The boy mechanic, book 3

by Unknown

Tilting Top for Camera Tripod

The Homemade Tilting Top Is Convenient in Making Photographs at a Variety of Angles

Pointing a camera up, or down, as in photographing tall buildings with the ordinary camera tripod, is awkward and requires much time to make a satisfactory adjustment. To overcome this, a tilting top was made for the tripod, as shown in the illustration. The extra top consists of two boards hinged at one end. The lower board has a tripod socket to fit the tripod, while the upper one has a tripod screw for fastening the camera. Two metal brackets are provided, having slots through which binding screws are fitted, and clamped with wing nuts. This permits the camera to be tilted at various angles, or reversed for vertical pictures, without removing it from the tripod. Several positions are suggested and a little experimentation will give numerous other possible uses. Devices of this character may be purchased, but the one shown is easily made and serves its purpose well.—R. C. Miller, Pittsburgh, Pa.

Homemade Electric Locomotive Model
and Track System
By A. E. ANDREW
PART III—Construction of the Track
System

Operation of the electric-locomotive model described in the [previous] [articles] is feasible only with a properly constructed track system. This equipment, including curves and switches, is to be described in this, the final, article. Two functions are to be performed by the track system: It must serve as a support and guide for the locomotive and provide a path over which the current from the source of energy is supplied to the motor within the locomotive and returned to the source. On this basis, then, the construction may be divided into two parts: the mechanical and the electrical features. If the mechanical construction is not practical and accurate, the locomotive will not operate satisfactorily. The electrical connections must be given due care also.

SECTION OF RAIL
Fig. 1

RAIL CONNECTION
Fig. 2

Shape the Rails from Sheet-Metal Strips, 1¹⁄₂ Inches Wide and 16 inches Long, to the Form Shown in Fig. 1. The Rail Connections are Formed as Shown in Fig. 2

The track should be of uniform gauge; the joints should be solid and free from irregularities, which cause “bumping” in passing over them. The material used should be stiff, so that it will retain its form, and preferably non-rusting. The rails must be insulated from each other, and proper means must be provided for making suitable electrical connections between the various sections. The construction of a straight and a curved section of track, together with a switch and signal, adaptable to various places on the system, will be considered in detail.

The straight sections may be made any suitable length; sections 16 in. long will be found convenient, as the metal pieces forming the rails may be bent into shape easily when they are short rather than long. The possibility of various combinations of straight and curved sections in a given area is increased by having the sections shorter. The rails may be made from tinned sheet-metal strips, by taking pieces, 16 in. long and 1¹⁄₂ in. wide, and bending them into the form shown in [Fig. 1]. The rails should be mounted on small wooden sleepers, ¹⁄₂ by ¹⁄₂ by 4 in., by means of small nails, or preferably small screws. The distance between the centers of the rails should be 2 in. The sections of track may be fastened together at the ends by means of a special connector, shown in [Fig. 2], made from thin metal, preferably spring brass. The type of connector shown in Fig. 2 will not prevent the sections from pulling apart, and to prevent this, a second connector, similar to that shown in [Fig. 3], should be made. The sleepers at the ends of each section should have one side beveled, as shown, and these edges should be exactly one inch from the end of the rails. A spring clip should be made, similar to that shown, which will slip down on the inside of the end sleepers and hold the sections together.

METHOD OF CONNECTING TRACK SECTIONS
Fig. 3

SECTION OF RAIL
Fig. 4

END CONNECTION OF RAILS
Fig. 5

A Spring Clamp for the Joints in the Sections is Shown in Fig. 3. An Improved Form of Rail is Shown in Fig. 4, and in Fig. 5 is Indicated the Method of Joining Its Sections

A better form of rail is shown in [Figs. 3] and [4], but it is somewhat more difficult to construct. In this case, instead of bending the piece of metal forming the rail over on itself and closing the space entirely, the metal is bent over a round form, such as a piece of wire, which may be removed, leaving an opening through the upper part of the rail from end to end. This gives a better form to the tread of the rail and at the same time provides an easy means of connecting the ends of the rails, as shown in [Fig. 5]. Small metal pins, about 1 in. long, and of such a diameter that they will just fit the circular opening in the top of the rail, are provided. One of these pins should be fastened in one rail at each end of a section, making sure that no rail has more than one pin in it, and that the arrangement of pins and rails corresponds in all sections. With proper care the various sections should fit together equally well, and they may be held together as shown in Fig. 3.

