From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Article from a series on fuel efficiency, detailing the checks for transmission and wheel alignment.
| Identifier | ExFiles\Box 156\4\ scan0001 | |
| Date | 1st October 1914 | |
| OCTOBER 1, 1914. THE AUTO MOTOR JOURNAL MILES PER GALLON. (Continued from page 1106.) V.{VIENNA}—THE TRANSMISSION. In the preceding articles of this series we have considered those factors which influence the fuel consumption, because of their effect upon the conversion of the heat contained in the petrol into mechanical work upon the crank-shaft. But having obtained the maximum amount of power from a given quantity of fuel, we must utilise the power in the most efficient manner—that is, we must eliminate friction as much as possible. Bad alignment, which may be due either to frame or other forms of distortion, or to the natural effects of wear in adjacent bearings, may be responsible for much wasted power, as in addition to work then done in overcoming avoidable friction due to excessive pressures on the working surfaces, where gear wheels are mounted upon these shafts, there is the possibility that gears may be prevented from meshing correctly ; and perfect tooth action is essential for a high efficiency. As an example, it may be pointed out that on some cars the joint in the clutch-shaft consists simply of the muff which fits over splines, squares, &c., formed upon the ends of a divided shaft and allows of the end movement only. In such a case, any wear at the engine main bearings or any displacement of the centre line of the primary shaft in the gear-box, must cause a considerable amount of friction at this point in the transmission, as well as at the bearings on either side of it, through overloading. This shaft may be checked for alignment by attaching a pointer to the driving shaft, A, to the gear-box (see Fig. 18), so that its outer end comes close up to the rim of the flywheel. On rotating the gear-shaft there should be a uniform clearance between the top of the pointer and the face of the flywheel, but the test should be carried out for several positions of the flywheel, so as to be certain that the latter is true with its axis of rotation. This defect can be eliminated either by re-setting the gear-box (for which purpose special adjusting gear may or may not be provided) or by fitting a proper universal-joint, the latter method being preferable since it prevents recurrence of the trouble. A similar state of affairs sometimes exists in the rear axle, which, however, it is difficult to remedy unless means are provided which allow one to set up the axle, such as is afforded by an adjustable tie-rod beneath the differential casing. In course of time the axle casing, practically always, becomes permanently deformed—it may be so small as to be almost imperceptible, but it is none the less appreciable when it is realised what small clearances are allowed in forming the wheel teeth and how susceptible roller, thrust and some form of ball bearings are to disalignment. The road wheels should also be examined to see that they are parallel to the longitudinal axis of the car, and that the axles are in their correct transverse position across the car. These defects would, if present, conduce to a higher consumption of fuel because they increase the road resistance, through the continual scraping action of the tyre on the road. The first test, to ascertain whether the wheels run true on their axles, should be carried out by rapidly rotating the wheels, and holding a piece of chalk close up to the rim. If the wheel is “out of truth,” the chalk will mark the rim on one side ; but the operations required to make it run true should be entrusted to a repairer, since it involves the heating of the rim, and the use of special tools which the owner has not at his disposal. When trued up, the parallelism of the wheels should be checked by stretching two wires, one on each side of the car, at the same elevation above the ground as the centre of the wheels, the wires being equidistant from the boss of each front wheel and of each rear wheel, that is, the distances marked A (see Fig. 19) should be equal, as well as the distances marked B; while the distances between the wires at the front and the rear of the car also should be equal, that is, x should equal y. Now set the front wheels so that P measured from the wire to the rim is equal to R.{Sir Henry Royce} Then Q should be equal to S. Also K should equal L, and M should equal N. If this is not so, as regards the front wheels, it is probable that the connecting link between the steering arms has been bent or damaged in some way, and its length should be adjusted so as to correct the error. Frequently the distances, P and Q, are made slightly greater than R and S respectively, so that when the resistance to forward movement comes upon the wheels, they will then track correctly. But there may be two reasons for any discrepancy in the measurements for the rear axle, namely, either the distance between the axles may not be the same or the axle itself may have become distorted from some cause. Usually the former is the correct reason for any inaccuracy (if the wheel itself is quite true) and this may be ascertained by placing a long lath against the wheels and marking on it the distances between the centres of the hubs on each side, when the front wheels point straight ahead. Should any error be discovered, its rectification is a matter for skilled attention and must not be attempted by an owner. Lastly, the wheels on the same axle should be equally inclined to each other. The car should now be placed upon horizontal level ground and the tyres on each axle pumped up to the same pressure (presumably the tyres on each axle are of the same dimensions). Take a small weight attached to a piece of fine thread and place the free end of the thread against the rim at the point, A (as indicated in Fig. 20). Then the distances marked... Fig. 18. Fig. 19. X/517 | ||