TESTING THE OVERHAULED VEHICLE.
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How to Carry Out a Road Test. Points Worth Remembering. Useful Hints and Tips in Connection With Our Articles Upon Overhauling.
• ALTHOUGH IT is difficult to credit it, there are '
people who, having put honest and conscien tious work into the overhaul of a vehicle, are content to pass it out for service without putting it through a, proper road test. Our descriptive articles upon the overhaul of various makes of vehicles are being widely read, and not only that, are being filed and preserved for reference by progressive traders and owners This article, which should be filed in connection with the others in the series, discusses a well-tried system of road testing which is wide enough in scope to cover all the types dealt with, and at the same time will make its appeal with equal force, both to the repairer and to the owner and user.
A short rim round the houses will not do. In fact, such a skimped test is misleading in many ways and, being so, is a waste of time and petrol. A vehicle which has been thoroughly overhauled, has had its body removed and, in the form of a completed chassia, is in an ideal state for the preliminary, or light test. A box seat should be rigged up for the driver and his mate, particular care being taken to board over the 'space between the seat and the dash—as serious accidents are liable to occur if that portion of the transmission between the clutch and the protecting seat is left uncovered.
Testing a heavy commercial vehicle is a two-man job, and a single-handed effort is as futile as the " round the houses" business already alluded to. The engine may have to be stopped upon the road, or it may stop involuntarily, and it is almost impossible for one man to " swing" and start up a big engine, stiff as it is, or should be, after overhaul. The timing of valves and ignition may have to be attended to, water or petrol may have to be fetched by one man whilst the -other stands by the machine. There are a hundred and one reasons why two men should be employed.
The First Test in Chassis Form.
The great value in giving the vehicle a preliminary test whilst in chassis form is that it is in no way supported or stayed by the body, nor set. comfortably to . the road by reason of its load, but runs as a flexible and lively construction. This is where the real value of the test comes in, as, if driven over a fairly rough course, at a sharp pace, the vibration set up will slacken off nuts and rivets improperly secured ; it will often reveal hidden and incipient cracks in the chassis members, at the spring hanger brackets and in the engine arms ; in short, such a test gives the vehicle a good shaking up, and if it cannot stand such a test, it will fare badly indeed when it has to carry a full capacity load under business conditions upon the harsh roads such as we have to-day. Should the chassis test (which need not, necessarily, include a hill) reveal any defect in assembly or material, such item may be easily got at and rectified. So soon as the chassis comes in from its road test it. should be carefully examined from axle to axle, and a list made of all the defects noted. This list should be worked through, and not until every item has been rectified should. the body be mounted. A. copy of the list should be kept for reference by the repairer, as, 'should any disagreement arise upon the completion of the vehicle between him and the owner, it will, at least, serve to show that he did his utmost to turn out a creditable job. We will suppose that the above test and the necessary rectifications have been carried out. The body may now be replaced and loaded up to its full weight capacity. It is, perhaps, hardly necessary to say that over the load test the greatest care should be taken. " Easy does it" at this stage. If the engine bearings have been taken up and various bushes and' other parts renewed, the condition is practically that of a brand-new vehicle. The parts must be allowed to bed themselves in by the actual process of running, to which, to a degree, the light test has already contributed its quota.
A slow run of about five miles should serve to indicate that things are going well and that there is no fear of a seizure. The speed may now be increased and, a little later, the test hill itself may be tackled.
The Test on a Gradient Under Full Load.
An ideal test hill should be of sufficient length and
gradient to give the vehicle a thorough gruelling upon a law gear. Once certain that the vehicle is " run in," no effort should be spared to e• arch out defects by severe treatment: on the steepest part of the grade stop the vehicle and make a standing start upon the lowest gear, changing up to as high a one as possible before reaching the summit.
• This process will try out the gears under severe conditions of load and gradient ; will give the clutch a crucial test ; will, in starting off, put a healthy strain upon the transmission and torque arrangeinents as a whole, and, altogether, form a very useful portion of the test. On reaching the top of the hill, it is as well to go over the vehicle once more, paying particular attention to the heat generated in the water circulation system and to the running temperatures of all bearings, and of the back axle, gearbox casings, and hubs.
Coming down the hill, the brake test should be carried out.. Let the 10117 rim free ;with clutch depressed and the engine idling over. When well under way, apply each brake in turn, then both together, and note how soon the machine can be brought to a standstill. At the bottom of the bill make any adjustments considered necessary to the brakes..
The The petrol consumption test should now be carried out, and, perhaps, the best way to-do this is to out off the main supply and connect up an auxiliary tank, containing a predetermined quantity of petrol, to the carburetter, and run it to exhaustion upon a give-andtake road, noting in the test book the mileage covered. Fill up the auxiliary tank and, returning over the same course, note the average consumption.
Carry out these tests, making adjustments the while, till you are certain the best results have been • obtained. Trials of three or four jets of 'different sizes will probably prove useful. This part of the • test should not be hurried over. With petrol at the present ruinous rate, too much importance cannot be attached to the consumption improving test.
The machine should now be about ready to put into commission, but it is very advisable to make another climb up the test hill, in order to ascertain whether the improved consumption has detracted from the machine's hill-climbing powers. It may be found to have fallen off very considerably in this respect. The happy mean between good climbing and good consumption must be struck, even if it means climbing the hill half a dozen times.
If a vehicle has been put through a test, as outlined above, and come through with flying colours, it will be a source of pride to the repairer and satisfaction to the user. A proper test is essential to good business relations.