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Boring Company

Discussion in 'The Boring Company' started by Grendal, May 17, 2018.

  1. mongo

    mongo Well-Known Member

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    One pod every 1.5 seconds is the rate at the tunnel level. With multiple load/unload points (end goal, not the single point to point set up of Chicago and Dugout), the departure rate at any one node is much lower. 40 nodes would be correspond to a pod a minute entering the system.

    One option is a set up up similar to PCB routing. N-S at 2 tunnel diameters down, E-W at 4-5 diameters down. Then, the tricky thing is directional changes, but the elevators could also do a rotation to handle that.
     
  2. bxr140

    bxr140 Active Member

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    They do, though I’d imagine that the diameter of that newest line (that’s still 40 years old...) was chosen specifically because of overall compatibility with the existing lines/systems, and probably also because of available design and construction techniques and tools. If the expansion were a white page solution like the Boring company its hard to imagine they’d go with that small of a bore size or that carriage cross section.

    I think its important to differentiate the discussion between a curved/angled wall and the super curved/overhung/knuckled wall configuration of the small Tube cars. Its hard for me to create a practical geometrical configuration that actually requires the later in a 14’ Boring tunnel. Of course it is feasible to still create a configuration with walls slightly curved/angled enough to create headroom problems.

    For reference, the cabin in a 737 is ~11.5 feet wide. If we assume 11.5' is basically the usable space for a Pod in a 14’ bore (which I think is pretty conservative for Elon…), one can imagine similarities with that 737 pax cabin and the widest possible Pod configuration/cross section, where the walls basically have a slight (~10 degrees) angle with a curve. Importantly, even though you’d obviously have headroom problems trying to stand at the 737’s “A” or “F” seat, there’s really no other configuration in an 11.5' cross section to better maximize standing room of the human form factor.

    I think there’s legit pros and cons for ‘outside’ wheels, though I think all wheel configurations have the ability to be pretty well optimized (in different ways) for an overall solution. I see the other wheel configurations as ‘undermount’ (like traditional trains or big rig trailers), ‘inside’ (basically, automobile-like) and, for lack of bxr imagination, ’tucked under’ (think double-deck trains or low-boy big rig trailers). I can also imagine a lot of overlap between the various options.

    Here’s a few things that might affect the trade study for wheel placement:

    -I think most importantly, the base Pod platform needs to be configurable for multiple cabin configurations. You might need a standing Pod for around town, you might need a sitting pod for getting out to a remote airport…
    -For short duration public transportation I believe maximizing standing room is almost certainly the best way to maximize the overall system
    -Height. Pax pod height is pretty well set by the human form factor, but these systems may also transport cars, trucks, and even shipping containers.
    -Aerodynamics. Pretty self evident: bigger is worse. For reference, you can feel the air mass being pushed by the bent-wall Tube trains a good 2-3 train lengths ahead of their arrival, because they’re so stuffed into the small bore tunnels.
    -Passenger loading. Outside wheels are not really compatible with traditional elevated platform loading.
    -Stability. Especially if the Pod rolls on something other than a traditional conical flanged wheel on a rail, wider might be better. I can see ride comfort being improved with a wider track as well.
    -High speed loading. I can see some super-cool solution to optimize Pod roll angle based on real-time feedback. Maybe even pitch..to work against acceleration and deceleration. Such a concept would probably work best with wider tracks.
    -Assembly and maintenance accessibility. Important bits on the side are easier to get to than important bits on the bottom…
     
  3. RDoc

    RDoc S85D

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    One design element, I think is present, is the large trench under the grating below the cars. Most subway systems, such as the Tube, don't have that, and the air in the tunnel is pushed ahead of the train which acts like a piston. This pretty much obviates any aerodynamic issues since the air doesn't flow over the car to any extent. I'm wondering if the point to the trench design is to allow the air to flow under the car to lessen air resistance.

    WRT seating/standing: I don't think they'd want different configurations because it would be much more convenient to have the same car switch between local (<2 km) and long distance (<20 km) journeys without reconfiguration. For example, when daytime traffic switched to commuters going home. One issue with standing is that it seriously limits accelerations, which in turn requires longer on/off ramps and turn radii.

    I'm not sure the 737 analogy is relevant since they plane uses the bottom of the cylinder for cargo which wouldn't be the case with the Loop cars. For the Loop, the "aisle" will be much lower, therefore narrower.

