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.
The other day I was looking over Jerry Schneider’s excellent ITT website for anything new and a link caught my eye. (It had the word “New” in red Italic, right after the title)
It turned out be a site that hadn’t been updated since 2003, so I guess it’s just new to the ITT site. Anyway, the hanging system described therein bares a striking resemblance to the system I have been piecing together. So much so, that I emailed the designer out of courtesy, telling him he deserved credit for a lot good ideas that many people (including me) thought were mine. A lot of what I have come up with has evolved as this blog has progressed and my thought processes have been fairly transparent. Yet it appears I could have just gone to this guy’s site and lifted almost every idea from him. So much for original thinking. Anyway the guy’s name is Tad Winiecki and he apparently started a motorcycle gang once that Unimodal (SkyTran) founder Doug Malewicki joined. Tad thought Doug’s designs were pretty unfriendly to handicapped and elderly, (That’s for sure) so he started playing around with his own designs. Particularly intriguing is his concept for creating track from roll-formed steel. Anyway, Tad, I really didn’t steal your ideas…Honest!
Speaking of SkyTran, I have long thought that the combination of PRT and high-speed levitated travel was an odd one. Whereas the concept of going fast in podcars is nothing new, it seems to me that the “bread and butter” of PRT is in neighborhood travel. The acceleration and deceleration distances, and rounded corners of a high-speed track would seem incompatible with city layouts and traffic dynamics. Inductrack technology assumes the need for wheels at startup. I would submit that it would be best to just use those wheels for most urban use, not because wheels are better, but because the track would be so over-priced for its low-speed function. That being said, the Inductrack technology is pretty remarkable. As I understand it, in a nutshell, it involves an unpowered bed or track on which a permanent magnet studded sled will levitate as long as it is kept moving. I believe a breakthrough aspect is this; it seems that to varying degrees there exists a “magnetic friction” which is produced as repelling magnets are drawn across each other. Apparently “Inductrack” is very efficient at controlling this effect. Although Mr. Malewicki sees this invention as useful for PRT, and NASA is interested in it for launching rockets, I see another use. It seems to me that they have invented the perfect magnetic bearing. I don’t know how it would miniaturize, but for large scale or platter type configurations it would seem to be ideal. I would be interested in how it would work in wind generators for example.
Speaking of wind generators, on his Jpods website, Bill James raises the possibility of covering PRT track with solar panels to power the “podcars”. (Yes, I am trying to warm up to the term after it was pointed out to me that podcars produces better search results than PRT.) Anyway the concept of supplying energy along the track rather than “piping” it in has a certain appeal, although I would question some of Mr. James’ premises. One thing that I learned years ago is that the energy “density” of solar radiation is not all that great. Far greater is the energy density of wind, although the fact that it cubes in power every time the wind speed doubles also means the reverse – as the wind slows, the extractable energy falls off a cliff. None-the-less in windy parts of the country it’s there for the taking. Here is a picture that caught my eye recently.
The concept of having the transmission towers produce energy themselves is rather poetic, don’t you think? Part of the problem with wind generation has been that it is often not generated near where the users are. If PRT starts going between cities, the reverse will be true. The track will need power away from the city. Perfect for periodically placed wind generators.
Speaking of cubing wind energy – One sure way to get increased wind speed is to go up. Here is a concept with nothing to do with PRT but that every PRT advocate will appreciate. Lighter-than-air wind generators. So big they increase wind speed just by forcing air to move around their shear size.
Oh, yeah. Speaking of towers, I couldn’t help but notice this one, holding up this PRT track.
Who published this anyway? Beamways? Very Nice. This form of bridge is called a “cable-stayed” bridge and is quite distinct, structurally, from suspension bridges like the Golden Gate, which have cables anchored in the ground. This style is just made for PRT…er… Podcars. It is even wind generator ready.
First a reiteration of the big picture. Designing a PRT system as logically as possible must start with a track that won’t put unnecessary limits on future usefulness of the system. Unfortunately, in an effort to get a product to market, most PRT venders have produced designs that fall short of having the potential to do anything but be small players in the transportation mix. Current systems, by and large, are not versatile enough to be used for anything other than supplemental vehicles in very densely populated city areas. That may be a perfectly fine business model, but the resultant designs fall far short of embodying PRT’s transformative potential. Where would the internet (for example) be today if it relied on proprietary networking cables rolled out according to the business plan of a single company for specific, cherry-picked markets? Standards based PRT track design is sorely needed.
I recently posted bogie design with tilted wheels. The purpose of design effort was not so much the bogie itself, but to see if such a design would require modifications to the track profile. Actually it has, but only slightly. The general design first described in post 39 has stood up to many challenges (outlined in subsequent posts) including multiple weight classes, speed ranges, station types, freight and industrial uses, propulsion types, turning radii and pitch angles, etc. What remains to be done is to explore braking and traction issues, to address the issue of forking (adding) track with minimal deconstruction, and general track construction methods.
