General > General Technical Chat

Elon Musk's Vegas Loop... Debunking.

**tszaboo**:

--- Quote from: nctnico on June 12, 2021, 06:55:50 pm ---The reality is that underground transport systems can easely be outperformed using a simple bicycle (let alone an electric bicycle). The effective speed of underground public transport is really low.

--- End quote ---

So, I looked up the speed of subway that I was taking on the daily basis in Budapest. The effective speed (with stops) is 32 Km/h. The average cycling speed 12.4 KM/h in the Netherlands. I would ignore the fact, that its the question of time when you end up in a hospital for using the bike in that city.

**nctnico**:

--- Quote from: tszaboo on June 14, 2021, 11:26:10 am ---

--- Quote from: nctnico on June 12, 2021, 06:55:50 pm ---The reality is that underground transport systems can easely be outperformed using a simple bicycle (let alone an electric bicycle). The effective speed of underground public transport is really low.

--- End quote ---

So, I looked up the speed of subway that I was taking on the daily basis in Budapest. The effective speed (with stops) is 32 Km/h. The average cycling speed 12.4 KM/h in the Netherlands.

--- End quote ---

What you are overlooking is that public transport always takes a detour and a bicycle goes from A to B directly. Travelling at 32km/h doesn't do you any good when you are going in the wrong direction.

**boffin**:

Station Capacity Calculation - aka "Why the 4400 number cannot be pphpd"

First, what is pphpd?

passengers per hour per direction is the standard measure of transit systems, so when you see "XXXX Metro carries 25,000/hour" that's the number they're using

examples:

Expo Line (Vancouver, Canada): 25,000 pphpd

L1 New York: 36,000 pphpd

Central Line (London UK): 32,550 (35 trains/hour * 930/train)

VEGAS LOOP

What we can assume:

40 second load/unload (cars have seatbelts, every ride I've seen people buckle up)

3 persons/vehicle

West and South stations:

8 load/unload bays

10 sec/minute lost to pedestrians crossing the loop (seriously - check out the attached image)

... 3000 operational seconds /hour

-> car leaves every 5 seconds (40 seconds / 8 bays)

-> 600 cars/hr (3000 / 5)

carrying 3 people each

= 1800 people per hour (not anywhere near 4400)

Central station:

5 load/unload bays

-> car leaves every 8 seconds

-> 450 cars/hour

carrying 3 people each

= 1350 people per hour (also not 4400)

--------------------------------

And I still stand by my "a tad over 3 minutes"

Boffin: "a tad over 3 minutes" (assumed some load/unload time)

Demo Video: 2m39s with no allowance for stopping (1m38s - 4m27 )

LVCVA (2019): "just over one minute" https://www.prnewswire.com/news-releases/las-vegas-convention-center-makes-history-as-elon-musks-the-boring-company-begins-tunneling-the-destinations-first-underground-people-mover-300959530.html

LVCVA (2020): "under two minutes" https://www.prnewswire.com/news-releases/development-of-elon-musks-innovative-underground-transportation-system-achieves-milestone-301059887.html

LVCVA (2021): "just under two minutes" https://www.prnewswire.com/news-releases/first-look-inside-elon-musks-underground-transportation-system-beneath-the-las-vegas-convention-center-301266042.html

Reality (from world of concrete - last week)

Video:

depart west station: 5:41

arr south station: 8:54

Total Time 3m 23s

-------------------------------

And the Math says...

Theorhetical fastest @ 44mph

What we know:

LVCVA: "Doing 40mph"

LVCVA: "10mph through the central station".

'speed zone' in the middle of 10mph (5m/s) is about 80m long

'speed zone' approaching the end station of a similar distance (note there's a 90 degree corner exiting one end, nasty)

total tunnel distance: 1350m (0.85mi) - (not 1.7mi, that's counting both tunnels)

What we can assume:

Let's give them the benefit of the doubt, and assume 20m/s and 5m/s (about 10% more than their claim, but makes the math easier)

Acelleration: 2m/s² (brisk, not back snapping)

START

accel: 0-20m/s @ 2m/s² for 10 seconds = 100m (ut + ½at²)

steady: 20m/s for 20 seconds = 400m

CENTRAL STATION: SLOW TO 5M/S

decel: 20-5m/s @ -2m/s² for 7½ seconds = 94m

steady: 5m/s for 16 seconds = 80m

CENTRAL STATION: SPEED UP AGAIN

accel: 5-20m/s @ 2m/s² for 7½ seconds = 94m

steady: 20m/s for 20 seconds = 400m

WEST STATION: SLOW TO ENTER STATION

decel: 20-5m/s @ -2m/s² for 7½ seconds = 94m

steady: 5m/s for 16 seconds = 80m (approach)

decel: 5-0m/s @ -2m/s² for 2½ seconds = 6m

END

time 107s absolutely best case assuming best case acceleration/deceleration, max speed maintained as long as possible, no impeding merge traffic, and no impeding pedestrian traffic (sad I have to add that 3rd one)

<sigh> I beginning to feel that people learned nothing from Solar Roadways and Batteriser

**sandalcandal**:

Good on you for doing the maths Boffin but I think you're still missing my points here.

4400 according to reasonable calculations as I said before cannot be met if you assume only 3 to 4 people per vehicle. I think you've taken this to mean the 4400 number is coming from counting journeys rather than a pphpd. My idea was that they are using "real" current numbers and extrapolating capacity on when the vehicles are capable of carrying 16 people instead.

107s for fastest possible most aggressive driving versus 159s real demonstration video. I mean you did the calculation yourself using "real" physically achievable values and you are getting a "just under 2 minutes" number. What's the problem? It is unreasonable for them to have done a similar calculation and used that as an estimated/advertised result? This is hardly on the level of Solar Roadways and Batteriser.

Edit: This is also still not factual evidence of how system capacity is being measured and marked as achieved. This is speculation based on assumptions and guess work which isn't unreasonable but still not "factual". Again my guess is that they are using performance values of the current system and extrapolating to when vehicle capacity is increased. AFAIK there was been no detailed reports released on how they actually determined the "4400 passengers per hour" target has been reached. All we have is speculations which have done little to rule out the ability of the system meet performance targets.

Again, I think we will see trip times taking >2min total but extrapolations (or actual achievement) using higher capacity vehicles.

**boffin**:

--- Quote from: sandalcandal on June 15, 2021, 10:45:49 am ---Good on you for doing the maths Boffin but I think you're still missing my points here.

107s for fastest possible most aggressive driving versus 159s real demonstration video. I mean you did the calculation yourself using "real" physically achievable values and you are getting a "just under 2 minutes" number. What's the problem? It is unreasonable for them to have done a similar calculation and used that as an estimated/advertised result? This is hardly on the level of Solar Roadways and Batteriser.

--- End quote ---

Just a reminder the 159 second trip time is a vehicle that DOES NOT STOP.

In order to achieve the magic under 3m (2m39s), they will have people leaping in and out of moving vehicles ?

The lack of critical thinking here is EXACTLY on the level of Solar Roadways and Batteriser

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