27> Designing For The U.S. Market

One thing I need to express is that, as an American, I cannot help but design for the U.S. market. Back in the 50s, then President Eisenhower spearheaded the construction of the U.S. interstate “super” highway system, and state and local governments quickly followed suit. By the late sixties suburban communities were popping up like weeds far from city centers, because without traffic lights and driveways greater distances were now commutable.

Fast-forward a generation and we have the great American suburban sprawl. Instead of a single “downtown” there might be ten. There are few pedestrians, because nothing is within walking distance. Traffic is not just confined to one direction. It is everywhere and may be worse thirty minutes from downtown than downtown itself.

Such a situation demands something much more ambitious than the little projects that the world has seen so far. It requires thousands of kilometers/miles of rail per city and speeds that are consistent with long commutes.

Obviously, no project can start on such a grand scale, but I believe any system that has a chance of adoption in the U.S. must be scalable to meet these needs. That means the cheapest possible track, the cheapest possible stations, and the fastest possible vehicles, designed for rides up to thirty minutes. That means a smooth ride is a must. The system, including stations, must have a minimal footprint. The station design, for example, promoted by the MISTER system is great, but only for about 10% of the stations, because, as I have said, there are no pedestrians. The sidewalks are empty but the streets are full.

Going fast means banking on corners or slowing for them, or clipping them (buying right-of –way) for larger radius turns. Banking track means more expense, complex engineering, and more specialization is required of the track builder. Perhaps there is a simple track design to do this but I have (so far)opted for the self-banking gondola design to address this issue. I am also inclined toward adaptable vehicle speed architecture rather than a set cruising speed. Empty vehicles should be very fast, traffic permitting, since there is nobody on board to get motion sick.

The U.S. transportation system is broken and needs to be fixed, and no little downtown “people mover” project is going to change that fact, just like light rail won’t nor will more buses, but that’s for a different post.

Finally, a question for my readers – In those systems with linear motors, what are the provisions for a power interruption? I was surprised to find that In the Taxi 2000 design they envisioned special “tow truck” type vehicles. Any thoughts on stranded passenger protocol?

26> Linear Induction Motor Tractor Unit

Here is a simple conceptual drawing of how Linear Inductions Motors (LIM) could be employed in a tractor unit for a gondola style Personal Rapid Transit (PRT) vehicle. Shown is a simplified track encasement, without outside structural support. The 3.2mm (1/8”) gap between is maintained by making internal rails (shown in orange) and the reactor plate (blue/green) both setscrew adjustable. With tight radius turns, the gap will be uneven and perhaps somewhat larger, but this diminished power and efficiency will not materially affect performance. By having two units in tandem closer gaps can be maintained. This design is compatible with the switching protocol illustrated earlier. The LIMS on one side must be turned off during switching, so the pod cannot accelerate strongly through the switching process. There are four LIMs. The proportions shown are consistent with the (Baldor) # LMAC16123D99. (12”x16”) (30.4 x 40.6 cm)

The performance of each are as follows. Each weighs 105 lbs. (48kg) and can produce up to 190 lbs. (845N) of pull (15% duty) and 38lbs. (169N) continuous. That’s a total of 760lbs. (3380N) max total, and 152 lbs. (676N) of continuous pull. The motors (total) weigh 420lbs. (190.5 kg)

The downside is this. These figures are for 60 Hz, 460 volt, 3 phase current. The maximum velocity for these LIMS at 60 Hz. is only about 15 mph. It is unclear how much pull would be sacrificed for additional speed, which is achieved by increasing the frequency of the AC current beyond 60 Hz.

Most past models for PRT have assumed speeds of about 30 mph. (48 kph) That may be fine for short haul downtown environments, but that’s where trolleys, shuttles and even light rail are most competitive. The urban/suburban sprawl typical of many cities (especially American) requires considerably more speed because of the distances involved.

25> Just Some Thoughts...

Here’s a bunch of loose ends.

It worries me that my blog is not that friendly to newcomers. It makes more sense to start from the beginning, which gets more buried with time. I am considering starting a general PRT advocacy blog to feed potential contributors,
I really don’t know what I will do if and when I get some volunteer engineers working on this. I don’t have Autocad, nor any web based design collaboration software. I’ve been told I should start a Wiki.

I’d like to thank Mr. Grant for another “to the point” link. This MISTER FAQ sheet also sights a design issue that I had raised earlier, that being the question of climbing steep slopes with a minimum of available onboard power. It seems they have opted for an external motor, the concept I took to the extreme in my post about raising a vehicle vertically.

