[scottydoh]

The short answer is yes. With out seeing your actual set up its hard to judge, but it sounds like you're driving an arm with said chain. That makes me assume its is a considerably long run of chain, and you will most certainly need a tensioner to assure the chain does not skip teeth as it stretches. As for which style is better, I'd say a traditional tensioner is probably better because if you have the drive motor pivot, it might loosen as the motor torques when its running.

Edit: You can also just use a block of delrin or a similar material just pushing against the chain...Andy Mark also sells a tensioner that rubber bands pieces of plastic around the chain.