    Overall, I'm surprised they went with 14' tunnels. Smaller tunnels are cheaper and faster to dig as well as being stronger. For individual car dispatching, you don't want too many people in one car either I wouldn't think, so unless the cars are going to be pretty short, I don't see the point to the larger tunnels. Perhaps they will be quite short, but with very close platoon spacing when needed.
     
  4. mongo

    mongo Well-Known Member

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    Perhaps the large tunnel size is done to allow airflow around the pods? In the land of trade offs, they only dig it once, but pay for energy usage forever.
     
  5. bxr140

    bxr140 Active Member

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    From a first order analysis of aerodynamics, a trench doesn't really matter. What matters is the cross section ratio between the train/pod/carriage and the bore--a trench would simply be the result of trying to maximize that ratio in a configuration that uses wide rails. If the Boring solution ends up with something similar to legacy rails, there will be no trench and the aerodynamic solution of the carriages will look something like what we currently see with high speed rail. Of course, there's a lot of value in tying rails on solid ground (like legacy rails) over mounting them spread far apart and on either side of a trench, but certainly if anyone can make wide rails work its Boring. But...it won't be cheap or easy--wide rails would be a sub-optimized element of a bigger picture optimization.

    Boring absolutely wants different seating configurations--they absolutely want units optimized to do this or that, and they absolutely want the ability to reconfigure them based on actual usage. Its very similar to the aircraft model--you can buy a 737 airframe and turn it into a two class pax, a one class pax (economy or business), a split pax/freighter, a BBJ, a C-40, etc...then when someone buys your 737 they can reconfigure. The good thing about Boring is that there will be another layer of configuration similar to the auto industry (including the S/X skateboard) where a commonized base vehicle can be permanently fitted to serve all manner of transportation needs (its also kind of like the aircraft industry where you can get a long haul or a short haul model on similar airframes).

    If you're talking daily reconfigurable, then I'd agree its unlikely they want to do that, but again if anyone can make it work its Boring.

    Of course. However, as previously noted, mandatory seating demands an aircraft-like passenger safety experience (and specifically the time component), which is a total non-starter for intra-city travel. Its also hard to imagine mandatory seating enabling a big enough time delta for longer trips either. Faster accel/decel saves seconds. Slower aircraft-like boarding and de-boarding wastes minutes.

    Also as previously noted, there's an opportunity for Boring to design roll and potentially even pitch control of passenger pods to reduce unpleasant g-loads on passengers.

    Its important to maintain context in multi-faceted discussions--in this case context is specifically the suggestion that Boring pods should have tube-like overhung walls/ceilings. I think we can all agree that the only real reason to have such a feature is if you're trying to maximize the width of a bore. As such, the 737 mental exercise is very relevant in context because it fairly accurately represents such width optimization exercise. And that exercise clearly illustrates there's no need for the overhung tube-like walls/ceilings. Its also very relevant because [again] regardless if your pax are sitting or standing, the pax deck height in a 737 is pretty well optimized for maximizing width within that cross section. In other words, if Boring was trying to maximize bore width, the cross section of the whole thing would look quite similar to a 737.

    Personally I don't think maximizing bore width is the ideal way to maximize the system efficiency (I think longer trains that minimize aerodynamic cross section is a better overall solution), and I think we can all agree that if you aren't trying to maximize bore width, you just make your carriage walls vertical-ish, similar to the sub-surface Tube carriages. Of course they'l have some profile that's aerodynamically efficient, but nothing like what we see on a small Tube carriage.

    Interesting perspective. IMHO, 14' seems like an obvious lower bounding condition. 12', for instance, puts the aircraft analogy somewhere closer to the cabin of an MD-80/717, and anyone who's been on the small Tube lines knows how cramped they can get. 12' all but eliminates the possibility of using the system to transport ISO containers (which are 8' wide and 8.5' tall). Smaller being stronger is a bit of a straw man--there's plenty of lager tunnels in the world. Cheaper/faster is a bit too narrow--optimizing the system is more important than optimizing a single element, like construction.
     
