This, to be sure, is not always the case; for there are a few builders of engines who place their reputation above everything else and who would rather lose an order than execute it badly. Others, unfortunately, prefer to have the order at all costs.
By retaining a consulting engineer, all these difficulties are overcome. In the first place, the engineer draws up a scale of prices and specifications which must be complied with in their entirety as well as in all details. Rival engine builders are thus compelled to make their estimates according to the same standard, so that one engine can readily be compared with another with the utmost fairness. In these specifications, penalties will be provided for by the engineer which will be levied if the warranties of the maker are not fulfilled. Otherwise the warranties are worth nothing.
The first consequence of engaging a consulting engineer is to render the matter of cost a secondary one. A factory owner who employs a consulting engineer and pays him for his services, is impelled chiefly by the desire to obtain a good installation which will perform what he expects of it. For that reason necessary sacrifices will be made to comply with the client's wishes.
If the purchaser considers the question of cost most important to him, he need not engage an expert to
supervise the installation of his engines. He has simply to pick out the cheapest engine. Unfortunately, however, the money which he will save by such a procedure will be more than compensated for by the trouble which he will later experience when his motor stops or when it breaks down, because it has been cheaply built in the first place.
The advice of a consulting engineer is therefore of importance to the purchaser, because an engine will be installed which will in every way meet his requirements. The gas-engine builder will also prefer to deal with an engineer, because the engineer can appreciate at their true worth good material and good workmanship and place a fair valuation upon them. The specifications of a gas-engine and gas-producer expert are accepted by most engine builders, because an expert will not introduce conditions which cannot be fulfilled. Some manufacturers refuse to consider the conditions imposed by specifications seriously, or else they fix different prices and make tenders on the basis of these with or without specifications. In either case the purchaser may be sure that he is not receiving what he has a right to exact.
Testing the Plant.—When the engine has been selected the consulting engineer supervises its installation, and, after this is completed, carries out tests in order to determine whether or not the guaranteed power and consumption are attained. The methods employed in testing a gas-engine are both complex and delicate. The quality of the gas, the proportions of the
elements forming the mixture, the time and the method of ignition, the temperature of the cylinder-walls, the temperature and the pressure of the gas drawn into the cylinder, all these are factors which have a decided bearing upon the results of a test. If these factors be not carefully considered the conclusions to be drawn from the test may be absolutely wrong.
Indicators of any type should not be indiscriminately employed; only those specially designed for gas-engine purposes should be used. Indicator cards are in themselves inadequate, and should be supplemented by the records of explosion-recorders.
The calorific value of the gas should be measured either by the Witz apparatus or by means of any other calorimeter.