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Written by: Peter Ballard (As fitted to Ural M61, M62, M63 and M66, Dnieper K750, MB650, MB750, K650, MT9, MT12) The Г414 dynamo is designed to operate at 6.5 volts at a maximum output of 10 amps, thus at a maximum power output of 65 watts (6.5 volts x 10 amps). Generally it is not advisable to operate such devices continuously at more than 80% of the maximum output, thus only 52 watts is practically available. Thus by the time the headlamp and side lamps are on there is no surplus capacity for any other electrical consumers such as a bright sidecar lamp, heated handle bar grips etc. The results of overloading are either a burnt-out armature or a ‘flung’ commutator where the lead solder has overheated and melted. The field windings however seem to be far more durable being closer to the cooling air flow over the dynamo casing. The heat produced by a resistor such as the armature or the field windings is equal to the square of the current multiplied by the resistance. Thus it is independent of the voltage! Thus it is possible to run the dynamo at a higher voltage to increase the power output without necessarily overloading the armature or commutator. If the dynamo is run at twice the voltage then the dynamo will produce around twice the power. The downside to this is that the field windings have to be loaded more. They must now carry more current for more of the time to excite the armature more to produce the higher regulated voltage. With the standard electro/mechanical regulator the voltage from the dynamo output is controlled by switching the field windings on and off many times a minute. To increase the controlled voltage output the field windings have to switched on for longer than they were with the lower voltage. This can be done very efficiently with an electronic regulator that can be reliable and also absorb less power. There are many alternators fitted to cars that run at a nominal 12 volts controlled by cheap, reliable, compact and fully encapsulated electronic regulators. These typically run at 14.2 volts. These regulators will easily and safely control the Г414 dynamos at 14.2 volts. Part Needed – Lucas UCB 100 37672/37647 or equivalent. At this doubled voltage, the armature and the commutator will tend to see half the current than before, for the same power output with the once vulnerable parts of the dynamo having an easier life. So it will now be possible to run at around 80 to 100 watts continuously with generally less load on the armature and commutator than before at around 50 watts! The field windings will run hotter, but are well exposed to the air flow; there is no evidence of them failing under this increased loading and in any case sadly there are many unserviceable dynamos around with destroyed armatures and commutators due to ill advised overloading whilst in standard form, but with good field windings. To carry out this conversion, there is no rewiring required to any of the wiring loom. The rewiring is restricted to the regulator box. The old 6 volt components on the motorcycle will need replacing; battery, bulbs, ignition coil, direction indicator flasher unit and maybe the horn but this will survive at 12 volts. Even ballast resistor can be used with the same resistance as the original coil to limit the voltage to the coil. Below there is a circuit diagram and a photograph of the installation of the new parts in the standard regulator box. The installation is quite straight forward. On starting the engine the dynamo will no come on line until around 2500 rpm or so. After coming on line it will regulate as normal, that is the red dynamo failure warning lamp will work as it should. The reason for this is that the dynamo field windings get no voltage supply when you turn the ignition on, thus the armature will only develop voltage from the residual magnetism in the field core. The armature thus needs to spin fast to achieve 14 volts at which point the regulator supplies and controls current to the armature to maintain 14.2 volts. A different regulator and more complex wiring and ‘ignition’ switch can be used to achieve a more conventional dynamo ‘start-up’ mode, but on balance this has not been seen as necessary. NB 1. As before it is essential that all connections are good and tight, all earth connections are also good and the battery is in good condition. 2. Do not be tempted to use a big car battery in the sidecar. A big battery that has gone flat will demand very high current to recharge, often a current higher than is safe for the dynamo to operate at. Even at 12 volts, the dynamo will be overheating if you try to draw over 10 amps from it for more than a few minutes. I have been running these dynamos at 12 volts with 100% reliability since 1986 with this system. 3. Check out your dynamo, clean the commutator with fine glass paper and rinse well with spirit, check the current drawn when run as a motor at 6.5 volts (manual quotes 6.0 amps maximum ).
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