I really have to say that there seems to be precious little difference between what I envision and the MISTER or Beamways systems. When I started this blog I was unaware of either. Simply getting a serious discussion about putting the track on top was reason enough to start the blog. I have since become more aware of the degree of consensus on most issues. In reviewing the rejection of the OKI project (Taxi 2000) I am struck by how just a few decisions did them in, particularly too big a turning radius, too big a track too low, too expensive, too proprietary, too unproven. I would like to change that type of outcome. A lot of the problem was the “single source” part. The transit people wanted independently verifiable proof. They wanted a 25 million dollar study. Why not? After all, a big corporation, (Raytheon) was trying to sell them a 45 million dollar, unproven product. Now what if, for example, there were five companies bidding on the track, three on the cars, four on the control system…(you get the idea) If all these people thought that they could provide THEIR parts for a given price and they would perform as advertised, wouldn’t the customer feel a bit more secure? This is not to discount the idea of a primary contactor, but rather the contractor that wants to provide ALL of the solutions “in house.” If the contractor proves inept, the transit authority is left with mud on its face. No, this hurdle, in the U.S., anyway, needs to be approached with a good deal more tact than that. I submit that this is more about pschycology than technology. It’s about public awareness, enthusiasm. It’s framing the issue. It’s politics. Anybody checked out the X prize site lately?

Lastly, about LIMs (linear induction motors) Does anyone have any links to manufacturers besides this (Baldor) site? After comparing torque, weight and frame style specs for various (rotary) motors, I have become a bit disillusioned, especially with the torque/weight ratio. It turns out that the Baldor LIMS compare a bit more favorably than I would have expected. Anyway, I’m toying with designs.

24> One Little problem.....

There is a problem that I have yet to solve with the gondola-like design I have proposed for PRT vehicle design. It is the problem of balancing the load. When two heavy people sit together, if the “pod” simply hangs by gravity alone, it will be very far out of level.

Let me back up and state the advantages of the design. The first is turning speed. If an ordinary vehicle makes a sharp turn at high speed, it creates sideways G-forces. The answer to this has always been to avoid such turns by designing the road with only gradual curves. (Consider the real estate consumed by a “cloverleaf”) Sometimes the roads are banked somewhat. The problem with gradual curves is that they are very unwieldy (design-wise) in an urban environment. With city streets generally designed with sharp corners, gradual curves have to use the airspace above valuable corner real estate. Right-of-way issues will be untenable. Highly banked track has drawbacks too, such as being banked only for a certain optimum speed, and adding expense to every curve and corner network-wide.

The second advantage is a quicker acceleration and deceleration rate. Any driver who has owned a compact car or a car with bad brakes or has tried to save gas by hardly pushing the petals knows that limiting acceleration and deceleration too much is a recipe for late arrival. If the name of the game is passenger throughput both acceleration and deceleration should be robust enough that having the vehicle be able to rock forward and back to minimize G forces would be desirable.

The third is steep slopes. In order to descend to street level without blocking driveways, or even just for versatility in a hilly town, handling steep slopes is a must.

Then there is the issue of passenger comfort and safety. The gondola design creates a means by which all G-force is diverted downward, toward the floor of the vehicle. This greatly enhances passenger comfort, safety and saves a lot of otherwise spilled coffee.

So the unsolved question is this; How do we keep the advantages of a free-hanging vehicle while not having it tilt from an uneven load? Note that making the vehicle wheelchair friendly tends to mean other seating is further from the center of gravity, making the problem worse.

So that’s the problem. If you have an idea, please post it, if it involves a picture, email it to me and I will post it for you.

23> Podcar Control part 2

I would like, first of all, to thank alert reader Mr. Grant for sharing this paper by J. Edward Anderson, who is truly an authority on the subject of PRT. Unfortunately the material seems somewhat dated. Although there is a date on the PDF, (2003) I suspect the paper was actually written a few years earlier.

Although I completely agree with most points in this article, (in fact most of it is a MUST READ) I have to say that there are a few points I disagree with as well. Since a monologue on my take on this article may be a bit more than many readers would want to wade through, I will include those as a comment on this post.

