Insert video of the final product
This robot is designed around the concept of drifting. It's a fun project if you're bored and want to make something similar to an RC car. This robot was built using VEX Robotics parts , although any pieces of aluminum or any material will work, and RobotC programming.
Step 1: Materials
x2 Aluminum works the best (between 7-17 inches)
x2 optional aluminum pieces for more stability
x3 omni wheels
gears of different sizes
motors ( I used 3)
Vex cortex or any other platform for powering motors
Step 2: Make the Base
The base should be two pieces of aluminum that are held together by the Vex cortex or whatever platform you are using to power to motors (an Arduino would also work, but I am not going to go over the coding for that).
A few metal pieces can be used to make the attachments more sturdy. A piece of metal can be placed perpendicular to the 2 parallel pieces and bolts down to make the structure less flimsy. Keep in mind that the axles and lock nuts will be the major structure that holds the robot together.
Step 3: The Fundamentals of Compound Gearing
Compound gearing is a simple way to increase the gear ratio without using massive gears. In this example, we will be gearing for speed. A typical speed gear ratio goes from big to small. This means that one rotation of the big gear will be many for the small gear. This will cause the small gear to spin very fast. If another gear was put on the same axle as the small one, the center would be spinning at the same speed. This works because the small gear spins the axle that it is attached to which causes the bigger gear on the same axle to spin at the same rotational speed. The only disadvantage to having a lot of speed is the reduction in torque which will cause the robot to either not move or start up slowly.
This system works by going from a gear gear to a small gear and having big gear on the same axle as the small gear which goes to a small gear... etc.
To calculate the gear ratio, you multiply all of the gear ratios together. For example, if you have a 3:1 gear ratio with a 3:1 gear ratio compound geared, you will have a 9:1 gear ratio.
Step 4: Gearing and Spacing
This is the most annoying step in the entire process and will easily take the most amount of time. In this step, you must find out where to place the axles to hold the gears. Once the axles are placed in an area where the gears will hit, you must add spacers so that the gears do not slide around everywhere.
The gearing must start at the motors that are powering the first axle. From there the gearing must go back to the last axle that is attached to the driving wheels. I chose to do a rear wheel drive for maximum drifting capabilities.
Step 5: Put the Wheels On
As you can see from the picture, the front wheel needs to be mounted differently than the other wheels. I had to get a perpendicular piece of aluminum to hook up a wheel that is perpendicular to the other wheels. This will still work because the omni wheels are made up of mini wheels, so when the back wheels push it forward, the front wheel doesn't affect the drive. Once the wheel is attached, the motor can be placed on the axle and secured.
The omni wheels can be seen above.
Step 6: Programming
For the programming, one of the drive motors will be reversed. This is because one of the motors has a 1:1 gear ratio to the other drive motor's axle. The motor will have to be reversed because every gear change that happens, the motors will be reversed. The picture is how I programmed it on Robotc.
The picture shows my program on Robotc. One joystick drives the robot forward and backward. The other joystick turns a wheel on the front of the robot that steers the bot.
Step 7: Final Product
Once you hook up the battery into the cortex and wire the motors into the cortex, you should be ready to go.