PROBLEM #180
Valve – tension roller
A forum member using the alias Experienced posed a challenging question to a community of motorists. The inquiry noted that modern engines and their systems host many valves. Valves exist in timing mechanisms, cooling circuits, the crankcase ventilation system, and more. Yet there is one valve that remains open whenever the engine runs. The question asked was whether this is the only valve of its kind.
Which valve is always open when the engine is running?
Brief answers would not be accepted.
Entries for the competition were to be sent by December 1, 2022 to an address in Moscow and were to include a contact phone number or another reliable way to reach the sender quickly.
Below is a summary of the results from the judging of the connoisseur competition published on December 1, 2022.
The task invited readers to explain why a car parked with wider lateral spacing tended to show more damage from open doors, and to relate this to stamping presses for auto parts and even engine operation. Vague replies such as simply naming a factor like strong wind or using harsh language about neighbors did not win. The winner provided a thorough explanation.
The central figure of the problem is the kinetic energy inherent in a moving object, specifically the car door. When a door is opened, a force is applied. The work done equals the force applied times the distance the door travels in its arc, which can be expressed as M = F × r × Δϕ. This energy is transformed into the kinetic energy of the swinging door. The longer the force is applied, the more work is done, and the greater the resulting angular velocity and kinetic energy.
Diagonal parking not only makes entry and exit easier but also allows for reduced lateral clearance between vehicles.
To stop the door’s motion, energy must be removed by applying a counteracting moment of force. Holding the door by the handle is ideal, though not always easy. If the door is accelerated through two thirds of its opening angle, the braking force required to bring it to a stop in the remaining one third becomes greater than the original force.
What happens if a child opens a door or wind pushes it? The excess kinetic energy can cause elastic and plastic deformation of the metal on the door and nearby cars, as well as heating of deformable parts and the generation of sound waves upon impact.
When the door opens by a small angle, the force has limited time to distribute, and the impact on neighboring vehicles is weaker. If the gaps between cars are large, the door can gain significant speed, and stopping it demands substantial effort, often leading to noticeable deformations. Consider how a doorstop can hold a door in place against wind, yet break when the same wind drives a different door open.
The kinetic scheme of a crank press is described as follows: 1 – intermediate shaft; 2 – gear connected to gear 3; 4 – multi-friction clutch; 5 – crankshaft; 6 – stamping table; 7 – slider; 8 – connecting rod; 9 – brake; 10 – a pulley with a flywheel linked by a V-belt drive; 11 – engine.
The kinetic energy of a spinning body can cause both damage and the creation of car parts. Crank presses are widely used in stamping processes. Their drive combines an asynchronous electric motor with a flywheel connected by a belt drive. The crank connected to the flywheel converts rotary motion into the reciprocating motion of the stamping die.
These presses operate as peak-load machines. When idle, the motor spins up the flywheel, increasing its kinetic energy. During a stamping operation, the flywheel’s rotational speed drops, and the stored energy contributes to deforming the steel sheet. Using a flywheel enables a motor with lower peak power to drive the system, improving efficiency by storing kinetic energy and delivering it during the work cycle.
The same physics principles apply to engine operation. During the power stroke, combustion releases thermal energy that is converted by the crank mechanism into kinetic energy in the crankshaft and interconnected parts, especially the flywheel. After the working stroke ends, the crankshaft keeps rotating, using the stored energy to overcome friction, expel exhaust gases, draw in a fresh air-fuel mixture, and compress it for the next cycle. Although multiple cylinders space the work cycles, energy storage and return remain cyclical in nature.
Evgeny Bobkov congratulates the winner on the victory.
- “Drive” can now be read in Telegram.