Anyway, I would suggest, as a guideline, to make traffic control decentralized, and make the individual “podcars” behave much like good drivers, I.E. following road signs, not tailgating, but seeking shortcuts and less trafficked routes. This begs the question, however, of how to achieve a redundancy of control to safeguard against malfunctions

Another missing piece of the control puzzle is exactly how communications reach a “podcar” (I still hate that term, but if it gets us noticed…) Anyway, I guess the problem is as follows: There is a constantly updating traffic map wherein stations and track segments are self-reporting their status. Their reports would probably be little more than a segment/station number, and a condition number, (like a scale of one to ten) This simple communcation needs to have a success rate that is near absolute. This communication could be optically/electrically/mechanically/wirelessly redundantly reproduced at intervals along the track so a passing “podcar” gets an update every so many feet/meters. Redundancy creates a multiplier effect in terms of reliability, and enables faulty components to be replaceable on a maintenance schedule

There is one other VERY important communication, which can take place from the track to the podcar. That is a report of having been just traveled upon by another podcar. If a PRT vehicle is to react much like a human driver, it needs to see ahead and slow down when necessary. If there is any aspect of this system that needs 99.999% reliability it’s the system that prevents “rear ending “ the vehicle ahead. This means redundant, separate reporting means so that anything less than complete agreement between sensing systems results in an immediate cautionary response. As part of such a system the track could inform a trailing vehicle that there is another “podcar” just ahead. Here is an example of how it could work. Imagine a little line of lights in the track illuminate when they sense the passing of a “podcar”, only to dim and go out over the next couple of seconds. (Imagine the tail of a comet) A light sensing, following podcar would know, by measuring the light intensity, how far ahead the first vehicle is. Why not just use taillights on each vehicle? Because of the problem of seeing around curves. What about Bluetooth, GPS or other wireless technologies? I, frankly, don’t know. This is where a small army of alert readers would help. Don’t feel like posting a comment? As always, I can be contacted at danverhoeve@gmail.com.

22> This Just In...

Yeah, I'll get back to PRT control soon. Sorry for my little vacation from the blog.
I'm working on a bunch of design work. Anyway, I had earlier written this piece on Houston's light rail, only to get a further insight on PBS tonight. It seems that more than 60 Transit authorities (nationwide) are broke, as reported on the News Hour. The PBS (NewsHour) site allows browsing by subject, recent stories, etc. I just tried to upload the MP3 audio of the program but Blogger wouldn't let me. It's http://www-tc.pbs.org/newshour/rss/media/2009/03/09/20090309_transit.

another link to transit situations is

http://www.pbs.org/wnet/blueprintamerica/reports/transit-in-trouble/overview/481/

Sorry to make you type it in, seems that even in Explorer my links are saved as Firefox documents.

21> 1.4 Billion?

I heard on the news a few days ago that the Metropolitan Transit Authority in Houston, TX voted to spend 1.4 Billion expanding it’s light rail system. I really haven’t figured out what to think other than it sure sounds like a lucrative business to be in. That is reportedly $73 million per mile. And apparently it doesn’t even cover all of the road “improvements”, but does include $118 million for new light rail cars.

I have always advocated for a place for other forms of public transport beside PRT. As I have written, most forms of transportation rely on fully or partially aggregated groups of people. A light rail system requires a fairly large group of people at each station to be efficient. This begs the question, “How did the people get to the station in the first place?” or rather “How COULD or SHOULD they get together to board this train?” I think PRT competes with buses more than light rail, because buses, rather inefficiently, stop for individual riders as well as groups.
But this kind of price tag gives me second thoughts. I wonder, for example, why don’t they just create a special road or lane and just run a fleet of buses instead of having them on a rail? (I confess I don’t know if Houston’s light rail is electric or what) How much does a bus cost? How many does $118 million buy?
It’s not that PRT CAN’T compete in the densely populated areas. (I would refer the reader to the “MISTER” system for what I consider the most efficient larger station design) It’s just that light rail really can’t compete in the one-passenger-at-a-time world.

Using a previously posted rail design I recently figured out the cost of steel per mile. (This was a VERY rough estimate) I came up with a between 1 and 3 million dollars per mile (depending on station frequency and support design) Of course this doesn’t include labor, and I’ll do all of this in some future post, but I just thought I’d mention it, being on the theme of money and all…And speaking of money…

I Googled (news) the term “cost of burying electrical lines” and came up with repeated estimates of $1 million per mile. This has been a much talked about issue after the recent massive power outages due to Hurricane Ike and the recent ice storms in the Midwest. Anyway, I’ll get back to the concepts of PRT control soon, but I just thought I’d post this stuff so I’m not the only one left scratching my head…

20> Podcar Control and Encoders

I’ve been wanting to start a conversation about PRT control for some time, so I thought I would start with this primer on motor control.

