Let's Make Robots!

identical motors, different speed

Hi all, I have 6 identical motors, or so I thought until I powered them all on at the same time for the first time and realised they all spin at different speeds.


Has anyone else observed similar behaviour either when using multiple identical motors, and/or when using the Arduino Motor Shield?  


I am using the Arduino Ethernet + Motor Shield rev3, with 3 motors connected in parallel to Channel A and 3 motors connected in parallel to Channel B. Each motor is connected to a wheel.

Wheel specialist

Hi, does anyone know of an online store specialising in wheels?

I mean really specialising in wheels?

I'm getting picky: I've been planning my robot for several months, and have calculated my exact requirements and I know exactly what I want - a wheel with tire, 80mm in diameter, must support approx 7.5kg in weight (so need to be quite wide) and I want gnarly/chunky off-road tyres, though my robot will be indoor-based, they must fit a 6mm motor shaft.