PHASE 3

2.2 LOKKA DIFFERENTIAL UNIT DISCUSSION PAPER

LOKKA is a fully automatic Differential Lock that does not require any manual operation. It does not have switches, external lines, electric or pneumatic controls of any sort. It relies on a simple but highly innovative mechanical design which makes use of two distinct sets of forces - the "ground driven" forces acting on a wheel when cornering (that force an outside wheel to turn faster) and the forces from the engine (power) turning the diff. The combination of these two sets of opposing forces and the unique design allow the automatic engagement and disengagement of the driving gears when a vehicle turns or requires differential action.

(FORM THE JOURNAL- John. Markel and A. H. Gray, LOKKA electronic differential concept the MITRE Corporation, Bedford, Massachusetts 01730, Vol. ASSP: 22, April 2007.

2.2.1 DIFFERENCE TO A NORMAL DIFFERENTIAL

1. A normal diff is designed to perform two main (traction related) operations.

A - Transmit engine power via the drive train to the wheels

B - Allow "differential action" – i.e. allow the wheels to travel at different speeds to allow cornering without drive train and tyre damage.

2. The traditional differential design allows for an infinitely variable rate of  differentiation ranging from the standard 50:50 where both wheels turn at the same speed (straight line driving & the ideal for off-road) to a ratio of 100:0 where one wheel spins freely and the other is not driven at all - (the big problem)

3. The design also allows for all power to be transmitted to the "path of least resistance" which is fine on bitumen because both wheels always have some degree of traction but off-road you often require substantial power and in this case even a small difference in traction can result in wheel spin and hence total loss of traction.

4. An LSD (limited slip differential) is simply a standard differential with either a fixed bias or a dynamic biasing mechanism which serves to only partially "lock up" the two axles by way of clutch plates or special gear design. However most require that both wheels still have some traction on the ground to operate and even when new will cause a wheel in the air to spin uncontrollably so as to be completely ineffective where off road traction is required.

5. LOKKA overcomes the traction deficiency of the standard differential so as to ensure that 50:50 power split is achieved when driving irrespective of ground (or air !) conditions, yet at the same time still allowing differential action when cornering on hard ground.

2.2.2 SIMPLE EXPLANATION OF LOKKA'S OPERATION

The LOKKA mechanism allows a wheel to turn faster than the speed the diff is driving it - (differential action), but never allows a wheel to turn slower than the speed the diff and engine is turning it - (traction). Thus a wheel cannot ever stop turning if the engine is driving it, but in a corner it can be forced to actually turn faster. Unlike a normal diff the engine can never drive one wheel faster than the other.

2.2.3 100% POSITIVE LOCKING MECHANISM

LOKKA is positive locking, meaning there is no slippage when locked - there is a mechanically solid engagement of all parts. In contrast an LSD is not positive locking and does allow slippage and one wheel "spin up" - the spinning of one wheel at twice the diff speed while the other wheel having traction remains motionless. This means that you get 100% of drive and traction to both wheels.

LOKKA design is by sight extremely simple - in fact so simple that most people cannot understand how it can operate so well. It uses less than half the mechanical components of others, weighs less because no new carrier is needed and for these reasons costs less.