My Roamer doesn't do a proper square
Roamer's accuracy can be affected by the surface it is running on. It will never have the sort of precision accuracy of the Valiant Turtle. It would cost a lot more money to get that sort of accuracy.
However it is possible to improve Roamer's accuracy in the following way:
(It is best to adjust it for the suface it is most likely to run on.)
Before drawing with Roamer, you can adjust it for accurate results.
Remember the Roamer cannot move as precisely as a Floor Turtle. If you require geometric precision, you should consider using a Turtle.

Adjusting the Roamer's Accuracy
  1. Fit a pen and pen bracket to the Roamer.
  2. Place the Roamer on a large piece of paper on a flat, level surface.
  3. Switch on the Roamer, clear the memory, program it as follows:
If the circle is like this the wheels should be moved in.
If the circle is like this the wheels should be moved out.
Adjusting the wheels
Note: It is only necessary to adjust the Roamer's wheels once in its lifetime.
  1. Turn the Roamer upside down.
  2. Slacken the screws holding the gearbox, but do not undo them completely.
  3. Move the gearbox as required.
  4. Tighten the screws. Do not over-tighten, as this may damage the plastic.
  5. Draw another circle. If further adjustments are necessary, make them in the same way. The Roamer isn't designed to be a precision drawing instrument so there will always be some inaccuracy.