The instructions for the base robot in the 9797 LEGO NXT Education Kit is the best stating point for students. It allows for the most customization with arms, attachments, and sensors and the instructions come with each kit. There are a few very common mistakes made by students and adults alike while building the base robot, these mistakes prevent the robot from working correctly.
The instructions are not very clear which pinhole on the smaller piece is to be attached to the larger piece
This is the common incorrect way students will complete step 6, if the robot is built this way the NXT brick will be loose and the base of the robot will have to be bent in order to fit, bending some of the beam pieces.
This is the proper way to complete step 6, as you can see the pin goes the corner pin hole on the smaller piece. Also the axel connects with the small L piece, which will hold the NXT brick steady.
In Step 8 the students make a second motor piece which is supposed to mirror the first and attach to it. Often times students will make the second motor identical to the first, with the axel sticking out the same direction. This makes it impossible for the motors to attach to each other, which is very frustrating for students.
This issue has an easy fix as soon as the student realizes the motor should mirror the other, just redo the sub steps 1, 2 and 3 in step 8.
A properly completed step 8.
Step 12 is divided up into 5 sub steps, which build the swiveling back wheel of the robot. the wheel has 2 small L pieces and the pieces shown above, students will often instinctively place the axel through the axel shaped hole, resulting in pieces like this. the correct way to complete substep 3 is with the pin hole have the axel go through it and the axel holes showing. As seen below.
Without the axel holes to hold the swiveling axel the back wheel will just fall right off.
Another common mistake in Step 12 is to build the back wheel like this with the axel sticking out further away from the wheel. This cause the robot to move awkwardly as the back wheel cannot turn as widely as when the step is done correctly.
A properly completed step 12