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  6. dmckinstry

    dmckinstry Model X 2019

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    Just adding to the thread since I didn't know where else to put it.
    With a boost from Shell, HyperSciences blasts past $3M in crowdfunding campaign
    The above link is to an interview on geekwire with Mark.
    Hypersciences is a startup by Mark Russell. My youngest daughter was just hired back by Mark to work for him on this project. She's an executive assistant, not an engineer.
    It's interesting in that the technique can bore up to 10 times as fast as any rotary drilling process.
    If Elon finds it useful, he could put it to use by the Boring Company.
     
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  7. BioSehnsucht

    BioSehnsucht Model 3 LR

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    Not sure how well it would scale to tunnel boring. That would be a lot of projectiles to fire, and then either you must clear them or fire through them?
     
  8. mongo

    mongo Well-Known Member

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    Need to clear the volume of rock plus projectiles.

    @dmckinstry Interesting, but doesn't apply to the soft soil shield TBM type of work Boring is currently doing.
     
  9. Grendal

    Grendal SpaceX Moderator

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    Very interesting concept that makes a lot of sense. I wonder if it can scale up to make large tunnels though. My instincts tell me that it wouldn't work as well on a larger scale but maybe it can be done on a smaller scale but with lots of them at once. Or would it help a large boring machine by "tapping the hole."
     
  10. Sean Wagner

    Sean Wagner Member

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    An interesting hybrid method of increasing the power density in a useful way at the tip of the digging tools.

    How about this for bigger projects going through rock: use many such drills roughly following the tunnel's outline, then dynamite the core and evacuate the debris.
     
  11. dmckinstry

    dmckinstry Model X 2019

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    I was thinking something like that too. Make a larger diameter hole by using a circle of the smaller drill holes, and a center hole in which to place explosives. Really same thought as yours.
     
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  12. Grendal

    Grendal SpaceX Moderator

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  13. mongo

    mongo Well-Known Member

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    Elon responding to NBC article:
    Twitter

    Also: Godot is back above ground:
    Twitter
     
  14. Bobfitz1

    Bobfitz1 Active Member

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  15. Grendal

    Grendal SpaceX Moderator

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  16. ecarfan

    ecarfan Well-Known Member

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    Was that video available last night? When I try to play it now, nothing happens.
     
  17. mongo

    mongo Well-Known Member

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    At one 4 person car per second (the value provided from the presentation), that is 4*60*60 = 14,400.
    If you want to argue about the base assumptions, that is one thing, but @Fact Checking 's math is not wrong

    So let's look at the 150 MPH, car a second use assumption:

    Regardless of the failure, a car is not going to stop instantaneously. Great tires can get you 1 G or so. At 150 MPH, that is 7 seconds to stop or a distance of 756 feet. Say a failure caused a 2 G deceleration (by grabbing both sides of the track). That is 3.4 seconds and a distance of 378.2 ft. One seconds of travel at 150 MPH is 220 feet, so the trailing car has 598.2 ft to stop in which is about a 1.26G stop rate (it can also grab the track to E-stop).

    Not seeing a problem.

    Boring Company financial discussion (Out of MA)
     
  18. KarenRei

    KarenRei ᴉǝɹuǝɹɐʞ

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    #78 KarenRei, Dec 19, 2018
    Last edited: Dec 19, 2018
    As for all of the talk about spacing being 1 second on the Autobahn, so 1 second spacing is safe in the tunnels... that shows how silly 1 second complaints are about the tunnels.
    • All tunnel vehicles are driven autonomously, centrally controlled, with an instantaneous response to any slowdowns for any reason.
    • Weather does not affect tunnel drivers.
    • Nobody is going to spontaneously change lanes; all entrances and exits from the tunnels are centrally planned, with space created for the merging vehicle well ahead of time.
    • There's no need for the driver to pay any attention whatsoever. I seriously doubt the system will even let them take control.
    • Even if you did manage to have some "incident" in one vehicle go unnoticed that caused the vehicle behind it to crash, at the very least, the second vehicle would detect that it was in an accident and transmit that, causing vehicles behind it to stop. Essentially rendering "many-car accidents" impossible unless every single one of them had an error in which they did not notice and transmit the fact that they were in an accident.
    It's nothing like the Autobahn; it's orders of magnitude safer.
     
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  19. KarenRei

    KarenRei ᴉǝɹuǝɹɐʞ

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    Then consider the 12-16 person passenger cars....
     
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  20. Buckminster

    Buckminster Active Member

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