They travel 200 mph and they don’t take off. Do they create downforce? How much downforce?
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They don’t need downforce, and long as they don’t create lift, which they do not, because lack of wings.
Since they travel on fairly level rails, the train weight is sufficient to keep it grounded.
In the grand scheme of aerodynamics, 200mph isn’t that fast, even more so for something not specifically designed to take off.
A large aircraft that is designed to take off, with wings(and lift from the design of the fuselage but that’s getting into fine details) designed to provide maximum lift while remaining light as possible, takes off at around 170-180mph. So a 150 ton aircraft with wings, and designed to be much less dense, needs to go the same speed. But a high speed rail train can weigh 715 tons, and is pretty dense, with no large lifting surfaces.
A much much denser train, with a shape that is not designed to provide lift, has less of a takeoff concern.
Aerodynamics are still important since as you go faster drag losses increase (exponentially or logarithmically, can’t recall offhand), and stability on crosswind is important, but speed in itself does not equal takeoff.
Interestingly though, some aerodynamic considerations like tunnels come into play. Japan redesigned their trains due to the large amount of tunnels in the country. Before with the standard round nose, if they would enter a tunnel too fast it would create a shockwave popping sound, so the trains would have to slowdown. Now the redesigned trains mimic birds that dive into water to better cut through the higher pressure in tunnels.
There is no lifting force. At least none to remotely counteract the force of gravity.
An airliner without wings would not fly, regardless of how fast it goes.
Other answers are right that there is a lot of weight, and no wings to generate lift.
But OP does has a point: Formula 1 cars and racing speedboats do take off at similar speeds. The difference is that these are wide and flat, to provide stability on tight turns, and relatively light, to improve both acceleration and braking.
Trains are not flat, and passenger trains generally try to avoid too much acceleration and braking (passengers do not have seatbelts), so weight is not a concern.
Also, unlike racing vehicles, trains are long. Lift does not come from air going below the vehicle, it comes from air going over the hill formed by the wing or the vehicle itself. Train is not a hill, it is more like a plateau. The only lift could comes from short conical sections and start and end of the train, while most of the train’s length is basically deadweight.
Finally, the front of the train is the locomotive, built around a very heavy engine. No way that thing will fly.
Yes, they create downforce. It’s called “gravity”.
Seriously, these things are heavy. And they don’t really have any lift-generating surfaces. So there’s no risk of them taking off.
F1 cars, to name an example, do have this risk because they are light and flat. Because they are flat, there’s a risk that the bottom of the car can become a big wing, if at any point the nose of the car tilts too far upward (e.g. if the car was going up a slight incline or a gust of wind got underneath), or if somehow you shaped the car like an airfoil (and thus created lift through Bernoulli’s principle). And because they are so light, it doesn’t take much lift to overcome gravity.
Trains, however, are not flat, so there’s no risk that their overall shape is going to act like a wing. And it would take very big wings to lift a train. Even if train cars were built to airplane-like densities (which they aren’t), consider that a 747’s wingspan is roughly equal to its length. And then consider that high-speed trains are typically hundreds of meters long. That gives you some idea of the total area of lift-generating surfaces that would be required to get a train to take off.
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