METHOD OF LAYING OUT CURVED SECTION
Fig. 6

LEFT SWITCH
Fig. 7

RIGHT SWITCH
Fig. 8

Lay Out the Switches and Curves, Full Size, and Fit the Rails to the Curves Accurately

The curved sections may be made from rails similar to those described above, but some difficulty will be experienced in bending them into a curve because of the necessity of bending the lower flange on edge. The difficulty may be overcome by crimping in the inner edge of the lower flange and expanding the outer edge by hammering it on a smooth surface. The radius of the curve to which the inner rail should be bent in order to give a section of convenient length, and not too abrupt a curve, is 21 in. The circumference of such a circle is approximately 132 in., which, divided into eight sections, gives 16¹⁄₂ in. as the length of the inner rail of each section. Since the tread of the track is 2 in., the radius of the curve of the outer rail will be 23 in. The circumference of the circle formed by the outer rail is 145 in., which divided into eight sections gives 18¹⁄₈ in. as the length of the outer rail of each section. These curved rails may be mounted on sleepers, their ends being held in place, and the various sections fastened together, just as in the case of the straight sections.

Some trouble may be experienced in getting the curved rails properly shaped, and it would be a good plan to lay them out full size by drawing two circles on a smooth surface having diameters of 42 and 46 in., respectively, and divide each of the latter into eight equal parts. The form of the curve between these division lines and the lengths of the curves will correspond to the shape and lengths of the rails forming the curved sections of the track. The pieces should be cut slightly longer than required, and after they are bent into shape their length can be determined precisely and extra portions cut off. Each curved section will correspond to ¹⁄₈ of the complete circle, or 45°, as shown in [Fig. 6].

The switches for the track may be of two kinds: left and right. They are named according to whether the car is carried to the left or right of the main track with reference to the direction in which the car moves in entering the switch. A left switch is shown in [Fig. 7], and a right switch in [Fig. 8], the direction of movement being indicated by the arrows.

DETAILS OF SWITCH
Fig. 9

The Crossings of the Rails must be Fitted Carefully, and the Movable Sections G and H Arranged to Make the Proper Contacts

A detailed drawing of a right switch is shown in [Fig. 9]. Rail A corresponds in form and length to the outer rail of one of the curved sections previously described; rail B corresponds to the inner rail of one of the curved sections except that 2¹⁄₂ in. of straight rail is added at the left end. Rail C is a straight portion of rail, 18 in. in length, with a part of the base cut away at the switch, and rail D is a section of straight rail, 15¹⁄₂ in. in length, with the base cut away where it crosses rail A. The ends of rails D and A are hinged at the points E and F, 3³⁄₄ in. from the left end, with pins driven into the ties. The outside edges of the pieces G and H are filed off so they will fit up against the rails C and B respectively. Both the pieces G and H are attached to a strip of fiber insulating material, I, at their left-hand ends, in such a way that when the piece H is against the rail B, the piece G is away from the rail C about ³⁄₁₆ in.; when the end of the piece G is drawn over against the rail C, the end of the piece H is drawn away from the rail B about ³⁄₁₆ in. With these two combinations the car may be made to move along the main track or to the right on the curved track. The two long sleepers J and K are to provide a mounting for the switch-control lever and signal.

