There are two fundamental ways to wire up an electric twin system to the propulsion battery pack: in parallel and in series.
Example: Suppose you have a hot cobalt motor that draws 30 amps on 6 cells. Wired in parallel to a 6 cell pack, two similar motors will draw 60 amps from the pack! This will run a typical 1400 mAH pack dry in 90 seconds! This strains the wiring and the poor nicad pack beyond sensibility. For this reason, parallel-wired setups are not often seen - but for motors that draw less than 10 amps (like the increasingly popular and cheap Speed 400 motors), this is an especially attractive choice.
Example: With the same cobalt motor as in the previous example, we would hook up our two motors to each other, and then to a 12 cell nicad pack. The current draw from the battery pack would be 30 amps. As you can see, there's no free lunch - either we drain the same number of batteries twice as fast (as in parallel-wiring), or we need twice as many cells (as in series-wiring). Make sense?
Tempted yet? Have I mentioned that those Speed 400 motors only cost about $15 each? Get out those B-17 and P-38 plans you've been drooling over! ...And continuing next month, we'll explore how to build two- and four-engined models for successful, enjoyable flight, using some popular kits as real examples. Also on deck is an autogyro article I think you'll enjoy...
Until then... Give me your Swap Shop advertisements, comments, article submissions; support your local hobby shops, avoid CA-ing your fingers together, and stay out of the puckerbrush. Happy quiet landings, everyone...