[rockit science]

We have always used #25 chain for drive systems until last year, when we went with #35. The biggest difference that I can tell is that #35 is much less prone to "jumping off" the sprocket if you get some slack from impact or if it's not optimally aligned. Also, due to the higher stress, #25 tends to stretch more over the life of the robot, requiring more frequent adjustments. A properly designed guide/tension system will negate these issues, but adds complexity to the machine. And just for the record, we've never had a #25 chain break on a drive system. The only drawback that I can see to #35 is the added weight of the chain and sprockets. Since our machines normally come in a good bit underweight (we usually end up adding weight for ballast), this is not a problem for us. Due to the forgiving nature of #35, we plan on using it again this year.