@neroden
I didn't say it was a problem, only that it is true that increased density (at the same speed) increases throughput.
What throughput is needed is a different question.
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Boring Company
- Thread starter Grendal
- Start date
I didn't say it was a problem, only that it is true that increased density (at the same speed) increases throughput.
What throughput is needed is a different question.
Well do the experiment. Take the subway. Use a stopwatch and see how long a piece of track is unoccupied. Spoiler: it's a long time.
I'm not saying subway is better than Loop. I'm saying if you put the Loop pods closer together going at the same speed you get a higher throughput (pure physics statement)
Yes, if you take number of pods the equivalent to the subway train capacity and space them over the subway train separation distance, and run them at the average subway train speed you get the same aggregate throughput. But Loop cars don't stop at each station. (I like Loop)
I'd like to see some references to train coupling systems that can operate while the train is moving at full speed. For someone with neroden's vast knowledge, coming up with several examples should be trivial.
Applying Netwonian frame of reference to the situation, couplers don't know that are moving, so as long as they are not under load, any automatic coupler system could disengage while underway.
The pod system is simpler due to no air lines to link and having individual drive units.
My thinking is that while urban Loop systems have lots of obvious advantages over existing subway and bus systems, the real win will be in regional transportation.
In the central Boston area (Boston, Cambridge, Somerville) as in many other popular urban areas, the cost of real estate has become such that commuter traffic is overwhelming the city. There's really no place to expand conventionally because the close suburban areas won't allow high density development and easy transportation doesn't reach them anyway.
However, there are several existing urban areas within 30 miles that would love to expand. The problem is that transportation is such a mess that they aren't considered to be part of the attractive Boston area. However, for example, if a Loop system connected Copley Square, Boston to central Lowell, with a travel time of 15 minutes and a wait time of 5 minutes, it would be faster than Copley Sq to Harvard Sq by subway (if the subway didn't break down).
With the short travel times that the Loop system promises, places like Lowell could very rapidly develop as effectively neighborhoods of Boston, much as Davis Sq in Somerville has.
In the central Boston area (Boston, Cambridge, Somerville) as in many other popular urban areas, the cost of real estate has become such that commuter traffic is overwhelming the city. There's really no place to expand conventionally because the close suburban areas won't allow high density development and easy transportation doesn't reach them anyway.
However, there are several existing urban areas within 30 miles that would love to expand. The problem is that transportation is such a mess that they aren't considered to be part of the attractive Boston area. However, for example, if a Loop system connected Copley Square, Boston to central Lowell, with a travel time of 15 minutes and a wait time of 5 minutes, it would be faster than Copley Sq to Harvard Sq by subway (if the subway didn't break down).
With the short travel times that the Loop system promises, places like Lowell could very rapidly develop as effectively neighborhoods of Boston, much as Davis Sq in Somerville has.
There's a lot of engineering between Newton's kinematics and an operational system. On all existing rail systems I'm aware of, an uncoupling at speed generally is treated as serious emergency. Then there's the matter of re-coupling at speed.
If you don't agree, let's see some references.
John Beans
Member
Or don't even couple them, just let them run close together. Uncoupled, they can easily go into a loading area one at a time, like they do at the log ride at Disneyland. Uncoupled cars can have a wide range of system density (max = cars touching, min = one car in system, in between just add cars).
I'm not saying regular trains are designed to couple/ uncouple on the fly (there is little use case for it) nor is anyone saying pods would use Janney couplers. However, there is no reason they could not (assuming the air line connections support it). The only requirement for uncoupling is to have the pin pulled and the coupler unloaded (which is needed to be able to pull the pin). The couplings autoconnect when one is pushed into the other (assuming they are aligned).
Consider that the Dragon berths at a much higher velocity...
My personal take is that couplers are not needed.
Clearly for Loop, physical couplers aren't needed or useful. Although, they might have something to deal with breakdowns. That's one of the many advantages Loop pods would have.
