Why doesn't my Finch Robot 1 move straight / turn accurately?

The Finch 1’s tether makes repeatable movements difficult – turns cause the tether to twist, causing a spring force that tends to resist continued turning in the same direction. The tether may also drag on the Finch, causing it to turn slightly when it should move straight. You can minimize the effect of the tether by:

• Driving the Finch 1 on smooth flooring – carpeting will tend to slow down the Finch 1.
• Turning the Finch 1 at slow speeds.
• Using sensors to help the Finch 1 move more accurately, by using cues in its environment. For example, the Finch 1 can follow a light source or a wall.
• Holding the tether overhead while the Finch 1 is moving, as in the photo below (pair programming means 1 student can "walk the Finch" while the other uses the computer :) 

Some variation in motor speed is common, even for industrial grade motors. You may have to “tune” your Finch 1 to get it to move straight. For example, setting one wheel to 100 and the other to 95 may get the Finch 1 to move straight.