Superelevated Curves

[johncolley]

Oh, you mean like "real world"? The joys of being a railroader!

[Anonymous]

OK thanks for the explanation on that. Actually Ive seen a pretty impressive "stringlining" wreck without even knowing it. It was on an N scal modular layout at a show. They were running a huge piggyback train. Probably 100 cars at least. They went around a sharp turn and starting in the middle all cars in the train tipped toward the center of the curve. Probably wouldnt have been so bad if it wasnt all those 5 unit cars. Anyway it was pretty funny watching the engineer pick up all those N scale trailers, took him the better part of an hour[(-D]

[Anonymous]

QUOTE: Originally posted by BigDarrin
Stringlining is where the pull on the cars makes them want to create a straight line through the center of the turn, rather than follow the track around. Generally leads to tipped cars and extensive derailments. I'm sure somebody else can give a better explanation than that.

I don't think I could improve on that - pretty well sums it up.! That is why on long mixed freights, I always try to position the heavier cars in front and the light cars toward the rear.

[Anonymous]

If you put in too much tilt for superelevation, is it called Megaelevation? heh heh j/k

Stringlining is where the pull on the cars makes them want to create a straight line through the center of the turn, rather than follow the track around. Generally leads to tipped cars and extensive derailments. I'm sure somebody else can give a better explanation than that.

Darrin

[Anonymous]

Im going to be running Amtrak and some small-medium size freights. No real drag freights though. By the way, what is stringlining?

[johncolley]

A word of caution, eh? Superelevation of curves is done to counteract the radial tipping forces encountered at high speeds going around them. The forces are not thesame on say a drag freight, in fact if excessive it could cause stringlining. So a little thought about what you are planning to run and how fast, is in order before building it in.

[Anonymous]

I superelevated it 4 scale inches. Just about prototypical. I dont think you would notice it if you didnt know it was there, but i can see it and i think it looks pretty cool.

[selector]

A word of gentle caution, Joe, if I may. Once you place a loco on that curve, I suggest you look carefully and ensure that the tilt of the loco isn't overdone. The tilt should be readily apparent, but not more than about 2-3 degrees. In other words, the effect you want is a subtle one, not a "Gosh, see how much that loco leans!" look.

Superelevation can be overdone.

[Anonymous]

I made my first curve last night. I used layers of the very thin styrene. It seems to work good, no derailments or anything, but it sure is tedious attaching all those little strips of styrene a layer at a time.

[Anonymous]

One way to handle transitions......decide where you want the full super elevation to begin, and start the string trimmer or shims or whatever you intend to use. Decide how long a transition you need from flat track to elevated. lets say you choose a 12 inches. Anchor the track at the beginning of the twelve inch transition.Allow the track to 'float between these two points. The natural flex of the track will give a natural smooth transition. Watch for sags..if you get those the transition is too long. Eyeball this for smootheness and graduality. When you are satisfied, 'back fill' with a filler or ballast material and white glue /water the mess together. This is similar to letting the natural stiffness/flex of plywood make vertical curve transitions, only we are just raising one rail. The track doesnt sag in the transisiton as easily as you might think, because the slight twist we are applying to raise one rail pre-tensions the track structure much like a torsion bar and the track is stiffer than you 'd guess. I have also used this floating track/backfill idea to transition from roadbedded areas to flat ground-level areas. It works perefectly for me and creates the smoothest transition i can attain.

[selector]

The tape will buckle at points, but you can shave those off with an exacto, carefully. The shorter the radius, the more the buckling, as I'm sure you realize.

You could us the exacto to cut narrow "V"s into the tape while it is still on the roll, about every three inches, and then lay it.

[Pruitt]

Joe -

I used 1/2 inch masking tape on a 30 inch radius curve and it kept wanting to wrinkle on the inside, but it smoothed down OK.

After that I started using 1/4-inch tape (you can find it at auto paint specialists - I ordered mine on the web) and had no problems at all.

[Anonymous]

More and more the tape method is sounding like a good idea. But does normal masking tape flex enough to go around the curves without buckling? My mainline minimum is 30"

[ndbprr]

I had superelevated curves at one time on a 30" radius curve that was at least a 3% grade and had no problems whatsoever with derailments. I spiked down the track and then raised the outside with a puttyknife and slipped an extra plastic tie under the outside.

[Leon Silverman]

Typical Weed Eater cord is .065" thick.
I have offered this advice (from experience) before regarding superelevation. Unless all of your rolling stock and engines have no more than four wheels per truck, model railroad superelevated curves have to maintain their elevation until the entire locomotive is on the tangent (straight track). This is because if the rear of the locomotive (or tender) is higher than the front of the engine while it is still on a curve, centrifugal force will cause the front of the engine to climb over the rail and cause a derailment. This is because the models (even those equipped with sprung drivers) lack the flexibility of the protypes.
This stiffness also dictates that there be no turnouts on these curves or within the transition areas on the straightaway.

