A FLUID FLYWHEEL.

New Zealand Herald, Volume LXVII, Issue 20602, 28 June 1930, Page 12 (Supplement)

A FLUID FLYWHEEL.

NEW DAIMLER INVENTION.

HIGHLY EFFICIENT UNIT.

Considerable interest attaches to a. new Daimler invention, known as the fluid flywheel, an ingenious devico recently perfected in England, which exhaustive tests have shown to dispense almost entirely with the need for using the clutch and gear-box, excopt in cases of emergency. Tho fluid fly-wheel is said to relegato the gear-box and clutcli to the position of emergency components, which oxist merely to bo used when very steep hills aro encountered. Tho tests described were carried out on a Double-Six ■ Daimler,, which was driven over a considerablo distance fitted with' tho fluid fly-wheel. Top gear was engaged, and tho engine then started, the clutch pedal being entirely neglected. To start, tho hand-brake was merely released and the accelerator depressed, when it was found that tho car would glide off, picking up speed with perfect smoothness. To stop, the accelerator was released, and the brakes applied until the car ceased moving, top gear being still engaged and the engine turning over slowly. One of tho most important features of tho fluid flywheel is that it doc 3 not affect normal methods of gear-changing, but reduces the need of changing to an absolute minimum. Changing up or down on hills op on the level is performed exactly as usual, and with the customary ease that a good gear change gives. The fluid flywheel resembles externally an ordinary enclosed plato clutch, but actually consists of two parts only, one of which is tho flywheel or driving mombcr and the other the driven member. Both tho driving and driven members are of saucer-liko section and are divided into a large number of cells of radial webs. A small gap separates the driven membor from the driving member so that tho latter may freoly rotate The driving member is of cylindrical construction so that the driven member is enclosed within it and tho whole compartment filled with oil. Transmitting the Drive. The fluid flywheel transmits power in tho following manner. Assuming the car to be stationary and the engine started, the rotation of the driving member by the engino' causes tho oil in its colls or cups to flow toward their outsido periphery. From here, as tho driven member is yob stationary, the oil flows past tho outsido periphery of its cups, through them, and past their inside periphery to the inside periphery of the driving member cups, pnd from there back again to their outside periphery. In other words, the oil starts on a circulatory motion between the cups of the driving and driven members of the clutch. In passing from the web 3 of the driving to thoso of tho driv;n member, the oil is retarded in velocity, and, therefore, releases kinetic energy which sets the driven membei in motion. Since, oven when the driven member has attained full speed, the load on it causes it to lag behind the driving member, the centrifugal forces in the latter are always largeri than thoso in tho driven member, 60 that the circulatory motion of tho oil, and, therefore, the transmission of power from the one to the other is always maintained. At ordinary speeds the oil needs but little retardation to develop the required driving torque, heiice the lag or " slip" between the driving and driven members is insignificant. At low engine speeds, however, the " slip" can become 100 per* cent, at full torque, thus providing the condition that the engine can develop full torque in gear without moving tho car. This occurs at a speed of about 600 r.p.m. on the Douljle-Six. The essential feature of the " slip" is it so rapidly diminishes as tho car begins to movo that exceedingly smooth starting and low speed running aro obtained without prejudice to normal running efficiency. For gear-changing there is an ordinary friction clutch between tho fluid flywheel and tho gear box, but this clutch is much smaller and lighter than usual because it does not have so much work to do. , Its lightness accounts for (ho exceptionally easy gear changing which characterises the cars fitted with fluid flywheel. Fluid Velocity the Key-note.

From tho foregoing it should be plain that the device is not a pump, and does not rely upon fluid pressure, but on fluid velocity. Velocity, and therefore kinetic energy, since tho fluid has weight, is imparted to it by the driving member. This energy is absorbed by tho driven member and passed^on as torquo to tho transmission and rear wheels, in much the same way, if ono may offer an admittedly loose bufr nevertheless descriptive analogy, as the wings of an aeroplane derivo support from tho inertia of tho air which they are trying to drivo downwards. The aeroplane cannot rise until it has attained sufficient velocity, after which its path is approximately positive. The fluid flywheel does not transmit torque until the fluid reaches a certain velocity, after which tho drivo ia approximately positive. Efficiency of 98 Per Cent. Under conditions of maximum acceleration of tho engine, the slip referred to dies rapidly away from 600 to 1000 r.p.m. At 1500 r.p.m. if is 8 pei cent, and at 3400 r.p.m. it has dropped to 2 per cent Under norma) conditions of maintaining uniform speed, tho slip is insignificant—about 2 per cent, aftei 1100 r.p.m. This indicates an efficiency of 98 per cent., which is considerably greater than most forms of gearing can give. ' Tho slip is converted into heat and dissipated by conduction, and tho degree of heat is low, as tho efficiency is high; thus in normal running the fluid flywheel becomes no moro hot than a good gear box. Tho fact that tho power is transmitted by fluid velocity rather than by pressure is important, for it means that tho device, v already self-contained, needs no high-pres-sure-tigllt joints It possesses but ono oil-tight gland in the centre, and this is called upon chiefly to rotain the oil' when tho car is stationary. The fluid does not deteriorate rapidly, aud consequently tho dovico very aeldojn needs replenishment. HIS « WATER-LOO." A certain owner-driver had a leaky radiator and carried on his. running board a petrol tin filled with water. Ono Sunday morning he ptopped at a wayside hotel, parking his car among a number of motor-coaclies. On returning to it after having had tea, ho went to fill tho radiator from tho can and found it empty. Closo by was a motor-coach, fully loaded, with the perspiring driver swinging tho starting handle with no result. " Won't she fire 1" asked tho ownerdriver. " No, sho blankoty, blankety, well won't!" tho motor coach driver hissed. " I havo been doing this for ten minutes. She was all right when sho got here." " How is sho oft for petrol ?" " All right; I have just filled up," was the answer. " Hard luck!" said the motorist. "By tho way, you did not seo anyone take a tin of wator off my car, did you ?" , As the motorist drove away there appeared to bo a glimmering of understanding in the coach-driver's face.