SAFEGUARDING THE TAXICAB PASSENGER.
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The Intricacies of Taximeters. How the Instruments are Tested Before Approval. Dealing with Those Overhauled Annually.
O,(1,NE of the most complicated and pieces of mechanism is the taxinteter, which in its several forms is a marvel of ingenuity and has taken many yeare to bring to its existing stage of perfection. Yet, de-spite' its intricacy, the 'public has become so confident in the unerring accuracy of the readings Of its dials • that doubts are seldom, if aver, cast upon the !fares which it shows..
=Some idea of the difficulties experienced in designing and manufacturing a meter of this type may be gained when we are told that a first-class clockmaker and repairer cannot satisfactorily repair or adjust a taximeter until he has had six months' thorough training in this special work. This is because the oicIinary clock has two functions only to perform—keeping time and sounding the hours—whereas a taximeter is partly controlled by mileage, partly by a clock
mechanism, bass to be stoppedleand started by hand through the medium of the flag, and has to have a separate mechanism for dealing with the first Pare which. is • indicated on. the dial imme
diately the cab is hired. This figure must remain constant until the distance or time, or a combination of both, for which this fare is charged in advance, has been run out.
Special totaliiers must be provided to show the total mileage, that with passengers, and so on. Then there must be a separate eontrol for the extras, this being operated by the driver.
The "clock is driving all the time the Hag is down at the equivalent of 6 m.p.h. If the vehicle travels at under this speed then, the dials.are actually, controlled by the clock. The same thing happens if the vehicle be stepped, but when it travels at over 6 m.p.h. the clock merely idles. The system may be looked upon as resembling two free wheels, and whichever goes the faster does the driving.
Every meter must have either a separate gearbox, the pinions in which can. be changed to suit various wheel circumferences, or internal •reduction gearing, but in the latter case the meters are stamped as being suitable for a certain wheel circtlinference.
The fare dials take a very short but appreciable time to return to their zero positions; consequently, a device has to be employed to prevent the flag from being operated so quickly as to trap the dials before these positions are reached. In some makes the flag has to be moved forward and then backed for a short distance before it can be pushed right down, the momentary halt affording sufficient time for the return of the dials.
In other instruments, the flag is halted for a few moments by a catch which is released after a small air brake has revolved a certain number of times.
Al! this mechanism is expected to last for at least a year in perfect condition, and usually does so, but at the end of this period, or before if the seals be broken, each meter must be tested by the National Physical Laboratory at their taximeter testing sub-station at Lambeth. Similarly, before a new type of taximeter is permitted to be employed on the streets it must be approved as to type, first, by the Commissioner of Police, and then by the National Physical Laboratory.
The police inspect the figures, dial, etc., test the stopping of the clock, the operation of the flag, etc., and if satisfied so far pass the instrument to the N.P.L., Teddington, where it is taken apart sufficiently to enable the working of the mechanism, its strength, etc., to be ascertained. If considered satisfactory it is tested on a bench for accuracy in recording distance, the clock is tried out for time-keeping, a check is kept on the totalizers, and a test is made of the clearing of the dials and of the first mile. The instrument is then taken out on a cab fov a test run on the Toad, the vehicle being supplied by the makers of the taximeter. It is thus tested under service conditions, but it has already had a good overhauling and it is seldom that anything goes wrong on this test. If a model, instead of being entirely new, be only one that has" been slightly modified, then it is not put through a road test.
Ordinary taximeters are sent in after being overhauled at the conclusion of their year's work, and are sealed befdre testing, as the seals are of lead' hammered into position, and if this sealing were carried out after the passing, some small loose part might be affected, and it is, of course, better that this should happen beforehand and thus be discovered.
Next comes what is known as nil hand test, during which all positions of the fleeare tried and it is ascertained whether when the shutter comes down the flag cannot be moved back.
Then the initial fare is tried out for clearing and length, far, as previously explained, this fare must be run out before further atovements should occur, and after this initial reading the figures are given in threepenny stages.
• It is of interest to note at this point that the fare to the passenger is always booked up in advance, thus -when the first shilling is used the succeeding threepence is immediately shown.
Continuing the test, the instrument is then secured to a special bench and driven by a flexible cable from a worm gear on a shaft rotated by an electric motor. There_ are three of these benches which can deal with 60 meters at a time, but any one can be used independently.
Each worm gear, consisting of one worm and two worm wheels, drives four flexible, one from each side of each worm wheel. Each meter is run the equivalent of 70 miles, and is coupled up to a revolution counter. It is then checked against a standard clock for two and a half hours, and run all night against the clock to see that the mechanism is strong enough to run for 12 hours without rewinding.
After each of these operations the figures on the totalizers are compared with the fares. Certain allowances must, of course, be made and, taking for example a fare of one shilling, this may be recorded during any time between 10 minutes and 10 minutes 40 seconds. In the same way, the distance run for the shilling can he anything between 1 mile and 1 mile 117 yards, but it is important to note that.time.or distance must be in favour of the pasSenger, and no allowance whatever is made on the other side.
Testing of the. drive from the wheel to the instrument is performed by the police. After the meter .leaves the testing sub-station it is fitted to a cab and taken to one of the _police passing stations. There it is run over a measured distance, and if it proves satisfactory the 'star wheel by which it is driven from the road wheel is sealed, the _flexible transmission_ is similarly sealed to the meter, and this, in turn,, is sealed-in position on the cab. In the same way sealing of the gearbox at the base of the meter, where one is employed, is carried out at"the sub-station. after it has been ascertained that the gear ratios are correct.
The Seals are made of thin lead and, in the case of the gearbox, the screws by which it is enclosed are drilled to take a wire, and the ends of the .wire. passed through the seal. It is squashed between dies in a special press, the cir
cumference of the wheel for which the gearbox is intended being embossed upon it. To prevent the ends of the wire from being pulled out Of the seal; the wire employed is of a special type, consisting of a strong core with another wire twisted round it.
A record has been kept of every test carried out since 1907. 'Each is Written in a .book to which reference is'made 'through a card-index SYstetn.: In the course of time .the faaltS found -become sto well known as to be referred to by a letter ;. this Salves-Much space.
The testingsub-station, which is, of course, ' a .branch of a Government' department, is run tort most econoraieal lines-, and the plant which was installed at the time of its inanguistion is still in active _commission:.-Even the :electric motor Which drives the meters has been' running constantly for 18 years With no 'attention other than cleaning and lubricating. The Same thing applies to the flexible, some of which however, have brokenand have been repaired. In the revolution cbunters there is a number of pinions, some of which Wear Out fairly quickly, but these are easily replaced by the laboratory.
Workshops. • • "
We think we have written sufficient to show those-interested ,what great care is being exercised to prevent the public from being overcharged.