Help! Laid all my cork roadbed and track, wired for DCC, and considering its my first layout, it’s pretty decent. But, I have one problem spot that keeps derailing no matter what speed I run the train over it. The part is a crossover made with two left hand Atlas snap switches. My theory is that since the turnout on these is actually slightly curved, the crossover makes enough of an S-curve to derail cars - can someone confirm or deny if my theory is correct? Thanks!
-
What is the frog number (or approximate) of the turnouts?
-
What is the spacing of the tangent (mains) tracks?
-
Is everything dead level across all of the trackage? I.E. are all of the railheads at the same height throughout the crossover?
That depends on the rolling stock type. If you’re running modern era rolling stock, that can be the problem, but it seems to be more of a problem with your trackwork not being level or smooth between the two switches.
You need to take a good straightedge, such as a ruler, and check to make sure there is no dip or hump in the track where the two turnouts are butted up to each other.
Check your rolling stock wheels with a NMRA gauge. Check the Atlas turnouts with an NMRA guage. Snap track turnouts are not very well made compared to other brands and the track may not be in gauge.
Make sure the trucks on your rolling stock are not so tight that they can’t swivel freely.
Thanks for the reply:
-
Still pretty new, so I’m unsure what this means.
-
There is no track between the two turnouts - they are connected directly together. So the spacing/tangent is the absolute minimum in order to save space.
-
I checked for leveling and it’s pretty good - did some filing just to make sure. I watched trains at eye level very closely at various speeds - derailments seem to be happening at the frog with the rear truck of a car. It seems like the first 3 cars almost always make it through just fine - cars 4/5 is where it derails.
Thanks again!
Thanks, I’ll have to get an NMRA gauge and check. Fortunately this is just a small temporary layout until I move in a few months - I’m building a much larger and more permanent one at our new location. But when I do, I’m hearing I probably should consider replacing snap-switches with another brand. I know this is probably a deal where everyone has their preferred brand - but can you give me some ideas of which ones you would consider?
It’s most likely wheel sets out of gauge or turnout out of gauge. Check both with your NMRA gauge and you ought to find something out of spec. Also check the the flangeways at the frogs and the wing rails is deep enough. If the flanges are touching ground in the flangeways it can boost the entire wheel up and over the rail head. Check wing rail positions with the NMRA gauge. If the wing rail is off, if won’t contract the inside of the flange and pull the wheel set over to the stock rail, in which case the wheel will climb up on the frog. Make sure the points pull in tight to the stock rails.
You say that the first few cars make it OK and it’s the third and fourth car that have trouble. What happens if you remove the third and fourth car from the train? Can the locomotive make it thru with no cars at all? Are your cars weighted up to NMRA standards? Light cars are more likely to derail. HO rolling stock should weight 1 oz plus 0.5 oz per inch of length. I weigh my rolling stock on an el cheapo kitchen spring scale
Snap switches have a bad reputation, because of the plastic frog, and because they are frequently, the first switch purchased by the novice. Because the two versions (18" radius and 22" radius), conform with sectional curves, they are of limited value on more advanced layouts.However, in certain circumstance, they are perfect for industrial sidings branching off of industrial leads.
Note that MR used 22" radius snap switches on the 2012 “Virginian” project layout, in addition to other frog size switches from several manufacturers.
I am currently building another layout, and am using a mixture of Atlas (#4.5, #6 and #8 frogs) in code 83; Micro Engineering #6 frog in both code 70 and code 83: Shinohara (Walthers) #6.5 curved in code 83 and #4 in code 70. Everyone has their preferences, but not everyone offers every switch needed to complete my track plan.
My preference is Micro Engineering, which are available in code 100, code 83 and code 70. They are of high quality, as well as made in the US. The down side, is that they are limited to a #6 frog.
It can be the “S” turn. I have 15" radius curves in my subway. They work fine because the wheelbase is very short on the subway cars. There is, however, a turnaround where parallel tracks turn back dog bone style. 3 car trains go through it just fine, but a 4 or more car train derails at the third car in the “S”, regardless of which car is in that position. I don’t have room in that location for wider curves so I just run 3 car trains in that area.
Can you replace those snap switches with #6s or #8s?