I don’t know a whole lot about brushless motors, other than that brushes are the means regular motors use to time the advance the magnetic fields ahead of the advancing rotor. With modern electronics, however, motors do not require mechanical means to achieve this timing. Triggering the magnets electronically offers great precision. Instead of “full-on, full-off”, magnetic forces can be ramped up or down; the motor’s rotation can be advanced or reversed, even held frozen.

Whereas in theory one could always know just where the shaft is, rotation-wise, under load the actual rotations or speed could differ from what is expected. One answer is the optical encoder.

My thanks to ikalogic.com for the logic diagram and shaft encoder pic. I just glanced at the site, but it looks educational. Sorry about the resolution. Click on the image to enlarge it.

The key is the C shaped “electric-eye”. (optocoupler) As holes in the disk align with the beam, a logic pulse is created. In the third picture, I depict how the same principle could be used to inform a PRT system on a pod-car’s position (and speed) along the track.

Some thoughts:
1. The track can be fitted with the PRT equivalent to traffic signs. Unlike drivers, PRT vehicles will follow their instructions to the letter. “Signs” in the track can trigger precise deceleration rates for upcoming turns, acceleration rates for merging, etc.
2. These “traffic signs” can be dynamic, reflecting real-time data.
3. The track itself should also receive data from the PRT vehicles. Track segments can “know” their traffic counts, for example, to upgrade or downgrade their availability factor, for routing decisions. It would seem that the process of merging would be the result of direct cross talk between cars and track.

There’s a lot more to be said about the division of control responsibilities, so I’ll save that for a separate post.

19> A More "Mature" PRT Track Design

Here is a section of a more mature PRT track design. I envision this with a skin to keep out the elements. Not shown in the picture is the soundproofing, except for the vibration absorbing material shown in purple, which isolates track vibration from the truss structure. The circular holes are for utility conduits. I have not figured out the cost or even the weight yet, but I must say it is dirt-cheap. Greater height and steel gauge enables longer spans. Note that the design does not show a great strength against sideways forces such as very high winds. A horizontally triangulated truss can cap the structure to address this, but it probably should be in removable sections, so as to provide access to the conduits.

In the traditional business model, a big company would keep the details of the track secret or proprietary, even though it could provide lots of local jobs and that could be a selling point. The integration of utility lines and street lighting could also be of interest to local companies, but again, if the PRT company wants to keep complete control, this is less likely to be in the cards.

The design obviously has to be made approvable by structural engineers for anticipated weight and span, but after that any structural steel fab shop can whip the stuff out. Any city has a dozen such firms. Let’s remember that city managers like to “bring home the bacon”. Also, once the track (at least the structural aspect) is free to be outsourced to locals, and city officials can get bids that they believe in, those in charge will be forced to justify the much greater expense of every subsequent road expansion project against the backdrop of this simple, outsourcable alternative. That would seem to be a battle that PRT can win.

18> PRT Motor-in-the-Wheel Design

This illustration shows how a motor can be mounted inside of a PRT “Pod-Car” wheel.
I was first inspired by a design from an electric “concept car” where the wheels were actually motors. The idea is simple. If you plug in a motor but hold the shaft, it will spin, (winding up the cord until it unplugs itself). So why not feed the cord through the shaft somehow? That way the motor itself would be a wheel, instead of mounting a wheel on the shaft? (Or more likely, a sprocket, gear or pulley) It turns out this idea is actually widely used. A Google search revealed that the concept is commonly employed to move conveyor belts, (drum motors) and to electrify bicycles in China (hub motors) and in fans, especially computer and ceiling fans.

Despite the obvious simplicity (and efficiency) of the idea, apparently the motors don’t perform well in terms of torque, as compared with a much higher speed motor fitted with a reduction gear. Also they are not exactly cheap or easy to find, so I bit the bullet and researched some more conventional motors.

My switching design calls for hard wheels, so I put in a bunch of them to have the traction to climb steep smooth slopes. I don’t really know how many is really optimum, at this point, but I checked out some “NEMA” standard sized brushless motors, and found that the NEMA 42 standard comes with sufficient torque that if each or the wheels had a motor within they could pull (together) with between 300 and 800 lbs. of forward power, while having a top speed of 60 mph. (Sorry, younger and euro readers, I am not natively metric and feeling lazy) Obviously, reducing the top speed increases torque proportionately, but it also worthy to note just how much of a trade-off is required between the weight, the steepness of the climbs and the top speed. There is no free lunch. For example a combined vehicle/payload weight of 1600 lbs. will probably not make a 45-degree climb.

