Roll with Resistance Definition
You may know of a situation where someone who seems to resist change denies having a problem or refuses to do anything about it. The rolling resistance coefficient Crr decreases significantly with increasing the weight of the railcar per wheel. [49] For example, an empty freight car had about twice as many Crr as a loaded car (Crr = 0.002 vs. Crr = 0.001). The same “economies of scale” can be observed in mining car testing. [50] The theoretical Crr for a rigid wheel running on an elastic platform shows that the Crr is inversely proportional to the square root of the load. [35] If the CRR itself depends on wheel load according to an inverse square root rule, a 2% increase in load results in only a 1% increase in rolling resistance. [51] The above example shows a resistance proportional to C r r {displaystyle C_{rr}}, but does not explicitly show a variation in speed, loads, torque, surface roughness, diameter, tire pressure/wear, etc., since C r r {displaystyle C_{rr}} varies even with these factors. The above definition of C r r {displaystyle C_{rr}} might indicate that rolling resistance is directly proportional to the weight of the vehicle, but this is not the case. The “rolling resistance coefficient” is defined by the following equation:[6] Resistance to change is common in our work and clients who show resistance change less frequently.
Resistance is what happens when we anticipate or drive change, when the customer is not ready for that change. When we encounter resistant statements or behaviors, it`s easy to fall into a pattern of reasoning or fight back. (See tip #65, The Recovery Reflex.) It is more effective to ride with resistance and work skillfully to evoke the customer`s motivation for change. How can we most skillfully ride with the resistance in this first moment when it presents itself? The very first things we do and say when we encounter resistance have a profound impact on the rest of the session and the client`s change process. “Riding with resistance” is a key technique that recognizes that attacking or confronting someone directly doesn`t always work – it can push people deeper into their shell or cause them themselves to be very defensive or confrontational. The drive torque T {displaystyle T} to overcome rolling resistance R {displaystyle R_{r}} and to maintain a constant speed on flat ground (without air resistance) can be calculated as follows: The above equation, where the resistance is inversely proportional to the radius r {displaystyle r}, seems to be based on the discredited “Coulomb law” (neither Coulomb`s inverse square law nor Coulomb`s law of friction). See Diameter dependency. If we equate this equation with the force by rolling resistance coefficient and solve for b {displaystyle b} , we obtain b {displaystyle b} = C r r r {displaystyle C_{rr}r}. For example, if a source specifies the rolling resistance coefficient ( C r r {displaystyle C_{rr}} ) as the dimensionless coefficient, it can be converted to b {displaystyle b} by units of length by multiplying C r r {displaystyle C_{rr}} by the wheel radius r {displaystyle r}. Rolling resistance, sometimes called rolling friction or rolling resistance, is the force that resists movement when a body (such as a ball, tire, or wheel) rolls over a surface. It is mainly caused by non-elastic effects; That is, all the energy needed to deform (or move) the wheel, platform, etc.
is not recovered when the pressure is removed. Two forms of these are the loss of hysteresis (see below) and the permanent deformation (plastic) of the object or surface (for example, the soil). Note that sliding between the wheel and the surface also results in energy dissipation. Although some researchers have included this term in rolling resistance, some suggest that this loss term should be treated separately from rolling resistance, as it is due to the torque applied to the wheel and the resulting slip between the wheel and the ground, known as slip loss or slip resistance. [1] In addition, only so-called slip resistance is associated with friction, so the term “rolling friction” is somehow a misnomer. The rolling resistance of steel wheels on the steel rails of a train is much lower than that of the rubber wheels of a car or truck. Train weights vary considerably; In some cases, they can be much heavier per passenger or net ton of cargo than a car or truck, but in other cases, they can be much lighter. The main cause of rolling resistance of pneumatic tires is hysteresis:[5] Materials that have a significant hysteresis effect, such as rubber, that bounce slowly, have higher rolling resistance than materials with a small hysteresis effect that bounce faster and more completely, such as steel or silica. Low rolling resistance tires typically contain silica instead of soot in their tread compounds to reduce low-frequency hysteresis without compromising traction.
[7] Note that railways also have hysteresis in the structure of the platform. [8] A low slip percentage can result in slip resistance well above the basic rolling resistance. In the case of pneumatic tires, for example, a 5% slip can lead to a 200% increase in rolling resistance. [46] This is partly because the tractive force exerted during this slip is several times greater than the rolling resistance force and therefore much more power is applied per unit speed (return power = force x speed, so power per unit speed is only force). Thus, even a small percentage increase in circumferential speed due to slippage can lead to a loss of traction power, which can even exceed the loss of power due to basic (usual) rolling resistance. In railways, this effect can be even more pronounced due to the low rolling resistance of steel wheels. Table of examples of rolling resistance coefficients[4]: Other strategic responses to resistance include re-emphasizing the youth`s personal control and autonomy, shifting the focus of the discussion to a less controversial topic, and ensuring that you give equal weight to exploring the pros and cons of change. The rolling resistance increases sharply with the torque applied. At high torque, which exerts a tangential force on the road of about half the weight of the vehicle, rolling resistance can triple (an increase of 200%). [46] This is partly due to a decrease of approximately 5%.
The increase in rolling resistance when torque is applied is not linear, but increases faster with increasing torque. For tyres on hard surfaces, it is stated that the influence of diameter on rolling resistance is negligible (within a practical diameter range). [37] [38] This fundamental principle is illustrated in the figure of rolling cylinders.