All of that being said, here are some explanations regarding that tilted wheel design. First of all, it is a response to the challenges of high speed. The design makes no sense for anything less than, say, 30 mph. It gets much more attractive at speeds over 80. The rationale is this. At very high speeds the guide wheels really get a workout. In order to provide a smoother ride and make less noise, all wheels should be made of a material with some give. (rubber or plastic, not steel) Such materials wear out, especially on very small wheels. The bearings, too, take a beating. Centering the bogie without guide wheels is a challenge, however, because of issues that are particular to the remedies. Flanges on wheels can wear and heat up. Having a wheel running in a trough generally means that all wear occurs only on a very limited ring around the wheel. The same is true if the trough is in the wheel. (Pulley wheel profile) While this can be tolerated to a degree, the issue is most acute on the drive wheels, which support the full weight of the vehicle. V-shaped wheels in a V groove wear rapidly because the wheel has multiple diameters contacting at once. This creates wheel slippage.
In the illustration below it can be seen that the angled wheels, through gravity, work to minimize any contact with the flange, which has a radius to minimize friction wear, and could be made of a harder material. The inserted detail shows how the bogie becoming off-center causes the entire wheel (and whole vehicle) to be lifted against gravity.
These drive wheels are characterized by their large diameters, which have plenty tread surface to distribute the wear, and revolve at slower speeds than smaller wheels would. It is assumed that these wheels would use tapered roller bearings, like cars, and so cannot tolerate very high rotational speeds like ball bearings, but can better support the vehicle weight and the sideways “thrust” forces associated with fast tight turns.
In the illustration above note that the running surfaces have been replaced by half-round, or bull nosed rails. (shown in white) While it is obvious that such a design would greatly increase wear on both rails and wheels, such a profile also allows an extremely tight turning radius. My thinking is that at very slow speeds, such as for station maneuvers, the wear will be a minor factor. After all, by definition, the sharper the turn, the slower the speed and the less distance traveled. What about medium turns? One thing that occurred to me is that such inserts could provide a banking angle, which would treat the bogie like it was going straight. With wheel motors the wheels toward the outside of the curve can be made to rotate faster, facilitating (if not actually causing) the turn. This is a work in progress…I don’t have all of the answers at this time.
This all raises another very interesting point. In the last post, it was pointed out that the steering guide wheels would come into and out of contact with running surfaces as needed, so they would not spin and wear unnecessarily. Here we have described other running surfaces that are not of a continuous, unchanging profile. There are other situations as well, such as very steep slopes, which might call for special “sticky” rails or other inserts. Having various inserts has a lot of advantages. They may be replaced and upgraded. They can be precisely finger-jointed to allow for thermal expansion to eliminate the repeating noise and vibration associated of expansion joints in train tracks and some roads. They allow one basic structural track profile to perform many functions without modification. They can be made of materials (such as stainless steel) that are too expensive to be used structurally. They can be rubber mounted for noise and vibration control. It becomes easier to add a diverging or converging track to a previously completed one when the running surfaces are modularized into precisely sized components. One interesting application for inserts is the technique used by Disney to detect any breaks in the tracks of their rides. They fill the tracks with compressed air. If there is any break or crack the pressure drops and they know it immediately and can stop the ride.
Finally, a note about the fifth wheel shown below; (in the center of everything else) There are several possible functions for such a part, from centering and holding down the bogie to additional braking, power and traction. Such a part can eliminate the possibility of wear on the wheel flanges altogether on straightaways. The truth is, however, that to do the design I had to either add it or not. Because it is easier to take it out than add it later, I added it. It could, in theory, prevent extraordinary forces, such as extreme cross winds or earth tremors from lifting the bogie inside of the track. It has a smaller diameter than the main drive wheels but it supports no weight, so ball bearings would suffice and wheel-wear would also be minimal. It is largely redundant, I know, but this is all a work in progress, and, as I mentioned before, it is really all about the track anyway.
This is off-topic. The regularly scheduled post will be along in a day or two.
Having a bit of a soapbox to stand on, I realize, has some advantages. I want use mine now to share an idea that’s been in the back of my mind for a couple of years now. The situation in Haiti illustrates a problem that occurs again and again the world over. It is the problem of distributing aid. Specifically it is the dependence of aid agencies on having a top-down system, where airports must be secured, warehouses must be secured, roads must be secured etc, all before food can get to people in need.
The traditional wisdom is that the aid packages cannot be parachuted in, for fear of crushing people and/or causing riots. As a guy who loves to design, giving up the whole idea drives me crazy.
The problem is distributing the aid fairly and evenly. In many cases gangs steal the aid by hijacking the trucks or taking over the warehouses. Often conflict prevents aid workers from getting to affected areas. In Haiti, there are villages that will be cut off (by road) for some time. Surely there must be some way to get food and water to the people directly.
I submit that the distribution problem is actually a packaging problem. If individual portions of food and water could be dumped from a plane in a form that would not clobber the people below, they would self-distribute on the way down. Long brightly colored ribbons would make them easy to find. When a maple tree drops its seeds, they disperse by means of papery little wings that make them gently spin to earth. Can’t we do the same for a food bar and a half a cup of water? Think about it. You can’t hoard what you have to search out to collect, and small amounts aren't worth stealing. In many cases the children in these disasters watch helplessly as their parents struggle to get the family through. This would give them a chance to go on an Easter egg hunt and be heroes. There would be no favorites, at least in terms of social position or gender.
