In December of 2020, I first shared my ideas for the 3D printed wheel centers for the Bachmann OO split chassis 4MT. You can find the post here.

After two test prints, the design was finalized and a set was painted, I used a basic acrylic black spray. They were then ready to be press-fitted into the wheels.

The two with the larger counterweights go on the center set wheelset with the drive gear. No glue was required but I put a pot of superglue near the center of the wheel just to be sure. Be careful not to put too much otherwise it will squeeze out.

Once the locomotive was reassembled it looked as good as new.

Now the wheel centers are flat-sided the side rods no longer catch and the locomotive runs nice and smooth. This particular model also needed the axles replacing as they had cracked, the other common fault with split chassis locomotives of this era. The axle set can be found here.

These wheelsets are now ready to be ordered and can be found using the link below or can be ordered through the group order service, send me a message through the contacts page.

Bachmann Mainline Replacement Wheel Centers

But the 4MT is not the only locomotive with this issue. The Bachmann Mainline 2-6-2 tank also has this same design and many suffer from the bulging wheel centers. But the 2-6-2 has much smaller wheels, at 19.9mm diameter (equivalent to 10.4′), so a new design is needed.

The crank pin is also closer to the centre of the wheel giving a different shape to the centre casting.

The plastic inset pops out just as easily allowing me to take all the measurements I need to draw them up ready for a 3D print test.

These wheel centres will be test printed along with my next 3D print order. This locomotive also has cracked axles but luckily those are the same as the 4MT.

Next week I hope to have some more development work to share with you on the HO Baldwin RT-624 project.