I build "Puffers" (see pics) get motors from
www.surpluscenter.com catalog #10-1564 12 volt $6.99, get a
1"x5/16" pulley for the motor end and a 12" "Swamp Cooler" pulley for the crank shaft end. this will give you the proper puffing speed. do not tighten belt too tight, adjust the belt with an amp meter to load motor to about
1.4 amps or less. The belt should be the most flexable one you can find. If Surplus Center does not have what you need to build a machine then you probably don't need it! They have a free 171 page catalog and one on the web site too.