For the answer to problem No. 177 “Harmful Parking” from the December issue of “Behind the Wheel” for 2022, Evgeny Bobkov from Moscow receives a Playme KVANT car DVR with a GPS informing function from Playme-Russia. And now, a new challenge!
TASK № 180
Valve – idler
A forum member with a pseudonym Experienced threw a tricky question to motorists: “There are a lot of valves in a modern engine and its systems. And in the timing, and in the cooling system, and in the crankcase ventilation, and in many others. But there is a valve that is always open when the motor is running. Maybe he’s not alone?
So which valve is always open when the engine is running?
Short answers are not considered.
Send the answer marked “Competition” by December 1, 2022 to the address: 107045, Moscow, Seliverstov per., 10, building 1; email: [email protected].. Specify your contact phone number or other way of quick communication.
Below we summarize the results of the connoisseur competition published on December 1, 2022.
In the task, readers had to explain why, when cars began to be placed in a parking lot with a larger lateral interval, there was more damage from open doors – and to be reminded of the connection with presses for stamping car parts and even with engine operation. Those readers who answered with a few words like “strong wind” or used unprintable expressions about car-loving neighbors, of course, cannot claim victory. But our winner explained everything in detail.
The heroine (or anti-heroine) of the problem is the kinetic energy of a rotating body – the car door. When we open a door, we apply force to it. The work done in this case will be equal to the product of the moment of force and the angle of rotation (in radians) or (the same thing) the product of the force and the radius of motion of the point of its application and the angle of rotation (in radians): M = F*r*Δφ.
The work done is converted into the kinetic energy of the swinging door. Obviously, the longer we apply force to the door handle, the more work we do, and the greater will be the angular velocity of the door and its kinetic energy.Diagonal parking not only facilitates entry and exit, but also allows you to reduce lateral intervals.
Diagonal parking not only facilitates entry and exit, but also allows you to reduce lateral intervals.
In order to stop the movement of the door, it is necessary to “take away” energy from it by applying a moment of force opposite to the original one. It is optimal, of course, to hold the door by the handle. But it’s not always easy. If we accelerated it by 2/3 of the opening angle of the door, then to stop on the remaining 1/3 of the path, the braking force must be greater than the original one.
What if a child opens the door? What if it got caught in the wind?
The “outstanding” kinetic energy will be used for elastic and plastic deformation of the metal of its own and neighboring machines, as well as for heating deformable parts and creating sound waves from impact.
When the door is opened at a small angle, the applied force does not have time to disperse it, and the effect on the neighboring machine is relatively weak – the metal deforms elastically and can restore its shape after the load is removed. If the lateral interval between cars is large, then the door will pick up a lot of speed, stopping it will require considerable effort and will be associated with serious deformations. Recall how the door stopper is able to hold it open under the pressure of the wind, but breaks when the same door swings open from the same wind.Kinematic scheme of the crank press: 1 – intermediate shaft; 2 – gear, which is engaged with the gear wheel 3; 4 – multi-plate friction clutch; 5 – crankshaft; 6 – stamping table; 7 – slider; 8 – connecting rod; 9 – brake; 10 – a pulley with a flywheel connected by a V-belt drive; 11 – engine.
Kinematic scheme of the crank press: 1 – intermediate shaft; 2 – gear, which is engaged with the gear wheel 3; 4 – multi-plate friction clutch; 5 – crankshaft; 6 – stamping table; 7 – slider; 8 – connecting rod; 9 – brake; 10 – a pulley with a flywheel connected by a V-belt drive; 11 – engine.
The kinetic energy of a rotating body can not only damage car parts, but also create them. Crank presses are widely used for stamping. Their drive is a combination of an asynchronous electric motor and a flywheel connected by a belt drive. The crank connected to the flywheel converts the rotary motion into a reciprocating motion of the die.
Such presses are machines with a peak drive load. During idling, the electric motor accelerates the flywheel, increasing its kinetic energy. When performing a technological operation, the flywheel rotation speed decreases, and the accumulated energy is spent on performing work on the deformation of the steel sheet. The use of a flywheel allows you to reduce the power of the electric motor, increase the efficiency of its use and increase the efficiency of the press due to the accumulation of kinetic energy and its expenditure directly during the work process.
The same physical laws are valid for the operation of the engine. During the working stroke, during the combustion of the mixture, thermal energy is released, which, by means of a crank mechanism, is transformed into the kinetic energy of rotation of the crankshaft and related parts, in particular, the flywheel. After the end of the working stroke, the crankshaft continues to rotate, spending the accumulated kinetic energy to overcome friction forces, remove exhaust gases, suck in and compress a new portion of the working mixture. The presence of several cylinders distributes the working cycles according to the positions of the crankshaft, but does not completely eliminate the cyclical processes of energy accumulation and return.
Evgeny Bobkov congratulations on the victory!
Photo: depositphotos.com, manufacturing companies and “Behind the wheel”
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