R. G. GRISWOLD

The design of a car printed in the September issue is, in many respects, very difficult for the amateur, if not almost prohibitive. There are many parts that could hardly be handled by the amateur of limited facilities, while in other respects there are many fea-tures that could be vastly improved. A car like the one to be described in the following series of articles can easily be constructed in five or six months by a man or boy of ordinary mechanical skill, as the entire car has been redesigned to meet the needs of amateur builders that are not fortunate enough to possess an entree to a well equipped machine shop.

This car, as here illustrated is of the popular detachable tonneau type that can easily be changed to a runabout in a few minutes. It will carry five persons with comfort, while seven can be accommodated by using corner seats in the front of the tonneau. The body is built on very graceful lines, and while it is extremely roomy, it is not at all difficult to build, provided the directions are closely followed. The painting and trimming will be taken up in due course.

This machine has proven itself extremely satisfactory in every respect, and has ample power to climb any ordinary grade on the high or intermediate gear, while on the low gear it has an abundance of power to negotiate very steep hills. It is easily handled and is geared for the following speeds when the engine is turning 1,000 revolutions per minute; twenty-five miles per hour in full gear, twelve and one-half miles on the intermediate, and four miles on both the low speed and reverse.

In general the car is of the latest accepted practice, a double opposed cylinder engine being placed under the hood in front, coupled to the driving shaft by a positive acting expanding clutch, which runs in oil and works metal to metal. The change speed gears, which give the changes mentioned above run in oil in an oil-tight gear case. The greater partof the machine work can be performed on an eleven inch foot-power lathe and bench drill capable of taking a half-inch drill. The operations requiring outside work are very few and inexpensive.

One of the greatest advantages of this design is that castings and forgings of almost every part detailed and described may be readily obtained at a lower cost than the amateur could afford to build the patterns for and have them cast. These castings have been made as nearly to size as possible in order that the machine work on them may be reduced to a minimum, and the fact that so little work is necessary greatly enhances their value.

It has been thought best to begin with a description of the various details of the car, taking up the hardest and most tedious work first, and gradually building up to the finished car. An advantage of this system is that the working room of the builder is not taken up by the body of the car while the small parts are being made, and when the running gear and body of the car are in process of construction these parts may be incorporated in their proper places. Owing to the lack of space the full design cannot be given in this issue.

Perhaps the gear case will be as good a part to commence on as any. This transmission is the popular sliding spur-gear type, three speeds forward and reverse. There are no driving spurs in mesh on the high speed, and the bevel gears are absolutely necessary in any type of car where the power is transmitted from a longitudinal shaft to a transverse driving axle. This change must be made either in the gear case or in the differential on the rear axle, as in the propeller drive. This is one great fault with the gear shown in the September issue. It is impossible to drive the car without transmitting the power through two sets of gears on high speed, where the effort should be transmitted as directly as possible. When spur gears are driven at a high rate of speed they make a good deal of noise unless they are very well fitted, and the wear 60on gives clearance between the teeth. Bevel gears are not so apt to do this.

As stated before, the gear shown in Fig. 2 is designed particularly to meet the needs of those unable to command a large machine shop where the planing of the two halves is generally done, as well as the boring for the shaft bearings. It is as light as is consistent with the duty required of it, while the gears and shafting are made unusually stiff and strong to obviate as far as possible excessive wear.

The upper half, or cover, Fig. 2 a, is provided with a cored hand-hole through which examination of the gears may be made without removing the gear case from its position in the car. This opening is closed wish a brass plate b 1-16 in. thick, secured by 8-32 round-head brass machine screws spaced about every two inches, a gasket of heavy cotton cloth or thick manila paper being placed in the joint, to render it oil-tight. The surface of the slightly raised edge around this hole can be easily dressed to a good surface with a file.

The joint between the two halves of the case, which is usually planed to a true surface, can be readily made with a large file in the following manner. The castings have been given very little finish at the adjoining surface to reduce the work of fitting. Of course the best job can be done by planing or milling, but a very satisfactory fit can be made by hand. Fasten the upper half to some firm bench by means of the little feet cast on the case, and with a large, sharp file work the surface down until a straight edge touches at every point on either side and ends. A fourteen inch file is about the size to use so that it will reach across from side to side. As to the accuracy of the joint, this may be tested by planing up a plank of hard wood 28 x9x2 in., so that a practically true plane results. Then, by laying this improvised surface plate on the work, any high or uneven places may readily be detected.

When the upper half is finished the joint surface of the lower half is finished in exactly the same manner. Then the finished surface of the top half is given a very thin coat of red lead in oil, and any excess rubbed off with the finger. The two pieces are then laid together in position and the upper piece given a very slight movement to and fro. This action will mark the high spots or points of contact on the lower piece, which are then dressed down with a smooth file when the cover is removed. This process is repeated until a perfect bearing is obtained.