LABORATORY TECHNIQUE, METHODS AND EQUIPMENT 260037
In undertaking any experimental work the first step is to plan carefully each successive step. Literature bearing on the subject should be examined to learn what work others have done on the problem and avoid needless duplication of effort. If the testing of only a simple accessory is involved, the results the device is intended to accomplish should be studied and an effort made to discover the designer's reason for believing that it will accomplish them. All conditions under which such a device must operate should be listed and the information needed from which to draw conclusions as to whether the device will meet them successfully should be determined. Before starting the actual work of testing, it is good policy to plan the necessary charts for presentation of the report.
This preliminary work means that the investigator will start well prepared but not with his mind made up as to what the results will be. It is necessary to be very careful in all experimental or research work; otherwise preconceived ideas are likely to result in finding what one wants to find rather than the exact truth. Prejudice is not the result of careful thinking and planning but of lack of such forethought. If a problem involves the investigation of a device on an engine, as for example a manifold, it is well to remember that there are other functioning parts and to be on guard against the temptation to attribute a sudden falling off of engine-power to the manifold when it may, in fact, be due to improper functioning of one of the other parts. New problems are more than likely to arise within, the major one as the work progresses and must be solved before the original program can be continued. Each sub-problem should also be planned carefully.
Methods to be followed in making an investigation are elucidated by examples of a study of adapting an existing carbureter to an existing engine and of a study of charge distribution by a manifold to the cylinders of a four-cylinder engine. It is necessary to do this with the use of numerical quantities taken from actual test results, but in the case of the carbureter tests the figures have no actual relation to one another and are not to be taken as representing achievements, as many were taken from experimental engines and other equipment. Before the effect of a given carbureter on the power and fuel economy of an engine can be studied, it is first necessary to learn what the engine is capable of doing when it is not influenced by the characteristics of the carbureter. After charts have been prepared from the ascertained data, the commercial-carbureter tests can be started. Each step for carrying these out is explained. All results are plotted in various ways for comparison and study.
A method that is thought to be easiest and surest for studying charge distribution is by measurement of the maximum explosion-pressures in the several cylinders of a multiple-cylinder engine. The equipment used and the method of doing this are described and the results given. Curves produced from the study indicate that power loss due to poor distribution is incurred by reason of (a) too lean or too rich a mixture and (b) improper spark-advance.
In planning the layout and equipment of a laboratory, a good way to begin is to make a study of the work that probably will have to be done in it and to realize that undoubtedly some problems will have to be undertaken that are not included in the survey, for which reason all equipment should be so designed that changes can be made easily, quickly and cheaply. Known essentials are that
Equipment must be bolted to the floor
Water must be drained away
Sufficient working space must be available
The entire space must be well lighted
The room should have a high ceiling
Good crane-transportation should be provided
Provision must be made for conducting away exhaust-gas
A model laboratory that answers all of these requirements is illustrated and described in considerable detail.