People could also be encouraged to migrate away from unsanitary conditions. If the drops occur north of town, people will pick up and go to where the food shows up.
I guess in one way this IS related to PRT. The key is to think small. The problem of making something safe to drop from a few thousand feet becomes exponentially harder as the weight increases. This strikes me as similar to the nasty tendency to think big with transportation, or at least not take small vehicle mass transit PRT seriously. It just seems that if you mention moving ten people instead of one or two, suddenly you are taken much more seriously. Small is counter-intuitive.
Similarly the idea of moving tons of food aid with thousands of little parachutes or whirly-gigs sounds ridiculous, until you consider that, as a society, we are already the kings of over packaging. We mass-produce and (over) package little items by the millions every day. These aid items just need to be highly compactable for transit, but, when falling, have enough drag to fall at speeds too slow to be dangerous. Is that really so hard? Not if you think small. Heck, I’m pretty sure my kid’s packaged lunches are almost ready to go as is! Think origami, and plastic that you can fold and will spring back. Think tails with multiple wind catching discs that stack tight for shipping. Let’s solve this problem before the next big disaster, shall we?
Here is a little detail of the bogie design I posted last week
I embrace the “in vehicle” switching philosophy, which is found in designs by J. Edward Anderson and others. I can see little logic for moving the track, as is the case for ordinary trains. This design, however, has generally involved a “bi-stable” guide wheel positioner, wherein one steering guide wheel always remains engaged. This prevents a situation where the vehicle is neither directed left nor right, and so crashes into the middle of splitting tracks. The problem, however, is that if the vehicle is going at high speed, maybe with no turns in sight, the small steering guide wheels end up racing for no reason. An obvious remedy for this is to have the engaging “fin” within the track be discontinuous. That way, one wheel set will still be in the engaged position, for safety, but it will not have any running surface to engage to with, at least when on the straightaway. There is no needless spinning.
In the picture above the running surfaces for the steering guide wheels are shown in blue. Because of expansion and noise, the running surfaces should be finger-jointed and rubber mounted, so making them discontinuous and tapering them into and out of contact position is not a problem. (This detail is not shown)
This results in a different problem, however, also exacerbated by higher speeds. The steering wheels, if not engaged, cease spinning. Then, upon re-engagement, they would have to go from zero to thousands of RPMs in an instant, which would tend to tear them up. They must, therefore, be caused to spin prior to engagement with the running surface, and preferably at exactly the correct speed.
There may be some motor and controller out there what would work, but my guess is that it would be very, very expensive, and way over-built. These wheels need only spin. They don’t actually need to drive anything, even thought the monster shaft size would be consistent with delivering the power of a midsize motorcycle. I say make our own.
The “motor” shown above is a simplification. Additional electromagnets can be added. Now I don’t know a whole lot about digital electronics but I have bread-boarded some simple circuits and I know that if there is a source of pulses (such as the encoders I discuss in post 20) the frequency can be easily manipulated by simple means such as a J-K flip-flop, (a basic building block chip, available on Ebay, for example, for about 20 cents) This output can trigger a $5. solid-state relay and Voila! A simple motor. Again, I am sure someone else could come up with a much more refined design but I think the principle is sound. Maybe I should market this idea to Boeing or Airbus. Ever see how those landing wheels smoke when they hit ground?
We, as a community of PRT advocates, are, sadly, a painfully small group. This blog is now quite easy to find on Google, but the fact is there just aren’t that many people looking. The collaborative design infrastructure included on this site is pretty useless if there are no engineers who are interested. It’s been forty or so years and still PRT is a curiosity that few know about or take seriously. There is no dialog, no buzz, relatively speaking, though there is a bit of a comeback underway.
In my last post I asked for nominations for best video. All of the submissions, save four, were promotional corporate videos for particular systems. These tended to portray the advantages of a PRT system as the advantages of their own proprietary solution. One of those four, posted in a comment by alert reader cmfseattle, was a rudimentary mash-up of three promotional clips. It “got me to thinkin’…”
The problem as I see it is that the case for PRT is a multifaceted one, and not well suited to sound-bite evangelism. Sure, there’s “On Demand”, “Point-to-Point”, and “No sharing, No waiting,” but that’s all true of everyone’s cars as well. The advantages of PRT, as shown in the various promotion videos, often emphasize a comparison to other forms of mass transit. The ordinary audience doesn’t care which form of mass transit is best. Many never ride it anyway. The only, (quite predictable) result of this type of sales pitch is to get the light rail companies up in arms. Because the videos try to be upbeat and optimistic, the countless negative consequences of failure to act must be minimized. (That will be a trick for any PRT video)
We need an audio/visual approach to PRT advocacy very, very badly. When someone wants to explain PRT to a friend they should be able to say, “Look up “PRT” on YouTube,” and that person would get the whole message in a few minutes and walk away a believer. I wish we could get a Michael Moore or Al Gore to do a real documentary, but that is actually “Moore” than we need. (Sorry, I couldn’t help myself…) Heck, we don’t even have a generic PowerPoint presentation. A well constructed, 5-10 minute narrated mash-up of pictures and clips could do more to advance PRT than anything else I can think of. A picture is worth a thousand words and often a video is worth a thousand pictures. Every group on the planet has promotional videos except us. And it’s really not that hard.
