Is it true that bicycles balance themselves?
Question from Artur de França, Rodeiro (MG) – do you want to send a question too? Click here.
Yes, dear fellow. As long as they are pushed, from the start, perpendicular to the ground (forming a 90º angle with the ground) and at a sufficient speed (if it’s too slow, it doesn’t roll) to maintain balance – which only lasts as long as the speed doesn’t decrease too much. .
I called Professor Cláudio Furukawa, from the Physics Institute at USP, for a ride and he gave me a class on the subject.
Always balanced, he first explained that, contrary to what he initially thought, balance is not caused only by the gyroscopic effect (tendency of a rotating object to maintain the orientation of this rotation) caused by the wheels turning, as is often explained, in a similar way. simplified, in physics classes and textbooks. “Dynamic equilibrium is more complex than previously thought, and the gyroscopic effect is not a primary factor,” he says.
Furukawa also points out that the conservation of angular momentum, which is what keeps the tops spinning upright, and which is supposed to be a key factor in the balance of a bike, makes no difference at low speeds, like our ride.
“It’s just that bicycle wheels are light and, at low speeds, have little amount of angular momentum. In the case of motorcycles, on the other hand, conservation of angular momentum influences balance because of high speeds, since tires have more mass and spin at high rpm.”
Digging deeper, Furukawa discovered that what keeps a bike upright goes beyond the human ability to control the handlebars or lean of the skinny one. What counts most, apparently, is the bike’s ability to correct its balance. And, as surreal as it sounds, she doesn’t depend on anyone mounted to do it.
Take a look at the following video to understand how this self-balancing works:
The loose handlebars, sensitive to terrain irregularities, are essential for maintaining balance. As the bike moves forward, whether someone is on it or not, it constantly adjusts, dancing back and forth to compensate for the forces that destabilize the vehicle. For those who followed Formula 1 in the 1990s, it is like an active suspension, which automatically adapts to ground deformations, keeping the car stable, without shaking.
In the video above, the experiments demonstrate another counterintuitive curiosity regarding that part of the bike that we rest our hands on – apparently, more to rest than to keep it standing.
Contrary to what it may seem, to make a turn, the first step is to tilt the handlebars slightly to the opposite side of what you want to go. Nobody notices, but everybody does it. The “invisible” movement causes the bike to lean to the opposite side, initiating the trajectory change. Only then do we turn the handlebars – not to guide the movement, but guided by the movement the bike has already taken.
Finishing the ride, Furukawa states that, both for balance (with or without a rider) and for starting a turn, “what seems to be important is the quick correction, with the handlebars turning in the same direction the bike is leaning. “
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