Sunday, January 31, 2010
Here is a little project that is still under development. I would have preferred to have solved all of the problems with it before posting, but I have had precious little time to devote to my PRT “hobby” lately, so I’ll go with what I’ve got.
The design is inspired by a very innovative aspect of the MISTER system as shown most clearly near the end of this video, Mister not only doesn’t require switches in the usual railroad sense, it doesn’t even need the connecting track to touch the main line. One great aspect of this scheme is that it gives remarkable flexibility in routing, even after a line is finished, because a branch can be added with little or no disruption to the existing track.
While I have taken a general track design approach that is much more similar to the designs worked out by PRT pioneer Dr. J. E. Anderson, (but turned upside down) I still wanted to maintain the possibility of track that could be added to with minimal disruption. The bogie designs I have been working on all share the quality of being able to completely support a PRT vehicle from either their left or right sides, like the MISTER system. I cannot claim the ability to add a switching point without any service interruption whatsoever, but the track shown may have either side removed and still be functional, if supported properly. Sections of such track could be used at points where future expansion plans might require branching. This would include entrance and exit points for sites of possible future stations. The trick, design-wise, is to build a box beam with the bottom element removed, without greatly weakening the structure. The main trusses must remain parallel to each other and square to the overall structure, yet removable.
The use of turnbuckles (shown below) evolved from a realization that the chances of getting this thing to fit together while hanging it from a crane were pretty close to zero, yet I had wanted cross members to stiffen those areas of the structure. In theory the turnbuckles could bend the plates enough to get the assembly started, exerting forces shown by the arrows. They then could be loosened, the plates bolted, and then retightened.
After assembly the cross bracing is continuous, as shown below.
I now believe the better course would be to have rigid bracing with permanently angled plates, but that involves a total redraw, and this series of pictures illustrates the general idea well enough, I think. I would also note that most designs can be greatly simplified after some careful study, but this project has not reached that stage.