It all starts with a great “storyboard.” The narrative is generally written below empty boxes, which can then be filled in with sketches or descriptions of what the viewer might see during those words. This is often done on a white board, because there is a whole lot of erasing and brainstorming involved. It does, however, make creating a coherent presentation much easier by preventing most effort from ending up “on the cutting-room floor…” (For you youngsters, that’s from when film was cut and spliced by hand.) Once a good storyboard is created, the “boxes” can be “filled” with specific images and video clips, presumably from the web, and the rest is relatively easy and cheap video editing. Speaking of editing, one thing I thought was a stumbling block is that the Flash file format used on YouTube. Yesterday, however, I downloaded a free program called “Any Video Converter” which makes downloading YouTube content a breeze and can convert files to any file format you can think of. This is a good thing for PC users because Windows Movie Maker (comes with Windows) seems (for me at any rate) to prefer WMV files over AVIs. (We will take a moment now to allow Mac users to smirk……. Thank you.)
Anyway, perhaps this site might be a useful vehicle for such a project to be done collaboratively. I do have, after all, the infrastructure in place. Just a thought.
Before everyone’s eyes glaze over from too much shoptalk, I would like to ask for nominations for the best videos to explain PRT to a complete newbie. It is time for me to update my “About This Blog” sidebar, and I want people who stumble on this site to go away believers without me having to waste a lot of space trying to explain it.
Speaking of the sidebar, I see my “Recent Comments” list is still blank - at least on my computer. If anyone is getting the list, or knows how to fix this widget, let me know. It would really help keep threads alive.
As most of you know, I am trying to finalize the design of the most cost effective, versatile PRT track design for suspended systems. Unfortunately, this entails exploring every conceivable use, limitation and bogie design. Higher speed. Tighter turns. Steeper slopes. Industrial. Freight. Heavier loads. Cheaper Stations. Manufacturability. Longer Spans… “Pod” designs may evolve, but the track stays, so we need to get this right. I have taken the approach that the running and guidance surface dimensions are a somewhat separate issue from the structural truss, and that these surfaces can basically be surrounded by a support structure. Inside, for example, most structure is no longer needed, because the running surfaces can be supported (hung) at frequent intervals. Anyway, it mostly comes down to the bogie design.
I have, lately, been working on a problem inherent to rail based PRT designs - the shear number of wheels required per bogie. Here I show an older bogie design with 18 wheels.
True, half of them need to fully disengage to switch tracks, but still 9 per side seems like a lot. In post 54 I show a much simpler configuration, with railroad style flanged wheels and little guide wheels that fit between the two halves, but this design is unworkable for high speeds. Post 56 shows a high speed-bogie, but with no steering wheels, so do not be confused. As you can see from the picture below, PRT’s acrobatic unpowered cousin, the roller coaster, requires many wheels as well, and would require still more if designed to switch tracks via steering guide wheels.
In railroads, they cut the number of wheels from 16 to eight by adding a flange to each wheel. The problem is that the flange creates friction with the track which would tend to overheat and wear it out at high speeds, smaller wheel diameters, or if it were made of some material other than conductive, strong (but loud) steel. To minimize wear, the designer must keep the wheels perpendicular to the rail surface, hence the 24 wheels per roller coaster car.
Some years ago, while arguing over a design detail of a piece of factory equipment I was designing with a machinist friend, I came up with this axiom. “There is nothing more efficient than absence!” I have returned to that thought many times since. So how can I get some of these darn wheels to be absent? Without flanging the wheels or track? While steering guide wheels can be disengaged for straight runs, guide wheels for centering the bogie cannot. One thought is to wedge the bogie in the track with angled wheels. Here is what I drew to help me think.
Could this line of thinking mean I need to take my track design completely back to the square one, after all of these months of exploration? The verdict is still out, and I have some more mature designs to share at a later date, which require some fairly lengthy explanation. But it is Sunday, and I’m in the middle of remodeling my bathroom, so I will bid you all a Happy New Year.
In the last post I touched on the idea that vehicles such as ULTra could be driven by “joystick”. This idea of driving by electronic controls (as opposed to the current practice of having actual mechanical connections between the pedals, steering wheel and the engine and brakes,) is not new. The use of electrical motors and regenerative brakes starts us down that road, which leads to the “skateboard concept.” (scroll down to post 50 for a picture)
Let’s take this line of thinking a step further. If the Ultra vehicles are guided by some kind of laser system that centers them on the track (with accuracy of less than a centimeter, I understand) such a system could presumably be fitted on private, steerable cars as well. An example of a steerable car which could presumably be easily modified for the ULTra control system is this Michelin concept car. The idea is that you drive your car to a ramp (or car “elevator”) and driver control is switched off and automatic control is switched on. Voila! You are now in a fully automatic PRT system until you are dropped off.
