Class 25/33: Step 9 Driveshaft Fitting (Drive Dog Coupling)

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Note: This description assumes old style bearings with long collars. If you have new style bearings, click here to see how they are orientated.

To identify which bearing type you have (older or later) click here.

If you have the drive dog couplings instead of the springs then the shaft is easier to fit into place.

  • Firstly, take the armature, the two “male” parts of the drive dog and two bearings. Fit the bearings onto the armature shaft, both collars facing outwards away from the armature. Cap the ends of the shaft off with the two “male” drive dog pieces. Now slot the armature / bearings into the chassis, making sure you have the commutator at the correct end, over the brush hole. Also, notice how the “male” drive dog sections are at 90 degrees to each other.
  • Next select one worm, one “female” drive dog piece and two more bearings. Place one bearing at the short shaft end, with the collar facing outwards, away from the worm. Next take the other bearing and place it on the other side of the worm, facing towards the worm. Now cap this end off with the “female” drive dog piece and slot into one end of the chassis. Picture 2 illustrates the bearing orientation very well.
  • Finally, do the same with the remaining worm and bearings at the other end, as shown in picture 3. Now use a pin and oil to apply the lightest touch of oil to each bearing where the shaft passes through it.

Tip: As a quick check to make sure you have all of the bearings orientated correctly, take a look at the shaft and bearings in the chassis. All of the collars should be facing “outwards” away from the armature.


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