Tipping the balance

While the older generation of tipping trucks and trailers were short, the current generation are the same width but up to three times longer, so when they are raised up, they only have one third of the lateral stability – which is often not enough. Problems always occur because the trailer is stopped sideways on a slope. It does not have to be very much of one – seven degrees is about the maximum that can be tolerated and trailers can topple on slopes significantly less than this if they are caught by a gust of wind, or the load is all on one side, and the wheels decide to sink on that side, or the telescopic lifting ram decides to bend. The problem is so bad, according to Ian Chisholm, head of technical services for the Society of Operations Engineers, that many construction companies have banned tippers from their sites because of the hold-ups they cause when they fall over. The European Union is considering introducing a total ban on tipping trucks and trailers within 10-15 years. The Challenge Our challenge this month is to come up with an alternative method of getting loose material out of a long trailer. One could go back to the nineteenth century and employ numbers of labourers with shovels and wheelbarrows, or one could perhaps bury a few bones underneath and persuade dogs to displace the material in order to get to them. However, what is clearly required is a mechanical solution based on modern technology, but one that does not add too much to the cost, and is preferably no more expensive than today's products. The main problem is not that there is no obvious solution but there are too many – and it is not immediately clear which is the best path to follow. When coming up with a solution, it must be remembered that it should be capable of dealing with materials that range from loose gravel through sticky clay to even more sticky, hot asphalt. Ian Chisholm came up with one short-term and two long-term possible solutions, when he revealed the true extent of the problem to a recent meeting of Inita – the Independent National Inspecting and Testing Association. We have since come across two more ideas. All are summarised below. Solution to Coffee-time Challenge The short term solution is that the IRTE (Institute of Road Transport Engineers) division of the SOE (Society of Operations Engineers) is developing a tipper driver's pack, so that they hopefully will not try to tip on too sloping ground when the wind is blowing, and refuse to handle a load which is all on one side of their vehicle. Ian Chisholm of the SOE also mentions the possibility of using trailers with moving floors that convey the material out of the rear end, or pushing it out with a moving barrier and a ram, as in a refuse truck. Roger Bishop, the editor of our sister publication, European Truck and Bus Technology, suggested having extending stabilising arms like those on a mobile crane, with large area pads to cope with soft ground. We recall that the road pavers we used to work with at Blaw Knox had chain conveyors, with a series of bars spaced some distance apart beneath whatever material the machine was laying, attached to chains on each side. In order that the bars did not bend, they used to have two chain conveyors side by side in each machine, the central section protected by an inverted, shallow trough. After working with asphalt, all working parts had to be spray cleaned with diesel oil or they became hopelessly stuck.