When trains stall, derail or stutter

Almost all poor running has one of four causes, and they are worth checking in this order because each is cheaper to rule out than the next.

Work down, not across:

1. 1

   Step 1: Is it everywhere, or in one place?

   This single question halves the problem. A fault in one place is track, wiring or geometry at that spot. A fault everywhere is the locomotive, the wheels, or the power supply. Mark the spots where it stalls and look for a pattern before touching anything.

   You will know it worked when: Layout fault or vehicle fault.

2. 2

   Step 2: Clean the wheels before the track

   Everybody cleans track and forgets wheels, and dirty wheels re-contaminate clean track within a few laps. Locomotive wheels and the pickup wheels on coaches both matter. Clean track afterwards with a track rubber or a lint-free cloth and a little isopropyl alcohol.

   You will know it worked when: The most common cause, removed first.

3. 3

   Step 3: Check the electrical joints

   Rail joiners are a mechanical connection carrying current and they loosen and oxidise. On any layout beyond a starter oval, power feeds every metre or so — rather than relying on joiners to carry current around the whole circuit — will transform running. This is the fix that most reliably converts an unreliable layout into a reliable one.

   You will know it worked when: Consistent power everywhere.

4. 4

   Step 4: Look at track geometry at the fault

   For derailments: a kink at a joint, a slight vertical step between rails, a curve tightening below the vehicle’s minimum radius, or a point blade not sitting fully home. Run a finger along the railhead across every joint — you will feel steps you cannot see.

   You will know it worked when: The mechanical cause of a repeatable derailment.

5. 5

   Step 5: Then look at the vehicle

   Back-to-back wheel measurement out of specification, a bent axle, a coupling pulling a light wagon off line, or too little weight. Light rolling stock derails far more than heavy, and adding weight to a persistent offender is a legitimate fix.

   You will know it worked when: The rolling stock, checked last and least often at fault.

Stalls only at points

Dead frogs, or blades not closingShort-wheelbase locomotives lose pickup across an unpowered frog. Frog juicers or switched feeds fix it.

Derails only when propelled

Geometry or coupling forcePushing reveals faults that pulling hides. Check the tightest curve in the move.

Runs badly after months idle

Oxidised rail and dried lubricantClean, then run for a while. Old grease turns to varnish and needs removing rather than topping up.

Worse at low speed

Pickup, not the motorAt speed, momentum carries a locomotive over a dead spot. At a crawl it does not.

One locomotive is fine, another is not

Wheelbase and pickup countA six-wheel locomotive tolerates dirt a four-wheel one cannot. The layout is still the problem.