[Pruitt]

I use the 1/4" masking tape method Mark C. (mcouvillion) talked about. Here's a shot of one one of the curves being laid (since photos don't show the staggered tape ends very well, I added a blue line at the end of the each one with a marker for the photo):



Here's what a train looks like on the curve:



The inward tilt is kind of subtle, but it adds a lot to the effect of the train rounding a curve. I've had no problems at all with derailments.

On my website I talk about how I build my superelevated curves. Here's the link to that page: http://www.thecbandqinwyoming.com/CM%20-%20Super-Elevating%20Curves.htm

[NZRMac]

Yeah the transition part is a little tricky!!

Ken.

Is this 500 posts? Yipee!!

[Anonymous]

I dont see how you can get a smooth transition with the trimmer line. The tape sounds like a good idea though. Im going to try the very thin styrene first just so i dont have to cut little strips of tape. If I cant get smooth transitions with the styrene I will probably use tape.

[NZRMac]

QUOTE: Originally posted by JPM335

also what thickness of trimmer line are you talking about?

I used about .8mm nylon line, it works well because it a uniform height thru out the curve. Once you've established the height you need, glue it in place.

Ken.

[mcouvillion]

JPM335,

Look in the archives, this topic has been discussed in detail before.

Use 1/4" wide strips of masking tape layered under the outside rail. Cut the tape on glass with a good metal rule and razor blade. Start laying the tape at least a foot before the transition spiral of the curve to hike up the outside rail well before entering the curve. Use two or three layers of tape from this point to the same point on the other end of the curve. At the start of the transition spiral, add another couple of layers of tape, and at the start of the arc of the curve, add two or three more layers. Continue the tape layers to the equivalent location at the other end of the curve. Your transitions should be gradual and smooth. Too much of a good thing does not work. If your track is laid properly, you will have a nice, gentle effect and no derailment problems. Using fixed thickness material like weedeater string is not a good choice. Tape is cheap and easy to use.

Mark C.

[jimrice4449]

I got good (partly) results w/3/32X1/4 stripwood. The trick is in the transition. I used a bench top sander but a hand sander would probably work, maybe better. I used double sided Scotch tape to attach the stripwood (2 pieces for each curve) to a piece of scrap 1X4 and sanded it to where about a 18" taper went from 3/32 at one end to nothing at the other. Works great when going into the curve...not so great coming out. My mistake was in making the taper start at an angle. Engines and cars would would tend to have the front wheels somewhat in the air as the rail dropped abrubtly away and the flange would continue straight as the rail curved away. My solution (not tried yet) is to resand the transition pieces so that there'a a gradual curve rather than an angle. It's on my list of things to do soon. If you don't try it first, I'll let you know how it works. Until they derail though, those beauties really look GREAT leaning into the curve!!!

[Anonymous]

While rummaging around in my box of scratchbuilding supplies. I found a bag full of .010" styrene strip. I think I might use this instead of the trimmer cord because it will be easier to mak easments. I figure 4 strips of .010" styrene at the highest part of the curve will look pretty prototypical.

[Fergmiester]

I've used wood shims 3/32nds", the whip cord would work just as well but I think it will be one of those things you'll have to experiment with. I have superelevated curves on 5% + grades but had to install a guardrail as some Steam Engines tried to climb the side of the rail causing derailments.

Fergie

[Anonymous]

also what thickness of trimmer line are you talking about?

[Anonymous]

does the trimmer line give enough elevation to be noticeable? It almost sounds too good to be true[:D]

[NZRMac]

I've seen someone using the nylon cord from weed eaters under one side of track, I've tried it and it works great. Then just shim it to flatten it out on the straight sections. I used it on a 22" radius and 2% grade curve.

Ken.

[Don Gibson]

SUPERELEVATING requires a vertical transition to and from flat for your engine and car's trucks to follow. Even though I had 48" r. curves and 6" of transition track into the curves they gave me derailment problem's.

[Anonymous]

I almost forgot, Is there any problem with having a superelevated curve on a 2% grade?

[Anonymous]

Being that my layout represents a modern (80's+) Class 1 railroad. I thought it would be neat to have superelevated curves. How would I go about making them? I assume you shim one side of the track, but what would I shim it with. What thickness, and how do I get a smooth transition back to level track?
Also, feel free to try and talk me out of it[:D]

Thanks