Fixing slow moving RS-3 MTH engines stalling on uncoupler magnet

I replaced the single pickup roller supplied with my MTH RS-3's with an MTH double roller, in order to improve operation through switches. These and some of my other MTH engines would stall on my fastrack uncoupler magnet when operating at slow speeds.  I would also get some stalling on trackwork that was a little above the normal rail height or when the trackwork was not perfect.

The cause of the engine stalling is that there is not enough space between the pickup roller and the plastic insulating piece supplied by MTH to allow the roller to retract all the way into the truck frame. The pickup roller would push against the truck frame and lift the drive wheels off the rail, thus stalling the engine. As a result, a slow moving engine may stop on the uncoupler magnet. (a faster moving engine would have enough momentum to overcome the friction at the magnet and pass over the magnet, even though the engine would "move or shake" a little bit)

The solution is to add a thinner insulating layer between the pickup roller and the truck frame. By replacing the thick insulating piece supplied with the engine, with a thin piece of plastic or electrical tape that is thinner than the factory plastic piece, allows the pickup roller to retract further into the truck housing. This prevents the truck from binding between the center roller and the raised uncoupler magnet.

I have include the fix in a PDF file for download.

 

Joe K

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Original Post
Joe K posted:

RS3 Double pickup roller MTH part number BD-0000098 was used to replace the single roller supplied with the engine. [Two Rollers - (8.0 x 10.8mm Roller) (33.2mm Long) ( Silver base - 10.8 x 12.7mm), One screw hole]

The revised instructions are also included

Thanks, I have an older premier alco s2 that I'm going to do this mod to, my s2 is very jerky and stalls on strait track and runs smoothly on curves... very weird. Any suggestions on what could be wrong?

Good idea, I'd make one small modification.  I'd probably substitute some thin Styrene sheet for the electrical tape.  I don't like what happens to electrical tape after a surprisingly short time, it becomes a gooey mess!

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