[OTTD] The Vactrain Set

[FooBar]

Would be a nice math problem though.

Count me out of this!

Oh heh. That was meant as a general remark, not specifically addressed to you

[Voyager One]

I know but math+me=Chernobyl... And to think that I've been in the math gymnasium...

[FooBar]

Yeah, I'm not too fond of it either

[Supercheese]

Would be a nice math problem though. Assuming acceptable acceleration values (take those of maglev) and assume infinite constant accelleration... what would your speed be if you don't brake?

Over nine thousaaaaaaaaaaaand (miles per hour)?

[FooBar]

That's correct, just slightly more though. Assuming an acceleration of 1.3 m/s^2 you have a speed of 36747 km/h or 22834 mph by the time you're one time round the earth. In just over 130 minutes.

If you want to do other calculations:
t = sqrt(2 * s / a)
v(max) = sqrt(2 * s / a) * a

with:
t = time
s = distance
a = acceleration
v = speed

If I've done my math right. Please correct me if I'm wrong; it's late already, so I may have overlooked something

[Emperor Jake]

...it is actually a bit strange to use monorail in the vacuum.

Whatever gave you the impression that there were monorails in the vaccuum tube? The GRF description and several posts here clearly state that they're maglevs. I just used the monorail track graphics because they looked better when combined with the vacuum tube "catenary". I was planning to draw my own tracks that matched better, but I haven't got round to it yet

[Zephyris]

... you have a speed of 36747 km/h or 22834 mph

...which is well over the orbital velocity of ~17400 mph at sea level so you would shoot off into space unless you were held down by quite a strong vertical acceleration! That is not quite the escape velocity (25039 mph) though, so you would fall back to Earth (eventually) if the maglev flew off the tracks after once around the equator.

[Emperor Jake]

... you have a speed of 36747 km/h or 22834 mph

...which is well over the orbital velocity of ~17400 mph at sea level so you would shoot off into space unless you were held down by quite a strong vertical acceleration! That is not quite the escape velocity (25039 mph) though, so you would fall back to Earth (eventually) if the maglev flew off the tracks after once around the equator.

Which brings us to those theoretical maglev space launch systems that actually accelerate to escape velocity, and would be used instead of rockets. If only OTTD extended into space...

[Transportman]

That's correct, just slightly more though. Assuming an acceleration of 1.3 m/s^2 you have a speed of 36747 km/h or 22834 mph by the time you're one time round the earth. In just over 130 minutes.

If you want to do other calculations:
t = sqrt(2 * s / a)
v(max) = sqrt(2 * s / a) * a

with:
t = time
s = distance
a = acceleration
v = speed

If I've done my math right. Please correct me if I'm wrong; it's late already, so I may have overlooked something

Looks correct, x=1/2*a*t^2 (integrating acceleration twice with respect to time), rewriting gives your equations (didn't check the numbers). Remember that this is only valid for constant values of a. For a(t) the integral changes but it is still relatively easy to solve, but realistic acceleration follows from Newtons law F=m*a, where F is the sum of all forces and is a vector (just as acceleration is). Because F also includes the drag force (which can depend on v in multiple ways), only iterative methods work and no analytical solution exists in most cases. (and as Zephyris points out, the maglev will not stay on the ground unless additional downwards force is added)

Small addition: the complete equation is x=1/2*a*t^2+v0*t+x0, because integrating gives a constant (and integrating twice gives 2 constants). Since we assumed v0=0 and x0=0, those terms fall out and you only have the x=1/2*a*t^2 part.

[lawton27]

To further aid this: the downward force required would be F = (mv^2)/r.

Which works out as at the maximum velocity and using the radius of the earth a force per kilogram of 16.3 N/Kg. (Ie centripetal acceleration of 16.3 m/s^2)

Taking into account the gravitational force already present from the earth this leaves 6.5 N/Kg which is less than one g so I think this is actually quite reasonable

Although I'm not entirely familiar with the electromagnet - electromagnet interaction equations I think this should be no problem for a good electromagnet (probably super-conducting I'd say )

[FooBar]

Looks correct, x=1/2*a*t^2 (integrating acceleration twice with respect to time), rewriting gives your equations

That's what I did

Because F also includes the drag force

In this case I assumed no drag, as it's magnetically levitated in a vacuum. So no wheel drag or air drag.
I also assumed constant acceleration. At departure you wouldn't go from 0 to 1.3 m/s^2 instantly, but that's probably negligable.

