Canadian motor design helps steam force come full circle (Reprinted from the November 1999 issue of Design Product News by permission of Action Communications Inc) "The more original a discovery, the more obvious it seems afterward." - Arthur Koestler After ruling the 19th century, steam has been relegated to the margins of power production in the 20th. But with a Canadian invention by TriTec Power Systems Ltd. of Markham, ON, about to go commercial, steam should be chugging along again in the 21st century. According to TriTec president Edward Tsang, the introduction of the internal combustion engine spelled the retirement of steam as a motive force option. Tsang, along with TriTec co-founders John Rowe and Manfred Timm, presented a paper to The Canadian Society for Mechanical Engineering back in 1996 that detailed their invention and its relevance. "The availability of a small, relatively inexpensive portable steam generator coupled with a revolutionary new concept of converting any expanding gas into useable energy could cause a rebirth of this ‘old’ power source", the co-authors wrote. The TriTec Power Unit (TPU) itself is a device that can take advantage of any kind of gas expansion, and produce peak torque at the moment of rotation. The TPU doesn’t have to be limited to the use of steam, said Tsang. "There’s a good chance that liquid nitrogen, with its distribution possibilities, could be a viable source of expanding gas for the TPU." The anchor of the TPU concept is built on the more efficient use of two simple mechanical principles: the power of the wedge and the power of leveraging. The unit uses a triangular transmitter (the wedge) to convert linear motion into rotary motion. The linear motion is provided by a series of free floating pistons placed so as to provide an in-line force to the centre of the unit (see inset above). Three bearings are positioned at the lower end of each piston extension shaft and held by a bearing pin. The outer two bearings operate in machined grooves cut into the front and back plates and thus can only move in a linear direction towards the driveshaft. The transmitter is key mounted onto the driveshaft and when gas expansion in the cylinder causes the piston to descend, the centre one of the three bearings operates on the transmitter, forcing it to rotate. The distance between the point of contact on the triangle and driveshaft provides the leveraging. The combined result is an engine that can produce torque at the moment of rotation and with the ability to attain peak power at a minute fraction of the cycle. The TPU is said to perform work (which is torque and not hp) more efficiently at much lower rpm than conventional motors or engines, therefore eliminating the use of reduction gears in most cases. In certain situations, an overdrive may be needed to gear up instead of gear down to obtain higher rpm. Because the concept of the TPU is very flexible, it allows for more cylinders to be added to a main body or for more units to be linked up in series (see truck engine above), both with minimum changes. In addition to adding more cylinders, the power combination for the TPU also includes: output controlled by varying the pressure of the input gas; various sizes of the piston and cylinder assemblies that can be interchanged without changes to the main body; and, multiple units connected through a common shaft becomes more practical because of the slim line design. Possible compressed air applications of the TPU include mining and the food industry, according to Alain Ouellet, vice-president of Engineering at TriTec. "With liquid nitrogen, the volume of the gas can increase drastically - from cubic inches to cubic yards - so it could provide an excellent standby energy source." Ouellet also said that TriTec is looking to cross license its patented technologies with other companies. One such firm is hybrid car manufacturer Microvel Technologies of Jonquiere, QC, which currently has a battery and generating system. And a U.S.-based firm is currently testing an 8-cylinder pre-production unit in a hoist application for oilrigs and barges. Another promising application for the TPU is robotics, where the unit can offer advantages in both torque and speed modes. "Engineering Services Inc., a company founded by one of this country’s most noted robotics experts, Prof. Andrew Goldenberg of the University of Toronto, was contracted to develop a unique direct drive electrical motor based on the TriTec technology. Early prototypes have demonstrated promising torque and positioning characteristics. The specially designed linear actuator technology will certainly enhance our company’s technology lead", said Ouellet Development work on the TPU is being done on SolidWorks MCAD software for design, Cosmos for FEA and Dynamic Designer for motion analysis. Parts implemented include SKF bearings for low maintenance and Dupont composite plastics for cylinders and other components. "TriTec is pushing the envelope in material and motor technology", said Ouellet.