Recent Atlas Loco Production - "Old" Wheel Profiles

[C855B]

... It is not a part of the half-axle?  Is the half-axle still made from steel?  Are you sure that the collar and half axle are not a single machined piece? ...

Three pieces. The half-axle is SS, the collar is same material as the wheel, some nickel-silver alloy, I would guess.

I agree, it's bizarre. The only guess I can make at this is some limitation of the milling equipment at the new factory, requiring a larger hole to hold the slab to turn the flange profile, so they have to use a reducing insert for the axle.

[Steveruger45]

Perhaps someone screwed up by drilling too big a hole in a million wheels and this was the fix in order to use those wheels. 😋

[peteski]

Perhaps someone screwed up by drilling too big a hole in a million wheels and this was the fix in order to use those wheels. 😋

You might be sort of onto something here.
Since those Chinese factories produce parts for model companies all over the world, maybe that wheel is also used for some European model where that design has both wheels isolated from a 1-piece axle. In that design the sleeve is made from Delrin, and picks up power via wheel wipers.

I guess what we might be seeing here is the result of the Chinese model manufacturers reshuffling last year (or was it 2 years ago now?).

Either way, it is too bad that Atlas does not make better wheels, with nicer wheel face, narrower tread, and low flange (liek Kato).