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28 minutes ago, YNM said:

It only mentions a negative coefficient of expansion (which means that weirdly it won't crack due to heat). Doesn't mention anything about handling tensile loads.

https://translate.google.ru/translate?sl=ru&tl=en&js=y&prev=_t&hl=ru&ie=UTF-8&u=https%3A%2F%2Fru.wikipedia.org%2Fwiki%2FСиталлы&edit-text=

It's OK with loads. 250 MPa, like metals.

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2 minutes ago, kerbiloid said:

250 MPa, like metals.

Still doesn't clarify about tensile.

https://www.azom.com/properties.aspx?ArticleID=1441

Quote

Compressive Strength       328.5 - 362.2 MPa

Tensile Strength                  32.9 - 36.2 MPa

10% is more impressive than concrete (and the value is as good as concrete's compressive) but still not enough to be said "strong as steel".

Also, I bet it's bloody expensive, and you can't make it in very large amounts (like, in one block 10 metre tall, 60x60 cm) and there's no way to join them (steel are welded, concrete and masonry are cemented).

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  • 1 month later...

Seems like the move to "transit" from moving individual cars is a mistake.

Real train services have security, etc, but if you get on the cool glass car, and the other person happens to be a loon, you're trapped. Seems like it would have to control who got on, for one. Full facial recognition, etc, with cameras all over. The fee might be $1, but it should have a subscription price (even if for life) that is high enough to keep the riff raff off.

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47 minutes ago, tater said:

Seems like the move to "transit" from moving individual cars is a mistake.

Real train services have security, etc, but if you get on the cool glass car, and the other person happens to be a loon, you're trapped. Seems like it would have to control who got on, for one. Full facial recognition, etc, with cameras all over. The fee might be $1, but it should have a subscription price (even if for life) that is high enough to keep the riff raff off.

Honestly, all of it seems extremely bizarre, unpractical and half-baked. Even more so than Mars colonization or hyperloop. Like, what if something happens inside one of these tunnels, how do you get out? How does the rescue get to you, if there are other cars on the same track, and moving at 200 mph? 

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1 hour ago, sh1pman said:

Honestly, all of it seems extremely bizarre, unpractical and half-baked. Even more so than Mars colonization or hyperloop. Like, what if something happens inside one of these tunnels, how do you get out? How does the rescue get to you, if there are other cars on the same track, and moving at 200 mph? 

Very very strange

 

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3 hours ago, tater said:

Real train services have security, etc, but if you get on the cool glass car, and the other person happens to be a loon, you're trapped.

... Just like on a gondola.

And guess what, it worked.

 

2 hours ago, sh1pman said:

Like, what if something happens inside one of these tunnels, how do you get out? How does the rescue get to you, if there are other cars on the same track, and moving at 200 mph? 

What about that self-driving AI they're talking about ?

They can also rescue from the other direction. And maybe Elon would be interested in a front-loader.

 

Edited by YNM
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2 hours ago, YNM said:

... Just like on a gondola.

And guess what, it worked.

The problem is that they are not at all similar.

I suppose security is such that if a crime happens in a pod, the pod is immediately diverted to a police station. The trouble will be suicidal people bent on mayhem, I suppose, but there is nothing to do about them, ever, anyway.

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15 hours ago, sh1pman said:

Honestly, all of it seems extremely bizarre, unpractical and half-baked. Even more so than Mars colonization or hyperloop. Like, what if something happens inside one of these tunnels, how do you get out? How does the rescue get to you, if there are other cars on the same track, and moving at 200 mph? 

I do suppose that there is nothing terribly different than existing metro lines. I ride a major subway system every day and it's pretty normal. If there's an emergency while you're zipping through a tunnel with 6" of clearance at 40 mph, there's really not much that can be done. 

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27 minutes ago, tater said:

Not elevators, stairs.

Yeah, just circular stairs.

1 hour ago, sevenperforce said:

If there's an emergency while you're zipping through a tunnel with 6" of clearance at 40 mph, there's really not much that can be done

Well you could disembark.

 

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9 minutes ago, cubinator said:

True, that wouldn't be so hard to implement.

Seems like it would be non-trivial, actually. You go from a parking space sized entrance, to one capable of evacuation via stairs... dunno.

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This is the bedtime reading Elon was talking about: http://eng2.lacity.org/techdocs/emg/docs/INITIAL_STUDY.pdf

I didn't read it myself, the info is taken from a reddit recap.

It is a 1.5k page study supporting a request for exemption from EIR for the proof-of-concept tunnel, claiming that it is built on less than 5 acres, and is eligible for exemption. It says that the tunnel is 14 feet in diameter, with a 1-foot thick lining. It also says that the TBM will draw 3,800 "kVA," whatever that is.

