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What Causes Scale Model Trains To Derail

Bill sent in these thoughts to share:

I find that derailments can happen if cars are not properly weighted to NMRA standards. For example, if you have an underweight car between properly or overweight cars on either side and a dirty section of track causes the pulling and or pushing locomotive to stop and lunge and thus the varying momentum of rolling stock, caused by this weight issue, can result in derailment.

Long standard gauge coaches running on a layout built for mountain climbing tight radius “Mine” trains with relatively short rolling stock can cause derailments.

model train derailmentImproper truck adjustment. From my experiences both trucks should swivel with one having less play than the other. Failure to maintain these and you are inviting problems.

Proper height adjustment of couplers. Again I am reminded of problems I have had with coupler “pins” catching on turnout points, resulting in….derailments.

The reason I know about all these issues is because I have at one time or another, ran into these issues. So I mention them from first hand experience and am still learning from my mistakes.

I have also found that even after all my learning mistakes, I am still not done.

I am reminded now about several Labelle boxcars (which are constructed of basswood without any weight to them), that I had built to NMRA standards, gluing weights from end to end and right down the center of the wood floors. Initially they all ran great and then I started having derailment problems. After several attempts of trying to duplicate the issue, it came down to one particular car. Intermittently the weights were sliding off to one side around certain curved track sections causing the car to lean to one side, pulling the trucks and couplers up and down causing an imbalance and derailments. Point being, unless I wanted to park this guy at the end of the line forever, I would have to “Open a door” and carefully try and re-glue the weight in proper position. (not a lot of fun for those of us that tediously build these cars!)

Maintenance, maintenance, seasonal or periodic maintenance of locomotives, rolling stock, track and all other components of a layout including sight check of trees (growing) to the point that they can derail locos and or rolling stock, and testing of all electronics, DC or DCC is a never ending must!

I am sure I am missing other potential derailment causes…would enjoy others’ thoughts on the subject!

One Response to What Causes Scale Model Trains To Derail

  • Garysays:

    Why Model Trains Derail and Troubleshooting ideas.

    This information is divided into 3 Categories; Common Causes, Less Common Causes, and You’ve got to be Kidding!

    Common Causes

    Track out of gauge
    Track not level (BOTH Ways) along the length and side to side. Note that properly installed track may be super-elevated but this requires detailed attention to Rolling Stock.
    Mismatched rail code causing height variation.
    Rail joint too large.
    Track obstructions (on or near) Nails, scenery, buildings bad weld or joint.
    Turnouts (not level, improper gauge or wheel clearance at guard rails or frog.
    Curve radius too tight for locomotive or rolling stock
    Improper Wheel Gauge
    Coupler height (coupler and trip pin).
    Kink at rail joint (easy to do with flex track)
    Turnout points not firmly contacting stock rail (both sides)
    Turnout points not shaped right to fit stock rail at top of points
    Wheels both in gauge, but slipped toward one end of the axle so that, when tracking, neither axle’s wheels are directly behind/in front of their counterparts on the next axle;
    Points rails not sharp enough;
    Couplers that aren’t really compliant or suited for matching;
    Couplers that aren’t mounted suitably for the curvature radius being used
    “S” curve in track
    Turnout not reset to proper position. (left switched to siding or spur).
    Turnout switch points dance around, not held in place by ground throw or switch machine.
    Turnout directly after curve causing a S curve.
    Turnouts too tight for longer locomotives or rolling stock.
    Loose ballast in a turnout.
    Wheel sets not properly set in trucks.
    Coupler ‘brake hose’ too low.
    Sloppy kinky laid track and old BB and Roundhouse cars hastily built with defects overlooked.
    Speed..Yup that “S” curve between switches taken at Marc one or light speed.
    Truck mounted couplers.
    Trucks to tight won’t allow trucks to turn freely-not sloppy by being to loose.
    Long wheel base engines and cars on sharp curves.
    Excessive Speed
    Everything on these lists going forward, double it for going backwards. Pushing a string even if everything is near-perfect.
    Stiffly sprung diaphragms on passenger cars, operated on sharp radius curves.
    Long cars being coupled to short cars because they have a different amount of overhang on curves and the longer car will pull the short car off of the track

    Less Common Causes
    Trucks are deformed wheels don’t all sit flat on track.
    The Steam loco is connected to the tender by the cable but the bar is disconnected.
    A piece of a loco detail or rolling stock has come off and is on track or causing wheels to lift.
    Vehicles or livestock on track
    Switch machine too close on curve causing loco plow or other body part/detail to hit.
    Un-coupler magnet to high or not flat/level
    Poorly adjusted truck movement on rolling stock
    Steam loco lead or trailing trucks not sprung properly
    Steam loco floating / sprung drivers not properly sprung (too strong or weak)
    Diesel loco wheelsets just a tad out of gauge. The flanges should be centered in the NMRA gauge slots, not just sorta fitting into the slots
    Sudden Grade Changes
    Axles not seated properly in the trucks’ bearing cones;
    Sags or humps leading through the points and toward the diverging leg of a turnout;
    Frog poorly designed or made allowing wheel drop or improper tracking;
    Wrong tire and flange profile for the NMRA-compliant turnout
    Lack of weight on leading trucks
    Sprung trucks taking an uneven set from track work and not leveling back out.
    Narrow guardrail gaps and tight spacing between frog point and guard rail inside edge.
    Truck swivel impeded by under body details

    You’ve GOT to be Kidding!
    Main higher than the sidings. Where the grade change for the siding occurs “inside” the switch. Very bad
    Problems at the ends of modules where the foam shrank and lowered all the track except at the end that sits on plywood
    Steam engine to tender connector that lifts the engine in a curve
    Hanging wires from motor/engine
    Unbalanced weight on engine
    Improperly installed pilot trucks on steam locomotives!
    Rail gaps that become too wide due to changing weather conditions

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