Thursday, July 16, 2009
A few posts back I revealed what I consider to be the most logical track design. Notably absent was any description of the drive units that would inhabit this track, so here is what I’ve got. I know that the parts as shown are held together by flimsy, non-braced plates that extend into areas where they do no good, among other issues. It is, however, mostly a drawing to identify and re-route interferences. (Areas where multiple parts are expected to occupy the same space) It is also about as far as I have gotten in “SketchUp”, Google’s free 3D drafting software. It is not ready to post for you, the readers, to work with yet, because I didn’t break it into editable components. This exercise has, however, revealed how stunningly simple the mechanics are, with “wheel-motors” as the propulsion, since there is no need for power transmission. The wheels just turn, with up to 20 hp each.
The system I envision uses the basic eight-wheel architecture of an ordinary railroad car. The first illustration is of one half of a one half, to show the details that would otherwise be hidden. Red arrows indicate the rotary to linear (cam) movement that controls the steering. The second illustration shows how a mirror image assembly completes the (half) unit. The plates in yellow are the structural elements from which a PRT “pod” would hang. It would be suspended between a pair of the double units pictured. Such an architecture would enable very tight station maneuvering in 3D, while distributing weight over a large area, (for the cheapest track) The four-wheel (half) units, as pictured, could be used as is, in factories or distribution centers, or even on the grid, (for light delivery) with weight loads in the 40-170 kg. range.
This final illustration shows a cam mechanism that could be used to alternately raise and lower he steering guide wheels. Two servomotors operate the camshaft jointly, yet either can operate it separately, because of the ratcheting mechanisms. If either motor fails, the unit can operate normally yet the failure is immediately detected by the encoders.