The rail A is not continuous where the rail D crosses it, but is broken as shown in the figure. A small notch should be cut in the surface of the rail D where it crosses the rail A, for the flange of the car wheels to roll through when the car is moving onto or off the switch. The sections of the rails A and D must be connected electrically. Rail A must be connected to rail C, and rail B to rail D.

It is obvious from an inspection of [Fig. 9], at L, that rail D will be connected to rail A when the car is on the switch, the car wheels passing over the point L, and a short circuit will result. This may be prevented by insulating the short section of the rail D at this point from the remainder of the rail, but the length of the insulated section must not be greater than the distance between the wheels on one side of the car; otherwise the circuit through the motor would be broken. If this is the case, and the car stops on the main track with both wheels on the insulated section, it would be impossible to start the locomotive until one wheel was moved to a live part of the rail.

The switch control is shown in [Fig. 10], and the letters C, G, and I correspond to those given in [Fig. 9]. A ¹⁄₈-in. rod, about 4 in. in length, is bent into the form shown at M. It is mounted in a frame, the details of which are shown in [Fig. 11]. A small arm, N, with a hinged handle, O, is soldered to the rod, after it is placed in position in the switch frame. The arm N and the lever P should be parallel with each other. If properly constructed, the handle O will drop into the notches in the top of the switch frame, and prevent the rod M from turning. A connection should be made from the lever P to the end of the piece I, which will result in the switch being operated when the rod M is rotated one-fourth of a turn. After this connection is made, the frame of the switch should be fastened to the ends of the long sleepers, which were provided when the track part of the switch was constructed. Two small disks, mounted at right angles to each other, will serve as signals when properly painted, or as an indication of the open or closed position of the switch.

SWITCH CONTROL
Fig. 10

TOP VIEW
SWITCH FRAME
Fig. 11

The Signals Indicate the Open or Closed Condition of the Switch by the Small Disk, Which is Regulated by the Lever Switch Control

The speed of the car on the track may be controlled by inserting resistance in series with the battery or source of electrical energy, or by altering the value of the voltage between the rails, by changing the connections of the cells forming the battery. The direction of movement of the locomotive cannot be changed unless the car is turned end for end, or the connections of the armature or field winding—not both—are reversed. The switch on the bottom of the locomotive reverses these connections.

Fig. 12

A small rheostat, which will give the desired resistance, may be constructed as follows: Obtain a piece of hard wood, 4 by 5 in., and ³⁄₈ in. in thickness. Lay out a curve on this piece, as shown in [Fig. 12] by the row of small circles. Procure eight round-headed brass machine screws, about ¹⁄₈ in. in diameter and ³⁄₄ in. in length, and 16 nuts to fit them. Drill eight ¹⁄₈-in. holes along the curve, spacing them ³⁄₈ in. apart. File the heads of the screws off flat and mount the screws in these holes. Make a metal arm, S, and mount it on a small bolt passing through a hole drilled at the center from which the curve was drawn, along which the screws were mounted. This arm should be of such a length that its outer end will move over the heads of the screws. Mount two binding posts, Q and R, in the upper corners of the board and connect R to screw No. 8, and Q to the bolt holding the arm S in place. Connect small resistance coils between the screws, starting with screw No. 2; screw No. 1 corresponds to an open circuit and is shown in contact with the arm S. Two stops, indicated by the black spots, should be provided, to prevent the arm from moving back of screw No. 1 or beyond screw No. 8. The board may now be mounted on a suitable hollow base, and the rheostat is complete.

Two binding posts should be mounted on the ties of one section of the track, and one of them electrically connected to each of the two rails, which will give an easy means of making the necessary electrical connections to the source of energy. After careful examination, to make certain that the locomotive is in running order, a test run may be made. If the locomotive operates properly and difficulty is experienced when it is placed upon the track, check up thoroughly on all rail connections, insulations, and other elements in the electrical equipment. Cars of a proper gauge may be coupled to the locomotive, and “runs” made as extensively as the track system will permit.