Greetings,
I have a 1960s vintage motorcycle with a motor from East Germany. It has a Bosch-type (field coil wired to armature) 6v/60w. Originally, this motor was designed for a motorcycle that had lights, battery, and a regulator. The motor was transplanted into a racing frame and successfully raced without lights or a battery. Unfortunately the wiring harness was lost and a mouse chewed up the dynamo wiring. I repaired the dynamo to spec but have no clue how it was wired to run.
The dynamo has sat a very long time so no residual magnitism. I created a wiring diagram of the unit, not showing a regulator. The dynamo as an integrated ignition circuit (points/cam/condenser) and the power contacts are D+, DF, and D-. The field coil is around 1.7 ohm and there's a 4.4 ohm "field resistor" between D+ and DF. The mechanical regulator operated by shorting DF to ground at a voltage designed to charge a battery. I've looked at just about every commercial dynamo regulator out there and none can control at this low of a field coil resistance, most require a battery.
My guess is that this bike was operated with a small battery pack to energize the field if it sat awhile. Past that, I see three options: 1) a small 6v regulator hidden someplace; 2) a big zener diode circuit to absorb the output of the dynamo at higher revs; or 3) they ditched the dynamo and just fired the ignition off a portable battery. I think #3 is unlikely because there is no place to mount anything on this bike and it raced in enduro races that stretched up to 500 miles over rugged terrain.
The machine is fully restored - regulating the dynamo is my last challenge. Firing the ignition requires only a modest amount of dynamo power. The ignition requirement is a 'nearly' fixed load. Depending on whether I use a standard coil (3ohm primary) or high output coil (1.8ohm) the current requirement would be, accounting for dwell, about 1.2A-1.5A or 2.7A-3.0A depending on the revs. I'm guessing that the ignition circuit can handle a pretty noisy signal. My simple electrical brain says 'keep strict control of the current through the field coil to prevent the dynamo from outputing any more power than needed'. If I can do that I'll avoid having to dump a lot of heat.
I understand that dynamo output depends upon revs and field current. There's very little performance data on this dynamo but I do know that voltage builds quickly once the motor fires. Though I'd prefer avoiding it, I think that a zener circuit is the simplest way to do this, but that might be totally wrong. If I have to use a zener option I would hope to control things sufficiently to minimize the heatsink site since there's little real estate to mount things on this machine.
I could really use your thoughts on this and how to design a regulator circuit that would work in this application. Thanks in advance for the help!
I have a 1960s vintage motorcycle with a motor from East Germany. It has a Bosch-type (field coil wired to armature) 6v/60w. Originally, this motor was designed for a motorcycle that had lights, battery, and a regulator. The motor was transplanted into a racing frame and successfully raced without lights or a battery. Unfortunately the wiring harness was lost and a mouse chewed up the dynamo wiring. I repaired the dynamo to spec but have no clue how it was wired to run.
The dynamo has sat a very long time so no residual magnitism. I created a wiring diagram of the unit, not showing a regulator. The dynamo as an integrated ignition circuit (points/cam/condenser) and the power contacts are D+, DF, and D-. The field coil is around 1.7 ohm and there's a 4.4 ohm "field resistor" between D+ and DF. The mechanical regulator operated by shorting DF to ground at a voltage designed to charge a battery. I've looked at just about every commercial dynamo regulator out there and none can control at this low of a field coil resistance, most require a battery.
My guess is that this bike was operated with a small battery pack to energize the field if it sat awhile. Past that, I see three options: 1) a small 6v regulator hidden someplace; 2) a big zener diode circuit to absorb the output of the dynamo at higher revs; or 3) they ditched the dynamo and just fired the ignition off a portable battery. I think #3 is unlikely because there is no place to mount anything on this bike and it raced in enduro races that stretched up to 500 miles over rugged terrain.
The machine is fully restored - regulating the dynamo is my last challenge. Firing the ignition requires only a modest amount of dynamo power. The ignition requirement is a 'nearly' fixed load. Depending on whether I use a standard coil (3ohm primary) or high output coil (1.8ohm) the current requirement would be, accounting for dwell, about 1.2A-1.5A or 2.7A-3.0A depending on the revs. I'm guessing that the ignition circuit can handle a pretty noisy signal. My simple electrical brain says 'keep strict control of the current through the field coil to prevent the dynamo from outputing any more power than needed'. If I can do that I'll avoid having to dump a lot of heat.
I understand that dynamo output depends upon revs and field current. There's very little performance data on this dynamo but I do know that voltage builds quickly once the motor fires. Though I'd prefer avoiding it, I think that a zener circuit is the simplest way to do this, but that might be totally wrong. If I have to use a zener option I would hope to control things sufficiently to minimize the heatsink site since there's little real estate to mount things on this machine.
I could really use your thoughts on this and how to design a regulator circuit that would work in this application. Thanks in advance for the help!
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