this may be a litte strange sounding ,but Im doing a seane on a corner area curve where the turnout cuve section is the main (since the main curves here) and the straite part is the siding route . is this an OK practice or a planning NO NO??? oh the curve is 48 radius and #6 atlas streamline so it looks ok to me, but someone with expertice may see it say “shame shame”. Jerry
I see no problem with it. I do the same in one spot of my layout and have probably had less problems with that one than any of the others.
It better not be shameful cuz that’s the way I do.
In the photo that follows, the divergent curves follows my outer track on the double mainline while the nondivergent section (the straight part, as you call it) leads into my passenger station annex. Incidentally, if you follow my double mainline tracks a little further (not shown in the first photo), I have another curved turnout set up the same way that also leads in to the passenger station, as shown in the second photo (please excuse the background mess, a professional photographer I’m not).
I believe the engineering preference is to use the through route of turnouts set into a main line. However, necessity, even in the real world, sometimes means you have to adjust. I would guess that, if the engineers know of a statistical reason for predicting more derailments/accidents at turnouts set into the main when the diverging route is incorporated into it, they would recommend slower speeds at that junction. So, if through freights were scheduled to run at 60 mph max, the slow order there might be 30-40 mph.
When you think about it, it is difficult to imagine many situations in which the outer curve is the main, at least on model railroads, because the inner curve would have more limited utility on the inside of the layout at the point of the curve. The inner curve is more likely to be the main while the outer curve has more open space to lead to something useful.
Rich
You also should consider the superelevation of the curve on the prototype, which would result in the siding rising considerably higher than the main, and then sharply dropping off after clearing the turnout. In your situation, however, the trackwork would be laid out flat, and the speed limit through the interlocking would be in the 15 mph range.
Jerry.
If the real railroads had a situation such as this I am sure they would place the turnout in a straight section and run the siding next to the main. Frogs and breaks in the rail surface is an engineering no no for the real guys on curves. Since we don’t seem to run the same tonnage they run, we can get away with curved turnouts and curves that are way too sharp for even a mine railroad. If it looks good and runs good then by all means run with it.
Pete
While it’s nice to follow the prototype as closely as possible, sometimes we have to compromise in order to build what we want. It’s true that the 1:1 scale railroads avoid turnouts on curves, but they have to deal with physical forces that are far greater than anything in a model railroader’s wildest nightmares. Unless you routinely run trains at scale speeds measured in Mach numbers, that turnout on a 48" model railroad curve won’t cause any operational heartburn.
The prototype MIGHT bring the siding around the curve to a point where the turnout could be placed at the end of tangent track, but if the included curve of the turnout is the same radius as that of the curve in which it is placed there is no speed-limitation reason for doing so.
One thing to consider is that the prototype can use a length of right-of-way greater than the scale length of my division point yard to adjust the alignment of a single turnout. Unless your train room is an old supermarket, that’s a luxury we can’t afford.
Chuck (Modeling Central Japan in September, 1964 - with turnouts on curves where needed)
I believe several years back there was an article in MR about a short line that had the main switch off the turnout, while the straighter section went to a siding. It may have been a trains of thought, I’m not sure. mh
In real life, this situation is rare for some of the engineering reasons mentioned previously in the thread. Sometimes it’s unavoidable in the model, but some find it looks a little unrealistic if overdone on a layout.
Note that the minimum radius at the tightest point through the curved side of your #6 is about 43", so it’s a little tighter than the rest of your 48"R curve. (Assuming HO)
You can refer to the typical minimum radius through a turnout on the NMRA’s Recommended Practices Pages. RP 12-3 is the HO reference. The line you are looking for is (11).
Byron
I can think of hundreds of situations where the outside curve is the main on a layout. There are many examples in my layout design gallery alone.
thanks to all for the input ,I like the idea of moving it up the line abit but that would put the turnout in a lift out/gate area where I wanted to keep things as simple as possible. there is a chance of moving it to the other end of the siding ,since the siding does somewhat parallel to the main. I’ll take a look tomorrow. thanks again to all…Jerry
I knew that I would regret that statement as soon as I made it. cuyama, thanks for the link. I have visited your layout design gallery before, and I would do so again.
Rich
I have several videos of trains that show situations where the main line is the diverging route of a switch and the siding is the straight portion, so it was not uncommon.
I have several places on my layout where keeping the main on the diverging route was the best solution:
Wayne
I do not see using the diverging route as the mainline. I would wonder why you are not using a larger number turnout such as a #8 or larger. Also, curved turnouts work great and help save space on the layout. The only problem I can foresee is derailments with large steam locomotives or 3 axle diesels going “50 MPH” or more through such a small turnout. I use #8 turnouts for the mainline and #6 turnouts for sidings and for the yard.
In my case, the diverging route was used as the mainline, with the straight route used to take the siding’s track away from the main at a sharper angle than would be possible with a curved turnout.
Also, if I read the OP’s situation correctly, he’s talking about a regular turnout with a straight route and a diverging one, not a curved turnout with a curved diverging route.
I’ve had absolutely no operational problems caused by this arrangement, and frequently back long trains through without incident.
Wayne
What small number? I ran 4-8-4’s and even crazy locos like GG1’s at warp speed front and back through Atlas #6’s on my old layout and nother ever derailed. Even when the GG1 was pullign a train of full length 85’ passenger cars. It’s sort of my tortoure test - if long wheelbase locos can run at very high unrealistic speeds reliably, then I am fairly confident that everythign will be fine at more prototypical speeds.
–Randy