That Michelin video raises an important point however. People are really in love with their cars. The very best selling point of this electric car seems to be its muscle. Then there is the addition of luxurious creature comforts, such as adjustable seats, high-end music, etc. It seems to me that private vehicles will always become more and more loaded with features and power until something or someone steps in to halt it. Electric vehicles, in themselves, are not without environmental costs. The electricity they use must be generated, and this, itself, generally involves combustion. The prospect of hundreds of millions of Chinese cars being recharged by way of coal (their principle source of energy) power plants is truly frightening. Coal is, of course, 100% carbon, so there is no fuel on earth that is worse for global warming. Anyway, the point is that there would need to be some kind of societal decision as to how much to limit the power and weight (and therefore luxury) of these vehicles. We can’t afford a guideway network for Hummers. Because any vehicle on the system would need to be meticulously maintained, (combined with the necessary luxury limitations noted above) perhaps some type of leasing model would be the way to go.
This scenario does not eliminate “ordinary” PRT operations. Fully automatic “taxis” could still populate the track. PRT vehicles could come down to ground level and use a special lane to get to stops which cannot be served by raised stations. This would, of course, create the same interferences with vehicular and pedestrian traffic that plague other forms of surface transportation.
The main problem with the whole idea is the same problem that plagues all supported PRT systems. All supported systems inherently discourage true point-to-point travel compared to hanging systems. If they come to the ground they interfere with other traffic and pedestrians. Ramps must be fenced off for safety and are ugly. Stations must be positioned so that ramps won’t block driveways. If elevators are used to raise the passengers or lower the vehicle, the station is considerably more expensive. This is a big deal if you consider the economics of the network. I believe that in many cities the ridership figures are such that a great percentage, maybe even most, of the city would go unserved by the PRT network unless simple “bus-stop” type boarding areas are employed. I think this is a point worth repeating. It is a very big problem if the cost of stations precludes their use in large areas of a city. PRT needs the “network effect” to fulfill its promise as a transformational technology. Of course this is just money problem. If the government wanted to switch some road funds into PRT that would be a different matter. From a business perspective though, there will always be a number of riders under which it becomes unprofitable to create local service.
For the time being I remain very wary of any system that can only take the “low hanging fruit” to market.
Merry Christmas!
There has previously been, in my mind at least, some question about whether ULTra is really PRT. After all, the 40 km (25mph) speed is hardly “rapid”. And the distances that passengers will be willing to travel at those speeds are somewhat limited as well, although I suppose they are far enough to be legitimately called “transit”.
I started writing this post with a number of negative suppositions. I have previously criticized the ULTra design for being little more than a golf cart, and wondered aloud what the advantage of automating such a vehicle really was. Actually I was about to call for ATS (The company that makes ULTra) to consider a purchase of company like Taxi 2000, or PRT International, as a way forward out of the constraints of it’s present design limitations. I am forced, however, to reconsider.
I have been selling the ULTra designers short, I now believe, and this is why. Many of the aspects I don’t like about ULTra are truly intermediary. They will not stop ULTra from becoming much better (and more versatile) in future iterations. It seems that the designers over at ITS have a motto of extreme simplicity and conservatism. Anything else is kept “close to the vest”. Here is one example. The traditional steering, (as opposed to track constrained steering) at first glance, would seem to have all of the negatives of cars. It would skid on ice, for example. Safety issues would seem to prohibit any kind of speed with an automated guidance system. The idea of a track would seem SO much better than trying to center the vehicle with lasers and sensors. So why didn’t they do it? Well for one thing, tracks are less versatile, because they prohibit the vehicle from being able to move freely on any paved surface. But it is mostly, I believe, because they didn’t need to. Tracks would offer the potential of much higher speed but they don’t need speed. It’s only an airport “people-mover”. But the fact is that a track or guide rail is still perfectly compatible with ULTra. They just chose not to use one, for now. Lasers can be turned off, but you can’t easily pull up the tracks. Therefore lasers win. If and when speed becomes an issue a simple rail that sticks up under the center of the vehicle could be added, with minimal modifications to the vehicle.
One interesting aspect of ULTra is that it could presumably be driven away by a human operator, using a plug-in video game style controller. This would seem like a natural way for mechanics to move vehicles around a maintenance facility, for example. That raises intriguing questions about dual-mode, doesn’t it?
Don’t be too put off by the weight. They are using the old, heavy, lead-acid batteries. But once again, the only trade-off has been to design-in some extra space. They can upgrade to Lithium-Ion or even third rail at any time. It was explained to me that track electrification was deemed too costly, but I can’t help but wonder about partial electrification, so that the batteries could get some on-route charging. The possibility of easily swappable batteries also comes to mind.
I also hate the track, especially as seen from below. That would seem to be a hard sell for city streets. This, also, is not really an issue that can’t be much improved. There is nothing that says that the track must be massive concrete, for example, although noise could become an issue of the track was pure steel. There is a gradation between rails and roads. If redundant road area (anything not in line with being directly under the wheels) is removed you are left with a pair of very narrow beams – seems pretty much like a pair of rails to me. ULTra can theoretically drive on such “rails”.
I guess the lesson here is to beware of false choices. This does not just apply to Ultra. I was bemoaning the huge turning radius of the Anderson designs and a similar thought occurred to me. There is nothing inherent in the concept that prohibits tight turns. It I just that it necessitates a more complex bogie than is called for in the current business plan.