It is also worth noting that the separate motors solve the fact that my system has no differential gears. For those who do not know what a differential gear is, here is a brief explanation – On car, when turning a corner, the outside wheels have further to travel than the inside wheels. Therefore they have to revolve faster, making more revolutions than the inside wheels. The differential gear accommodates this, preventing one or both wheels from slipping on the pavement, which would create wear and partial loss of control. Even though the right and left wheels in my PRT design are fairly close together, the same phenomena would apply to a lesser extent. With separate right and left motors, however, the RPMs of the wheels can be precisely controlled to actually create the appropriate steering forces.

17> The Role of a PRT Standard

A good PRT standard would
1. Give all decision makers (city, state, federal) the security of knowing that the system design was not rushed, coerced, short changed, tailored by self-interest.
2. Give those decision-makers the assurance that the design is suitable for competitive bidding in initial construction, expansion, and maintenance and therefore they are not utterly dependent on the initial contractor.
3. Give PRT contractors a vetted design more likely to be accepted by the public.
4. Reduce PRT contractor’s liability risks.
5. Make a PRT project easier to manage and subcontract.
6. Give customers more faith in the system
7. Allow innovation in system components outside of the standard.
8. Be divisible so that variations can be introduced without scrapping the entire standard. (A proprietary car for a standard track, for example)
9. Be designed with altruistic intent, including benefit to the environment, local contractors and other vendors, as well as commuters and the communities they pass through.
10. Be continuously updated
Did I leave anything out? Anyway, A good set of open-source specifications would greatly enhance the chances of a truly ambitious implementation. Let’s remember, a scaled down test will always go from a place where people congregate to different, similar place. In other words, companies with millions tied up in engineering and marketing and testing and selling have to recoup costs by jacking the cost of track so high that only a loop is affordable. Meanwhile cities have to ensure usage by placing stations only in congested areas. Almost by definition, then, a simple shuttle service will always be more cost-effective. Only confidence and optimism can produce a first implementation that is scaled for success.

So what would a first standard be? I would think that the first stage would be (for example) to standardize a track profile, switching and control protocol and weight limits. If there are deep-seated divisions in these matters, there could branching specifications. For example, I outline, in the last post, a method of using external power to lift cars up very steep (to vertical) slopes. A “podcar” designed for the track, weight, and switching specifications but incapable of this adaptation might be called PRTSO 100.2 compliant, but not PRTSO 100.2.5 compliant. A city could look at a proposal and decide whether this would be an issue or not. At any rate, they would know what kind of track to buy.

It is interesting to consider that, for design Darwinism to occur, one needs a number of competing designs. It is therefore not the function of this site to design a single system, but a number of competing systems to see what common threads emerge. None-the-less, it is equally important that each idea be critiqued, as though it is the one and only alternative.

16> How to Lift a Podcar

I want to start by noting the obvious difference between the designs I have shown and those of the other two hanging pod designs I am aware of, Beamways and MISTER. Neither has the vertical connecting beam I have illustrated. Besides the obvious advantages of having the track being high and out of reach, the connecting beam has one other advantage.

I have long wondered if PRT vehicles, (OK, Podcars), would need a transmission of some sort. Clearly the advantages that have led to their universal adoption in automobiles would seem to apply here as well, although I am led to understand that electric motors are a bit more forgiving in this regard. Anyway, my concern was about the on-board power needed for steep ascent, and my thoughts went to roller coaster design, where the cars are pulled up the track by a means outside of the vehicle, so there is no need to carry around a heavy motor.

I have taken a design philosophy that is consistent with open-source by seeking to not foreclose options that someone else might find useful, and the roller coaster method seems to have enough merit to at least keep as a possibility, Then the question becomes, “how steep?” Obviously straight up is as steep as possible, so my attitude is “why not?”
One problem that our societies must someday face is our land usage footprint. The future is UP!

Since vertical ascension, however, is not part of any immediate plan, I will not explore the matter further, other to say it’s not challenging, engineering-wise. Now you know another reason for the “beam”. This design also has some comfort (g-force) advantages, and possible collision safety advantages. One challenge, however, is with how to deal with loads that are highly unbalanced, front to back. Inventors, engineers,.. we need you!

