13> A Mid-afternoon Dream

I was sitting in traffic the other day behind a Wal-Mart truck. We both were creeping along together, both going to the same place. Actually I was going to Northern Tool, but still in the same “mixed use” retail area, kind of a mall of sorts, but with no coordination and lots and lots of traffic. The fact is that 75% of that traffic was bound for one of the many sprawling parking lots in this area. It occurred to me that Wal-Mart had two problems. First it was burning Petro-dollars, engine life and driver salary trying to make a delivery, and second, the traffic Wal-Mart alone generates tends to keep potential customers away. If there was a place I could park my car, grab a PRT and be dropped at their front door, I might just stop in for a six-pack of socks. But what if delivery pod cars brought those socks right into the building, maybe right to the correct aisle from a warehouse that also was fitted with indoor PRT style track? Well for one thing, out of stock items could be replaced in a matter of minutes, even during rush hour. And Wal-Mart would be the king of “green.” (environmentally AND cash wise) Now the big question. What would Wal-Mart pay? Would they buy or share track? Contract for rights of usage? Subsidize a station? And what about McDonalds? (Hmmm… refrigerated pod cars. Now there’s a thought.) Can you imagine NOT having a station just down from Wal-Mart? And what about the other merchants? I could see an area I like this becoming a much more attractive destination because of PRT. And wouldn’t a track going to the nearest high density residential area be a logical next step?

This is one reason I believe that “pods just gotta hang.” They are much more parking lot and warehouse friendly. It is also why I now believe reverse is a must for any standardized drive unit. PRT is only as useful as the network of tracks is extensive. Finding uses other than public transit and adding alternative sources of funding can only be a good thing.

12> Station Safety and Sinking Santa

First of all, I wish to thank alert readers timote and Dave Smith (TO?) for their valuable contributions. (Also Transportation Enthusiast, who I have since witnessed eloquently correcting a (less-than-enlightened) anti-PRT blog.
The question of collisions at the loading zone/station is a very real one. I had originally imagined “pods” as being very small, probably just 2 seaters, as the idea of building miles of track gauged for third and forth passengers, which statistically don’t exist seemed wasteful in terms of steel, and would make the track and supports thicker and therefore more visually intrusive. There is also the matter of safety, as heavy objects obviously carry more inertia, particularly at cruising speed. At the time, however, I hadn’t given much thought to light freight usages nor traffic density control. My current thinking is that the possibility of freight delivery could be lucrative. As I have written in a soon to be published post, delivery in gridlock is an expensive fact of life for many companies. These entities might have some influence towards PRT adoption. For them bigger is better. Also claustrophobia is an issue with some people, and a little extra space and larger windows would help. Personally, a port-holed coffin sized pod is fine for me, but I’m not your average person. Anyway, as for collisions at stations, I had always thought of a total load (pod, motor, and payload) of less than 750 lbs, traveling at walking speed. This is probably one half of the actual weight I’m comptemplating now, although I am still for excluding four “large” adults. So the question is, “how slow would a (beeping) object of, say 1500 lbs. have to move to not require an expensive station infrastructure?”
My guess mix is 10 ft. per 20 seconds, with striped pavement, possibly cordoned off with chains, a low to medium volume beep-alert, and tilt/bumper sensors on the pod, so that it will cut power if it hits an obstruction that can’t be pushed with just a few pounds.
Part of the reason that open-source PRT is superior to waiting for a company to sell us the solution is that the safety decisions don’t require the overkill that we would want from a corporation whose decisions are primarily profit-based. Certain risks are assumed to exist. Sidewalks are more dangerous because they’re close to streets. So what? I have yet to see the lawsuit requiring cities to move them or demanding damages. Trains and subways and buses and, yes, PRT can’t stop on a dime. But safety parameters designed by a non-profit open-standards organization are not particularly tasty bait for litigation, and PRT could get very slow as it descends.
Finally, Happy holidays! Here is a depiction of me Photoshopped into a Santa Claus photo that went on to consider the ramifications of global warming on the Santa’s base of operations. Imagine Santa’s waterfront property. And the cats? Hey, Everyone loves cute kittens…

