The car is not going to disappear anytime soon and neither is the combustion engine, despite the inevitable rise in fuel prices. We have said it before, electrical motors are an energy-efficient method for driving vehicles but battery technology is simply not going to advance quickly enough for all-electric vehicles to be a practical reality for most uses anytime soon. The near and mid-term future is undoubtedly a combination of compact combustion engine generators charging dense battery packs that drive electric motors - the "range extender" option. We reported on one possible candidate, the disc motor, a couple of months ago. Now, after nearly twenty years of development another candidate is going through final testing and it is a work of elegant genius - Dr. Herbert Hüttlin's Kugelmotor.

Dr Herbert Hüttlin is a 67 year old flow engineer with over 150 patents to his name, mostly in the field of pharmaceutical production machinery. In 1991 he began to look at the traditional "Otto/Diesel" combustion engine and how its efficiency could be improved. After twenty years and three design iterations the good doctor, with help from Freiburg University, has created a compact spherical motor/generator combination that is radically different from the traditional in-line combustion engine with significantly fewer moving parts. Its mode of operation is simple but hard to describe, the video at the bottom should help to make it clear.

Two opposing curved twin-piston heads rock on the same bearing. When two heads are pushed apart the opposing pistons are pushed together. Because this is four-stroke engine the cycle will be induction (apart), compression (together), combustion (apart) and exhaust (together). This obviously has the effect of rocking the cylinder heads back and forth. Here's the genius bit. On the top of each of the four piston heads is a large titanium ball bearing that runs in a channel that is circular in one axis and a sine wave in the other. The channel completely encompasses the pistons and their rocking causes them to rotate on an axis perpendicular to their bearing axis by "swimming" along the channel.

Genius bit #2. The ball-bearing guide channel is fixed to one side of the spherical aluminum housing whilst on the other side a permanent magnet ring is attached to the rotation axis of the cylinders. Fixed to the inside surface of the enclosing sphere is a ring of electromagnetic coils and the interaction with the spinning magnet causes the generation of electricity.

Genius bit #3. With the principal "kinematics" proven and working, three different variations can be created with simple design changes. The first is the basic generator that produces electricity from the combustion engine as described above. There's also a hybrid form that takes a drive shaft off the rotating pistons for traditional mechanical drive (plus the electricity generation). However the combustion pistons can be disengaged and drive reversed back to the engine (under braking for instance) to rotate the coils and generate electricity, or indeed the electrical flow reversed and the coils become an electric motor producing drive. There is a third variation where the pistons do not rotate but the guide channel is driven around them by the motor coils causing them to rock and become a compressor/pump. It's the simplicity yet ingeniousness and versatility of the arrangement that suggests the Kugelmotor (sphere-engine) has great potential longevity.

Pre-production prototypes of 1.18 liter capacity have been in testing for some months and power output at present is 74kW (100hp) at 3000rpm with torque up to 290Nm (213ft-lb). Dr Hüttlin expects efficiency to increase by another 40% with reduced bearing friction and optimization of the combustion. The engine weighs 62 kg and consists of only 62 parts, while a conventional engine has at least 240. The doctor has set up a corporation, Innomot AG, to license the engine design and expects to have a major car manufacturer on board before the end of the year.