By the way, that brings up one obvious problem with this site and format. You can’t post pictures. For the time being, if you have a pic that you think would help out the cause, send it to me at danverhoeve@gmail.com and if it’s worthy, I’ll make a post out of it. Meanwhile, I would be interested in suggestions on how to get a past this problem for good. Wiki? Forum? Tell me what you think!

15> The "Podcar" and the PRT Dream

First, I HATE the term “Podcar” or “pod”. Unfortunately, Since the PRT thing in Ithaca last summer, it seems that a lot of “PRT” Googling results in this awful term. Are people who ride “pods” considered “Pod-People”? (Anyone remember that movie?) Anyway, I use it here in the title solely for the cynical reason that it might bring in some (Googled “POD”) readers, and some of them might become contributors to the cause. I would like to reiterate that cause now, as many people might tend to scan the site, without realizing it’s purpose, which is buried in the end of the “About this Blog” section
The ultimate dream would be to realize the world’s first large-scale open-source mechanical, software, legal, environmental and social engineering project, with a full set of blueprints, contracts, position papers, environmental studies, etc. provided by the masses, for the benefit of humanity and the planet. A “Wikipedia” of how to build a truly 21st century transportation system with local talent and resources, with a hefty “how –to” section on every possible situation. A framework by which primitive “model T” iterations of PRT are skipped, leading to successful and ever more efficient and beneficial implementations worldwide.
But on a much more humble scale, a bunch of us are “second-guessing” each other, on the topic of the day, or week, and our thoughts are being archived in the “cloud.” Anything we say may provoke a design breakthrough, or cut off some bone-headed approach that would only be a setback. In other words, it’s all good, as long as we get enough contributors to be a real resource that can, at least, be found.
I am not free to work toward this full time, but it is my passion. I wish I could post daily, but I can’t. I have many more ideas than I have posted so far, but I have to meter them out. I don’t want the best ideas buried too deep. So to any readers out there- Please post your thoughts about anything I write or any comments you read. Please spread the word! At some point I will start an email campaign to known advocacy groups and academia, but I need a blog gushing with comments, arguments, and ideas. If we, the people, reach a definable consensus, that is powerful stuff. It is the stuff of dreams.
Last but not least . Enjoy the illustration. I would like to note, however, the motor units shown don’t represent any particular design based on inner parts, size of the inner workings or anything else, for that matter. It’s hard enough just making them look shiny. But sometimes a picture says a thousand words, (and one blog address). I wanted to get this out sooner rather than later.

14> Personal Rapid Transit and Streetlights

I heard, the other day, about a proposal whereby streetlights would be turned off to save energy but could be switched on by cell phone. Odd idea, but it gets the old mind working. I was mostly working in Tucson, AZ for the last few years, and they have a number of observatories near town, so they are keenly aware of what is called “light pollution.” I fly a lot, and have for many years, and I must say the brightness below is really getting out of hand. Remember a barrel of oil saved domestically is as good as a barrel of oil produced domestically. Energy is wealth, and the celestial glow of the city is the glow of would-be prosperity diffusing into space.

So how does this apply to PRT? Well let’s imagine the ideal street lighting. First, it wouldn’t blind you, so your eyes could see more with less of it. It would be more uniform, softer. It would shine away from you, not at you. It would be directed mostly toward important things like signs and curves in the road and blind driveways, If there was no one to see it, it would go out, or at least cut back. Intelligent street lighting is an idea whose time has come. PRT could be the platform and catalyst for that change. . This is just one more selling point to PRT that shouldn’t be ignored.

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.

7> PODS JUST GOTTA HANG..

It’s been a while since my last post, as I have been very busy. I have, however, given considerable thought to my little project here. I have decided that hanging the PRT vehicles is really the way to go, unless switching is more of a problem than I think.A close look at the PRT 2000 drawing (posted earlier) shows a elegantly simple means of switching tracks. By not having any moving parts on the track itself, such as is the case with ordinary railroad trains, the whole scheme of things is greatly simplified. As I have stated earlier, the track is everything, since the network is everything. I have prepared a list of reasons why hanging is better than on top of, or straddling a track, but it’s a little long. I’ll try to abbreviate it in a later post. Sometimes a picture is worth a thousand words. Here’s one that shows just how simple and versatile hanging PRT is. Note that the station pictured here could be in a parking lot or on any city street. It’s better to have more stations that are cheaper, rather than a few expensive ones. Again, the network is everything.