11> Personal Rapid Transit Drive Unit

Here is a sample drive unit. I have left off the track-switching units for clarity. There would be one on each end. (I don’t say “front” or “back” because the unit can move forward or backward equally) I know that my earlier renderings show a “car” with a front and back, but I have evolved my thinking. Notice how the vehicle weight pinches the track between the wheels. Most of the complexity is due to need for sharply turning track, both vertically and horizontally. Note the dual motors. This is because with the unit hinging in the middle the power transmission would be extremely complicated. Also note the offset bearings, which enable dimensional changes. Furthermore, because I envision brushless motors, (RPM is externally controlled and very precise) they may work reliably in tandem. Brushless motors are commoditized products anyway, and this adds a level of redundancy. Furthermore, it occurs to me that half of this unit could be used for light parcel or mail delivery. If six-wheel drive seems a bit excessive, remember that the wheels, being long wearing solid hard rubber, do not have the traction of pneumatic tires. That is just as well, as this design has no differential gears. I envision a track insert designed for slight slippage on curves.

10> A Couple of Issues

I need to address a couple of issues. First the matter of getting exposure. As I Google “PRT” I find that this acronym stands for more than Personal Rapid Transit, or Personal Rail Transit. I find this blog is nowhere to be found. But then again, did I even say “Personal Rapid Transit” in previous musings? If I say “Personal Rapid Transit” again and again, will it come up in a search? PERSONAL RAPID TRANSIT! PERSONAL RAPID TRANSIT!

Now on to other business. So far I have rejected the notion that “pods” sit on top of a track… Well my opinions go way further than that. So here’s a little something to chew on..

1. Cars shouldn’t be just one size. They should be sized and in quantities based on need.
2. Cars shouldn’t just carry passengers. They should carry parcels as well.
3. Cars shouldn’t just go one way…(on each track) Why not go both ways? It would be handy when backing out of private property, good for third lane options where the third lane flows tward the city in the morning, and away from the city at quitting time.
4. I believe that vehicles can go both ways on larger streets. (The “one way” assumption seems to be based on problems making tight turns, spacing of cars, making elevated stations, and other issues connected with cars that ride above the track. I believe that PRT could share stops with buses, on both sides of the street.
5. Unlike previous models, I believe cars should be spaced dynamically, based on weight and speed. I do not think this is too complicated for present technology.

I think cars should be able be able to ascend and descend very steeply, even if the means is external. (roller coasters are easily and reliably grappled and lifted, so why not PRT vehicles?) They should also be able to turn (right, left, up, down) very tightly. This is just common sense, because the system should be as versatile as possible, and that should include track that can be constrained to placement over existing easements.

9> SWITCHING TRACKS

Here is a sample switching system that requires no moving track parts. In reality, the track would be pinched between upper and lower wheels, as in the previously posted pencil rendering, but the lower wheels are not shown here. The wheels should be solid and of a hard rubber-like material. Multiple drive wheels overcome the traction deficit inherent in these solid tires.

8> No eyeballs, No Surrender

So far my blog seems to be lost in the sea of others. I have had only a single comment so far, and I thank that reader for his observation. I have made several renderings, both because I believe in the hanging vehicle concept and because I had hoped that having the images online would bring people to the site, via Google’s image search feature. As far as my belief in an open source PRT design is concerned, it remains undiminished, although I have to admit that my compulsion to re-examine the design fundamentals of PRT may be a bit unusual. This is not the first time I have tried to “re-invent the wheel.” But then again, I am an inventor, and I guess that’s just what guys like me do…So this is what I am going to do next. First, I want to re-examine the definitions and assumptions surrounding PRT, or rather give the reader that chance, for I already have my own opinions. Next, I will re-invent PRT piece by piece. If I am speaking to a vacuum, so be it. I will do it anyway, because sooner of later I will be heard, and I might as well have a body of work on record. Anyway, one thing I was considering was how any reader, even if he/she was a closet engineer, could post design ideas. I tried drawing a design idea on paper, to see how well it could be digitized with a simple digital camera. Here is that effort, from a Sony Cybershot camera. I am not sure if Google compacts the images or not, but they seem to come out pretty well. For anyone who hasn’t tried it, clicking any picture on this blog enlarges it.