[Andrew Schreiber]

Allow me to share two stories, one from work and the other from robots.

At work part of my job involved finding a way to provide support to users of a product. Being competent programmers we could have written a custom application to handle this for us. Being smart programmers we realized that searching for COTS solution that met most of our needs was a much better use of our time and resources.

In robotics I often have the need to reduce the speed of a motor. In 2011 I needed to reduce the FP motor to a reasonable speed. To do this I could have built a custom transmission but I determined that using the COTS transmission designed for the motor by people much smarter than I was a better idea. Instead we took some time to figure out a good way of interfacing with it. Was this an 80% solution? Absolutely!

Point is, in engineering, if you can find a COTS product that meets most of your needs you can save yourself a lot of work. Am I capable of producing custom transmissions? Yup, but I'd much rather spend a little extra money and buy one than dedicate the hours to developing one.

Another data point for you, if you decide to order mecanum wheels (or any COTS part) you can order them before season and have them on the shelf as long as you don't assemble them. For international teams this might not be a terrible idea as shipping times tend to be long. If you decide to make your own you cannot produce the ones you run on your competition robot until the season starts.