Chain Tension-er?

[MisterG]

We found that flexible sprocket device too and I was wondering if something like that could be 3D printed out of some material that would give a similar effect. Anyone have thoughts about this?

Also from my reading it seems like tensioning addresses at least two separate factors. The first is making the chain the correct length for the application. This can also be solved with careful design and manufacturing. The second is compensating for chain stretch. Which of these sounds like the bigger factor for an application like a drive train?