A major manufacturer of earth moving vehicles and equipment has recently launched a new range of motor graders with a little bit of help from British firm, Renold Chain. Each grader in the new range is designed to be at least 30% more powerful than the model it replaces, and that was a big selling point. Customers would be able to invest in smaller graders, capable of doing the jobs of larger ones, and the company would steal a lead over its competitors.
This all looked good on paper until the designers realised that the extra load on the chain used to drive the grader's four rear wheels would significantly shorten its service life. The next size up in the heavy-duty chain they were using would handle the extra load; the problem was, its increased size would mean completely redesigning the vehicle's chassis, which wasn't an option.
Finding a chain that would cope with the extra power wasn't going to be easy because they were already specifying a heavy-duty class chain, and changing brands was unlikely to produce the results they sought. What they needed was a new 'super' chain.
The design team working on the new motor graders took what was beginning to look like a mission impossible to Renold's research and development department. What the earthmover team didn't know was that Renold had recently been experimenting with new materials and had made some interesting discoveries. New materials alone, though, wasn't going to solve the problem and if a solution was to be found it was going lie in the complex world of chain geometry. Varying the size of a chain's components in relationship to each other, even by the smallest amounts, can have a dramatic impact on the chain's performance.
Renold's engineers embarked on a series of very lengthy calculations to predict the chain's performance after minutely altering the size of its component parts. There are an almost limitless number of permutations in the relative sizes of a chain's components, and to the uninitiated it would be like looking for a needle in 100 haystacks. Chris Lodge, Renold Chain's engineering manager, takes up the story:
"We knew where we had to look and the answer lay in a mass of calculations. We were like physicists looking for the elusive theory of everything and we even had to make up new formula for some of the calculations as no-one had ever done this before."
In the end the breakthrough came by varying the relative sizes of the pin, inner plate, bush and roller. "There was some new materials technology in there as well," explained Dr Lodge, "but the details of that will have to remain a trade secret."
The proof of the pudding comes in the eating and to test the new chain it was fitted to motor graders operating in what must be the most arduous application on the planet - a quarry near the Arctic Circle.
The huge dumper trucks that carry aggregate in and out of the quarry destroy the dirt track roads on which they operate. So, in order to keep them in good condition, the motor graders work day and night following each truck out as it leaves and then return with other trucks as they arrive back at the quarry. When the chain was fitted, Renold predicted a six-month service life but, so far, it has been operational for ten months and there are no signs yet that it will need to be replaced anytime soon.