Lynch motor

The Lynch motor is a unique axial gap permanent magnet brushed DC electric motor. The motor has a pancake-like shape and was invented by Cedric Lynch in 1979, the relevant patent being filed on 18 December 1986.

The Lynch motor is built from ferrite blocks sandwiched between strips of metal, instead of conventional copper coil windings, and is held together purely by magnets. The motor is available in several sizes from 3 kilograms (6.6 lb) to 11 kilograms (24 lb) weight and provides a power of 1.5 kilowatts (2.0 hp) to 11 kilowatts (15 hp) within an efficiency range of 80% to 90%.

From 1985 through 1992, the Lynch motor, and tooling were gradually improved, by Lynch, with much input from Richard Fletcher and his project team, including William Read, at London Innovation Network (LIN). LIN financed the patents, in Lynch's name. LIN also financed the construction of prototypes, including a batch made by Ouroussoff Engineering, which incorporated some ideas used in subsequent motors.

From 1989, LIN sought a company to manufacture the motor, having already successfully made small batches and individual units. These included the motors used in the Countess of Arrans world electric boat speed record attempt in 1989. Those motors were assembled by Lynch, with help from William Read, who assembled armatures in his hospital bed after a car accident (Motorboats Monthly Jan 1990).

Hotax, where Trevor Lees worked, was approached but, after Lynch showed Hotax how to make the motor they lost interest. Instead, Lees left Hotax in January 1993, and joined the Lynch Motor Company (part of LIN), as factory manager, to assist Lynch to set up larger scale production, which used tooling previously developed, and new tooling designed by Lynch. Some of the new tooling was made by a local toolmaker, Roger Cox.

Lynch and this small team engineered a production standard motor, which was manufactured by the Lynch Motor Company Ltd and named the Lynch motor. Following a rift between Lynch and LIN and the Lynch Motor Company in November 1996, the intellectual property rights were held by Lynch I P, with the Lynch Motor Co, having 50% rights. A new company was formed, LEMCO, which held the other 50% of the rights. This consisted of J P Hansen group main shareholder, with Lynch and Lees as small shareholders. Lynch joined the Indian company Agni Motors in 2002 where the Lynch Motor is built and marketed as the Agni motor. A further licensed design was made by Briggs & Stratton as the Etek DC Motor. The latest model of Agni Motor is manufactured and distributed by Saietta Group, which has been formed following the merger of Agility Global and Agni Motors in May 2015.

The traditional Lynch motor design has a spinning armature held on a spindle between two banks of eight fixed permanent magnets. Also stationary are eight brushes (four negative, four positive) on the front side which allow electric current from the power source to reach the armature.

The design of the Lynch motor armature is significantly different compared to other types of motor. The armature coils are formed from insulated copper strips each in a 'U' shape (like a tuning fork). One leg is then bent 45 degrees clockwise, while the other leg is bent 45 degrees anticlockwise. Each coil leg contains several bends before reaching the outside of the armature to be able to pass radially through the ferrite ring before the ends finish 90 degree apart. At the outer edge each copper strip has a crimp forming an electrical connection to its companion 90 degrees rotated. The inner edge of the copper strips have the insulation removed on the front face only, to form the commutator surface where the brushes make contact.