It is easy to look at a system from afar and the hard choices that have been made and to rap them up as defining that system, rather than see them as a collection of business decisions. ULTra is not a clunky, slow, heavy vehicle on an ugly, massive roadway. ULTra, like other systems, is an architecture first, and the rest of it is a means to salable iteration of that vision. This architecture, I am finding, is surprisingly tweekable.
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.
One of the essential steps in any kind of open-source collaboration would be some kind of classification shorthand to enable the parties to better reference their work, and the work of others. For example, if I want, presently, to refer to a system in which the vehicle is perched on a vertical extension of a captive bogey which extends from a slotted track, I have call it an “ITNS” or “Ed Anderson” design and mention Taxi 2000” or “SkyWeb Express”, (or vice versa) to be evenhanded. Making comparisons and design offshoots using those and a few other systems in a single discussion could get pretty confusing. The confusion would extend to procurement, contract awarding, etc. At some distant future point, someone will create some kind of certification process for aspects like track construction. That’s kind of hard when you can only describe the track in terms like, “It’s like the ULTra track but it will have screened middle sections like MegaRail…with a third rail…”
Originally I was going to fold this all under the “SMARTS” umbrella, (Small-scale Modularized Automated Rail Transit System) but realized that some important systems fall outside of that description. (A little note here. I think I like “Standardized Modular Automated Rail Transit” better. It is more descriptive of what I am up to…) Anyway, I believe breaking up the systems by key attributes, rather than vendors and inventors, allows a more substantive dialogue.
There are also obvious disadvantages. First of all, without the above picture as a key, nobody can use the system to classify anything. Secondly, who really knows the exact numbers to put in for the various systems except the designers themselves? I imagine one half-solution would be to simply “x” out the unknown latter details, so that the ULTra would be a “BGBxx” while MISTER would be a TIxx and I have been designing a TELxx, but Anderson likes the BELxx.
All I can say is that just because I don’t have the resources to make something happen, it doesn’t mean it is entirely useless to point the way. After all, classifications are essential for everything else, including roads, bridges and the vehicles on them.
Finally, I would like to thank alert reader “afransen” for pointing out that I can feature recently posted comments on the main page. (On right, scroll way down) This may help stop threads from going dead so quickly. Unfortunately it doesn’t show which post the comment refers to. Perhaps very alert readers will learn to preface their comments with a post number when they are commenting on older threads, which I will do myself. We’ll see how it goes. I’d love to see the threads get more content rich over time.
This feature is one of what Google calls “Gadgets” and it turns out that there are a whole lot of them, including the our new search feature. Believe it or not, I have been spending time every day this week creating an index. If I had known about the search “gadget” I would not have bothered. Now that it’s half done, I will probably finish it. If anyone cares, it is post zero. (oldest of the old posts) It links to posts by subject matter. When it is more complete I will show it as a link under the search bar.
One concept worth considering is making track from prestressed concrete. I’m not sure how it would work for the inner city or spans with a lot of curves or branches, but it might be a good candidate for freeway medians.
The groove on top and the corresponding hole in the support structure is for electrical or communication cables, and is meant to be covered by a metal cap. One might be tempted to question whether it is really feasible to cast such a shape. Actually it is really excellent, because by piping steam through a collapsible inner form, the concrete can be caused to set much more quickly. Beams can, in this manner, be removable within hours, allowing multiple castings per day.
The picture above shows the various rubber-mounted running surfaces associated with the previously shown designs. In a situation such as a high-speed longer distance application, not only would the rubber be unneeded, (concrete absorbs sound which, in freeway median applications, wouldn’t be and issue anyway) but most of the steel itself could be dispensed with, as well.
In applications with lots of stations and curves and branches it is easy to imagine a track in terms of a profile that serves all of those needs. For the duration of long, straight runs, however, the metal “fins” used in switching need not be present. Furthermore, larger wheels are probably in order for higher speeds, as suggested in post 56. Therefore the running surfaces normally used for the smaller low speed guide wheels should be removed or recessed, so that the small guide wheels don’t spin. In fact, I’m not sure that any of the steel shown is needed.
Without any buried utilities to prevent more closely spaced support posts, this might be a very cost effective way to handle the commuter market and reduce freeway traffic.
By the way, it occurs to me that most readers, even those with some engineering instincts, would be intimidated by the thought of trying to learn a new program, especially a 3D modeling program. Well the folks at Google are no fools, and they wouldn’t get into the 3D software business if they didn’t have something pretty special.
Here is a chair that I drew in under 3 minutes, following this YouTube tutorial. Try it. It’s fun!
Many of you who have followed this site, which is now nearly eighteen months old, may be wondering about this “Open-Source” thing. Obviously just showing my own design ideas isn’t really open-source. At the same time, I started at a readership of zero. I had to achieve some visibility. There has always been a compromise between what would grow the site and what would populate it with engineers. Anyway I have decided that it is time to take this project to the next level.
