Maintaining the TinySurveyor wheels

TinySurveyor has three wheels: one caster wheel at the front and two motor wheels at the rear. Make
sure that these wheels fulfil the guidelines listed here at all times.

• The caster wheel is fixed with two bolts. One bolt fixes the wheel to the aluminum frame, the other
  fixes the wheel itself. Make sure that you sufficiently tighten both bolts before operating
  TinySurveyor. The air pressure of the caster wheel must be 36 PSl/250 kPa/2.5 bar.
• Each motor wheel is fixed using two MlS nuts. Make sure that you tighten all four nuts with 30 Nm
  before operating TinySurveyor. Use a thread locking fluid to lock the nuts properly.
  Both motor wheels must be aligned with the vertical plane. The air pressure of the motor wheels must be 35 PSl/240 kPa/2.4 bar.