Table Of Contents

1. IT'S THE ROADS, STUPID! 
2. NO WONDER WE HAVE TRAFFIC 
3. First, there is the track 
4. Here is My Idea of PRT 
5. Like-minded Engineering in Poland
6. Table of Contents
7. Pods just Gotta Hang
8. No eyeballs, No Surrender
9. Switching Tracks
10. A Couple of Issues
11. Personal Rapid Transit Drive Unit
12. Station Safety and Sinking Santa
13. A Mid-afternoon Dream
14 .Personal Rapid Transit and Streetlights
15. The "Podcar" and the PRT Dream
16. How to Lift a Podcar
17. The Role of a PRT Standard
18. PRT Motor-in-the-Wheel Design
19. A More "Mature" PRT Track Design
20. Podcar Control and Encoders
21.1.4 Billion?
22. Link text
23. Podcar Control part 2
24. One Little Problem
25. Just Some Thoughts...
26. Linear Induction Motor Tractor Unit
27. Designing For the U.S. Market
28. An "AH-Hah!" Moment
29. Thinking Outside the Box on Earth Day
30. Active Wheels
31. Fired Up!
32. I Just Can't Let This Stand Unchallenged
33. In Defense of the "Track-on -the-Bottom Design
34. Access for the Disabled
35. Troubled
36. Back to Designing
37. Coming...Soon?
38. The 16th Rule
39. Progress on theTrack
40. PRT: The Best Idea that Nobody Knows About
41.The Future Revealed!
42.Design Time!
43. Crash Tests, Anyone?
44. Going, Going, Gone
45. A Critique of PRT International's Design Approach
46. Many Vehicles, One Track
47. Serial vs. Parallel
48. PRT Stations...Continued
49. In Search of Gridlock and Opportunity
50. Dualmode and Modular Design
51. A New Kind of Motor
52. 3D,2D and Skyhooks
53. SMARTS
54. SMARTS Part 2
55. Chasing Trucks
56. High Speed
57. Roads, Roads and More Roads
58. Defining the Problem 
59. A Milestone and a Call to Arms
60. Prestressed Concrete Track for PRT
61. Classification if PRT, PAT
62. Mission and Miscellanea
63. ULTra - Architecture and Iteration
64. The ULTra Architecture, Continued
65. The Efficiency of Absence and Angled wheels
66. "Luucy! We got some 'Splainin to Do!"
67. Motorized Steering Guide Wheels
68. Haiti and Thinking Small
69. About that Angled Wheel Design...
70. Speaking of...
71. Switching Tracks
72. Stop That!
73. Overwhelmed by an Underpass
74. Tilted Design, Motorcycle Tires
75. Happy Tails to You...
76. Autonomy
77. The Times, They are a Changin'...
78. I've Got Control Issues
79. Something's Buggin' Me...
80. Twisted
81. ZZZZZZZ.......
82. A Sermon for Earth Day
83. Get Smart
84. Leaking Oil Solution?
85. The Enemy if the Good
86. Can't We All Just Get Along?
87. PRT Track and Bridge Design
88. Gone Fishin'... Sort of...
89. On the Road Again...
90. Let's Take It From The Top
91. Dan the Blogger was Writing... 
92. Crack in the Track, Jack...
93. In Search of PRT's "Killer App"
94. Say Cheese!
95. Call the Cable Guy!
96. Control Issues, Part II
97. PRT and Suburban Sprawl  
98. SPEED UP! SLOW DOWN!
99. Pic of the Week
100. One Hundred and Counting
101. PRT Merge Control
102. The PRT Business Model
103. A Little Something...
104. Pondering Infrared
105. A Voice from the Woods!
106. Simple Circuits
107. An App for That
108. Putting a Foot Down for PRT
109. Harnessing "Anti-Gravity" for PRT Control
110. Google's Robocars
111. Capacity
112. Interview with Santa
113. 2010- Historic!
114. In Search of a Cheap Lunch
115. Swing-Low-Sweet-PRT
116. Parkin' on the Hill...
117. Snow Day Musings
118. GM and Segway's Unintentional Dual Mode Platform
119. Further Thoughts on Dual Mode
120. Back to the Drawing Board
121. Solving traffic with 3D PRT
123. Thoughts on Track Size and Switching
124. While We're Still on the Subject...
125. What's in a Name?
126. A Few Good Destinations
127. Really, Really Fast
128. Learning from Roller Coaster Design
129. Emergency!
130. Progress Report
131. Climbing a Chain
132. Forward Compatibility
133. Maglev Mania
134. Good Tidings!
135. In Search of a Parking Space
136. Hot Rod
137. Playing Monopoly
138.  Imagine
139. PRT and the Art of Cabinet Making
140. Piping Hot Ideas
141. GOT IT!
142. Dodging Bullets
143. Waiting for SkyTran…
144. Compromise
145. How fast is fast?
146. Big Wheels
147. Pearls of Wisdom
148. Off-the-Shelf PRT
149. Tower of Babel
150. A Little Present for Myself...
151. Forward Compatability ans extensibility
152. Standardizing for the Future
153. Railbotics!
154. Fractals!
155. For Example...

