New Gears For A Bachmann N Scale Doodlebug

The first post of this year showed you the problems with split axels on a Bachmann N Scale Doodlebug, which can be found here. In this post, I’ll show you the result of the 3D print.

The four 3D parts, as pictured below in the top of the image, are the two drive gear axels and two free axels.  The Doodlebug does have other gears between the motor and the wheels but it’s only these parts that break as they have metal axles forced into them, causing them to crack over time.

The two parts in the middle are an original cracked gear and axel, and at the bottom are an original gear and axel with the wheels fitted.

Before I fit the wheels to the new parts I pass a 1.5mm (0.058″) drill through each part. The drill is ever-so-slightly smaller than the hole in the part, so no actual material is removed, but it cleans out the 3D print residue and ensures a good fit.  If there’s residue the fit can be too tight and cause the new part to crack.

One thing to note; two of the wheels have traction tires and both fit onto one of the axels.  If, like me, you accidentally fit a regular wheel to this axel it can be very difficult to remove and there’s a good chance you’ll break a tooth on the new gear, which is what I did.  That’s why in the new set below I still have one original gear that wasn’t cracked.

The drive gear set clips into the truck tower, with the new gears meshing with the originals.

The plain axels for the trailing truck simply rest in the cutouts.  Both trucks have a plastic clip that holds everything in place.

With the trucks refitted, power pickups replaced, and truck sides attached, the chassis is ready for a test.

And it ran very well, smooth and free, so I refitted the shell.

At some point, I’ll fit a DCC decoder to the Doodlebug, but first I want to tone down the paint job.  Although it’s in the UP colors or Armour Yellow and Harbour Mist Gray, I do find it a bit bright.  But with some weathering, I think it’ll look just fine.

The 3D printed replacement axles for the Doodlebug are now available through my Shapeways shop and can be found here.

I’m slowly working my way through the older Bachmann locomotives which I’ve found tend to have split gears.  I’ve got the first two versions of the N Scale DD40AX and the N Scale PCC Interurban Streamlined Car next on the workbench and will be drawing designs for those for replacement 3D printed gears too.