[KrazyCarl92]

Brian,

I wanted to comment on a couple of factors that influence chain selection that had yet to be mentioned. Others have already hit on items like larger wheel sizes, sprocket size, alignment, tension, etc.

I know that in at least one past year, 2791 has run their drive gearboxes at the corners rather than the middle of the robot. This can be great for making space for a mechanism low down in the middle of the robot, but it also means more tension on one of your chains. Instead of having 1 chain carrying torque to each corner from the center axle, you now have a chain from the gearbox corner carrying the torque for BOTH the center wheel and the far corner wheel. Not sure whether this is in play with this year's bot, but I wanted to mention this.

In 2013 and 2014, Team 20 consciously used #35 chain to reduce part count. The machining resources were certainly more than capable of hitting the tolerances necessary to run #25 chain, but would still require a proper tensioning method, likely including cams and bearing blocks. Instead we chose to directly press our bearings into the 2 x 1 x 1/8" wall tubing and use dead spacing + 0.012" to take advantage of the extra lee-way afforded by #35 chain to reduce complexity and part count. In 2013, this was with 6" AM HiGrip wheels, and in 2014 this was with 4" colsons.

We threw one chain in 2013 at least in part due to a brain fart in design (my bad...) which led to using a half link to get the proper number of chain links.* But with a direct drive center wheel, even that wasn't a big deal and was easily replaced between QF matches. No issues were noticed for 5 events thereafter.

*When doing center spacing for a chain application, design for a C-C distance with an EVEN integer number of links. An odd number means you will be using half-links.