Under the letter B have been classed considerations of maintenance and construction.
9. Protection, more or less complete, of the machinery against the
action of dust and mud.
10. Regularity and smoothness of motion.
11. Capacity for passing over curves of small radius.
12. The simplest and most rational construction.
13. Facility for inspecting and cleaning the interior of the boilers.
14. Dead weight of the train compared with the number of places.
15. Effective power of traction when the carriages are completely full.
16. Rapidity with which the motor can be taken out of the shed and
made ready for running.
17. The longest daily service without stops other than those
compatible with the requirements of the service.
18. Cost of maintenance per kilometer. (It was assumed, for the
purposes of this sub-heading, that the motor or carriage which
gave the best results under the conditions relating to
paragraphs 9, 10, 12, and 13 would be least costly for repairs.)
As regards the first of these, viz., protection of the machinery against dirt, the machinery of the electrical car had no protection. It was not found in the experiments at Antwerp that inconvenience resulted from this; but it is a question whether in very dusty localities, and especially in a locality where there is metallic dust, the absence of protection might not entail serious difficulties, and even cause the destruction of parts of the machinery.
In respect to the smoothness of motion and facility of passing curves, the cars did not present vary material differences, except that the cars in which the motor formed part of the car had the preference.
In the case of simplicity of construction, it is evident that the simplest and most rational construction is that of a car which depends on itself for its movement, which can move in either direction with equal facility, which can be applied to any existing tramway without expense for altering the road, and the use of which will not throw out of employment vehicles already used on the lines; the electric car fulfilled this condition best, as also the condition numbered 13, as it possessed no boiler.
In respect to No. 14, viz., the ratio of the dead weight of the train to passengers, if we assume 154 lb. as the average weight per passenger, the following is the result in respect of the three cars in which the power formed part of the car:
9,350 lb.
Electric car. --------- = 1.78
154 × 34
15,950 lb.
Rowan. ---------- = 2.30
154 × 45
22,000 lb.
Compressed air. ---------- = 2.55
154 × 56
The detached engines gave, of course, less favorable results under this head.
Under head No. 15 the tractive power of all the motors was sufficient during the trials, but the line was practically level, therefore this question could only be resolved theoretically, so far as these trials were concerned, and the table before given affords all the necessary data for the theoretical calculation.
As regards the rapidity with which the motors could be brought into use from standing empty in the shed, the electric car could receive its accumulators more rapidly than could the boiler for heating the exhaust of the compressed-air car be brought into use.