Using Electric or Gas Mains to Aid Starting
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Interesting and Practical Suggestions for the Use of " Town" Electricity to Provide Current for the Starter. Substituting Gas for Petrol as a Fuel for the Purpose of Starting
DCRING cold weather the enginestarting problem reaches its acutest stage and in cold garages, where no special provision is made for starting up, there is often much trouble
and loss of time, to say nothing of loss of • temper and consequent inefficient work on the part of drivers. Not infrequently men suffer strained wrists or bruised hands, or even severe internal injury, brought about in the efforts to start a recalcitrant engine on a cold morning.
Starter batteries are run down and often their plates are buckled, motor commutators and brush gear suffer from overload and, more serious still, an undue dilution of the lubri cating oil often occurs as a result of the engine being turned over for long periods without firing, but all the time drawing in neat petrol from a strangled carburetter.
What are the steps taken to overcome these difficulties? The heated garage is, perhaps, the simplest, but every garage cannot be efficiently and effectively heated, the area is too large and the cost of heating apparatus prohibitive. As an alterna tive the engine is kept warm either by means of some heating arrangement in the immediate vicinity, such as an electric heater or an oil lamp ; sometimes the heating is produced at the risk of a fire being started.
Portable engines of the motorcycle type are frequently used for cranking up big bus or lorry engines and these have met with a considerable amount of success, although they are somewhat cum bersome and, at times, are themselves
not altogether free from trouble. In a few cases compressed air is used to start
up the engines, passing the air into the cylinders, via special connections, but this also means special valve gear and considerable expense. from The Possibilities of Gas.
Very little has been done in the way of making use of the gas and electricity supplied from the mains. To suggest the use of town gas for starting up a petrol engine may sound absurd to some, but really there is no reason why gas should not be used when mixed with the correct proportion of air and drawn in via the carburetter, with the petrol turned off. Such a mixture will, on a cold morning, give more rapid starting than a low-grade petrol with poor vaporizing qualities, and there will be no risk of crankcase-oil dilution, such as there is with poor petrol.
Although gas can be used in this way as an aid to starting a cold engine, it does not overcome the difficulties of the 132
initial " turn-over " of the engine, and a cold engine with unsuitable oil takes a good deal of power to crank round, frequently far more power than a single man or a starter motor can exert for sufficiently long to enable the engine to get going.
From time to time suggestions have been put forward in regard to taking current from the mains in place of that from the starter battery. This is not quite so simple as many seem to believe, but it is possible.
In the first place, it must be clearly understood that a 6-volt, 12-volt or 24volt starter motor cannot be started with current tapped straight off the mains. The pressure in the supply mains is seldom less than 110 volts, and is usually betweu 220 volts and 460 volts; it may, in isolated cases, be so high as 550 volts. Furthermore, direct, as opposed to alternating, current is required for the starter motor, so that where the supply is alternating this is an additional barrier.
These voltages can, however, be reduced, not, in the case of alternating Current, by means of a transformer, as this would reduce the voltage, or pressure of the supply, but still leave it alternating. In the case of direct cur
rent it would not be possible to use a resistance; although it would reduce the voltage, or pressure, the amount of current required from the mains—anything from 50 amps. to 200 amps.— is out of all reason and would necessitate special main's and meters, switches, fuses, etc., which would be prohibitive in cost, even if the supply authority would consent to these being put in.
A Portable Source of Current.
The required voltage can, however, he obtained by means of a small and inexpensive motor-generator or rotary converter. Current would be taken from the mains to the motor end of the machine, which would drive the dynamo end, thus providing the required amount of low-voltage current.
The complete plant for converting either alternating or direct current to the required voltage, including converter, switch gear and wiring, will not cost more than £50 to I60, and such a set would be capable of supplying current to the largest engine-starter made.
The cost of running would be negligible and the amount of current required from the mains would be roughly as follows :—Current at starter 100 amps. x 12 volts = 1,200 watts ;
cul-rent in motor-driving generator = 1,200 watts plus losses in machine, say, 25 per cent. = 1,500 watts; 1,500 watts at 440 volts = 3.4 amps ; 1,500 watts = l unit per hour.
From these figures it will be seen that the current taken from the mains will not be more than 34 amps., and with current at even 6d. per unit the cost of running the set (fully loaded) for a whole hour would only be 9d.
It is obvious that a motor-generator set of this type ivould soon pay for itself where a number of vehicles has to be started up every morning. The saving of battery deterioration alone would be sufficient, but, in addition, quick starts would be ensured and, consequently, there would be no lost time, and dilution would be reduced to a minimum.
In installing plant of this kind it should be borne in mind that heavy leads must be run from the dynamo end of the motor-generator, or rotary convertor to the starter motor, and a suitable plug or connections must be used.
Though heavy leads may be run to various parts of the garage from a common bus bar, it is preferable to mount the set on a light trolley and arrange so that it can be placed close against the engine to be started, using only a short length of heavy cable for the starting motor current and a light flexible wire for the current supply to the portable set.
A portable electric motor may, of course, he used for cranking the engine, instead of the portable engine referred to earlier, but this often requires special forms of starting handle.