HYDRAULIC BRAKES. SAFER MOTORING.

Greymouth Evening Star, 22 March 1935, Page 4

HYDRAULIC BRAKES.

SAFER MOTORING.

MAINTENANCE BY AMATEURS.

It is justifiably claimed that f ol ’ 1 * wheel hydraulic brakes have two desirable teatures; automatic equalisation and a smooth and powerful action, which does not call for great P ed( “' uessure. The general principle of operation, with which all motorists who have cars with such equipment should be familiar, is that when the brake pedal is pressed down it operates the plunger of a master cylinder filled with special brake fluid; though the pipe-ways leading to the individual brake cylinders, this plunger exerts a hydraulic pressure which is conveyed to all the brake shoes. It is obvious that since the lour pipe connections to the brakes are, so to speak, in common circuit with the master cylinder, the pressure at each brake will be equalised, but it is a mistake to believe that hydraulic brakes will always retain good equalisation if their mechanical parts are neglected. The system , also become defective if air is imprisoned in the master cyclinder and the pipe lines. The routine upkeep is to keep the reserve tank • well filled with the special brake fluid, and should it be found that the pedal has too great a travel, is “springy” when operated, and perhaps can be depressed until it touches the floor boards, to “bleed’ all four brakes, so as to drive out the air. It cannot be emphasised too strongly that only the special fluid should be used for “topping up” the reserve tank, and thaT improvised mixtures such as engine oil broken down with kerosene are not only unsuitable, but will also undermine the piston of the main hydraulic cylinder and the flexible rubber piping.

The “bleeding” process referred to can be carried out easily by an amateur, but certain precautions must be taken. First of all, the reserve tank should be refilled with the proper brake-fluid. Then, each brake must be “bled” in turn. To quote an oversea journal: “On the back of each brake plate usually at the top, will be seen a small hexagon-headed screw and what appears to be a lock-nut. This assembly forms the valve by which the brakes may be ‘bled.’ Each c.’ the valve screws should be cleaned Lby scrubbing it with kercsene on a “tiff brush and then wiping it dry. In the tool-kit should be a length of rubber tubing provided with a small mass nipple at one end. In all probability there will also be a box spanner with a fixed handle at its rear end. This is for undoing the valve nuts. A clean receptable such as a glass jam jar will also be needed. “Having made these preparations, unscrew the outer nut, which actually is a plug, from one of the valves and screw the brass nipple (on the rubber tubing) into the hole thus exposed. The next step is to thread the rubber tubing through the spanner and insert its end* in the glass receptable. The spanner is then engaged with! the remaining nut, which is formed on the shank of the needle valve itself, and given about one turn. That should suffice to open the valve. “All is now ready for the actual “bleeding” operation, which consists of pressing down the brake pedal slowly to its full extent, and letting it return to the limit of its travel. This action must be repeated at least ten times, each downward movement causing brake fluid to be pumped out into the receptacle. Always check the fluid level after each ten strokes, and, if necessary, add more fluid.” “If an assistant is available to do this pumping the operator can keep an eye on the glass jar and watch for bubbles being blown up through the fluid. When no more appear the valve can be closed, the adaptor unscrewed, and the plug replaced, taking care to see that the spring washer which aids in locking, it is in place. This routine is then carried out on the remaining three brakes, but it is essential to see that the reserve tank is kept at least half-full all the time.” The fluid which has been pumped cut may be carefully strained through muslin or similar material for further use. It will be of a cloudy yellow colour, while the new fluid is perfectly clear. The cloudiness does not affect its" efficiency so long as it is mere colouring and not particles of giit. Dirt in any palpable form is most harmful in hydraulic brakes; that is why one has to be so careful to clean the brake-valves properly before opening them, and in filtering the pumped-out fluid.

If these instructions have been followed conscientiously, all air should have been expelled and the brake pedal will have only a small amount or tree travel before it operates positively. Any springiness after a fair degree of pedal movement is a symptom that there is air in the system. The initial travel should be about 1-inch, and it is also desirable to make sure that the pedal-lever does not foul the floor board for, should it happen that its return- motion is checked, the fluid will not feed back completely into the master cylinder, and so the brakes will not be fully released.

Although the attentions described are the principal duties associated with hydraulic braking systems, it must not be forgotten that certain adjustments should be made to the individual brake shoes, of which there arc two for each wheel, to correct the effects of normal wear and tear. Theoretically, the hydraulic system is entirely self-equalising, but in practice it will be found that an oily or glazed lining will upset the good balance of the brakes.

