Mechanical Design

Hydraulic Components are mechanical . . .

Although I have spent a large chunk of my working life in power hydraulics, I have always considered myself as a mechanical designer first, with hydraulics being an interesting part of mechanical engineering.

Hydraulic components are after all only mechanical devices, sometimes very intricate ones, requiring all the usual mechanical design skills and knowledge of tolerances, material selection, heat treatment and so on. The constant quest for improved performance at lower cost leads to investigation of new manufacturing methods and material treatments - all providing for a broader knowledge of things mechanical. Also hydraulic systems have mechanical inputs and outputs so one is lead naturally to the design of gear systems, winches, conveyors, vehicles and so on.

10 Tooth Pinion . . .

Most mechanical designs for capital equipment utilise standard components and are made to the appropriate Engineering Standards, but sometimes it is advantageous to go back to first principles and work from the ground up. For example, to minimise the size of a 6:1 internal gear reduction set, a 10 tooth pinion was found to be the best answer in providing optimum strength, not to be found in the gear standards.

The trick is to know when to use the Standards approach and when to start from scratch. Clearly, the Standards approach is sensible for one-off manufacture of common constructions, such as a normal conveyor system; while mass production items often require individual attention to provide the best cost to performance ratio.

 Innovation and Standards are almost mutually antagonistic, but innovation should only be used where there is no suitable standard solution.

The ability to come up with inventive solutions is one of the marks of a good mechanical designer, but so is the ability to avoid the temptation of unnecessary innovation.

 10 tooth pinion
Ten Tooth Pinion in Internal Reduction Gear

The quality is in the details . . .

Quality is the most important, and least understood, aspect of mechanical design:

  • The final cost of making a machine is pretty much set by the original concept. It is in coming up with good concepts that engineers can earn the right to say "an engineer can do for one dollar what any fool can do for five".
  • The funtionality of the machine is set by the design of the major features and components, including selection of materials and finishes.
  • But the quality rests primarily in the details.

If one is forced into making little savings by sacrificing detail quality in order to make a costly concept cheaper, the end result will be a low quality machine. We have all known maintenance nightmares where little things keep on going wrong, because the detail quality was poor.

 "Quality is remembered long after price is forgotten"

Quoted from Joseph Lucas, founder of Lucas Industries. Short-term and lazy thinking concentrates only on the lowest first cost, while long-term thinking considers appropriate quality and long term operational costs. Getting the right balance is hardly ever easy.

 Dredge cutter
Basket Cutter for Cutter Suction Dredge
Terms of Use | © 1999 - 2004 Hugh Frazer and Associates Pty Ltd. All Rights Reserved. | Support