Road and workshop
Page 34
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Loads and forces (14)
• In lots of ways our industry can be its own enemy when it comes to load safety and security. With legislation setting the road fund tax in 5cwt steps above 1-ton unladen, a search often takes place for weight savings in the purchase and preparation of a vehicle for general freight, that can be regretted later after some costly load spill.
While there is a platform vehicle, tractive unit or trailer available for most tasks, there is still a tendency to "Yoke a little pony to a big plough"—in other words to buy the lighter range of equipment and place it in competition with the "big fellows", expecting the same results in terms of revenue, simply because as a complete vehicle it has the equivalent body dimensions available with apparently good weight savings.
The dangers of putting the lighter machine to the heavier tasks because it may legally accept them, are just as real as deliberately setting Out to operate at a regular overload. I frequently see these light tractive units nearly, tearing their insides out while pulling a big trailer, for no matter how potent the smaller power unit may be—and some are really good—engine, gears and transmission must have a shortened life. Thus there is no real economy at all as earlier increases in revenue are later submerged in high repair costs.
In the same vein, the purchase of the ultra-light rigid or trailer platform, and then releasing it to the hazards of general mixed freight, instead of to the work and purpose for which it was really intended, is inviting the risk of failure when subjected to the stresses imposed by higher speeds, roundabouts, and so on.
I am in no way "knocking" the designers of light equipment, but I do see with surprising regularity the failures and upsets brought about by operators expecting too much from the lighter range, "flinging them to the wolves" in a misguided attempt to offset rising costs.
Among many of the road incidents that I have been concerned with, and in particular roundabout escapades, inspection has shown that this search for weight saving in platform and sub-frame construction has had a bearing on particular overturning patterns. For example I have seen outer members or outriggers that have sagged under load sway and simply failed to recover, light channel cross-bearers that bent and opened in such a way that they lost their resilience and were unable to return to their original position and as a result the chassis which otherwise may well have recovered from the lean and sway, was, however, taken into an angle from which it could not possibly recover, when the depressed members took on a new position and locked there.
Apart from an actual overturning, many of these light platforms suffer heavily from cornering under heavy load at speed, when given regular work in excess of their intended capacity. I agree that such factors as speed and high loads, which I discussed in earlier articles, started the process of load sway, but had the body design been such that members did not sag and give way under this stress, many vehicles would have stayed on their wheels.
At this time of testing and plating with attendant costs and time out of service, many operators are being subjected to pressures, and can be influenced by both customers and competitors to seek ways and means of carrying that extra ton or so legally. Quite a number achieve unladen savings, but lose sight of the fact that the gap between acceptable load and road safety and the point where flop-over or load spill can be brought about by body weakness or collapse, has been seriously narrowed in the process.