a smooth grade transition once the tracks come back parallel, with probably far less chance of derailment. On a grade transition immediately after the turnout diverge route, the track is trying to twist the bogie 3 different ways simultaneously on the bogie pivot pin. Remember most of our model axles are fixed and unsprung, - and the wheels won't be able to follow the rails as well as a real bogie can follow a track misalignment.  

Where it gets interesting is on the vertical curves. I wholeheartedly second Neil's caution about vertical curves -ESPECIALLY AT THE TOP OF THE GRADE - where your transition comes from the grade back to the flat. At the bottom of the grade, you just simply leave stuff behind. Get this wrong at the top of the grade and you have an instant runaway. 

I can get away with vertical curves in the above photo because I am running short single wagons across this track BUT if you couple 2 wagons together then there is NO WAY you will be able to pull off grade transitions like these without leaving stuff behind. 

Please have a look at  https://forum.mrhmag.com/post/middle-school-model-rr-vertical-curves-12198545 both the concepts in the original post and the "Whoosh Factor" post. The Whoosh Factor post also should give some idea about the type of rail butchery required to get smooth vertical transitions without kinking the rail itself.  

Please also be aware if you have more than 1/2 a KD coupler head height mismatch between wagons standing on a vertical curve then you are entering "breakaway territory" where a minor track imperfection or any "bounce" in the train caused by a minor loss of traction/speed variation/etc can cause a catastrophic misalignment failure at the coupling head and a WHOOSH. 

If you are running bogie rolling stock, then you may be in for a nasty surprise at just how gradual the summit vertical curve has to be and how much horizontal distance this vertical curve will chew up to avoid a WHOOSH. It gets much worse if you are planning to run long passenger cars and autoracks through the summit vertical curve rather than 40' or 50' long box cars only.   

This top vertical curve is probably going to be he most critical piece of track you are going to have to lay on your whole layout. The consequences of getting it wrong will be rapid and spectacular.

Good Luck, but with some careful planning hopefully you won't need it,  

Concur with others,

just ensure you don't change grade in the vicinity of the turnout.  Absolutely critical.  Otherwise, don't worry about it.

However, if the turnout is part of a passing siding, for example, remember that if the siding is on a grade, you'll have a fun time keeping a cut of cars on it while you run around the cut...  

Blair

You will be okay

As long as the turnout itself is level on the grade you should be okay.  

You also want to make sure track connected to the turnouts are either level to the turnout, (at least a length equal to your longest car), “or” any change in the grade is very shallow and smooth.  

Where you can run into derailment issues is abrupt or sudden changes in grade.

Joe

Thanks all

Thanks all, not sure where I got that notion about avoiding turnouts on grades - obviously the prototype has them!

It's not a siding, actually the other way around, the grade is a single track and it splits at the bottom to head off in two directions, and is crossed by a bridge right after the split. The main route and diverging route both curve off to the same side as the diverging route. So unfortunately, the vertical transitions will have to be on a curve.

I have about 16" after the turnout on the shorter of the two routes before the point where  the other track crosses above the rails in question, which is where the bottom of the grade or end of the vertical transition has to be, so I should be able to do a 12" vertical transition and then still have 4 inches of track left before getting to the turnout. 

I don't know what my longest car is, but I'm in HO, so I'm just using 12" for now. I'll have some passenger cars that are about that long. 

Since this assumes extending the grade through the turnout, and the 16" beyond, I can get the grade down to 1.5% or so (depending on what I do at the top end of the grade), so the vertical transitions should be gentle.

  "I have about 16" after

I'm not sure what you are describing but I'd try to keep the grade thru the turnout the same for one car or engine length before and beyond the turnout then start a gentle vertical transition, not changing the grade by more than 1/2 percent for the next half car length for example, then one percent max for the next car length. The best way to visualize it is put some cars on a piece of flex track and see how their coupler interface changes as the track is raised up or down to change the grade. You want to keep the coupler interface at about 80% or better so by experimentation find the grade change that accomplished that....DaveB

A later thought

Hi EW,

A later thought based on your last post, 

For your transition grades after you leave the turnout,  please make sure that both tracks don't develop a twist on the curve in your vertical transition curves. The diverging path is more likely to do it. but the track on the straight path could develop a twist in the curve after the turnout.  

Don't try to mix the super-elevation normally seen in a curve and a vertical transition curve. Just keep the tracks "dead flat across the track" while you are curving on the vertical transitions.

Yes you can have different vertical curves for each track like shown in my previous photos, but that track headed down to the Screens developed a twist further down as it came off the grade onto the flat on a reverse curve to line up with the lower level track, probably because the of the tightness of the bends in both axes. It's a whole lot tighter than you are planning on bending stuff, but be on the lookout for any unplanned "twist" on the vertical transition curves that will cause problems for your longer rolling stock when coupled together. Forewarned is fore-armed,   

The only issue I've ever seen

The only issue I've ever seen with turnouts on gradients (besides the inconsistent grade problems others have pointed out) is the tendency for train cars not weighted down by a locomotive to roll back onto the main line or roll all the way to the end of the spur.  Track that cars need to be spotted on should be level no matter what, but the turnouts themselves should be able to work at any angle, within reason.

Grade Transitioning Dilemma

John, I found your posting here very interesting,..  
https://forum.mrhmag.com/post/turnout-on-grade-12216338

I'm going to have to give it some more thought, and have a look at that link you provided.

I am working on transitioning one side of my stone viaduct down to mainline track level,...and it is very close to a turnout on the mainline track,..

 

....more photos to better explain coming later today

fear not! it works on minor grades

I have many on 1-1.5% grades, and one that actually is at the crest of a hill.. but the elevation of the middle is very (!) minor... maybe barely over 1/8 inch. 

It has a nice appearance, and the two  nearby turnouts complement the complex look... it's not complex, but looks that way.

If you have any scrap turnouts, take one and get it working, then 'stretch' it the way you intend to see if you get good results ... also note, the rail code can make a Big difference. (Mine is HO Code 83)

Transferring my photos and

Transferring my photos and question over to my Stone Arch Viaduct discussion as I had not noticed this was a blog rather than a topic discussion,....and my turnout is not actually on the grade itself, but rather just at one end of it.
https://forum.mrhmag.com/post/stone-arch-viaduct-bridge-12213517