RE: Electric Jackscrew
Jay,
Can't get much info from either a 6V or a 3.6 V motor. Torque available to the load is motor torque multipled by the gear ratio less friction. If you don't have torque specs, I'd use the 3.6V motor because if I needed more power it would be readily available using 4.8 or 6 volt packs. Also another consideration is how often is this going to be cycling? If often, battery life might be paramount, then lower current draw would be a priority. Lower draw would result from higher gear ratios on the jackscrew at the expense of slow actuation times. Everything is a compromise.
Have fun,
john