Electric Bus Costs.
Page 4
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For certain classes of werk, and particularly where the distances run from a central depot are comparatively short, not exceeding 20 miles out, the electric vehicle would appear to be without a rival, and the prospective commercial-vehicle user having in view work of this nature whether it be for public service or for goods transport would on prima facie evidence be strongly inclined to purchase this type and no other. It is simple both in construction and control. A close and comprehensive examination of the relative merits of the electric and petrol vehicle under conditions of working common in this country and extending over a long period of use is as yet hardly possible. With one or two exceptions, no one in this country has been operating electrics for more than a couple of years.
Brighton and Hove Electric Buses.
Some figures relating to costs of running, which have recently come into our hands, although they are not complete or "all in" costs, are nevertheless important as they comprise, in respect of a particular installation, those expenses which are particular to this clas9 of road vehicle. Weare, moreover, able to give a direct figure of comparison between the cost of tile electric and petrol bus in similar service and under the same management. We refer to those vehicles run by the late Brighton, Hove and Preston United Omnibus Co., Ltd., now sold to Tilling's.
It is perhaps only fair at this point to remark that the conditions under which these electric buses have been running are severe and unfavourable in several important aspects. The chassis were built some 10 years ago, and it is undoubtedly a fact that the design of this class of vehicle has considerably improved during the last three or four years. Laden, each bus weighs nine tons. The batteries empleyed are of the good-quality lead type. The route covered by these buses includes the severe gradient of North Street, which, as will be shown, has had an important effect on the maintenance costs of the buses. On the other hand, and speaking of the electric generally, from the point of view of public service, it must be 'recognized that its lack of speed on even the slightest gradient, a fading inherent on the electric chassis on account of the low power of the motors usually embodied, and which, moreover, cannot be increased without still further adding to the already excessive weight of the electric, is a telling point against it. It cannot be denied that, given the choice, the average passenger will undoubtedly select the faster vehicle every time. Moreover,, as an offset against the claim for the electric, that its mechanism is' simple, it mustibe pointed out that the battery, even on the most modern yehicks, is not reliable without skilled attention.
The number of electric buses owned by this company was 12, of which 10 generally were in use. The mileage per day from each varied from 80 to 90, and the total miles per annum from 220,000 to 227,000. As stated, each vehicle weighed, when loaded, nine tons. They were fitted with niclor cells, the total capacity of each battery being 500 amp.-hours; the maximum rate of 'efscharge allowable 'was fixed at MO amps. Each chassis was driven by two motors, each of six nominal horse-power, driving the rear wheels direct. The average mileage per charge works out at 25. The length of the route on which these buses worked was six miles. Each bus was removed from service in turn, at the end of, say, 25 miles of running, and taken to the charging station, a short distance from one of t's termini. The current.for the charging plant was supplied at 460 volts. The batteries to be charged required an average voltage of 120. The current was taken from Corporation mains at 460. and was split up by balances into 230. Two batteries were charged in series, and the necessary raising or lowering of voltage was dome by using boosters. It was ex 026 pected as a result of this special arrangement that, owing to the boost only being given to a small portion of the current, a high efficiency would be achieved. This object was not _realized; the percentage efficiency was only 76.
1.91 Unit Input Tor Each I•22 Used.
In working it was found that although, as shown by the meter on the bus, the actual current used amounted to L22 unit per mile, the current received, and paid for, was 1.91 unit per mile. In attempting to ascertain the total cost for current per mile, we must add to these figures the additional current required for recharging after repairs to the batteries. l'he actual life of the positive plates was 8000, say, three months running, and of the negative plates 14,500 miles, approximately five months of running, if the running was continuous ; but, as one battery was being charged another was on the bus, and vice versa, the period of replating was longer, as it took over six months for a battery to run the mileage-2i batteries were allowed to each bus.
After renewal to either class of plate, it was necessary, of course, to recharge the battery from zero. For this the consumption works out at 300 units. Taking the all-round figure of lid. per unit, the cost for current alone is 2.86d. per mile. This item cannot be taken as the complete fuel cost for purPoses of comparison with other types of mechanically-propelled vehicle. We must add to it any expenditure of maintaining the batteries in an efficient and workable' condition. The batteries used on these buses were maintained by the makers at a charge of about 3d. per mile. If it be objected that this figure is high, we must point out that several other battery manufacturers and vendors had been afforded the opportunity to tender, but after consideration they invariably found themselves unable to perform the service required at a less figure. The total fuel cost per mile is therefore the sum of the actual charge for current and the maintenance charge for the batteries-5.95d. Now as regards cost of maintenance of the chassis mechanism. We are often told that this expense in connection with the electric is at a minimum. We were unfortunately unable to obtain the actual cash values of the work needful to keep these buses mechanically fit. That the figure was not a negligible one may be judged by the fact that the motors, owing to overloading, were subject to very frequent burn-outs ; whereas, in some cases. a motor might last for many months, it was not an unknown thing for a motor to fail very quickly. Fortunately the motors were easily removed and as easily replaced, so that this frequent necessity for repair did not entail so much disorganis sation as might appear.
On behalf of the electric it may be, stated that neither batteries nor motors are really large enough to cope satisfactorily with the, gradient in North Street. As already stated, the maximum rate of discharge allowable for the batteries was fixed at 300 amps. ; on North Street this was invariably raised to 35'0. The motors were each designed with a normal capacity for 6 h.p. On the same gradient 35 h.p. was demanded. The high rate of discharge was undoubtedly responsible for more rapid deterioration of the batteries than might otherwise have occurred, and the high horse-power demanded on the hill raised the temperature of the motors to such an extent that although the insulation did not actually burn out it nevertheless got so hot that after a comparatively short time it fell off in flakes. Hence the frequent need for re-winding.
A useful figure is available as showing a comparison between the electrics and petrol buses run by the same concern. With petrol being purchased during this year at is. 2d. per gallon, the excess of cost on electric buses over petrol buses was 2itl. per mile.