5> Like-minded Engineering in Poland

Wow. What I’ve just learned…. I really didn’t think anyone would ever find my blog, let alone read it, so I’ve been doing my other things, which, for the last month and a half, has been living “off-the-grid” in a cabin in New Hampshire. No cell signal, no internet, solar and car battery energy only. It’s something I do. Anyway…
I got a comment, just one, that said, “looks like the “MISTER” system”.. with a link http://www.mist-er.eu/home-page.html
Now I suppose anyone who has seen this blog probobly has figured out that I’m a bit of a closet engineer; How gratifying, then to find, out of the blue, that someone else has taken the same info, looked at the same problem, and come up with the same answer. I get it. They get it. There’s hope!
I am still in NH, with Wi-Fi internet only available at the town library, and me far from there, so “bear” with me (pun-fun) if I have missed something they said on one of their pages. I haven’t even read them all yet… but…
I’m a real fan of Bucky Fuller, even built a geodesic dome or two, but the use of the tetrahedron based track, I believe, is impractical. It may suit their purposes, as they, (wanna-be track suppliers) can bid track multiplying truss pieces, but there are, in my mind, real questions about assembly in the real world. Perhaps they want to be the only vendor for track, and feel that this design gives them a leg up, as any competing firm would need to duplicate work which they have already done. If the object is to help the world through PRT, then this is wrong-headed thinking. This is why this blog exists and why meaningful PRT implementations don’t. The flaw is in the business model. The previous and current model is “This is what you need, and we make and sell it”. The superior model is, “This is what the latest concensous is on this type of transportation solution, and we are vendors designing, building, problem-solving, into that evolving environment.”
I am also puzzled by how they expect to switch tracks. As a matter of fact, all of the really challenging engineering details are left out. What type of motors? How is electricity transferred? How does the computer system know where each car is?
None-the-less, I believe they are on the right “track”.

4> Here is My Idea of PRT

Notice the doubly articulated swing arm. This enables steep, even vertical ascension and dissention, as well as speedy, tight turns and rapid starts and stops. An adjustable hydraulic mechanism (similar to a door-closer) would dampen the swinging movement.

3> First, there is the track

First there is the track. This is the most important part, and is half the reason the world needs to “open source” PRT design. I have not seen a single PRT system that I think will ever find any success in the U.S. and here is why. PRT can not compete with buses or light rail in situations where people can aggregate at a point A in order to make a straight line journey down a main drag to points B, C, etc. It is simply inefficient to load and transport many small vehicles as opposed to a few large ones.
As we all know, however, mass transit has real problems competing with cars because it can’t effectively reach less trafficked areas. Yet many people are coming from a less trafficked area, and are destined for a less trafficked area, and are effectively forced to commute through highway and intersection bottlenecks. Mass transit though these bottlenecks is unworkable because there is no infrastructure on either side of that bottleneck that would enable a commuter to complete the journey.
The answer is cheap, go-anywhere, go-over-anything, rails, and go-exactly-where-you-want cars to compliment them. We don’t need a couple of loops. We need a network. This is a critical mass situation. The system needs to have more destinations than is practical with the alternatives or else the alternatives should get the funding.
One problem with the current development model is that the companies hoping to build a PRT system covet the idea of the never-ending construction job that would be the track. It is no wonder that they tend to envision more grandiose guide-ways than the needs would seem to indicate. The same is true of the cars. Just like GM liked the business model of producing SUVs, instead of compact cars, so does the potential sole supplier of PRT “pods” covet the endless production of larger, more expensive vehicles.
Here is a picture of the Raytheon’s idea of a PRT vehicle.

PRT 2000

Is it any wonder that the cities that Raytheon approached eventually rejected it? Note the 72” x 72” track size. Clearly minimal cost was not the object here. The use of a 36” horizontal tubular support beam is a particularly odd choice, as ordinary “I” beams are cheaper, stiffer, less resonate, easier to handle, easier to bolt to, and more available.