It’s possible, but besides decreasing the speed of the motor, the gearbox also multiplies its torque. Finding a motor with enough torque to reliably drive the vehicle without using a gearbox could be difficult.dudeincolorado wrote:Is it possible to build an EV with out gearboxes?
Belt drive is one alternative to a gearbox. One can be made by connecting a pulley on the motor to another pulley on the drive axle/wheel with a rubber band or large o-ring. I have seen designs where the tire was removed from the wheel and the o-ring/rubber band placed around the wheel. The wheel served as a pulley and the o-ring served as both the tire and the drive belt. When used in this manner, the pulleys are actually a form of gear system. Using a smaller pulley on the motor than on the drive axle creates a mechanical advantage that reduces the vehicle's speed and increases the available torque. The mechanical advantage produced is equal to the ratio of the diameters of the motor pulley and the drive axle pulley. It can also be calculated using the radius or circumference of the pulleys.
MA = Diameter(Drive Pulley)/Diameter(Motor Pulley)
Or
MA = Radius(Drive Pulley)/Radius(Motor Pulley)
MA = Circumference(Drive Pulley)/Circumference(Motor Pulley)
I have always found it difficult to produce reliable results with this method, but I have seen others that were quite successful.
One of the most interesting gear boxes I've seen was made using gears salvaged from a $3 wind-up alarm clock. I haven't checked recently, but I think they may still be available at places like K-Mart & Target's.
Gearboxes can be salvaged from almost any battery-operated, motor driven device. Re-chargeable screwdrivers are an especially good source. The motor is designed to produce high torque from a low voltage (2, 3 or 4 rechargeable cells to provide 2.4, 3.6 or 4.8 volts). A high current source is necessary for getting the most torque they can provide. The higher internal resistance of heavy duty and alkaline cells may prevent them from sourcing the necessary current. You will probably need to use some form of secondary (rechargeable) cells.
A couple of other items I have seen used are: A rear axle assembly (including motor and battery box) from a $5 radio controlled car, a battery operated TOY screwdriver. In one case a whole battery operated car with one of the rear tires removed was mounted on the vehicle. A large rubber band was used as a belt to connect this wheel to the drive wheel of the vehicle.
You may be able to get more ideas by looking closely at the Battery Buggy photos in the photo gallery.