# Bicycle and tackling inertia at higher speeds

• VVS2000
In summary, you would need to model the microstructure of the road surface, the 3D structure of the tire surface, the human body, and the motorized tricycle to corner around.
VVS2000

How do you think you might do it?

VVS2000 said:
While going on a bicycle, how can I take a quick turn when there is a obstacle ahead of me.
Unplanned direction changes with single track vehicles are difficult:
https://en.wikipedia.org/wiki/Countersteering

I would lean forward above the handlebars so the bicycle becomes a freewheeling unicycle, and then stick out a leg to one side while counter-steering by the appropriate magnitude to avoid the obstacle. This simplifies the equations to the forces acting on only one wheel.

metastable said:
I would lean forward above the handlebars so the bicycle becomes a freewheeling unicycle, and then stick out a leg to one side while counter-steering by the appropriate magnitude to avoid the obstacle. This simplifies the equations to the forces acting on only one wheel.
Wow. I would not have though of that but if you could pull it off (I'm confident I could not) I think you are right that it would be a possible solution.

That’s how fixed gear cyclists stop all day with no brakes, they “unweight” the rear wheel by leaning forward, lock their legs (the bike has no freewheel mechanism so doesn’t coast), let the rear wheel fall back down, initiating a controlled skid which turns the rear tire into a brakepad. These skids can be arbitrarily long depending how far they lean forward.

VVS2000 said:
Summary: While going on a bicycle, how can I take a quick turn when there is a obstacle ahead of me.
In addition to the other tips, keep in mind that different bicycle geometries will be able to maneuver more quickly than others. The "rake" and "trail" of the front forks will have a big impact on how quickly the bicycle can steer.

When I bought a mountain bike a few years ago, I went to a bicycle shop that allowed test rides in the parking lot, and had very knowledgeable people there to help me find the right MTB for me and my planned riding. Since I have a background in motocross, I wanted a bike that I could jump with and was quick on tight single-track trails. I test rode 3-4 bikes, and picked the one that had the quickest steering and lightest front end (for lofting it over obstacles). It was also a bit unstable, but that is the tradeoff you make when you want quick steering.
VVS2000 said:
Summary: I cannot slow down
That is not a good thought to have. You can pretty much *always* slow down some, even while you are turning hard. It takes practice (especially on a street motorcycle), but it should become a muscle-memory reaction to get on the brakes hard (with good braking balance front-to-back) while you are taking evasive maneuvers. At the very least, if you end up hitting the thing you are trying to avoid, the energy of the impact decreases as the square of your velocity, so hitting it at half speed will hurt you a lot less than hitting it at full speed.

Practice your emergency braking and evasive maneuvers before you need them, and ride safe and smart!

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berkeman said:
Practice your emergency braking and evasive maneuvers before you need them, and ride safe and smart!
There is always the advice that you should never be going so fast that you can't avoid hitting 'unexpected items'. That's impossible to do without going at walking pace - but it is possible to cycle (and drive) with that advice in mind, taking blind corners slowly *slower) etc. etc.. Unfortunately, the majority of fast cyclists tend to be young men who have testosterone-enhanced force fields around their cycles and also, immortality. (Times ten for motorcycles.)

phinds said:
How do you think you might do it?
I mean I was actually looking for a mathematical point of view, like cornering your way around and therefore making an angle with the ground and resolving forces... like how you do it in a banked road situation

I think unless you plan on modeling a metal wheel on a metal road, first you’ll have to define the 3D microstructure of the road surface and the 3D structure of the tire surface and how it deforms under dynamic loads. Next you’ll have to model the human body and how movements of various muscle groups translate into forces acting on the wheel, while factoring that the wheel is also acting as gyroscope.

Perhaps you’ll have an easier time modeling a tricycle that isn’t allowed to tilt taking evasive action, as it isn’t inherently unstable, and therefore doesn’t depend on the human for dynamic balancing. Then you make it a motorized tricycle with automated steering. Assuming no wheel slip, perhaps the 3 wheels will follow predictable tracks for a given steering input.

