Axle Gear for Spectrum 4-4-0 and 2-6-0, New Part

[Fred2179]

My 4-4-0 recently coasted to a halt so I suspected the axle gear had cracked.  (It hadn't - that's another thread about different gears breaking.)  I ordered a new one from Parts and got this:



It's clear the NWSL gear won't fit on this axle, though it should fit on the original axle.  What isn't clear is whether they updated the material so this gear won't crack?

[veetwelve]

Hi Dave,

In answer to your last question, I'm guessing that the nylon gear material has NOT been updated, because I think it doesn't need to be based on the new mounting method.
My degrees are not in engineering or physics, but I'm thinking that the reason Bachmann had so many problems for so many years with their nylon drive gears is because they took the easy way out and press-fit them to the axles.  That may work long enough for a kid to tear up his toy, but long-term, the press-fit solution places a radial tension on the entire gear, and over time the nylon material is bound to fail.  The "D" shape to key the gear to the axle places no such stress on the gear material, and is a much more elegant (and reliable) solution, albeit probably more expensive to produce.  A metal gear from NWSL could be made to work, but it would require a blob of solder or epoxy in the round hole, and then filed out to match the "D" shape of the axle.

Looking forward to hearing how that new worm gear combination works!
Jay