HINTS ON MAINTENANCE.
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How to Get the Best Out of a Vehicle, to Secure Reliability and to Avoid Trouble.
CONTRIBUTIONS are invited for this page from fleet managers, drivers, garage foremen, and mechanics, works staff and draughtsmen, and will be paid for on a generous. scale. Every system, make, and type of commercial motor vehicle will be dealt with, and the matter should be written with a view to the disclosure of workshop and garage practice in the maintenance of a vehicle—practices which, whilst they may be quite normal, are peculiar to the particular vehicle and may not be generally known to those responsible for its running. Expedients and suggestions for overcoming roadside and other troubles are covered in the tollowing page, headed "Roadside and Garage." Communications should be addressed to "The Editor, The Commercial Motor, 7-15, Rosebery Avenue, London, E.C. I."
111—Fitting Foden Axle Bearings.
The fitting of the new axle bearings to the Foden 5 ton steam wagon, or the taking up of wear on same, is a task of no mean order if it has to be tackled by a single pair of hands, but this job can be done without much difficulty if a few points, which are generally overlooked by the averagekgarage mechanic, are attended to.
After the wheels and axle have been removed from the chassis, the further dismantling is carried out in the following manner :—Support, by means of trestles under each end, the spring which is to be removed. Then undo one of the spring bolts. Place in the hole vacated by it a short bolt and screw up the nut finger tight. The remaining three bolts can now be taken out and the short bolt will prevent the cast-iron lower half of the bearing from dropping. The spring can then be removed, and the twodparts of the bearing separated by removing the short bolt.
The top half of the bearing has a semicircular bronze sleeve, honsed in a cast-steel spring pad. The bottom bearing is formed by the cast-iron oil box. The bedding of this bearing is a job that -repays the trouble of fitting, and a crown bearing is recommended by the makers. The latter send out standard parts, and sometimes these, when required for repair work, do not accurately fit owing to wear. The mechanic is therefore advised to test the bearing's with red lead. This can be accomplished by holding the spring pad and fastening. the oil box into, position with two short bolts positioned diagonally. Shims are positioned between the halves of the bearing, and if the latter is loose one of the shims should be removed. After tightening up and using the red lead, the high spots, as shown by .the red lead, should be ,scraped down. When the bedding of the bearing is completed, the axle must be cleaned and oil rubbed over the journal. After this, replace the two parts of the bearing and insert one short bolt, which keeps them together. Lift the spring into the recess in the pad and re-assemble in the same way as the disassembling was
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done, withdrawing the single short bolt after the other three main bolts have been fitted, and finally inserting the remaining bolt. Do not forget to use the proper sized split pin for each bolt.
The springs should be lined up by measuring the distance between each end and the wheel at that side. The distances should, of course, be equal.
115.—The Care of Link Chains.
In this hint we are not referring to driving chains or to silent chains, but to those used for ordinary purposes, such as slinging loads, chaining them down, and to chains employed in many steam wagon steering gears. When it is remembered that a faulty chain may result in loss of life, the necessity for care being taken with them will be realized.
The proper lubrication of a chain greatly lengthens its working life. The common method of applying lubrication with the chain extended is ineffective, as it leaves the working surfaces untouched. The chain should actually be dipped bodily into grease. All chains of half an inch or less in diameter should be annealed at least once every six months and if a chain shows any signs of failure it should' be annealed at once, as during this process the dirt and grease will be burnt off and it can then be examined for any, dangerous defects.
Where a large number of chains is in use the care of them may be facilitatad by numbering each, and keeping a list showing the safe load for each size and the last time it was annealed. If the safe load of any chain is not known it may be determined, by using the formula — = safe load in tons, where D equals 10
diameter in one-eighths of an inch. Thus • the safe load limit for a half-inch chain of good quality (4)2
is — = 1.6 tons.
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116.—Timing Magneto on Four-Cylinder Standard.
The magneto must be cleaned at its base, also the platform carrying the magneto should be made a good bed with the aid of a file and red lead, if this is not done the vibration caused by the engine will upset the timing. When the bed is true tighten the magneto down securely.
If the magneto drive is by a tapered shaft and gear leave the gear loose, but if the drive is by means of a keyed gear or coupling tighten the gear up, and leave the engine gear loose until the setting is finished.
The motor should now be turned in the ordinary direction (clockwise), then see if the magneto rotates in the direction shown by the arrow on the oil cover at the driving end. When this is done turn the engine until the piston of No. 1 cylinder is nearly at the end of the compression. stroke ; this position is invariably marked on the flywheel. The next operation is to rotate the armature until the distributor brush is on the brass segment of No. 1. The timing lever must now be fully retarded, and the armature spindle turned slightly until the contacts " break." The driving wheel or gear is now tightened up, care being taken that neither the spindle nor the gears move daring the operation. When the timing is finished the sparking plug of No. 1 cylinder (or the cylinder to which the magneto has been timed) must be connected to the terminal marked Fig. 1 on the distributor disc, the terminal No. 2 is connected with the sparking plug of the cylinder which comes next in the order of firing, and the other two are connected up in the same manner.
It is as well to mark the various cylinders of the motor according to the firing sequence. When replacements are refitted to the magnet(); it is necessary to keep these very clean. Also, when adjusting the platinum points it is often advisable to insert between the points a thin piece of emery cloth and tub them gently with this, which has the effect of removing dirt, etc. ; wipe with a clean cloth when finished.
Never over-oil a magneto ; many do not bave oilers. in order to prevent this.