How much damage can flux contamination cause?

Enough to kill a commutator.

When soldering coils into the risers of a commutator, the worst potential consequence is flux contamination, especially in solid riser comms. The same flux that cleans the copper to permit the solder to adhere uniformly to the risers creates a potential for contamination that can destroy a commutator. Flux contamination can occur during the soldering process when flux and/or excess solder seeps away from the riser slots and finds its way to the underside of the commutator. Because the flux and solder are conductive, they render the mica insulation useless. When the insulation can no longer prevent electricity from jumping from bar to bar, the commutator shorts out. Once the mica insulation is contaminated, almost nothing can be done to restore its insulating properties. When the commutator shorts out due to flux contamination, there are usually only two options: Reinsulate (replacing all mica insulation throughout the commutator) or rebuild.

When inspecting a commutator for flux contamination, look for discoloration of the copper bars. The discoloration may take several forms. Streaks of solder and flux are silver in color; carbon residue where arcing has occurred is black; contaminated copper bars can take on a darker, mottled and greenish coppery hue, or the contaminated area may just appear lighter than others. Compare the rear dovetail to the front, since the front will be free of contamination. As always, when taking a comm apart, be sure to band it tightly and bake it before attempting to remove the v-rings.

There are several ways to reduce the risk of flux contamination during the soldering process:

  • While soldering, angle the comm so that flux and solder run away from, and not toward, the bottom of the comm.
  • Use flux and solder sparingly.
  • Flux and solder small sections of the comm at a time.
  • Use a rosin-core solder to reduce the need for flux, or a flux- based solder so the solder contains the flux.

If the commutator is contaminated, some solvents will clear minor contamination, but call your ICC representative at any time for advice on how to proceed.

If you have any technical questions don't hesitate to call, we can talk you though the troubleshooting process. 865-983-7444