I haven’t used my 1953 G3LS very much in the last year due to health issues…which have now been resolved. One thing I wasn’t sure of in 2021 and early 2022, was that the 6v battery was charging correctly. I tend to manually top up the charge on my batteries every couple of months when the bikes are not in use.
My bike uses an electronic regulator originally supplied by Dave Lindsley. There are no moving parts and it used to work well. After the dynamo sprocket came off, the dynamo was sent to Peter de Kremer at Rutland Dynamos for a full rebuild…it made sense as he has all the necessary tools and doesn’t charge a fortune for his time.
When it came back, I tested it as received, and then changed the wiring to suit the regulator from David Lindsley. Once on the bike, I managed to convince myself that there was a small charge going in to the battery, all carefully regulated. I’ve had a nagging doubt in my mind though, so decided to double check; I discovered that there was nothing coming out of the dynamo. Having previously checked it, I assumed the regulator must be faulty…but decided to check the dynamo again, set for full output without the regulator.
It worked, but the resistance readings were weird. There was quite a low resistance, around twenty ohms, from the dynamo armature to the frame of the bike…even with both armature wires disconnected. I removed the brushes and brush plate and all was revealed. You will notice in the picture, two brush holders; they normally have coil springs attached. Each is held in place by two brass rivets. On the back of the brush plate are the other ends of the rivets, the heads of which were standing proud of the insulated plate. Peter had put insulating tape on the back of one side of the plate, but not the other, meaning that it shorted at very low resistance to the frame of the dynamo and bike.
When the dynamo is rewired to run with the regulator, the other armature winding is grounded and the uninsulated (in my case) wire feeds the regulator. Because of the missing insulation, both ends of the armature were grounded, hence no output. Luckily the field had not been activated, or the dead short on the armature could have destroyed it. Once the insulation was put in place and the dynamo reassembled, it was quite clearly charging the battery when tested.
You might just find yourself in this situation after a rebuild if you rewire the dynamo, or the original brush plate may have become burnt and shorted out. The resistance between the dynamo armature and the frame of the dynamo and bike should be pretty much infinity…with both wires disconnected.