Sunday, December 6, 2009
First on the agenda, readers may note that our “Recent Comments” feature has disappeared. It was rather peculiar. I was on the phone with someone asking if it was just my machine, which it was, and then he refreshed his screen and it was gone for him too. It turns out that it’s a third party “widget” and I have left a cry for help on their site. We’ll see what happens.
I have recently included an index under the search box. It is very incomplete at this point. It is actually a link to post number 0, so if you find I have a glaring omission you can say so in the “comments.” I will try to periodically delete these comments as I address the issues to which they refer.
I want to clarify something. I have shown a lot of different designs since this site started and one might be tempted to think I am just throwing them out there, to see what sticks, or that every design cancels the one before it. One might think that I am inventing and improving “my system.” This is not exactly true. Actually what I have been doing is trying to verify a “best” suspended track design and finalize its dimensions. My reasoning is that while a PRT provider could go out of business and vehicles may come and go, wear out or be improved piece-by-piece, the track will stay until someone tears it down. We cannot know what technologies or configurations will be desirable or employable in, say, 30 years. (Or how the city’s transportation needs might change) We can, however, create a design that is as flexible as possible. This flexibility can include the ability to accommodate different neighborhood types, vehicle weight classes, speeds, special purpose vehicles, propulsion types, and station types, turning radii and slopes, while being easy to construct, deconstruct, and connect to.
I do not think it is altogether coincidental that the two active PRT platforms run on a road-like surface, which can be used for other vehicles if the projects or companies fail. It is simply insurance for the buyer.
Therefore one of my aims is to provide a track profile that is not entirely incompatible with the various PRT technologies available. I would like to see a track that could be readily adapted by one or more PRT venders, so that the track expense does not represent a total financial and political risk. In this respect I diverge from most would-be providers, who require absolute faith in both their proprietary products and their companies. (Most of which are not scaled for any actual contract) I hate to say it, but this seems extremely naive. Is it any wonder that their proposals don’t carry much currency with those entrusted with the public’s money? We, in America at least, have seen many of our pillars of industry and finance file for bankruptcy in the last couple of years. Do these “companies” actually think that they can scale up to manufacture vehicles, lay track, and manage an untried network all at once? More importantly, do they think they can sell that scenario? There’s a clock named after this kind of optimism.
My approach, again, (43% of this site’s readers sample as new, so I repeat myself with purpose) is this. Standardize the basics. Document consensus. Establish common ground.
Where do the companies promoting bottom-supported PRT fit in with all of this? It is my intention to eventually examine these systems as well, with an eye toward addressing any major shortfalls constructively. (Readers will note that in Post 48 I suggested a way to double the throughput of a small-footprint elevated station for almost no additional expense, for example).
A common pitfall in design stems from starting with a set of assumptions and continuing from there. The more you invest in those initial design assumptions, the less likely you are to consider that, perhaps, you were wrong in the first place. I have invested a good deal of time exploring suspended systems, and almost none with the supported designs. Perhaps my original objections can be easily addressed. How can one tell without actually going back to square one?
Finally, there are a couple of obvious flaws in the classification system I suggested last week. One is the use of the letter “x” for both spacers and to mean “Does not apply.” A minus sign would be seem to be a good alternative. Also, (as pointed out by an alert reader) the term “articulation” is not self-explanatory. It does indeed refer to tilting the cabin with respect to the track to adjust for slopes and curves. Pitch and Roll are aviation terms. In the system I did not allow space for both Pitch AND Roll articulation. This, as you can see, is a work in progress.
Posted by Dan at 2:11 PM