For several months now, this site has had the capability of enabling not just the sharing of my designs and ideas but of yours as well. Unfortunately, I’ve had a lot of problems figuring out what I was doing so I could clearly explain it to you, the readers and potential users. The problem was compounded because it really takes more than one computer and IP address to experiment with a system like this. Luckily I have recently found the time to at least partially figure it out, so, without further delay…HERE IT IS! (Corks pop and the sounds of noisemakers ensue)
First, if you want to not just look at my designs but play with them like you had drawn them yourself, I have posted the address of a download site to the right. (You will currently need Google’s free 3D modeling program “SketchUp”, although later the site may be populated with many other file types.)
Furthermore, they may be improved and resubmitted, or you can share your own projects. PRT control software would be nice!
It works like this. Google holds the files. We each have folders, which, when updated from the Google site, will have identical contents. Each of us can then open any project file in the folder and work on it. When we want to quit, we simply close the file in the usual way. It can then be either submitted to be shared, or reverted. If it is submitted, a text box will open where you will hopefully describe your work, so the rest of us do not get confused. You can also share your own project files by putting them in the folder and submitting them. Another option is to branch a project by changing a file and submitting it under a new name.
This is all done by a magic little helper program. (SVN) I am using one called Tortoise. It runs in the background and you access it by right-clicking the file or folder to get at its menus. It places little badges on the file icons in your folder – blue for one you just added, red for one you just modified, and green for the shared version that Google is holding. (A note on SVN jargon - Submitting a file is called “committing”. Your folder is called a “local repository”.) So anyway, by right clicking, you can ADD, REVERT, COMMIT, (individual files) or UPDATE. (The folder)
To get started, just go to the OpenPRT site, and go to “downloads” to get a MS Word doc with step-by-step instructions. By the way, those files under “Downloads” are already old. It’s best to go to “Source” > browse> svn>trunk to get the whole up-to-date library. Right now all I have is mostly the models that I used for illustrations for this blog. At some point we will need to start designing in earnest, from scratch. Note that there is even a wiki. This might just become the most important part of the site because wikis are great at linking related subjects. The design of any part of a PRT system inherently relates to many other parts, as well as to statements of design requirements, such as safety, cost, modularity, replacement/repair cycles, etc. With a wiki, every part can have it’s own page, and everyone can contribute and edit. This part-by-part discussion can then be put into 3D and worked on via the SVN. At the present the wiki is like a big unopened box. I invite you to create the first page.
It has become clear to me over the past months that I will need a lot of help with all of this. I think it is worth starting discussions about how to incorporate volunteers and create some kind of formal administrative structure. Wikis, SVN, managing open source projects…. None of this is really up my alley. I really hope we can get some good discussions going in the comment section this time. I really could use some guidance as to how to make this thing unfold.
One of the hallmarks of PRT/PAT travel is that the vehicle takes you from your origin directly to your destination with minimal waiting time. There are no transfers, no stops for other passengers, etc. The track, being for small vehicles, can be so light and inexpensive that it can be built into very extensive networks very cheaply.
In practice, however, the initial track layout will be extremely limited and it will take many years to spread citywide. Therefore it probably won’t take you from origin to destination. Furthermore to really make an impact, PRT should address the commuter, not just travel around the central business district. What is the point of PRT if you need to drive 10 miles and pay for parking to get to it? Do the models that various PRT venders are promoting address the crowded freeways? Is any PRT model that addresses the freeways even close to the model that addresses the central business district? What about the suburbs?
If the need were only in the Central Business District (CBD), I think I would give the edge to the general design parameters envisioned by ITNS/Skyway Express models. This will surprise many, as I have a record of advocating a hanging system. The difference is, in the CBD, the main emphasis is footprint. Speed, and cost of track and stations are secondary. Having elevators in every station is actually a pretty good way to economize sidewalk space, and it takes less energy to lift a passenger than a whole vehicle. In an environment of all multi-story buildings, second floor stations can be accomplished with little more than a balcony.
The situation changes markedly as the system expands outward from downtown, however. Here, the expense of the track and stations becomes critical as individual station ridership begins to drop. In these areas, bus rides to town are short and convenient. Putting up elevator-equipped stations on every block is far less attractive than it was downtown. Now the advantage, in my opinion, shifts to hanging systems, because they are generally more versatile in terms of slopes and curves and multiple speeds, and can accommodate open-air stations that may double as bus stops. Because of population density, stations should still be within walking distance of each other, but many passengers will just be passing through.
Next comes the suburban sprawl. This mixed-use area goes on for miles and is punctuated by mini urban centers, residential neighborhoods and distribution parks. There is enough housing and employment that many of the residents never go downtown. Here distance, and therefore speed, starts to become a real issue. The potential riders currently utilize a variety of road types to get around. Often there is a freeway nearby. The challenge for the PRT planner is to provide a system that can match speed and convenience with the combinations of freeway and back street shortcuts that are utilized by the drivers living and working here.
Because of the sheer size of the suburban sprawl, it is unlikely that any form of PRT will blanket such an area for quite some time. This suggests a “low hanging fruit” strategy, where major “hub” areas are accessible but many low volume routes are not incorporated at first. City buses (horrendously inefficient for long trips because of the many stops) could, none-the-less, be a reasonable option for going a few blocks to get on the PRT grid.Here it would seem to make sense to have some kind of PRT express lanes that go quite fast to connect community hubs. This is an entirely different model than the CBD, both in terms of preferred track and stations and preferred vehicle. Speed, versatility and track cost would seem to be the main design factors.
