Dynamo and Regulators

Lucas E3L and E3H dynamo rebuilds, nickel-plated dynamo body. Fully tested.

Electronic dynamo regulator boxes for 6-volt and 12-volt, positive and negative earth.

At SRM, we specialise in renovating these particular models of LUCAS dynamos.

In the 1940s, the LUCAS E3H (40 Watt) unit was used extensively on various British single-cylinder engines, later replaced by the more powerful LUCAS E3L (60 Watt).

British twins such as the BSA A10, TRIUMPH T100, T110 and NORTON DOMINATOR used the E3L dynamo.

The design of this dynamo is the same throughout the range, but different drive shafts are used for different models.

Each dynamo is tested on the CRYPTON ELECTRICAL TEST BENCH to determine its condition, and an estimate of the cost to renovate the unit is produced.

To fully restore the dynamo, we fit a new armature, field coil, and bearings. The outer body is nickel plated, and the alloy ends are bead-blasted. We also include new brushes and then thoroughly test the dynamo.

Available for BSA A10, Triumph T100, T110 and Norton Dominator.

We found that the most reliable way to convert to 12 volts is to leave the dynamo at 6 volts and use an electronic regulator box in conjunction with the SRM dynamo belt drive. The dynamo belt drive is geared to speed up the dynamo relative to the engine and produce more voltage. The system would charge around 1400 - 1500 rpm and reliably produce 60 Watts. We would also use a 35W/35WW Halogen headlamp bulb (as bright as a 50W/50WW standard bulb) and an LED rear lamp to conserve power.

SRM produce our own toothed belt dynamo drive for the BSA A10 and A7 engine – available on our webshop.

An alternative to the dynamo is the ALTON alternator. 

The conversion involves a small, powerful alternator condensed into the size of a dynamo. It directly replaces the dynamo and comes with a 12v rectifier regulator box.

Available for BSA A7/A10, Pre-unit Triumph and Norton Dominator.