Rubber Bands Run This Flivver (Jan, 1932)
Rubber Bands Run This Flivver
by DICK COLE
Using strips cut from old inner tubes as motive power, the Flivver-car described in this article by Mr. Cole can easily be built by any boy and will be an endless source of fun.
HERE is something which will gladden the heart of any boyâ€”a car which goes by itself. The motive power is a rubber band motor. Just as twisted strands of rubber are used to whirl the propeller of a model aeroplane, so heavier strands can be used in a similar, manner to provide mechanical locomotion.
Before going into the details of the construction of this car, it is well that the prospective builder should have a clear insight into the principle employed. The blueprint shows the plan and the elevations of a model Flivver-car in its simplest form. This is really a remodeled coaster wagon. With a little ingenuity, any boy can add a rumble seat and an old auto steering wheel and have a classy, rakish looking roadster.
The motor and its operation is clearly shown in the blueprint. It consists of multiple rubber bands cut lengthwise from an old 30″ inner tube. The rubber must be live and “springy.” Suitable discarded inner tubes can be bought for a few cents a pound at any vulcanizing shop.
The rubber bands are stretched along the center line of the car between the axles. The rear end of the bands is attached to a stub axle on which is a bevel gear. This engages with another bevel gear on the rear wheel axle. One of the rear wheels is rigid on the axle, the other turns freely on the axle. So, when the rubber bands are wound up, the torque is communicated to one of the rear wheels and the car is driven forward.
Provision is made for winding up the rubber band motor at the front end. This could be achieved in a number of ways, but the method illustrated is simple and effective. It consists of a grooved wooden pulleyâ€” maple preferredâ€”attached rigidly to the front stub axle. A length of light weight sash-cord is passed around the pulley. One end of the sash-cord is led to a long coiled spring on the under side of the top. A spring from an old shade roller is recommended at this point. The other end of the rope is led to a point convenient to the rider. By pulling upon this end, the rope is “snubbed” on the pulley and the pulley is turned, winding up the rubber bands. A ratchet and pawl prevents back-turning. When the rope is released by the operator, the spring pulls it back to get a new grip. This is the same principle as employed on a ship’s capstan. This car is capable of traveling 200 yards on one full winding.
It is probable that any boy building this car will use his old coaster wagon for the purpose. Since coaster wagons vary in their construction, it is impossible to give exact dimensions that will convert the coaster wagon into a Flivver-car, so the blueprint is offered to suggest a simple and satisfactory way to make the conversion. The dimensions given are most suitable to a car with 12″ wheels.
To apply a rubber band motor, a Flivver-car must be much longer than the usual coaster wagon. It should be at least 56″ between center-lines of axles. This means that the top must be about. 72″ long. A suitable design for the top is shown. Soft wood, white pine particularly, is recommended. The width of the top is 18″ but it need not be in one piece. 3/4″ is ample thickness. The top is screwed to the axle brackets with long stout screws.
The first axle assembly is in two pieces. Oak is recommended for these parts. The top piece is recessed on the front side to receive the ball race of an old Ford front wheel bearing. Ford bearings can be picked up at a junk-yard or can be bought new very cheap. The wheel axle is set in a groove on the lower side of the bottom piece. Slender wood screws will hold it in place. A length of 3/8″ rod 18″ long, threaded at both ends, will serve as a wheel axle. The hubs of the wheels may require other than 3/8″ rod, but 3/8″ is the standard on most coaster wagons.
A pivot bolt cannot pass completely through the two pieces, so a lag-screw and washers are used instead. It is necessary to drill a pilot hole for the screw, but care should be taken that the lag-screw screws in very tightly. A steering handle bracket is attached to the lower piece as with any coaster wagon. ,The upper piece should be braced to the top. Dime store shelf brackets will serve as braces.
Rear Axle Bracket
The rear axle bracket must be cut out as shown to receive the rear end of the rubber band motor assembly and the big bevel gear. The wheel axle is of 1/2″ round rod turned down at the ends to 3/8″ to receive the wheels. The wheel nut on the right side is drawn up tightly to hold the wheel rigidly on the axle. On the left side the lock-nuts are adjusted so that the wheel turns freely on the axle. The axle turns in bushings made of brass pipe clamped in a groove on the underside of the axle bracket. The clamp serves also as a brace. The gear is pinned to the axle with a small taper pin. A spacing sleeve between the frame of the rubber band motor and the bevel gear holds the gear in a fixed position and maintains a. perfect line-up of the gears.
Rather than building the rubber-band motor to fit the car, it is better to build the car to fit the motor, so the dimensions and design given can be followed closely for any car. The group of drawings should make the construction obvious. The main frame must be made of fairly heavy stock to prevent buckling. When the rubber bands are wound up tightly, several hundred pounds pressure is exerted against the stub axles. It is because of this excessive end thrust that ball bearings must be used. The cone of a Ford wheel bearing will have to be bushed to fit the 1/2″ stub axle. A 1/2″ pipe nipple, with a little filing, will serve as a bush. The grooved maple pulley is held firmly to the stub axle by drawing up the end nut tightly. The ratchet wheel can be made from a disk of soft steel. The ratchet teeth can easily be cut with a file.
The acquisition of suitable gears may be a problem. If one lives in a city there is usually a large hardware store which carries a variety of gears in stock, or one can write to a number of manufacturers who carry “stock gears.” The bevel gears of a large breast-drill might be employed. Discarded gears may be picked up in a junk-yard or at a machine shop. With 12″ wheels a gear ratio of 1-1/2 to 1 is recommended but not absolutely essential. A 1 to 1 ratio can be used with 8″ or 10″ wheels. The large gear should be approximately 5″ in diameter.
Different driving results can be had by using more or less rubber bands. The fewer, or the more narrow the bands, the greater number of turns can be had. This results in a longer coast without rewinding. If more and heavier bands are used the car will have more initial power and a quicker get-away, but the power is more quickly expended. A little experimenting by the builder will determine the size and number most suitable to his requirements.