[mathking]

I have read a lot of posts, and like that this thread has not turned too heated. So here is my two cents. As a teacher, I don't think using COTS parts necessarily mean students learn any less than they would without them. It is all in how you conduct your design and construction process. We do make use of COTS parts. We also have used chassis we designed and built for 10/14 FRC seasons. We go through a brainstorming - prototyping - testing phase in which we use whatever resources we have at hand to build and test various mechanisms. Once we settle on a basic design, we look for how best to implement it.

For example, last year one of our mentors found a place that was selling some old garage door opener lead screw assemblies. We used these because they were affordable. The students then had to use a combination of calculation and testing to figure out what gear box assembly would be the best to operate it. The calculations showed that we were right on the edge between two and three motors, so we selected a Vexpro gear box that could be used with two or three motors. After a couple of failures we settled on a AndyMark hex hub bored out on one end to accept the lead screw. In the end the kids had a good device and understood its operation well.

I think there is a software analogy to be made here. As techhelpbb pointed out, where kids start today with languages and processing power is amazing compared to where I started (fortran punch cards on an old VAX-11/780). As someone who teaches programming, I also know that my students in general use much better practices in designing programs than I did. Precisely because they are not worried about things like using short variable names to take up less space in memory. I know a number of people who lament that kids learn Java or C++ or Php before learning Assembly. "They need to know how computers really work." But that isn't Assembly, which is really just abstraction at a lower level. "They don't learn how to optimize a program's performance." Wrong. Plain and simple. They still learn about optimizing, but they optimize algorithms and not code. Using prebuilt libraries. Because that is the way they will need to operate when they get jobs. I find that students who learn assembly first tend to write code that is very difficult to read and maintain. It is much easier to teach (and learn) assembly after students have a solid understanding of higher level language.

OK, I am getting a little far afield now. So back to my main point. If you are a mentor and thinking about this question, your students are probably doing fine and learning well. Because the real question isn't whether they build their own gearbox or use one from AndyMark. It's whether they understand what the gearbox does and why you chose it.