MattD: assuming that your trackage is flat and there is no kink at the joint between turnouts, are these used or new? If used, examine the plastic frogs for wear.
A general rule for S curves is to put a length of straight track between the curves equal to the longest car length. This can be relaxed if the curves are broad enough. Geometrically, the key in an S curve is the distance between a car’s bolster center and the coupler mounting, since greater distance will cause a bigger lateral offset between car ends, and derailment when the swing range of either coupler is exceeded. Cars that are longer, not well weighted, or having diaphragms that touch all tend to increase problems, usually worse when backing.
I used Peco 75 turnouts which also have near-continuous curves, and found that an unspaced crossover using medium (36") turnouts would not pass 85 ft cars with body-mounted couplers. Changing to large (60") radius turnouts fixed things. So I would guess that with 22" turnouts, you might get away with 40 ft cars, but maybe not 50 ft or longer cars.
Hal
Thanks all, think I have it as fixed as it will be for now. The suggestion about flanges being slightly low was a good one - that definitely caused some of the problem. I also went back and re-leveled the turnouts. Turns out I missed a track nail in the center of one of the turnouts, wasn’t much, but the vibration and tiny heights difference were enough, with the flange, to cause problems. Running pretty solidly now thanks to those fixes.
Thanks for all the suggestions. Definitely will look at micro engineering and peco switches on my new layout.
Matt,
Good for you in finding and fixing the problem.
A crossover made up of two indentical turnouts should not cause derailments if laid level. But, level means level. The roadbed must provide a solid surface. If nailing, be sure not to pull the rails out of gauge and do not leave the rails uneven, where one rail is higher or lower than the other.
My suggestion is to replace the snap switches on your permanent layout with Atlas Custom Line #6 turnouts. That setup provides a more gradual S-curve.
Rich
Two Atlas snap-switches, diverging route to diverging route, equal one SEVERE S-curve - almost guaranteed to cause excessive coupler side force on anything longer than an ore jimmy, That’s why most Atlas plan book layouts place crossovers at the entrance to a curve.
With a standard numbered turnout, where the diverging route is straight, the distance between frog points should be as long as your longest car - over coupler faces. That avoids strong side thrust. With parallel tracks on two inch centers, #4 is not recommended for anything longer than 40 foot cars. #6 is OK up to 60 foot, and #8 will handle even full-length passenger cars and stiff, long-wheelbase steam locomotives. (The lowest-numbered prototype frog I’ve ever seen is a #7, on industrial trackage.)
Away from turnouts, you also should never abruptly reverse the direction of curvature. Building with sectional track, one full length of straight between curves in opposite directions is just about the absolute minimum.
Matt,
Follow this advise as you continue in the hobby
As a minimum #6 is the way to go for these crossovers. A much gentler transition that will allow for longer cars and locomotives and trains.
Good Luck
John R
Matt,
Excellent advice here. I’ve found that a line level works very well when checking to see if turnouts are level.
Here is just one example from Amazon that sells for $1.49: http://www.amazon.com/Johnson-Level-Tool-Contractor-Aluminum/dp/B00002N5NZ/ref=sr_1_5?s=hi&ie=UTF8&qid=1335744383&sr=1-5
Good Luck with everything,
Wayne
It is said that ignorance is bliss. It never occurred to me that there could be any problems when I laid two cross overs and there haven’t been
I’m on my first layout and wanted crossovers on the two track main and used a pair of Peco left hand and right hand SMALL radius turnouts…
My longest cars are Intermountain cylindrical hoppers. (Longer than 50’ but I don’t know the lenght)
Have had no problems
Bob
If you have solved your problem, GOOD. Since it is a temporary layout, if it is working, I’d leave it alone.
In the future, if you use Atlas #4’s instead of the Snap Switches, they have a better reputation and are a little less of an S curve. Atlas Track Books have a section in the back that shows crossovers made with #4’s and #6’s, giving you several track spacings and the length track needed to accomplish them.
Good luck,
Richard
Having use “snap switch” crossovers on small switching layouts I will tell you up front a 50’ car will traverse those crossovers with no problems thanks-and that’s many thanks- to the side to side movement of the car’s couplers.This helps these longer cars through that terrible S curve.
BTW…I do not recommend snap switch crossovers-its better to use #4 and larger switches for crossovers.