Gearbox/ Dual Motor Setup

[Tristan Lall]

If you look closely at the above picture, you'll notice the chains being used to reduce the output from the motor are connected to a small sprocket on the shaft of the motor itself. There are three possible problems that might crop up with this arrangement.
Having such a small sprocket on that chain limits the maximum power it can reliably transfer. This was part of the reason that Blizzard 4 suffered several chain failures during the season. (Our drive sprocket was too small--25-pitch, 20-tooth.) Linked here is a (13 MB) reference that contains charts of maximum power for various sizes of chain (in terms of rotational speed and size of sprocket). These start on page A-6 (or 17 in Acrobat).
Related to Blizzard 4's chain troubles, there doesn't seem to be any idler system on that chain. While this can work (and has worked on many robots), the lack of an idler can put you at greater risk of chain slippage. If the chain isn't exactly the right size, you might find yourself missing a chain at an inopportune moment (and with chain, "exactly" isn't always a plus/minus one link situation).
Lastly, watch for the possibility of side loads on that motor. Some motors are more tolerant of this than others, depending on the way that their shafts are mounted in their bodies, and whether or not they incorporate internal gearheads. In general, a load (such as that introduced by an over-tightened chain) will tend to wear the motor at a significantly increased rate. (You might remember the warnings to never subject the Globe motors to a large side load, for this reason.)