02-02-2019, 09:16 AM
(This post was last modified: 02-02-2019, 09:24 AM by Bob Culver.)
For any that may be curious, if the field is connected in reverse, when an output begins to be produced it produces a field current which cancels instead of reinforcing the residual magnetism.... so no net output. Reversing the residual magnestism reverses everything and the situation is unchanged.
Sometimes after long standing , dismantling etc the residual magnetism becomes so reduced that the dynamo will not get under way. Operating it as a motor (or trying to if on the car) will restore any residual magnetism, polarised depending on the connection. (field and output terminals joined and connected to battery, dynamo frame to battery earth, whichever pole is earth in the car. ) Although motoring is a test it is not necessary to do to restore or reverse residual magnetism (polarise). Just connect the isolated field wire briefly to battery, frame to battery earth (as in car). Should draw enough current to spark. In the car prodding the cutout is fine but it must not be allowed to stay locked down.
To test the dynamo output connect field and output wires togehter and drive in normal direction .Between linked terminals and frame, should produce well over 6v as revs rise. The dynamo body must be negative if the car is negative earth.
An old 6 or 12v headlamp bulb is a good test load.
Sometimes after long standing , dismantling etc the residual magnetism becomes so reduced that the dynamo will not get under way. Operating it as a motor (or trying to if on the car) will restore any residual magnetism, polarised depending on the connection. (field and output terminals joined and connected to battery, dynamo frame to battery earth, whichever pole is earth in the car. ) Although motoring is a test it is not necessary to do to restore or reverse residual magnetism (polarise). Just connect the isolated field wire briefly to battery, frame to battery earth (as in car). Should draw enough current to spark. In the car prodding the cutout is fine but it must not be allowed to stay locked down.
To test the dynamo output connect field and output wires togehter and drive in normal direction .Between linked terminals and frame, should produce well over 6v as revs rise. The dynamo body must be negative if the car is negative earth.
An old 6 or 12v headlamp bulb is a good test load.