Electric System Diagram

Circuit Diagram

Ignition Systems

The 9120cc N type is fitted with two independent ignition systems, one for starting and one for running.

Starting system

A trembler coil is run off the batteries I the side box. This has the low tension switched through both the switches on the bulkhead and inside the distributor. The High tension side is switched between different cylinders using the distributor.See Trembler Coil Theory.

The running system
The N-type can run on either a Simms or a Bosch Magneto, for details of how to work on these consult the relevant manual.


The Headlights were originally Hudson, but are now CAV Model B

Trembler Coil Theory


Trembler Diagram
Trembler Diagram

The basic principle is the same as in a transformer with the trembler arm developing an alternating current.

When the trembler coil is switched on the contacts on the trembler arm are closed. The current flows in the primary coil and induces a magnetic field. This induces a much higher voltage in the secondary coil. At the same time the trembler arm is pulled down and the contacts open. The current is switched off, the field dies off and the arm is sprung back and closes the contacts again.

Why have a condenser?

The condenser is just another name for a capacitor. When the trembler stops feeding the coil, the field collapses, inducing flow. The voltage, in this open circuit, builds rapidly toward infinity and eventually it must go somewhere, and arcs across whatever is handy. This happens to be the trembler’s contacts. The condenser absorbs this in order to prevent rapid pitting of the contacts.


A bundle of soft iron wires are formed into a cylinder. A few turns of insulated thick copper wire are wound around this cylinder and a thick insulating tube put around this coil. Much thinner insulated copper wire is wound around the insulation many times and is insulated between each layer with paper.A condenser is manufactured from tin foil and waxed paper.The whole assembly of coils and condenser is then coated in paraffin wax.

The vibrating trembler is constructed such that it can operate as quickly as possible.