Steam engine binding

Model Railroader General Discussion (Model Railroader)
1

I recently purchased a bachmann spectrum pennsy k-4. When I track tested it, the wheels would only make one revolution and then bind up. Seems like rods are binding. When I take it off the track to examine it, the wheels are locked in place until I try to move them. They break free after a little wiggling. The same thing happens when set back on track. Is something out of place? Are the rods out of position?

2

On or more of the driver wheels may have rotated enough on its axle that the engine no longer qualifies as “quartered”. If so, this is what you would expect. It may have a bad gear inside. Or, the valve-gear rods or main rod, or a retaining pin or nut somewhere in the drivetrain is impacting something else as the wheels turn.

Have you inverted the engine and powered it via a tender axle to see if the rods all turn freely?

Crandell

3

I can give you a few ideas to check for

  1. Look for any screws/hex nuts that have worked loose from the driving wheel connecting rods. Sometimes one starts to work loose and rub enough on the main crank rod to cause a bind.

  2. Check the eccentric crank. This sits on the main crank pin and controls the motion of the valve gear. On my brass engines these can rotate (sometimes the set screw can work loose that holds these in place) and cause the valve gear to bind. Rotate them (on the crank pin) and tighten any set screw until you find a position in which they won’t bind.

  3. Check the crosshead to see if it is out of place or off the guide rails. The piston rod should also be going into a hole in the cylinder

Have you removed the gearbox and tried to just push the mechanism? Maybe it is a cracked gear?

Chris

4

Pretty sure you have a loose drive wheel on it’s axel. Hold one drive wheel and see if they are tight and not turning on the axel. If they are loose you will have to put the drivers back in quarter and fix that wheel in the correct place.

Bob

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5

I’ve had a couple of Spectrum engines that had that problem when first taken out of the box. It’s the side rods - eccentric rods causing the trouble. If you turn the engine upside down in a cradle and apply power to the wheels so they turn slowly you can usually find the problem. A slight adjustment, like bowing a rod out slightly, usually does the trick. My Spectrum 2-10-0 did exactly what you describe, after adjusting the rods it ran perfectly.