MOTORS & MOTORING

Dominion, Volume 14, Issue 59, 3 December 1920, Page 2

MOTORS & MOTORING

(By "Clutch.")

The Valve Springs, There are few parts of the cnr which Die motorist forgets more than the valve spriiigs (eo long as they work), and, of course, these are now -usually of such good material that a long service may be expected before a new spring is necessary. It is a pity, however, t.liat the average motorist should wait until a spring actually breaks before giving it a little attention. In view of this, it is worth- while to discover just what ill-effects may result from using springs that have lost n certain amount of their original elasticity ami in order to do this it is necessary lo llavo a' clear understanding of the work the spring has. ita perform. The work which the spring has 'to do does not consist merely in closing the valve—even a. weak spring will do this; (he spring must close the valve as quickly as the cam will allow. This, of course, does not mean that the quicker the valve closes tlio better, but' that the cam is 'shaped so as to obtain tHie best average closing speed. The cam, therefore, is capable of controlling the rate of valve 'closing, hut. to do this it is necessary for the spring to he capable of moving tlio valve.so rapidly that the tappet always I' "follows" iilie cam' at nil speeds within reasonable limit?. ■ Now. the valve does not close at uniform speed, but usually commences to close comparatively slowly, increasing in ■ sneed to- a high velocity, and then, as the.valve nenrs its seating, slowing down its again lb a gradually decreasing speed until the valve is seated. After a time valve- spring!* become "fatigued" —and the result is a poor running engine owing to the valves and' tappet failing to follow ,the cam fnstl enough. This results in noise dne.to impacfc-besjde wear and pitting of parts—as the .tappets get behind their work and come into violent contact with the cam. Springs do not cost much—and it's a payable proposition to, have a:new set .fitted after some months of use on the inlet and exhaust valves. • It means higher, efficiency, and a "sweeter" running engine. . Exposed.Brake Parts. " -Much 'trouble with brakes is duo to ' mud and wet and rust in the toggle levers, outside levers; or in the bearings of the lever rods from outside into the interior of illie drum. These are in a. very 'exposed position, and are often, neglected as to lubrication. They should havo big (screw-down greasers, which .should be regularly attended to. A good deal of skidding and danger is.d'uo to brakclevois and toggles working stiff on one side While the other is free. The brake compensating gear cannotl deal with this irregularity, and skidding results when the brakes are applied.. .Carburettor-Troubles. . ' When' an engine, afifrr starting, runs for a minute or two .and stops, the first placo to look for-the trouble is the petrol .'feed line. A partial stoppage in the fuel supply pipe will lessen the flow of 'ftiel, so that, the float chamber fills slowly. On being started the engine will quickly consume the benzine in the chamber and stop.; Another possible cause for the fault, is the float sticking, and if'tho float sticks in the high position the flow of fuel will be greatly'lessened, or may bo stopped entirely. Water in the petrol is also troublesome as a drop may get into the feed-pipe or the spray-nozzle and interfere wttli prompt starting or reliable feed of fuel. Foreign matter around the filter screen in the feed line is also responsible for restricting the fuel flow, especially in ■ cars using the gravity feed system. A Chattering Brake! "One of the common troubles encountered in the brake assembly is a tendency to chattering, which is extremely, annoying. This is generally induced by a deposit of burnt oil on the bands, and 'it may usually be cured by applying hot kerosene "to tflie parts. If tins does not serve, the only remedy is to Jnirn oft the deposits with 'a' blow torch. This operalion is carried out by removing the bands and soaking them in petrol over night and then applying the -torch. 'H>cpn>poller shaft brake-is peculiarly, liable to this trouble, as.-if the transmission case contains a little 100 niuch.oil the . excess lubricant is thrown ilhrough tlin siiaft bushing on ib the hands. If nil application of graphite is used instead of oil- for lubricating the brake bands, it will lessen this trouble. . Lubrication of Springs'. . • Springs wear at illie shackles, and at the trunions in the case of those springs of the cantilever variety. This wear is generally duo to lack of lubrication. Shackle bolts have worn nearly, intwo through neglect in this respect These small items requite conscientious attention. ■ and ' need a .regular renewal of grerise at stated intervals. lhe lubricators are often placed -in awkward and inaccessible positions, but/ this should be no reason for neglecting 'them.. It. is a good plan to make a list. Of those occasional lubrications which should be carried ' out. and to note the speedometer mileage on each occasion when these receive attention. Using the mileage recorder in conjunction with such a list will add-to the life of the car and often render renewals unnecessary or infrequent..-' ';. Noisy Gearboxes. Noisy' gearboxes -are a great sonrco of annoyance to the careful motorist. If the hearings of a gear, shaft get worn, the pitch circles of'the engaging teeth fail to coincide, and .the teeth of the gears meet each other.at,:the wrong pare.of their contour.- 'This causes excessive I wear since the teeth slide instead of rolling upon each' other, as they are I theoretically designed.to do.. A worn spigot bearing between the primary shaft and-the second shaft-will cause the axles ! of the gear shafts, to get too far away from each' other at one end, and cause the teeth to meet at the edgcs-iustead of all along the face.' This causes excessive wear and noise. Gear shafts should •be periodically examined, and when.unfitted. The same applies to the bearings should be re-lined, if it is of the parallel type, or a new ball-beanhg should befiled. The same applies to llhe bearings of the main shaft. The Sparking Plug. ' The modern spark plug operates for extremely long periods without giving trouble, ' but occasionally the motorist encounters persistenti plug trouble mid cannot! explain the cans. Plugs, as now made, (Should not give tirouble for six months if the operating conditions 'are right. The greatest source of plug 'failure may Jie traced to leaking in the plug itself. This refers to hot gas leakage brought about by noii-gas-tightness of joints in the plug. The loss in power due to reduction in compression pressure, is hardly worth, considering as compared 'with illie damage done by the heat of the gases. The excessive heat causes insulators to crack, and because of carbon contained in the gas there is a black-soot deposited which also interferes With plug operation. Where the plugs are so locatVd as to receive no benefit from jacket water tlio conditions are still worse-' because such plugs run normally hot. Grit in Wheel Hubs. Those motorists whose vehicles are fitted with detachable wheels should make a special point of seeing thau the hubs and the wheel hub shells are quite clean ami free from dust, mud, or grit before attaching the wheels. Otherwise Iho wheels will inevitably become looso after the cur has travelled evcii a shorii distance'. Grit prevents the, wheel beiua pushed home on Oho taper" seating, and when locked tight it is actually locked, on to the griti 'When the vehicle is driven the load pulverises the gritty particles, and the wheel will be found to. be loose. If-this looseness is allowed to continue, it results in the bedding surfaces of hub and shell becoming disturbed, and the result is a permanently wobbling wheel. The hub of the wheel should be cnrefnUy cleaned and greased, and the greatest care should' be taken to ensure that no foreign matter gets between' ijie hub and lhe shell. Lighting up .time.—To-day, 7.9 p.m. A'ext Friday, .".1G p.m. .

The longest tunnel in Grout Britain Is four and. 11 wolf mill's long," ami curries tins Ureal Woslcrii Jtnilwny from Bristol to Cardiff /undor the estuary of the ltivw Severs.. "