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From Quarry Face to Crusher 01
Page 40
Page 41
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Vaporizing Oil
By P. A. C. Brockington, A.M.1.Mech.E. WHEN Mr. G. P. Bradley. transport manager, Judk ins, Ltd., Tuttle Hill Granite Quarries. Nuneaton. voiced his decision to experiment with tractor vaporizing oil for the petrol engines of the "site " tippers, his knowledgeable friends condemned the scheme as impracticable. He was warned that the lubricating oil would become diluted, that engine performance and reliability would suffer, and that the exhaust smell would he
extremely unpleasant. The warning against the smell is the only one which, judging by practical results, appears to have been warranted.
Austin three-axled ex-W.D. tippers. carrying a 10-ton Toad and a body weighing over a ton more than the standard type, use 11 gallons of vaporizing oil, in addition to two gallons of petrol for starting and for a period before stopping, compared with a consumption of 15 gallons -when operating continuously on petrol. The vaporizing oil being free of tax, this rep:esents a fuelcost reduction from £2 19s. 8d. to 18s. 2d. It is necessary to keep the engine running when the vehicle is loading and unloading, and fuel consumption is recorded in gallons per day. The saving per vehicle-day is between £1 and £2 according to conditions and the hours worked.
The same compression ratio is employed, and it is claimed that on warm days the engines pull better on the steep gradients of the quarry. Apart from the fitting of a special intake manifold, the only non-standard modifications are an increase in the distributor-points setting of 0.010 in. and the fitting of three-point, in place of singlepoint sparking plugs.
Of the 10 Austin three-axled tippers enraged onheavy " internal " haulage, 86 seven are equipped for vaporizing oil operation and three are fitted with Perkins P6 oil engines. The conversion parts of the Austin engines are supplied by the Lodden Engineering Co., Ltd., Lodden, Norfolk, for about £18, including the cost of the auxiliary tank and a three-way tap.
The manifold is of light alloy, which heats-up very quickly after the engine has been started. on petrol and allows a change to vaporizing oil in a few minutes. Deflector plates give a turbulent flow to the incoming mixture and diffuse the liquid droplets. Judging by the smooth pulling of the engines,
distribution is good, and tests of the lubricant show that dilution is not aggravated.
These, vehicles are part of a tipper fleet of 14 site-transports and 33 delivery lorries, all of which are of Austin manufacture with the exception of three Commer forward-control 7-tonners. The remaining tippers on site work are Austin 54onners, and eight of the road vehicles are Austin 10-tanners, of the same type as the site transports, fitted with the original Austin petrol engine or a Perkins P6 oil engine. The fleet collects about 12,000 tons a week of finished products from the screening plant, and a tonnage 15 per cent, in excess of this figure is carried to the crusher from the quarry face, the difference in tonnage representing waste material.
Tippers Save Labour
Three years ago, transport from quarry to crusher was by rail, and loading by hand. This required a labour force of 150 men at the rock face; with the introduction of excavators working in conjunction with tippers the force was reduced to six.
The petrol engines of the road vehicles average 12-15 m.p.g. and the oil engines about 16 m.p.g. The petrol. engine cylinder heads are removed for a top overhaul at 20,000-25,000-mile intervals and Cords piston rings are fitted after 60,000 miles runntrig. The mileage between major overhauls is about 85,000, the total distance varying according to engine condition.
The Perkins-engined road vehicles normally run 100,000 miles without attention to the power unit, apart from adjustments. On site work, the oil engines show to greater advantage, the man hours spent on their maintenance
being about one-fifth the time required for petrol-engine overhauls. Detergent oil of S.A.E. 20 viscosity is used in the Perkins engines, and straight mineral oil of S.A.E. 30 or 40 in the petrol engines.
The lubricant is reclaimed in a Stream-Line filter for use in hydraulic tipping gear and for mixing with S.A.E. 50 oil to replenish any engine which must continue temporarily in service after the oil consumption has become excessive. Sumps are drained and refilled every 4,000 miles.
The manner in which a
vehicle is driven is an all-important factor in the useful life of the engine; in one, instance, a careful driver ran his petrol-engined vehicle 140,000 miles before a major overhaul was required. Both site and road vehicles remain in charge of one man and, wherever possible, this rule is practised to the extent of laying-up a vehicle in the absence of the driver. A policy of "leave it to the men to get the best results" is adopted with regard to all employees, many of whom have been with the company over a long period. High wages are paid and an appropriate Christmas bonus is given.
The heavy, steel bodies of the site vehicles are of the American type. They have external box-section ribs at the sides, back and below the floor, and heavy, steel sheet is used to reinforce the floor. These bodies withstand rough handling indefinitely, and their use represents a cost-saving measure, despite their weight of 50 cwt.. and the cost of fitting.
The wood bodies of the road fleet, which are constructed in the operator's workshops, have steel floors to a design calculated to reduce maintenance to a minimum. All vehicle are fitted with Dunlop rubber mudguards.
The tyres of the road vehicles run up to 30,000 miles before renewal becomes necessary. and the tyres of the site vehicles are generally worn out after 27,000 miles. Standard 34 by 7-in. covers of any make are fitted to the twopiece front wheels of the Austin threeaided tippers, and 36 by 8-TI. Pirelli tyres at the rear. Although three-piece wheels are invariably used for the 36 by 8-in, covers, the two-piece type is found satisfactory at the front. All cuts that develop in the rubber are filled in with solution to prevent the entry of sharp flints.
Checking Tyre Pressures A tyre gaug,e is issued to every driver, who tests the pressures at least once in two days. This is done when the vehicle is waiting on the site to load or unload, or after a stop on the road. The traffic manager personally makes periodic spot checks of all tyres.
The workshop personnel numbers 12 men, including eight mechanics, an electrician, a welder, a refueller and a "tyre man." Although the organization is based on an appropriate division of duties, and each man is regarded as master of his own trade, no-one stands on principle when called upon to tackle the other man's job in an emergency. Each is a specialist with a knowledge of general overhaul principles, which can be used to good purpose when the unforeseen happens. The men appreciate working as a team, as it widens the scope of their abilities, and the management encourages it by placing trust in the decisions made.