WORN PISTON RINGS.

Press, Volume LXIII, Issue 19150, 5 November 1927, Page 4

WORN PISTON RINGS.

HOW TO REPLACE THEM. POINTS FOR AMATEURS. The car owner who intends to replace worn piston rings should have tome mechanical knowledge before attempting the task, as, although not a difficult operation, care is necessary and a certain amount of experience a advisable if the job is not to be bungled. Bungling the job will result in either scored cylinder walls or knocking big ends, or both. Providing the owner feels competent to .tackle the operation, procedure is as inllows: We will assume tljat the car has been dismantled. For Satisfactory work a pit is needed, or, failing that, the car may be jacked up on bricks or braes to ensure ample room in which to work •underneath. Having removed the Bump, the starting handle is first turned until two pistons aro at the bottom of the stroke, preferably commencing with number one piston. Now get under the engine and remove split pins from the big end bearings and unscrew the retaining nuts. The bottom half of the big end will now drop into your hand, or will come r.drift very easily. Hold it in the same position as when on the crankshaft, i.e., do not allow it to be turned round; then remove any shims (thin brass sheets between tbo two halves of the bearing), taking care that these are kept on the proper side of tho bearing Hold the connecting rod and gently push upwards until you have room to replace the lower part of the bearing exactly as it was before removal The whole thing, piston, connecting rod, and complete bearing can now be pushed out towards the top of the cylinder until you feel that the rings are free. The piston must not be twisted inthis process, as it is necessary for it to be withdrawn in the same relative position as it had in the cylinder. The reason for tin's is that if the position is not known and the piston be replaced incorrectly, an improper fitting big end may be the outcome.

Marking. As with tho valves, all pistons can be withdrawn before attending to the rings, or each one can be fitted and reassembled, separately, according to taste, but for the amateur perhaps it will bo better to do each one separately. If all are withdrawn and removed, the next step is to mark each one with a punch. One mark for No. 1, two for No. 2, etc., on the connecting rods. Also be careful t'o mark all of them on the same side of the connecting rod, either to front or rear, bo that they go back in the same position. If you intend to remove the pistons, these must be marked separately in the same way. Should the gudgeon pins bo a good fit, there is no necessity to remove pistons from connecting rods. The rings can now be examined and careful note should be taken if a scraper ring is fitted, as this is probably a different shape to the others. Note the difference in shape, if any, and the position of that ring on the piston. Remove all rings by gently levering them out of their grooves with a pen knife or similar article. An old hack saw blade, broken into three parts, is useful here as these can be inserted between the ring and the piston, allowinc the ring to be withdrawn without breaking. They are easily broken and great care must bo exercised. The grooves can now be cleaned of carbon and dirt and the whole assembly washed in kerosene.

Fitting. Test the rings both in the cylinder and the grooves. In the cylinder, it fiould bo a tight fit but should not be so tight that the aperture of the ring is completely olosed. In the grooves, it should also he a nice snug fit. If there is any play in the grooves in * vertical direction, discard the ring, and the same advice holds good if it will not compress in the groove to th© diameter of the piston, whereTer new rings are needed, obtain them from an accessory shop, taking the piston with you for measurement for dia-

meter and width, if unknown. New I rings must be carefully fitted both into 1 grooves and cylinder. If too wide for the grooves,. grind them down on a piece of glass smeared with grinding composition, and if too .tight in the cylinders, file away the opening of tho ring (taking care to keep a true face), until it fits snugly. It can now be fitted to piston and returned to the cylinder, taking care to replaco-it as it was withdrawn. The piston will drop to the level of the lowest ring and now a piece of string or tape can be placed round the ring.to compress it, while the piston is gently pushed down to the level of the next ring. This procedure is followed with all rings, and the piston pushed right down. Then get underneath the car again and, removing the lower half of the bearing, reassemble in the same manner as it was removed. Care must be taken to get an exact fit 6n the big end. The bear-J ing should be, tight, but not tight enough to make it hard to turn the: engine and, above, all, it must not be tight at one spot and slack at another.'It should not be difficult if you haive been careful to replace all the shims, as they wer e found. This procedure is followed in all cylinders and everything reassembled as before. Care must also be taken to get. the openings of the rings away from each other on the piston, as if they are all in line gas may he forced past them and compression lost. The piston and cylinder must be well oiled before re-ass'emblv.

ON A SLIPPERY 1 GRADE.

Driving down a slippery grade is a Problem that bothers many motorists. When doing this, do not disengage the clutch. Keep the brake on and shift into first or second speed.

If you skid, turn the wheels in the same direction in which the skid occurs, but never under any circumstances turn the wheels clear over. If you do this you moke check the force of the skid. 60 suddenly that the car is thrown over.

If you are unable to get traction, a few old burlap hags, or. a box of sand and some rope may be useful in setting you going again!

FOOLPROOF LUBRICATION.

To-day we seldom hear of engine failures or engine inefficiency due to improper or neglected lubrication. Lubrication systems have been made foolproof. The responsibility for efficient lubrication has been largely shifted from the owner to the designer and the manufacturer, except the periodic replenishment of the oil of the crankcase. But in respect to the chassis it is only lately that the desired attention has been given to it. Designers now adopt one or the other of the wonderfully efficient force pump lubrication systems and install force pump lubrication on all the articulate parts of the chassis. Some designers, recognising the liability of the chassis lubrication to be neglected, try to avoid it as much as possible, and we see cars in which the number of places, to bo lubricated have been reduced to one or two. No doubt (says the "Australasian") we shall soon see designs that call for no lubrication at all, and in this direction we have already self-lubrication bolts and shackles which have brushes impregnated with graphite, which gives a dry lubrication which is efficient and long-lasting, requiring no attention But the trend of design so far as the chassis mechanism is concerned is on the lines of doing away with any jolts in which metal moves on metal as a bearing.

Flexible spring connexions for springa, operating rods, etc., are now available, and may become very generally used. Eventually the periodical filling of the crankcase or some central oil container will be all that is necessary for the complete lubrication of the whole machine. It can certainly be done, and we shall expect that much will be accomplished in' this. With the increasing use of the motor-car by people who do not want to be bothered by any mechanical details or fiddling attention, the demand for self-lubricating cars is being met.

- Never oil rubber spring supports at spring brackets, because it will destroy the action, and possibly cause them to pull out.

Use a rubber eraser to clean the dis tributor parts.