After the system has been “bled’’ it is a good plan to make a practical braking test from say 25 or 30 m.p.h. from a given point, noting both stopping distance and equalisation. There is an individual adjustment for each shoe. The procedure is to jack up the wheel and to apply a spanner to the two cap nuts which project from the lack of the brake plate. The nut which operates’ a small cam should be turn&J. until the shoe is just ’’•fishing against the drum and then backed off until the wheel spins freely, each shoe being thus adjusted in turn. That done, the brakes should net only take on quickly but also be j eifectiy equalised; if it is noted that there is any irregular action, the susI ectcd piake should be examined bv ..moving the wheel and drum Oilv slices, ir not too saturated, can bi put right by scrubbing with petrol or

ENGLISH SUGGESTIONS

A campaign for safer motoring in England during 1935 was launched by the London “Sunday Times,” whose motoring correspondent, H. B. Symons, put forward many sound suggestions in the following article: — All toad users must combine in a ■Teat effort to make 1935 a year of safer travel, and one section or another of the public must be prepared tc sacrifice their “rights,’ where necessary, for the common good. It should be realised that modern transport demands modern methods of administration. Tradition should not, therefore, be allowed to loom too large in the minds of those who control transport in this country. Before any worth-while reforms can bo achieved it is necessary that an end be put to the “class war” of the reads. The bickering between pedestrians, cyclists, and motorists helps no one except those interested in travel other than by road. The morerestricted, the more tiresome thai motoring and cycling become, the more people will tend to ask: “Is road travel worth while?” and flock back to enjoy the complete peace of mind provided by railway travel.

In the dawn of the world there was only one way to travel, and that was on toot. For so many- aeons had the pedestrian enjoyed the sole usq of the roads that his indignation can be imagined when cattle, horses, and presently wheeled chariots began to usurp his privileges. Way back in 1662 there was an outcry against ‘road-hogs,” these being the drivers of the London • hackney carriages, who were exhorted to “Leave in any case that ill-habit ye have of running over people in a dark night and then Lid them stand up.”

PEDESTRIANS AND CY'CLISTS.

The safety of all types of road users is the concern of all. A pedestrian may endanger the lives of motorists as well as his own; as a user of the highway there is no reason at all why his movements should not be restricted as are those of his brothers awheel. One of the many good things that Mr Hore-Belisha has <one has been to render the person on foot “traffic conscious,” pointing out that .it is just as undesirable for pedestrians to disobey light signals ci’ the orders of policemen on point duty as it is for cyclists, van drivers or motorists.

As far as cyclists are concerned, their safety is being provided for by special tracks alongside our new arterial roads. Had such paths been made, without asking the cycling associations if they wanted them, they would now be in general use without there being any compulsion to use them. Although the new tracks will provide a great deal of protection, the cyclist will not really be out of danger cntil rear lights are made compulsory. The whole trouble is that unless the headlights are switched “full on,’’ the reflectors op most cycles simply do not throw back'the required red light. It is an anomaly that motor cyclists who are seldom overtaken, should be obliged ta carry tail-lamps, while cyclists, who are constantly being overtaken, should be allowed to go about with only very poor reflectors.

It should be made an offence to park a vehicle, either by night or by day, except ou. the side of the road on which it would be when travelling under power. On very dark nights or in foggy weather the side-lamps of vehicles parked on the "wrong side” cl the road are most confusing and lead to accidents, while there is nothing more dangerous than to swing across the road, in the face of oncoming traffic, in order to park a car close to the offside kerb. A stationary car with the head-lamps switched on should also be made an offence. In America half the road deaths occur after dark, and this is said to be due to the inadequate lighting arrangements on American cars. In the typical American headlight the effect of anti-dazzle regulations is clearly shown; the light is thrown downwards by thick, light-absorbing lenses, and it is easy then to run down a cyclist or pedestrian or to drive under the tail-board of a lorry.

It is, to my mind, scandalous that any vehicle should be allowed to tow more than one trailer, especially as a siugle lorry and its drawbar and one trailer are allowed to have a total length of 63ft! What is to be done with these veritable “trains of the road” belonging to itinerant showmen, where a ponderous traction engine frequently tows five trailers? I yvpuld suggest that such “trains” should be forbidden on the roads, and should be conveyed from one town to another by rail. They should be allowed on the wad only so as to reach the fair grounds between, say midnight and 6 a.m.

Finally, let it be definitely decided once and ,ior all that traffic from the right be given precedence at road junctions, although 1, for one. would not be greatly concerned if it were settled that vehicles from the left should be given right of way instead. The point is to settle that on e side shall take precedence, thus avoiding hesitancy and doubt where roads of equal importance meet. Naturally the “main roads’’—plainly marked as such—would take precedence over all others, as do the routes nationales in France, AUSTIN MAGAZINE. Acknowledgment is made of receipt ft om David Crosier Ltd., Christchurch of January issue of the Austin “Magazine.” It has special appeal to drivers oi Austin’s, but contains well-illustrat-ed articles interesting to all motorists The travel copies include towns in the English countryside and abroad, and besides a short story, there are articles on golf (by Bobbv Jonesi dogs, etc.

methylated spirits, but any leakage of oil from the tear axle should be traced to its source and corrected, the usual remedy being new felt oilretaining washers. The various linkages in the mechanism should be. lubricated lightly, as rusting at such points might retard the action of the brake.