Let's Make Robots!

Dagu rover 5 power supply

Hi, I have already made the start here robot and I am now moving this idea onto the dagu rover 5 robot chassis. When I turn the robot on it moves very slowly I think this is because the motors are designed for 5-7 volts and the 3 AA baterries are just under 5 volts and that there are 4 motors to power. If I use the 6 AA battery holder that comes with the chassis I am guessing I will need to use resistors so that the sharpe IR sensor recieves the correct voltage and not way too much. However, I do not know where to conect the resistors on my picaxe 28 project board. I also dont know whether the resistor array that the start here robot instructions uses already solves this problem. 

If you have any advice I would be pleased to hear it.