Road and workshop by Handyman
Page 41
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Loads and forces (21)
• In times of traffic famine there is a tendency to accept any load offered, then, providing that it will go on the platform, meet and deal with the problems as they arise. This, of course, leaves one very much dependent upon the skill and experience of the loading driver.
An example of what I mean occurred when a large travelling-jib crane, for use on multi-storey sites, was to be moved up the country. As the crane was not required on site for three weeks, and was already dismantled into its various pieces and sections, several vehicles dealt with the overall job. The lower bogie and electric motors went on a rigid eightwheeler, the control cabin and its subframe on another, with the 130ft mast and cross jib sections laid out for any vehicle that could carry them.
Various vehicles were sent along, large and medium artics, and each driver took what he could fit on his vehicle with the timber and tackle he had available —this was, in fact, something of a spare time job that could be worked with other traffic movements along the route. Four large sections of the vertical main frame or mast were the final items, and whereas three of the four were safely dealt with by one extensible 45ft trailer and two 40-footers, a driver turned up with a 30ft flat platform trailer for the final piece which was exactly 40ft long.
This presented something of a problem but the driver had been ordered to take it, and distribute its extra length over the trailer, which was, of course, 10ft shorter. To do this he decided to have 3ft of the mast over the trailer headboard on one bolster, and 7ft over the trailer rear on a second but lower bolster. He first positioned the bolsters at the extreme ends of the trailer and had the heavy section lowered on, but as this was obviously going to place too much weight rearwards of the two-axle bogie, he re-positioned the rear bolster centrally between the trailer axles, which meant a length of 12ft unsupported, rearwards of the rear bolster.
However, he decided that his was the best method to equalize the load; the next problem was how to secure it, and for this he was unfortunately poorly equipped. He had ample soft rope, but only one chain and one leverlock tensioner. He lashed the fore part of the mast with rope to the head of the trailer, and in the same way passed rope around the overhang portion at the rear. He then arranged his main lashing with the chain and tensioner midway between the bolsters, and considered that in this position it would do the most good as he could apply a fair amount of tension.
However, he was about two-thirds of the way to his destination and using a motorway, when he was signalled that his load was flexing rearwards of the bolster. He pulled off the motorway on to the hard shoulder and re-tensioned the chain in the centre position. As regular road undulations were causing the long overhang from the rear bolster to whip vertically, this became too much for the tensioner which snapped. The chain fell away and the load hinged and slid rearwards snapping the soft ropes in the process.
This worsened the situation for the driver, for as the weight transferred further to the rear, steering adhesion was lost, and the vehicle swung out of control to the nearside, striking a roadside check rail hard enough to crush the engine sump and dislodge the axle. Luckily there was no injury to the driver Or other road users. The lessons to be learned here, are to check the true nature of any special load, send the right vehicle with adequate tackle, and above all, use an experienced driver.