In my article, A Power Functions Primer, I discussed using Power Functions with trains and gave an example of a geared bogie that could replace a 9v motor. It works well, and I'll continue to use the design, but it is far too big to use on small locomotives, especially small steam engines with even smaller tenders. What we need is a much more compact geared bogie.
Well, over the past few days, I, along with a bunch of other Flickr users, have been trying to come up with just such a compact truck, a "minitruck". Ideas went back and forth, and finally, between user Shuppiluliumas and myself I believe we've finally come up with a design that works. I call it - the "Sava-Shupp Minitruck".
He calls it the "Shupp-Sava Minitruck", but I'm the one writing this blog entry, so there!
A note on the design - the horizontal 12-toothed gear on top would be attached to the rest of the truck via a 2x6 technic plate and a technic axle (not shown to reveal the rest of the design).