This is a letter from the Brentwood Resident's Coalition, saying that an EIR is required, as the eventual size of the system will be larger than 5 acres, and there should be a margin around the current system when accounting size: http://clkrep.lacity.org/onlinedocs/2017/17-1342-s1_pc_4-19-18.pdf#page=3

Info from presentation:

They want to make supports/lining out of the muck they dig out. They also said the bricks will be $0.10USD, and stronger than cinderblock. (5,000psi) I'm pretty sure compressive strength isn't very important beyond what cinderblock or concrete already has, and they're likely to be much heavier than cinderblock, but the price is surprisingly low. They're going to sell "lego" kits made from the bricks.

They eventually want to go 0.3mph, 1/10th walking speed of humans. Goal right now is to beat snail speed, 0.03, which is 10x faster than TBM goes right now.

They're using an electric locomotive with model 3 batteries to haul muck, they think it is the largest battery electric locomotive ever.

They say it will cost 1$ per passenger.

They're partnering with the LA metro, to link their stations. It didn't sound like they were going to connect the tunnels, just have Boring co stations near metro stations.

The next TBM will be called "Prufrock," and (I think) be built from the ground up by the Boring co.

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  • 4 weeks later...
On 5/21/2018 at 5:33 PM, Mad Rocket Scientist said:

It also says that the TBM will draw 3,800 "kVA," whatever that is.

1 kVA = 1 kilo Volt Ampere = 1 kW /PF

PF is "power factor" and represents the power lost in the circuit due to a differnce between the phase of the voltage and the current. So if you supply 1 kVA to a circuit, it ends up doing less than 1 kW of work.

https://en.wikipedia.org/wiki/Power_factor

It's a thing with AC power because AC is complex (with imaginary and real components). Only the real part of the power does work. The imaginary part is lost to the power factor.

Edited by mikegarrison
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On 5/22/2018 at 7:33 AM, Mad Rocket Scientist said:

It is a 1.5k page study supporting a request for exemption from EIR for the proof-of-concept tunnel, claiming that it is built on less than 5 acres, and is eligible for exemption. It says that the tunnel is 14 feet in diameter, with a 1-foot thick lining.

... with tunnels 2.7 mi long.

This is absolute LOLs.

Wouldn't pass off in London.

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Anyone who listened to the long talk about the Boring Company that Elon gave knows why they want the exemption. They want to use the test tunnel, then solicit public input before they commit to making a huge EIR for what will then have to be the cast in stone final product. It's hard to be agile if gov regulation requires a few years worth of paperwork to get permission, that then needs to be entirely redone if literally anything about the design was to change.

Measure twice, cut once.

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4 hours ago, mikegarrison said:

1 kVA = 1 kilo Volt Ampere = 1 kW /PF

PF is "power factor" and represents the power lost in the circuit due to a differnce between the phase of the voltage and the current. So if you supply 1 kVA to a circuit, it ends up doing less than 1 kW of work.

https://en.wikipedia.org/wiki/Power_factor

It's a thing with AC power because AC is complex (with imaginary and real components). Only the real part of the power does work. The imaginary part is lost to the power factor.

OK, thanks.

The Boring Co. youtube just posted this:

 

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26 minutes ago, tater said:

Anyone who listened to the long talk about the Boring Company that Elon gave knows why they want the exemption. They want to use the test tunnel, then solicit public input before they commit to making a huge EIR for what will then have to be the cast in stone final product. It's hard to be agile if gov regulation requires a few years worth of paperwork to get permission, that then needs to be entirely redone if literally anything about the design was to change.

Measure twice, cut once.

I sympathize with that perspective, but a few years ago, I subcontracted to work on a couple of Tesla Supercharging stations. Their modus operandi was to bully all the local permitting staff, push ahead of other projects in the queue, and attempt to subvert standard permitting procedure as much as possible.  Likewise, we contractors were under a huge amount of pressure for very little money. And we're talking about a couple of minor projects that could have waited the additional month it would have taken.

I understand the desire to maintain momentum, but I have 20 years in this business, and we do things in a certain way because it produces good, reliable, responsible results. We also strive to maintain good relationships with the permitting agencies, because 90% of the people that work for them are smart, flexible, solutions-oriented people who want projects to succeed.

Anyway, the whole experience left a bad taste in my mouth. They were literally the worst clients I've ever worked for, and had no professional or institutional respect for anybody. You'll forgive me if I'm highly skeptical of any statements about permitting that one of Musk's companies puts forth. This isn't the first project in history that's operated in phases, so something is fishy about this story.

Addendum:  Civil Engineering may seem boring and fixed, but we frequently have to adapt to new design and construction technology and methods. The Boring Company isn't the first innovator that we in the industry have ever dealt with--They're not special, and they don't deserve special treatment.

Bonus: Part of the the background mapping for one of the stations (My company holds the copyright, so no issue posting it.)l1U3iZU.png

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