45 Tonner

Overview

This little diesel is interesting in that it has siderods.

It is supposedly 1:20.3 in scale, but since it was a small switcher, it could be mixed with some 1:29 stuff.

It'a about 15 inches long (18 with couplers), 6" wide, 7.5" tall. there's a motor in each truck, with a double gear reduction drive. Nice detailing, metal siderods, mostly metal detail pieces.

The are ok runners, and the drive mechanism seems rugged enough.

Track "brush" / pickup failure

The power pickups are small "brushes" (which are metal pins) rubbing against the back sides of the driving wheels. The power flows from the wheel, to the metal pin/brush, through an internal spring (that keeps it in contact with the wheel) to the metal housing and to the main circuit board.

The weak point in this type of arrangement is the spring that maintains tension is necessarily thin, so if too much current flows through it damage is done to the temper of the spring, so it loses tension or completely collapses. (this is a common failure with all similar manufacturers that use this configuration)

In the case of the 45 tonner the brush housings are difficult to get to, remove, and also appear to be a sealed unit. The best repair other than buying a new motor block (I do not believe the circuit board is available from Bachmann), is to remove the board and modify the metal housings to accept a brush/spring replacement that is available, LGB is the typical parts used.

(Pictures courtesy of Mike Lafferty)

Remove the circuit board

You need to remove the 2 gears from the unit first. They are each held in with a shaft that has one end knurled and is a press fit into the metal housing. If you look carefully you can see which end of this shaft has the knurling. If you cannot, use a punch to move it a bit, and if the end that is coming out does not have the knurling, tap it out the other way ;-) .

Once the gears are released, you can remove the 2 circuit boards with the 4 screws you see.

Modify the circuit board

With the circuit boards removed, you can unscrew the spring holders are screwed on from the bottom side. (makes sense huh?) If they had been screwed down from the top side all this disassembly would not have been required.

In Mike's case, the excessive current not only ruined the brush spring, but burned up a trace on the board.

Mike used a small Dremel die grinder and opened up those small cast spring holders to accept the LGB spring loaded carbon brushes.  It took some time and a little finesse but it is completely doable.  - they will fit with enough grinding. In the end, they will look like very small "u" holders used to clamp copper pipe onto a wall.  You may have to use some shims to hold in the new brushes.  Mike used small, thin pieces of gasket cardboard.

Mike then just soldered a wire between each pair of brushes (each side) and then sent another wire from each side, up out of the truck to the cab. He bypassed the small circuit boards completely. You may have to open up some holes in the cab to do this depending on the wire you use.