However, that is not at all equivalent to a rail system physically connecting together cars, which was the original contention. In particular, if you've ever watched couplers on light rail while in motion, they are always jerking around due to the cars' ends moving at varying speeds in 3D relative to each other. To make a physical coupler work at high speed would require some system, such as Dragon uses, to match velocities, but with much tighter space and time constraints, inches and milliseconds, not miles and hours.
I am extremely doubtful that any such system exists or would even be practical, but I'm waiting for neroden's examples to be posted.
moving this post from the General thread ...
Depends on the location in question. In areas where everyone of all classes uses public transportation, it tends to be safe. In places where only "the poors" use it, it tends to be unsafe (under policed among other problems) as well as less clean, and other various problems, that make it undesirable for anyone who can halfway afford a car.
Of course it's sort of a chicken and egg problem. With low ridership and/or poor public perception, comes a lack of funding for maintenance (including cleaning), expansion of service (both lines and operating hours), security, etc. But without those things, you won't convince anyone to take it, and if you tried to pass a measure forcing it (by banning cars from the city streets) you'd just trigger an exodus rather than solve the problem.
Depends on the location in question. In areas where everyone of all classes uses public transportation, it tends to be safe. In places where only "the poors" use it, it tends to be unsafe (under policed among other problems) as well as less clean, and other various problems, that make it undesirable for anyone who can halfway afford a car.
Of course it's sort of a chicken and egg problem. With low ridership and/or poor public perception, comes a lack of funding for maintenance (including cleaning), expansion of service (both lines and operating hours), security, etc. But without those things, you won't convince anyone to take it, and if you tried to pass a measure forcing it (by banning cars from the city streets) you'd just trigger an exodus rather than solve the problem.
Do we know what size tunnel Dugout is supposed to use? Do we know they aren't considering larger tunnels (not the size of traditional subways perhaps but bigger than their current Godot tunnel) ?
They are claiming that one of the main ways they lower costs is by boring smaller 14' tunnels. One thing to keep in mind is that the London Tube tunnels are about 12' in diameter.
This is a variant where the roadway is out to the edge of the tunnel, which looks a bit more reasonable.
This is a variant where the roadway is out to the edge of the tunnel, which looks a bit more reasonable.
They have been working on software platooning on normal roads for years with large vehicles using ICE powertrains.
Loop is lower mass vehicles with electric drivetrains on a closed course with better dimensional accuracy along with design restricted lateral positioning.
If they have a bumper with 12 inches of travel and a 12"x24" profile, they can even go mostly sensorless. Concider, by having the approaching pod go 0.6 MPH faster than the front pod. Speed delta of 0.88 ft/sec with a 1 foot compression zone (half of bumper pair) and linear deceleration rate yields >2 second joining event. Acceleration of 0.44 ft/sec/sec or 1/70th of a g.
And that assumes no contact sensors on either pod to change the motor setting. For instance, on contact, the front pod could go light regen (or a power level less than its own drag) to maintain coupling. Bumper compression sensors would also allow for continued monitored contact during the journey.
This is already done via bump drafting in NASCAR.
One significant difference is that in the Tube, the wheels/suspensions are under the carriage, not on the side. The Tube also uses curved walls with full standing height only in the center of the carriage. I don't see what the point is to the Boring Co. design with straight walls and wheels on the outside of the carriage.
The central trench, I suspect, is there as a vent to prevent high pressure air buildup in front of the pod when it's moving at high speed, so the design the Tube uses, with the trucks under the carriage, probably wouldn't work. However, a more conventional automobile design with the wheels at the four corners, inset into the body, would allow a wider pod, albeit with some increase in length.
Well, I wouldn't assume anything about the pod design is too locked down. I think the renders we've seen are for the concept of a pod where the sled can have the pod removed and you can drive a car onto it (a sort of universal sled), but they might end up going with dedicated pods instead of pods on car sleds. Needing to be able to drive a car onto it certainly explains why the wheels are outside ...
Even though they haven't been pushing that concept for a while, the pod renders are more or less the same since when they were.
Even though they haven't been pushing that concept for a while, the pod renders are more or less the same since when they were.
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