Stators and Armatures – Part 3: Armature Restoration

I’ve saved the biggest part for last- the armature.
The armature is the heavy wound copper and metal hunk that mounts on the end of the crankshaft and spins around the stator, producing electricity in the process.
Stators and Armatures come in pairs, and were manufactured by two suppliers; Siba and Bosch. They do the same thing but are not interchangeable. As a rule of thumb, earlier scooters and cars had a better chance of having Siba electrics than later versions.
The stator/armature pair was part of a complete electrical component system supplied to Heinkel by these manufacturers. Other components included an ignition coil, points and regulator (also known as a “control box”). Bosch made other electrical parts including switches, and headlights.
The biggest difference for most people is the color of the armature. Sibas were brick red and Bosches were green (depending on who you talk to, either a “pukey” green or olive green, although I’ve seen black ones too). I think the taper on the crank was different, which definitely makes them not interchangeable. The control boxes and coils can be used with either system.
Assessing Condition:
If you are restoring a car or scooter you should keep the armature on the car until you are ready to work on it. Why? Because if you drop it you are in trouble. Here’s a photo of an armature that has been dropped. Once this happens you can’t really fix them (although I’m sure you could find someone who could). In this case the copper winding has deformed and it won’t provide enough clearance for the stator. Maybe I’ll give it a second life as a doorstop or practice curling stone.

Heinkel Cars and Cabin Scooters
Damaged Heinkel Stator Winding
The first thing to do is clean the armature. As I mentioned in a previous installment, the stator has four carbon brushes that rub against the armature. As the brushes wear against the armature they create a fine dust. This dust is gets impacted throughout the armature. I suggest sucking it out with a vacuum, and then blowing the remainder out with compressed air. Wear a mask though as the dust goes everywhere and who knows how hazardous it might be.
You might have a situation where some of the insulation on the winding has chipped off. It is difficult to tell what the original clear insulation was made of. You can fill in any chips with non-conductive materials such as hot glue or Cyanoacrylate glue (Crazy Glue). You can get Cyanoacrylate glue in various thicknesses at woodworking supply stores, or just use regular thickness glue available just about anywhere to make a repair. 

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You can use Krazy glue to fix damaged insulation
The next thing to assess is that there are no shorts in the system, specifically that the copper windings are insulated from the steel frame. You can do this with a circuit tester or continuity tester. If you have a short I don’t know what to tell you or how to fix it. You can buy remanufactured pieces from the German and English clubs on an exchange basis (you have to return your non-functioning piece). Given the weight of the armature that might be a pretty expensive proposition. A local electric motor winding company might have some suggestions.

Assuming you’re good so far, you can work on reconditioning the exterior. The outside of the armature is built up from thin metal pieces .You can see them in the picture below:

Outside is made on thin metal plates
This is a easy to repair by sanding down and repainting.

The bottom edge might have some flaking shellac insulation. Once again you can scrape off the loose pieces and replace with two coats of shellac from the hardware store. 

Heinkels, Trojans, and Kabines
Remove this flaking shellac insulation with a Dremel buff and recoat
Repainting is easy. Here’s an example I completed over the course of an afternoon:
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Original condition removed from the Heinkel Kabine

Heinkel Cars and Cabin Scooters
Paint Removed and Taped

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Ready for reinstallation
They clean up very well. Even if they don’t you can’t really see them, but for a small amount of effort the rewards are quite satisfying. 

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