I'm rather new to the field of gear systems, and to the field of RC models to which this case applies. I'm trying to design a system where a single variable speed engine would drive two different propulsion systems (in this case, rows of oars on a model galley). I want to be able to steer the galley by means of differential rowing.
I could use a double differential like in a tank, but it seems unnecessarily complicated, as I don't need to vary the turning radius continuously, in fact I only need three fixed configurations, RC-ed by a selector switch: both sides rowing, left only (turning right), right only (turning left). It could be go up to five if adding neutral turns left and right (the two sides rowing in opposite directions).
A major additional difficulty is the need for synchronization: although it would only minimally affect performance, visually it's quite important to have both sides rowing together when going forward - this is also a point where a double differential would fail, in my understanding.
Can anyone think of a relatively simple gear system to solve this problem?