What length of trains are you running? 35-40 cars is pretty much a minimum for me.
Do you have grades?
I have posted pictures of my trackwork, I VERY fussy about those same things, but even at 36" and larger curves, much of what we do is rig
It depends upon how far apart the top and bottom segments of the S are located. The longer the S, the less problematic the curve will be. The problem arises with a tight S, especially where there is an adjoining tight S.
Rich
Some have touched on it, but I don’t think anybody has come right out and said it - two true numbered turnouts in a crossover do not make an S curve (opposite curves with no straight between them). “Trainset” turnouts, with curving diverging rails will, but true numbered turnouts have a much shorter curved section and straight diverging rail and as such will have a short straight section between them.
Stringlining has to be a phenomenon of a single curve. I don’t see how an S curve would make a difference.
Stringlining forces can be reduced by inserting mid train locomotives just as in the prototype.
If the S curves are eased then the intervening straight so often recommended is not required?
A crossover is eased in the sense that only the point and closure rails are curved so the reverse curves involved in crossing are not as abrupt as they will be in say a sectional curved S bend. We have tried to ease all curves.
A Wye turnout in a 24" radius curve does ease all three curves, albeit one forms an S bend. A double curved turnout will also ease 24" radius curves at all three track connections. Is that enough?
As an engineer there is a vast difference between an S curve and a crossover. The S curve has both trucks on curves for a long period of time and the crossover typically has a much shorter moment of deflection in opposite directions and a much shorter section of curves limiting problems.
Yes and no. Traveling through a curve increases resistance, so if the back half of the train is in a another curve it increases the lkelyhood of stringlining, but because of the increased resistance, not the geometry of the curve. It would be the same as if the train was topping a clmb and the back half was still on the slope.
Correct, in fact, good easements are much better than back-to-back curves with a straight between them.
I think of it as the ‘straight’ or transition zone in the middle being of adequate length to steer the longest truck or wheelbase smoothly from one ‘curve’ across into the other. I would advocate for back-to-back spiraling with an actual straight equal to ‘that wheelbase’ between the spiral exits, but that may be difficult to achieve in practical layout compression – it’s already wildly impractical to use prototype spiraling even in N gauge…
First, note that I am in Free-mo, where modules are built by individuals.
Max length of trains is about 35-40 cars, because of the length of sidings in turn-around loops.
No.
Curves are 48" or larger.
From my experience, the biggest cause of derailments is track quality. Since most of the track used on Free-mo modules is pre-fab, not hand laid, it’s difficult to understand how someone can screw up track installation badly enough to derail trains. But I’ve seen it.
On the plus side, I run some trains with Sergent-equipped cars.
I am, by the way, a big fan of three-point car suspension, where one truck uses side bearings, and the other truck does not. I took it up because of the irritation generated by seeing a freight car shimmy-shake in the middle of a train at a ridiculously high frequency.
A side benefit is that each truck can follow the trackage. In that sense, the car is “equalized”. But not the trucks, internally.
Ed
An easement has a certain length. That length is measured from the end of straight track to when the “true radius” of the curve is met.
How long should that be? The people I know who use them advocate for a car length. 12" is that length, unless you don’t run passenger cars, auto racks, intermodal…
My two modules are 22 degree curves. Track is Shinohara Code 83. Curve radius is 5’. Easement length is 18". They are superelevated to about .03". There has never been a derailment on these modules.
Free-mo design requires a 6" straight track at the end of each module. So if you connect two modules in an S-curve configuration, you will still have a 12" piece of straight track between the curves.
Ed
I found the following statement in “BNSF Railway Company Guidelines for Industry Track Projects”
“A minimum tangent length of 50 feet must be placed between reversing curves.”
Note that this is for industrial trackage. Mainline curve rules would likely be more conservative.
Ed
And slip switches, especially when used in bypass mode, produce interesting S bends. That was also a factor in my musing about the “rules” applied to S bends.
I don’t know what “bypass mode” is since it is not a term I have heard used in this hobby or prototype railroading regarding a slip switch, and you will not post drawings or photos, BUT, a slip switch by itself is not and S curve, it is a crossing that allows you to get on the route crossing your straight thru route. It is a simple curve changing the direction of travel no more than about 10-12 degrees.
Now if you are talking about a yard lead full of slip switches, where one track crosses and connects many yard tracks, that too only creates geometry equal to a crossover.
Any other use or positioning of a slip switch such that other curves are that closely adjacent as to create an S curve is neither prototypical or well advised.
Still waiting to see a drawing to explain a long list of things you feel it necessary to create your own terms for.
S curves built with proper easements or proper length straight transitions pose no operational issues.
MANY curves on the prototype have NO fixed radius and are actually just two long easements back to back reaching a minimum radius only at the vertex of the elipse they are part of.
And S curves can and are layed out the same way on the prototype when necessary where the co-vertex of an elliptical easement goes right into an elliptical easement in the other direction.
The net effect of this at prototype radii is, regarding coupler and truck swing, a functional straight section longer than any protoype car.
So Mike, please draw me a picture of “bypass mode” with a slip switch…
Sheldon
Byron was really good at explaining proper terminology for all kinds of railroading things.
I miss his informative posts.
-Kevin
Is something up with Byron? He has a post dated just this past Monday?
But his profile page shows no activity - a typical forum glitch?
Sheldon
A slip switch is a crossing with points. It seems pretty clear that the main purpose of a slipswitch is to provide a crossing or turnouts would be used. Normal setting for a slipswitch would therefore be as a crossing.
To bypass the crossing points are thrown. That creates a curve in the intersecting tracks.
What else could “bypass” mean in the context of slipswitches?
If you think very hard, you will see that two turnouts arranged points-to-points DO provide a crossing of routes in the same manner as a slip switch. The point of a slip switch is to condense this physically.
“Normal” settings for track switches, including slip switches, are for the mainline route.
The problem here is that this usage is not self-evident. Except to you. And it should be self-evident to a much larger population to be of any communicative use.
I suggest using the terms “straight route(s)” and “curved route(s)”.
Ed
Sure. If a slipswitch is used then the mainline would one of the straight through routes. Any other setting of the slipswitch would bypass the mainline.
The slip switch can either be used as a turnout or a crossing but not both concurrently.
If “bypass” isn’t self evident then what word would be?
I have been seeing exhortations against S curves since the first issues of MR I read back from 1947 (from an older thread).
I bet a bright shiny nickel (or even a dirty old dime) the whole thing started with taking toy trains through S curves of back to back toy train curves with no easement and no straight between them, and hitting them at full throttle.
In his book, “Track Planning for Realistic Operation” (3rd ed’) John Armstrong makes references to S-curves and dealing with them in Model R/R’s (I note his use of the word “horrid”, on pg.80)
But I don’t think JA exhorts against S-curves. He acknowledges that they “insidiously creep in on you”. Ways to avoid running problems by designing the S-curve into your Track-plan, to gain some tolerance are discussed.
I have two Turnouts back-to-back and after reading JA’s book, I will arrange them as fig.B (Fair - Pg.80) due purely to lack of space for the more preferred option of a minimum straight section between the Points.
Agree, except that we customarily use the terms ‘through’ and ‘diverging’ already, and they can be applied to any appliance with points…?