...which is well over the orbital velocity of ~17400 mph at sea level so you would shoot off into space unless you were held down by quite a strong vertical acceleration!

Then at some point one would need to switch from magnetic levitation to attracting forces that keep the the thing on earth!

On the other hand, it would make no sense to go around the world and then be at max speed. It only makes sense to go about halfway and then stop, so you could accelerate to about a quarter the way and then start decelerating. That would only give you about half the speed, well under 17400 mph.

[Buggi]

I recently built a run of these in my game and they're sweet! You should include a unique sound for them. Like a low "THUUUMMM" Like you get if you hit the end of a long PVC pipe.

On another note, could you make the 'vehicle' carrier more general and compatible with ECS? So it would be a cargo carrier. I want to send my iron, sand, and steel across the map at 2500 mph... muahahahahaaha.

[Supercheese]

I recently built a run of these in my game and they're sweet! You should include a unique sound for them. Like a low "THUUUMMM" Like you get if you hit the end of a long PVC pipe.

You know, these are vacuum tube trains, and as such the trains would be fairly silent as they move along. Still, the viewport is on the outside, and there would be some sound from the tubes themselves oscillating as the train goes past, and perhaps some from whatever force drives the train (electromagnets, etc.) and maybe from other sources I'm overlooking. Even so, any noises going on inside the tube would be pretty inaudible from the outside.

[lawton27]

I don't see why there should be any noise whatsoever, if the train is suspended by magnets the only forces acting on the tube would be magnetic ones from magnets on the train, this shouldn't cause any ( / much significant at all) vibrations to make sounds given the structure is sturdy which it must be to hold a vacuum .

[brownan]

Hey, I'm new at OTTD in general, but a few friends of mine and I setup a server with Vactrains, but we're having some problems. As soon as one of us starts up a vactrain, everyone gets kicked with a "Network Synchronization Failed" error. The game runs fine if there are no vactrains running... as far as I can tell, it only happens when one is running. When I dock my vactrains, the game runs just fine. Once I start a vactrain up, it gets to the other side of the map and then I get ejected from the server.

We're running OTTD 1.1.5, and vactrains is the only newgrf we have activated. The players don't get kicked immediately, maybe after 10 to 30 seconds when a vactrain is running. There doesn't seem to be any pattern that I can tell, like crashing when it arrives at a station or anything.

One more bit of information: not everyone always gets kicked when a vactrain is running. We have 3-4 companies/players on our map. We tried it, and me and another person would get ejected with "Network Synchronization Failed" but a third person remained in the game just fine.

Do you have any ideas? I'd really like to use your vactrains, but they're not working for us

[Emperor Jake]

That's a strange problem indeed. My guess would be that it is a bug in OpenTTD which causes a desync when the train is too fast for the clients to keep up with its position. The 10-30 second lag until the desync would be the time the vactrain takes to get to a high speed from a standing start. The friend who doesn't get kicked likely has a faster computer or internet connection, because his client is able to keep up with the train's speed.

I can't think of any way to fix this, except for reporting a bug in OpenTTD.

[planetmaker]

"Network Synchronization Failed"

That is (in itself) never a NewGRF bug. You might try the 1.2.0-beta3 or even the nightly of today as some issues which can cause a desync have been fixed.

Btw, a desync is never caused by a too slow client either and not related to the client speed at all; basically desync means that clients have a different idea of how the map (with all vehicles and stuff) looks like than the server.

[brownan]

Okay thanks for the info. We could still reproduce this with the beta and with the latest nightly, so I'm submitting a bug.

http://bugs.openttd.org/task/5007

[brownan]

Just as a follow-up, the bug is reportedly fixed now in r23855.

For anyone else that may run into this, we've since found a workaround: choose the realistic acceleration option; this seems to avoid the desync we were seeing and lets us use the vactrains.

By the way, the vactrains are really awesome! Thanks!

[Andre_]

Hi!

Thanks for the great addition to the game!

Could you please implement cargo transportation possibilities? If you don't have enough time for the graphics, please just have one generic look for the cargo trailers, but having them would be awesome!