Ultra-efficient motor? Now you're torqueing

An engine invented in New Zealand could revolutionise the diesel world. That is the firm belief of Gray Shepherd, inventor of the Shepherd New Concept HTO (High Torque Output) axial diesel engine. It also appears to be the belief of the management of at least one major manufacturer.

When Shepherd unveils his new engine at the Hutchwilco New Zealand Boat Show on May 14, he will be supported by representatives of Gough Gough and Hamer, New Zealand distributors of the giant Caterpillar brand.

The Shepherd HTO is a completely new concept engine. It seemingly ignores many of the "givens" of traditional combustion engines and certainly looks completely different.

There is no crankshaft, no connecting rods, no cylinder head, no cylinder head gaskets, no camshafts, tappets, poppet valves or pushrods.

Shepherd says this not only improves efficiency, it also makes the engine far simpler to build. This is because there is no need for complicated cylinder head castings with their intricate cooling waterways and complex lubrication requirements.

However, efficiency is the real key to this engine. Shepherd points out that traditional crankshaft diesel engines are, at best, only 30 per cent efficient (petrol engines are, apparently, even worse). On the other hand, his low-revving engine is roughly twice as efficient as traditional diesels and produces three to four times the torque.

As opposed to a traditional combustion engine where pistons on a crankshaft move up and down in stationary cylinders, the Shepherd engine has only two major moving components. These are the reciprocating sleeve and the rotating outer sleeve or flywheel. (A conventional engine has six major moving parts: piston, connecting rod, crankshaft, drive train, camshaft and flywheel.)

The Shepherd engine also inverts the motion of key elements of the conventional engine. There is a fixed piston at each end of each unit. The outer ends of a reciprocating sleeve then operate as engine cylinders, moving over the fixed pistons at each end of the unit. Combustion of the fuel drives the reciprocating sleeve to and fro between the pistons.

There are also precharge chambers. The motion of the reciprocating sleeve slightly precompresses the combustion air in these precharge chambers then transfers this to combustion chambers via a transfer valve.

The precharge chambers also provide effective scavenging and create an effective two-stroke operation. In essence, power is delivered from every cylinder of the Shepherd engine on every second stroke, as opposed to every fourth stroke for more conventional engines.

Shepherd says the high and more uniform torque output should also reduce transmission losses, further enhancing fuel efficiency.

As there are no sideways forces between piston skirt and cylinder wall, there is also very little need for oil.

"As hot oil in a crankshaft engine is what causes nitrous oxide emissions, this is also good for the environment." The first Shepherd HTO prototype is on display and running at Motat. However, Shepherd points out that this is not well balanced.

"The second prototype, which will be revealed for the first time at the boat show, will be perfectly balanced and smooth running." Shepherd is also the inventor of the Fisherman's Mate, a fish de-hook device said to be more humane and much faster to use than a gob stick or set of pliers. Shepherd is selling his Fisherman's Mate devices to raise funds to further develop and market the HTO axial engine.

"If we can successfully get this to market, the benefits for the country are immense."