the electrical current is to be used for lighting as well as power it is, of course, necessary to provide an actual surplus over the power needed to run the shop in order to furnish the current for illumination.

As practically all automobile mechanies are familiar with the explosive motor, owing to its almost universal use as a prime

mover in automobiles, it is reasonable to expect that many isolated repair shop owners will avail themselves of the opportunity to use a source of power with which their workmen are thoroughly familiar. A one-cylinder vertical engine adapted for stationary power is shown in section at Fig. 22. Two large flywheels are used to insure steady running, and the power generated may be delivered to the shop line shaft by direct belt connection between the engine pulley and a corresponding member on the shaft. The

method of installing a horizontal engine adapted for stationary power and the provisions made for cooling the cylinder and disposal of the exhaust gases are so clearly shown in Fig. 23 that it is unnecessary to describe the installation further. For the very small shop using but few machine tools, it is not necessary to use the type of cooling system required by the larger powered engines, as the two or three horse-power necessary to operate a small lathe, drill press and emery grinder can be delivered economically from the simple hopper cooled engine, such as shown at Fig. 24.

FLYWHEELS

PULLEY

WATER HOPPER

BASE

Where a gas or gasoline engine is used for power, it is necessary to provide a substantial foundation composed of masonry and concrete as shown at Fig. 23, or of heavy timbers as shown at Fig. 22, in order to prevent excessive vibration of the floor. If possible, the engine bed should not rest on the floor, but the foundation should be carried down to solid earth. The smaller hopper cooled engine of two or three horse-power may be bolted directly to the shop floor, as these will not vibrate enough to be objectionable. A marked advantage of an isolated generating set such as shown. at Fig. 20 is that it may be housed in a structure separate from the repair shop proper, reducing the first risk, whereas, where an engine is belted directly to the line shaft, it is usually in the same building as the machinery it drives.

Fig. 24.-Gas Engine Suited for Small
Repair Shop.

One of the important advantages accruing through the use of a gas or gasoline engine is in the economy of this form of power, If an engine is used capable of running on fuel oil instead of asoline, there will be a marked saving, and the absolute limit in the low cost of power production will have been reached, the aly forms of power showing to better advantage being those de

rived from natural sources, such as wind and water, neither of which can be applied universally. The table of power cost presented herewith shows the relative expense of various forms of power among which are included three forms of steam engines, the gas engine using manufactured or natural gas, the internal combustion motor using gasoline, the electric motor and the oil engine. Where the power requirements are not severe, the gas or gasoline engine in the smaller sizes will not prove so expensive to operate as to call for the use of an oil engine which is not as easily started or kept in operation as the forms burning gas derived from the various gas-producing methods or by the vaporization of volatile hydrocarbons, such as gasoline.

Power Required for Machine Tools.-The amount of power to be provided in a repair shop depends entirely upon the character and number of machines to be driven. If a line of shafting is to be used to turn the machinery, and especially if there are individual countershafts for each machine, as is needed for most machine shop tools, it will be necessary to double the power requirements of the tools used, as given in the accompanying tabulation, to take care of loss of power through belt slip, journal friction, lack of machine alignment and other causes. The figures given are taken from the best mechanical authority and are an average of some widely different estimates for the same class of machine.

Installation of Machine Tools.-The placing of the machinery il depend entirely upon the ideas of the master mechanic and the best method of installing line shafting will, of course, depend upon the character of the building and the materials of which the

wall or ceiling to which it is attached is constructed. If the floor space permits, the machinery should be arranged so that all may be driven from a single main line of shafting. It is well to remember that a reduction of the length of the shaft and the number of hangers for its support decreases journal friction and consumes less of the shop power. If the machines are on the ground level, as is the case with most small shops, the floor may be made of heavy planks, attached to substantial beams laid over a foundation of cinders or well grouted crushed stone. A floor of cement should always be planked over because the wood flooring is much easier on the feet of the workmen. It seems almost unnecessary to mention that a perfectly level floor should be sought for. It is imperative that the floor be substantial enough so it cannot vibrate and have sufficient strength so it will not deflect under the weight of the machine tools. There is some danger from this source, if the machine room is placed on an upper floor of a converted building that has not been especially constructed for automobile repair work. All machinists and millwrights agree that the foundation for the bed of a machine should have no deflection, if the life of the machines and the accuracy of the work performed upon them is to be given consideration. The problem is considerably simplified when one considers that in automobile repairing, machine tools of great weight are not used, so there should be no difficulty due to either floor vibration or deflection in any ordinarily well constructed building.

The floor plans presented at Figs. 3, 4, 5 and 6 inclusive show logical arrangements of machine tools that can be followed to advantage. The lathes, milling machines and shapers should be installed where there will be plenty of light upon them, and it is well to group all lathes together, if possible. Drilling and boring machines must be installed with ample floor space around them so the large work can be handled to advantage. Ample room should be allowed around each individual machine, and there should be sufficient space between the benches and tools to allow the workmen at the bench to pass between the operator at the machine and the bench with room to spare. An ideal method of installing an electric motor, if this is used as a source of