As a part of team 357, I have been working with my team on different variations of Mecanum wheels for the past three seasons. One misconception we have found is that mecanum wheels cannot push or will be pushed very easily. However, we have found that mecanum wheels are good for what they are designed for. For example in 2005 we wanted a fast, highly maneuverable robot. We decided to use mecanum wheel with a fast drive train. Our design worked very well for us ad we were very happy with the results. In 2006, we modified our design to accompany a ten inch wheel, up-sized from our six inch wheel in 2005. By enlarging the wheel we got a much larger contact patch with the ground. As a result we found that we could push many robots, in all directions. In one competition we were able to push one robot, then another at the same time, preventing both from scoring in the upper goal. While mecanum wheels are not usually designed for pushing and are well known for their maneuverability, if they are designed right, and for that purpose they can be pushing force to be reckoned with, as well has having the known maneuverability of traditional mecanum wheels. If you want more more information our team is always glad help at
www.team357.org or you can PM me.