Finally there are the outlying suburbs and satellite communities. Commuters typically travel at posted speeds until they get close to town and then traffic backs up. These people generally have large engine vehicles because aggressive driving, for them, is somewhat of a survival skill. Keeping these cars out of city limits would do a city a lot of good. Here 30 mph PRT would be useless. It must be much faster to compete with the freeway. People in outlying communities cannot expect to have PRT vehicles come by their homes. Dual mode vehicles would be a poor substitute for the pick-up trucks and SUVs that get them around now. To be perfectly honest, I have serious doubts about whether PRT is the right tool for this job. It certainly calls for fast vehicles on a fast track, but why individualized vehicles? A park-and-ride GRT (Group Rapid Transit) station on the out-of-town side and an ad hoc drop off scheme might be a more efficient. Here is some thinking on this.
The main drawbacks with group travel are waiting and having the station locations that are catered to the average passenger but are not anyone’s exact origin or destination. I believe, however, that with automation and an intelligent system these problems can be largely solved. For example, the problem of fixed scheduling and associated waiting is largely a communication problem, as is inconvenient transfer locations. (Passengers and transit have had to meet at a prearranged time and place, because it is presumed that they can’t talk to each other.) If the “system” knows the complete itinerary of every passenger, the right size vehicle can be sent at just the right time for the group. Is transferring a really the problem if the time waiting for the transfer vehicle is eliminated? After all, PRT vehicles can swarm incoming GRT vehicles moments before arrival, and the “system” can decide where this meeting would take place. GRT requires heavier track, but the other choice may be requiring all PRT vehicles to be more costly and robustly configured than would otherwise be the case. Building super fast PRTs to go slow is a waste. Building high-speed high-capacity track might be a better investment. After all, this might find dual use for freight. There is also the matter of spreading the weight. Perhaps a “fast lane” with greater headways between vehicles and greater spacing between bogies would not need to be that much more expensive.
The track profile I have been working on is specifically designed to be adaptable for multiple weights and speeds. This brings up the question of track “permissions.” Obviously a heavy vehicle must not use light track, but light vehicles could use heavy track. Clearly slow vehicles should not hold up fast ones, but fast ones might want to use a slow track, on occasion. These questions are for a different day, but, to rap it up, I suspect automated transit is not a “one-size-fits-all” technology, and different parts of a city have differing transit needs, and therefore different optimal designs. I also wonder… What starting configuration gives the most bang for the buck?
Next week: The long awaited grand opening of the design collaboration site.
I would love to hear from you. I might even include your thoughts in a future post. (Only with your permission of course) Just email me- danverhoeve@gmail.com.
Want to download editable copies of the designs pictured in this blog? These (generally done in Google’s free 3D program“SketchUp”) are now available at our design collaboration site,http://code.google.com/p/openprt/Instructions for sharing, improving and updating designs via SVN are also posted there, under “Downloads.”
ABOUT THIS BLOG
Everyone knows that automobiles, as we know them, cannot continue to be the primary way the world commutes forever. There is the emergence of an enormous commuting class in the developing world, but it’s not just that there will not be enough fuel. The cost will be so high as to humble the world’s great powers, and be the cause of future wars. The impact on Global warming will be catastrophic. The health effects for residents of large cities is already significant. The lost productivity caused by grid-locked traffic currently takes a big bite out of our standard of living that we don’t even recognize. It will only get worse. Clearly something needs to be done. The problem is that there is, currently, no alternative. The car now offers the only real transportation system which has a prayer of offering a traveler a nearly straight line, nearly non-stop, essentially door-to-door journey. (I am leaving out bicycles and motorcycles, and scooters and Segways, etc. because they can all be problematic in bad weather, for older persons, etc.) Enter the PRT, or PERSONAL RAPID TRANSIT. . Though promising in theory, this concept has failed to deliver, and I think I know why. The problem is that the PRT systems developed thus far were developed not to solve this great world problem, but rather to create a business. This bias toward profit has poisoned the decision making process and created products with limited usefulness. I am not against profit. It is just that there has been too little emphasis on what a city wants and too much on what the corporation wants to offer. The system needs to be designed as a versatile, practical set of solutions, not as a product offering that reflects the strength and weaknesses of the company offering it. Proprietary or patented specifications and single source suppliers can only discourage a city government from taking the leap of faith needed to make PRT a reality. Enter this blog. This is but a timid first step on what could be a world-changing journey. What if the complete specifications for a working PRT system were developed and continually improved via posting online? What if the system was modular, with all of the various parts and pieces being individually ready to be out-sourced to the lowest bidder? What if the next company interested in being a PRT provider didn’t have to re-invent the wheel? What if the next city government considering PRT could have easy access to the thoughts and experiences of their peers in other cities? What if all the concerns - environmental, macro- and micro-economic, political, technical, fiscal, legal, even psychological- could be so completely vetted that cities world-wide could institute PRT programs with confidence and competence? So get on board, spread the word…and let’s change the world!
