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Next, we attached the bearing flat on the inner drive C-channel using one zip tie. That’s because the screw joint will also help to secure the bearing flat in.
After that, we found the best spacing for the screw joint. We used washers on both inside edges to reduce friction, and keps nuts to hold the screw joint in place.
Here’s how it looks when it’s all put together:
Before we could add the bearing flats, we had to shave down the corner of a few so they wouldn’t hit the motor caps. We used a sandpaper attachment on a Dremel and cut the corners like so:
Then, we attached all of the bearing flats on the inside of the drive using zip ties. The shaved upper corners of the bearing flats are circled in green.
Next, we attached the three motor caps using 0.25” locking screws:
Then, we added the rest of the wheels using the same screw joint:
Next, we mounted the bearing flats for the motor axles, using zip ties to save weight.
After that, we found the best spacing for the motor axles. Again, we used washers to reduce friction. The shaft is 3” long, and fits perfectly into the motor without sticking out past the bearing flat.
And with that, the left side of the drivetrain is complete!
We made the right side in the exact same way, except mirrored. To attach the back cross-brace, we boxed the back hole of the C-channel and attached it to a 1” standoff going up. The boxing adds extra stability and prevents the C-channel from bending.
We attached the rest of the cross-brace in the same manner, like so:
Finally, we added the front cross-brace using 0.25” locking screws and eight ½” standoffs. Two cross-braces greatly increases the stability of the drivetrain, and prevents it from bending over time.
With that, the drivetrain is complete!
Motors
Vroom Vroom
Motors are an essential part of VEX Robotics, as they convert the chemical energy stored in the battery into usable mechanical energy. There are two types of motors: 11-watt (11W) and 5.5-watt (5.5W) motors.
11W motors
Specifications:
* Power: 11 Watts
* Torque: 2.1 N⋅m
* Weight: 0.342 lbs or 155 grams
​ ​
5.5W motors
Specifications:
* Power: 5.5 Watts
* Torque: 1.3 N⋅m
* Weight: 0.20 lbs or 91 grams
​ ​
Each robot is allowed 88W of motor power total. Here's a table showing some possible combinations of motors that can be used on the robot:
# 11W motors
# 5.5W motors
8
0
7
2
6
4
...
...
Motor Cartridges
There are three types of motor cartridges for the 11W motors. Each one spins at a different RPM as shown below:
Hot Swapping
Hot swapping allows teams to change out broken or overheated motors for good ones without having to unscrew the motor cap (an arduous process). Hot swappable motors have rubber bands that keep the motor body secured to the motor. To make a motor hot swappable, remove the four screws that keep the motor cap secured to the motor body. Then, wrap two rubber bands around the motor as shown in the picture below. Make sure the motor is securely in place, and replace the rubber bands regularly.
Example hot swap
Metal
Structural stuffs
The basic structure of every VEX robot uses metal. Specifically, aluminum C-channels are used to construct the chassis and other mechanisms on the robot. These C-channels are relatively lightweight, yet still are very resistant to deformation under stress.
Standard 1x2x1x25 C-channel
Here's a few other types of metal structure available:
5-wide C-channel
2x2 L-channel
3-wide C-channel
However, sometimes a C-channel is overkill for applications on a robot. By cutting a C-channel in half (the long way), you can form 1-by L-channels like the following:
These L-channels are good for areas of the robot that aren't under a lot of stress. That's because they're very light, but also less robust than a C-channel.
However, teams have innovated ways to use other metal pieces for support. For example, high strength shafts are exceptionally durable and highly resistant to bending. They can be attached using the shaft collars or by drilling holes through the shaft.