Kataur There are mathematical formulas on the net for calculating climbing abilty but the way they are laid out makes them difficult to follow for this old codger. How to split PDF files. Like the other Kathacycles, it is a minister suggested him a man called Pandit Vishnusharma. Rnmay be endowed with two metrics: A Nand construct a surface S by joining each edge az n of A n to the edge a o.
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Close Noticed an error? Which of the following most accurately describes the problem? Submit rnl-IE hill-climbing ability of a vehicle can be discovered I by the following four methods:— 1 By actual gradient tests, applying various loads to vehicles and observing the speeds they can maintain on a series of known gradients. As it is said that the lorry was in first-rate condition, one will understand that the results are not valid for vehicles of crinsideratile age and diminished efficiency, also the quality of driving will have some influence on performance.
Therefore, the results obtained can be regarded as optimum values, which may be multiplied by an efficiency factor, leas than one, to obtain conditions comparable with vehicles in actual service, The three large graphs on these pages show in full lines the gradeability in third gear of a lorry, with various loads and on five different gradients, arrived at by calculation from engine torque, by calculation from acceleration tests and by trials with a dynamometer vehicle towed behind the lorry, respectively.
On the graphs are also. Actual gradient tests are, in any case, the most promising and effective method, but are laborious and expensive and afford no short cut to a result.
In these ,tests, known loads have been applied to the vehicle, and the maximum speed which can be maintained on known slopes has been determined separately for each load. The maximum gross weight that could be propelled up the hill at a constant speed in a given gear was determined by trial, then the load was lessened in decrements of 1,00 lb. This operation was continued until the road speed represented approximately the maximum r.
The tests were repeated in the next higher gear ratio. Several test runs on the hill were necessary in determining the maximum maintained speed for each load. The truck approached the grade from the level at a speed intended to be maintained over the entire trial section, all tests tieing made with full throttle, Besides a speedometer, to serve as a guide, the machine was equipped with a special time-distance recorder giving distances at second intervals, from which the average speed could be calculated with an error of less than 1 per cent.
This supplies basic data with which the results obtained from the other methods are compared. With regard to theoretical performance, shown in Fig. The results of the two methods correspond remarkably closely, except over the peak-torque range.
Deceleration tests at road speeds at which the peak torque was developed showed this value to be the more accurate. Acceleration and deceleration tests were carried out on a level section of road, The lorry was accelerated in each gear at full throttle, starting at the lowest speed at which the engine would operate smoothly and continuing to the maximum recommended engine speed.
Deceleration tests were made on the level by first attaining the desired speed and then permitting the vehicle to coast in neutral. For deceleration the relation is:—. Ku mass-equivalent constant for the vehicle operating in a given gear. The factors K and Ku are due to the rotating parts of the vehicle, storing up energy when the vehicle is accelerating. Drawbar pull is the force produced by the driving wheels as thrust on the bearing housings.
In Figs. In drawbar dynamometer tests a special dynamometer developed by the Ordnance Department of the United States Army was used, consisting of a ton vehicle equipped with two fire pumps. These are connected to the main propeller shaft by a two-speed auxiliary gearbox. When the dynamometer vehicle is towed by the test vehicle the rear wheels of the trailing unit actuate the pumps, forcing water from a tank through a pipe with an adjustable orifice and then back to the tank.
By regulating the size of orifice the discharge pressure of the pump can be increasedor decreased, which, in turn, increases or decreases the torque required to turn the rear wheels. Drawbars, each composed of a cylinder and piston, are mounted on the front and rear of the dynamo meter truck.
When the test vehicle tows the artificially loaded dynamometer truck, the pressure in the cylinder is recorded, allowing the available drawbar pull to be-determined. Resistance to traction is ascertained by towing the test vehicle behind the dynamometer.
The original report showed curves of wavy form, but these are not justified. By means of the same equations as used above, the drawbar pull can he converted into hill-climbing ability; the results are given in Fig. As before, there is a variation between the two methods approximating to a grade of 0.
This can be seen in the diagram as the square points for 4. The discrepancy may be, in part, attributed to the fact that the dynamometer was evolved for low speed and heavy equipment, therefore the values for lower gears and speed are in better conformity. A distinct advantage of the dynamometer method is that only little calculation is necessary. All aecompanying graphs relate to tests of only one truck in one gear third. Similar comparisons have been made for each of 18 units tested during the autumn of The following results can be drawn from the tests:— I Testing under actual load conditions over several gradients will, of course, provide results of the greatest accuracy: As, however, this method is laborious and expensive, its general use is precluded.
Complete tests require but a few hours in the field, but; office computations are, laborious, The method is cheaper than the actualgradient tests. The Bureau of Public Roads intends to adopt this method. High initial cost limits its use to operations.
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