that may clog up the gas passages. Mufflers are easily taken apart, usually being held together by long through bolts in those forms where the muffler consists of a number of cylindrical shells of varying diameter held between cast end plates used to support the shell. Even in forms where a large number of chambers are provided, these being adjacent, the muffler is held together by bolts or by being assembled on a central member usually a continuation of the exhaust pipe. After the muffler is taken apart all carbon and burnt oil residue should be scraped off and all the parts of the muffler thoroughly cleaned with kerosene before reassembling. It is also well to go over all the holes designed to break up the gas with a sharp punch or fine taper reamer to make sure that these have not been reduced to less diameter than they should be by acumulations of burnt oil or carbon.

Chassis Lubrication.-A very important point that is someimes overlooked after a car has been overhauled is proper lubriation of the chassis. A typical six cylinder chassis of the Locomobile design is outlined at Fig. 370, with all points needing lubriation clearly outlined. Practically all of the chassis parts are luricated through the medium of grease cups which are indicated y a circle with the numbers in it, the numbers ranging from 1 to 2 inclusive, beginning at the bottom of the diagram and running o the top. It is important to go over all the grease cups when a hassis has been overhauled and make sure that they are filled with good grade of grease of suitable density which must resist the etion of water and contain no acid. Grease cups Nos. 3, 4, 5, 6, 1, 22, 27, and 28 are very important and should receive attention -ery day that the car is in use. Graphite grease is recommended or these points. In addition to the grease cups there are a numer of oiling plugs which are indicated at black squares and a letr. Beginning at the bottom of the diagram, oil plug A should removed to supply oil to the timing gear. It is said that one and e-half pints of oil are necessary every 500 miles. The magneto ive coupling B should be filled with grease. C is the plug through ich grease is introduced to the steering worm gear case. New ease should be supplied when overhauling, then the operator ould be cautioned to replenish the supply every 100 miles. D,

indicates the oil opening for filling the oil pump gear casing with grease.

The disc clutch housing is provided with oil plug E. The makers of the car illustrated recommend that this plug be removed at the end of every 1,500 miles and the clutch case turned over until the old oil runs out. The interior of the clutch casing should then be washed carefully with gasoline and refilled with new lubri cant. This may be a mixture of one-fourth pint of spindle oil and one-fourth pint of kerosene or a mixture of one-third pint of kerosene and one-sixth pint of three-in-one oil. It is stated that these proportions and quantities are important. The transmission gear case is filled through oil plug F. The gear case should be lubri cated with some good quality non-acid grease of about the con sistency of vaseline. It is stated that 201⁄2 lbs. of grease are needed to refill an empty transmission case after overhauling. The beve gear housing at the rear axle is provided with a plug G, through which grease can be introduced to lubricate the bevel drive gear ing. It is recommended that this be thoroughly washed out dur ing the overhauling process even if the rear axle is not take apart. It takes one quart of grease to fill this housing to th proper point. The oil plugs H and I indicate minor driving coup lings, which do not require attention very often, inasmuch as th makers advise filling with grease every 5000 miles. It is als necessary to keep the interior of the wheel hubs filled with suitabl grease.

Among the minor points that need lubrication are the fan bear ings, which may be packed with gear grease at the time of th yearly overhauling. There are a number of minor points indicate by round black dots that are oiled with a hand oil can or syring by means of oil cups and oil holes. The most important of the are as follows: Starting crank, oil every week. Magneto, few dro every 2000 to 2500 miles. Foot pedal shaft bearings, oil copious every month. Steering column, squirt plenty of oil through th hole in the steering column every week. Oil also the fixed en of the spark and gas lever. Hand lever shaft bearings, lubricat every week. Brake shaft bearings, oil about every 2000 miles Dynamo bearings, forty drops every 100 miles. Steering univers

joints, indicated by the letters B, J, remove the leather boots and pack with good graphite grease every 1000 miles. The universal joints on the propeller

shaft, which are indieated by the letters U J and S J, should be inspected, cleaned and packed with grease about once a season. Care should be taken to make sure that the power plant also has the proper grade and quantity of lubricant before the car is permitted to leave the shop. Most cars em

Fig. 371.-Method of Testing Acetylene Gas
Piping for Leakage.

ploy constant level splash systems, which have been previously described, the only precaution is to make sure that the oil is at the proper level in the engine crank case. The strainer screen that filters the oil before it goes into the pump should be cleaned every week, and it is recommended that after 1000 miles road service that the old oil be drained out of the engine base.

Locating Acetylene Gas Leak. Before the general adoption of electric lighting practically all automobiles were supplied with acetylene gas burning head lights, the gas supply being from a carbide generator, Prest-o-lite or similar tank. In many cases trouble is experienced through leakage of the gas which escapes from minute leaks in the gas line, which usually consists of copper tubes running in the frame channel and connected to the gas tank and lamps with flexible rubber tubes. While the overhauling process is being carried on, it is well to test the pipe lines to see if there are any leaks in order to replace the copper tubes with new ones should they have chafed from contact with a frame member or loose clip or if a seam has opened up with vibration. A very simple method of determining whether there is a leak or not shown at Fig. 371, was described in the Automobile. The apparatus con

sists of three pieces of rubber tubing, a three way pipe connection and a glass U tube. The burners of the acetylene lights are re moved and the ends of the rubber tubes are placed over the projecting pipes as shown in the illustration. The valve on the gas tank should be closed while this is being done. Water is now placed in the U tube but not enough to completely fill it. The needle valve on the gas tank is slowly opened until the water in one arm of the U tube is lifted higher than that in the other because of the gas pressure. The valve is then closed and the water level in the U tube watched. If water drops to the same level in both branches there is a leak. A leak may be found by going over all the pipes with oil or a thick soap-suds solution, taking especial care to cover those portions of the pipes that are resting against the frame members and also all the soldered joints. The escaping gas will cause the soapy solution or the oil to bubble at the point where it escapes.

CHAPTER IX

THE REAR AXLE AND DRIVING SYSTEM

Rear Axle Nomenclature-Semi-Floating Axles-Three-Quarter Floating Axles -Full Floating Types-Taking Rear Axle Apart—Adjusting Bevel Drive Gears-Worm and Spiral Bevel Drive Gears-Two-Speed Axles-Double Reduction Axles-Internal Gear Drive-Four Wheel Drive Spur and Bevel Gear Differential-Chain Drive Troubles-Trussing Weak Axle Housings-Axle Lubrication-Oil Retaining Means-Types of Axle Bearings-Care and Adjustment of Axle Bearings-Brake Forms and Adjustment.

OWING to the advances that have been made in metallurgy and a more general appreciation of principles of design by engineers, the rear axle is a part of the car that seldom gives trouble and which usually needs attention only when the car is thoroughly overhauled. Very few motor car manufacturers build their own rear axles and most of those used are the product of specialists who make nothing but front and rear axles. The result of this concentration upon one product means that the various details of proportion of parts have received careful attention which has been based on a wide experience. The material best adapted for the various parts have been carefully determined and practically the only condition that interferes with proper rear axle operation, barring occasional accidents, are those due to natural wear. Before describing the method of taking down rear axles it may be well for the reader to become familiar with the different axle types and their method of construction. The designs used vary widely. In some types it is possible to get at all the essential parts in a relatively short time without removing the rear construction from the chassis. In other forms it is necessary to take them completely apart before access may be had to the differential gears or the axle shafts and their supporting bearings.