Hi all. I am new here, so not sure if this is the best place to ask my question.
I ride a 72 year old "utility" motor cycle (1937 New Imperial of 150cc). It has a "curious" ignition/ battery charge system, called a "Maglita". It was originally manufactured by "M.L.", later by "Lucas".
Two flat plate permanent magnets on front and back of unit "feed" the field to laminations.
An armature with a 4 segment commutator rotates within this field. There is only one winding, so two of the segments are dummies. A DC output is taken from the two brushes, for power to a six volt battery, with a maximum lighting load of 20 watts.
At the top of the unit, in an area unoccupied by the laminations, is an ignition coil. It has a primary winding energised as the laminations of the rotating armature cross this top part. In conjunction with a contact breaker and capacitor, a high voltage to the spark plug is developed in the secondary.
This "two in one" unit was a low cost, low performance unit, whose principal drawback is interaction between the two functions. There is an optimum point at which the contact breaker should open for best spark intensity, but when current is drawn from the DC generation side, the spark weakens and the engine misfires. This also appears to happen when the unit gets hot, possibly as a result of the approach towards the curie point of the magnets. (Having said that, also I think when it is very cold it plays up! As it did 2 days ago!) Retarding the manual ignition control will bring back the spark intensity, but to the detriment of the engine's performance.( I think for my particular unit, retarding ignition merely brings it closer to the optimum intensity position. However, it is not possible toalter this point within the unit.) Furthermore, this weakening of the spark is most evident at higher engine speeds. If the headlamp switch stays in the "No charge/ no lights" position, the spark is always satisfactory. Sometimes it gives no problems whatsoever with lights demanding maximum DC output.
I think that a simple voltage control circuit would help reduce this to a considerable degree. (Obviously not a "shunt" system). I could probably draw up a traditional series circuit, but heating / transistor breakdown would be a likely problem. Whilst the design output is about 3.5 amps, at high speeds it can probably produce 6 amps due to the permanent magnet design.There must be a suitable modern and hopefully inexpensive switch mode circuit I could adopt. I am OK at troubleshooting circuits, and also constructing them, but NOT at design.
Any suggestions please.
I ride a 72 year old "utility" motor cycle (1937 New Imperial of 150cc). It has a "curious" ignition/ battery charge system, called a "Maglita". It was originally manufactured by "M.L.", later by "Lucas".
Two flat plate permanent magnets on front and back of unit "feed" the field to laminations.
An armature with a 4 segment commutator rotates within this field. There is only one winding, so two of the segments are dummies. A DC output is taken from the two brushes, for power to a six volt battery, with a maximum lighting load of 20 watts.
At the top of the unit, in an area unoccupied by the laminations, is an ignition coil. It has a primary winding energised as the laminations of the rotating armature cross this top part. In conjunction with a contact breaker and capacitor, a high voltage to the spark plug is developed in the secondary.
This "two in one" unit was a low cost, low performance unit, whose principal drawback is interaction between the two functions. There is an optimum point at which the contact breaker should open for best spark intensity, but when current is drawn from the DC generation side, the spark weakens and the engine misfires. This also appears to happen when the unit gets hot, possibly as a result of the approach towards the curie point of the magnets. (Having said that, also I think when it is very cold it plays up! As it did 2 days ago!) Retarding the manual ignition control will bring back the spark intensity, but to the detriment of the engine's performance.( I think for my particular unit, retarding ignition merely brings it closer to the optimum intensity position. However, it is not possible toalter this point within the unit.) Furthermore, this weakening of the spark is most evident at higher engine speeds. If the headlamp switch stays in the "No charge/ no lights" position, the spark is always satisfactory. Sometimes it gives no problems whatsoever with lights demanding maximum DC output.
I think that a simple voltage control circuit would help reduce this to a considerable degree. (Obviously not a "shunt" system). I could probably draw up a traditional series circuit, but heating / transistor breakdown would be a likely problem. Whilst the design output is about 3.5 amps, at high speeds it can probably produce 6 amps due to the permanent magnet design.There must be a suitable modern and hopefully inexpensive switch mode circuit I could adopt. I am OK at troubleshooting circuits, and also constructing them, but NOT at design.
Any suggestions please.