RickO posted:Paul Kallus posted:
Anyway, my Polar RR K4 model is in the same category (former K-Line design) as the PRR K4 with gear box issue, above. I had speculated whether the undersized motor (and possibly being run under heavy-load) and the way the motor is mounted (towards front of model) could've caused the gears falling out.
The motor is not the problem. The gearbox is, too delicate. There's 4 gears not including the worm. Great for fine slow speed control but terrible for reliability where the typical worm gear turning the axle gear is bullet proof.
The weak spot is the shaft for the intermediate gear as I mentioned above. Once the bushing on the load side of the shaft wears, the gears will slip. Mine had substantial wear but hadn't reach the point that the gears started chattering. The Loco had light run time for being 7 years old.
Most folks don't even know this extra shaft exists and it needs a drop of lube just like the axles. It's hidden behind the spokes of the powered axle. This gearbox design is used in many legacy locos and the reason I'm reconsidering some tmcc versions of legacy models I have....before it's too late.
You can see this shaft spinning in the bushing behind the 3rd pair of drive wheels starting at about the :20 on this legacy Mohawk video ( not mine):
https://m.youtube.com/watch?v=0y60BIICyng#
Anyone who owns the new legacy h10 can easily remove the bottom plate and view this complex and somewhat fragile gearset.
Rick, is the shaft for that gear the root of all evil? Do you know what that shaft material is? Do you think the shaft is just too small or something causing it to tilt and move away from it’s mesh? ...... Pat