For reference:

The Schwalbe Fixed Gear Longest Skid Competition London

& the winner's posture:

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VVS2000 and gmax137
metastable said:
That’s how fixed gear cyclists stop all day with no brakes, they “unweight” the rear wheel by leaning forward, lock their legs (the bike has no freewheel mechanism so doesn’t coast), let the rear wheel fall back down, initiating a controlled skid which turns the rear tire into a brakepad. These skids can be arbitrarily long depending how far they lean forward.
That's really not what you want to do though if you want to stop quickly. Fixed gear cyclists do this to show off. If you want to stop quickly with no front brakes, you need to shift weight as far back as possible so you have as much weight on the braking wheel as you can, and then you want to hold the brakes at just the right level so the wheel almost starts skidding (but doesn't actually lock up - grip levels are higher for wheels that are rolling).

If you do have front brakes, you still want to lean back, but you want to get on the front brakes hard. Ideally, if you have enough grip, you want to be on the front brakes right to the limit of picking up the rear tire. If you don't have enough grip for that, you want both front and rear to be just on the limit of skidding, though as I mentioned before, you don't want to actually skid.

As for the OP's question? The only way to turn at speed on a bicycle is countersteering, so you'll have to do that. I second the statement that you want to be on the brakes as well though.

VVS2000 and berkeman
If the obstacle only exists at the surface of the road, such as a pot hole, you can positive steer around it quickly, but this is an uncoordinated turn, and the bike will be leaning after passing the pothole, requiring correction to straighten it back up. For example steer right so that the wheels pass by the right side of the pothole, which results in the bike leaning left, which you correct after passing the pothole.

If the obstacle requires turning the entire bike (as opposed to just the contact patches of the tires), then the harder you counter-steer, the faster the rate of change of lean and the sooner you can start turning. Note while counter-steering to initiate a lean, the center of mass of the bike is turning the "wrong way". I don't know if there is an ideal amount of counter-steering torque for obstacle avoidance, versus just using a lot of counter-steering torque.

berkeman

## 1. How does a bicycle overcome inertia at higher speeds?

At higher speeds, a bicycle overcomes inertia by relying on the force of friction between the tires and the road. This friction creates a counteracting force that helps to slow down the rotation of the wheels and maintain stability.

## 2. What role does the rider play in tackling inertia on a bicycle?

The rider plays a crucial role in tackling inertia on a bicycle. By shifting their weight and using their muscles to pedal, the rider helps to maintain balance and control the direction of the bike. The rider's actions also impact the force of friction between the tires and the road, which can affect the bike's speed and stability.

## 3. Can changes in the design of a bicycle help to tackle inertia at higher speeds?

Yes, changes in the design of a bicycle can help to tackle inertia at higher speeds. For example, aerodynamic designs can reduce wind resistance and improve the bike's overall efficiency, allowing it to maintain higher speeds with less effort. Additionally, lighter materials and improved wheel designs can also help to reduce inertia and improve handling at higher speeds.

## 4. How does the terrain affect a bicycle's ability to tackle inertia at higher speeds?

The terrain can greatly affect a bicycle's ability to tackle inertia at higher speeds. On flat, smooth surfaces, there is less friction between the tires and the road, making it easier for the bike to maintain speed. However, on rough or hilly terrain, the bike may encounter more resistance and require more effort from the rider to overcome inertia and maintain speed.

## 5. What safety precautions should be taken when tackling inertia at higher speeds on a bicycle?

When tackling inertia at higher speeds on a bicycle, it is important to wear appropriate safety gear, such as a helmet and reflective clothing. Riders should also be aware of their surroundings and follow traffic laws to avoid collisions. Additionally, regularly maintaining and inspecting the bike for any potential issues can help prevent accidents and ensure safe riding at higher speeds.

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