# Advice 1: How to find the stiffness coefficient of the spring

From the point of view of classical physics, a spring can be called a device, which accumulates potential energy by changing the distance between the atoms of the material from which the spring is made. Referring to the perceived load of the spring differenziata on: springs, compression springs, bending springs, torsion and spring tension. In characterizing each of these springs is of great importance to the ratio of its stiffness.
You will need
• - spring;
• - the range;
• - cargo;
• - handle;
• - notebook;
• calculator.
Instruction
1
Please note that during the deformation of the springs occurs the force tending to restore the original size and shape of the body. This force is caused by electromagnetic effects between the atoms and molecules of a substance from which made the spring. This force is called the elastic force. The simplest form – deformation tension and compression.
2
Will mount vertically one end of the spring, the second end Express free. Use a ruler to measure the length of the spring: the result write down in a notebook, setting it to x1.
3
Hang onto the free end of the spring gold load and re-measure its length. Obtained during the measurement the result write down in a notebook, setting it x2.
4
Calculate the absolute elongation of the rod, which represents the difference between x2 and x1. At small strains or compressions of the spring the elastic force is proportional to deformation: it is aimed in the opposite direction from the movement of the particles in the body under deformation. That is, Fупр = |kx|, where k is the coefficient of rigidity. This ratio expresses the essence of Hooke's law. So to find the coefficient of rigidity of the spring, should the stretching force of the body divided by the elongation of the spring.
5
Not knowing what is the tensile force of the spring, it is impossible to calculate the ratio of the stiffness, so find the stretching force. Elastic force or tension balances the force of gravity acting on the suspended load. This force arises solely under deformation of the body. So, Fупр = - N = -mg. It follows that mg = kx. And hence k = mg/x. Substitute the known values into the formula and calculate the coefficient of stiffness of the spring.
Note
Remember: substitute in the formula for the value transferred should be in the SI system.
The stiffness coefficient of the spring depend on the material from which made the body, and spring length and shape.

# Advice 2: How to determine spring stiffness

Spring is a component of the car's suspension, which protected the car from irregularities in the road, but also provide the desired height of the body above the road, which greatly affects the handling of the vehicle, comfort and payload capacity. As a result of the tests for each vehicle select the optimum stiffness of the suspension springs under certain traffic conditions.
Instruction
1
If you experience "breakdowns" suspension spring is too soft. In such situations, the drivers become unstable in control. Ideally, the spring force must be equal to the value that prevents excessive body roll.
Stiffer springs require the cars prepared for racing. In different types of races using the same car involves the installation of springs with different stiffnessYu. Pay attention when passing any corners for body roll that, when properly selected springs should be no more than two or three degrees.
2
For the front and rear suspension pick spring stiffness pairs. However, it is not immediately possible to achieve the desired height of the suspension, because the spring sits and at some point may "get lost" that's really bad. This is due to lack of bearing capacity, even at full compression, but with the stiffnesss, providing the necessary height of the suspension. This is determined always easy: between the spring windings should be a gap of less than 4 mm.
3
Choose the springs so that when refilled the car the gap between the turns of the springs was slightly more than 6.5 mm. it is Desirable to set the soft springs, even though they will give a roll of the machine within acceptable limits. To use stiff springs, based on the opinion that they reduce the roll of the car, improving handling, as a rule, incorrect.
4
Check the stiffness of the spring by a product code or for applying labels or stamping paint). Also determine the stiffness of the springs using the hand pump, floor scales and measuring line in kilograms per centimeter.
On everyday scales fit a piece of wood (thickness 12 mm) square at the larger end of the spring, and the top is a spring. Then, on the upper end of the spring is placed a second piece of wood is measured length of the spring. With a press of the spring compress to a certain size (e.g. 30 mm) and take readings of the weights, thereby computing the stiffness.
Note
The pressure on the spring is measured according to the testimony of the weights, but this method of determining the stiffness of springs is dangerous as the spring can fly off at a sufficiently large distance.

# Advice 3: How to change the springs in the couch

Repair furniture at home is a difficult task, but doable. On the one hand, specialist furniture is guaranteed to fix a broken sofa. But on the other hand, the overall delivery of the furniture to the repair shop - a very troublesome and expensive task. With a strong desire to repair the sofa at home on their own.
You will need
• - wrench;
• - flat screwdriver;
• - pliers;
• - a knife for the foam;
• - new foam.
Instruction
1
Before you begin to repair, prepare the necessary space. To repair happened quickly and efficiently, prepare all the necessary tools and a set of new springs to replace. Remove the rug or carpet, put a thick and dense film to protect the flooring from accidental fall of a heavy tool or item of the design of the sofa.
2
Start disassembly of the sofa with detaching sidewalls. Wrench Unscrew the mounting, possibly holding them from free fall.
3
Any convenient way to label the parts of the folding cushion of the planes on the right and left in order after repair to collect them in the correct order. Disassemble the mechanisms.
4
Continue disassembly of the sofa, alternately disengaging the seat back. If you have the pallet, you need to dismantle it.
5
To remove the covers, use a pair of pliers and pull the bracket. Avoid strong jerks, try to do everything carefully. Otherwise, you can damage or even rip the fabric covers.
6
Proceed to repair the spring box, pre-pulling the mattress. Take a damp cloth to remove dust and wood chips, which are usually present in abundance at the site of attachment of the spring unit to the bottom of the sofa.
7
Test all sofa springs. This can be done without dismantling, but experts still recommended to pull out the entire unit and to determine the suitability for further use each spring separately.
8
A broken spring will remove it with pliers. Installing new, use furniture foam and dense old blanket for greater elasticity of the spring unit and increases the operating life. To do this, take a knife, cut the foam and stuff them spring unit, and then cover with a blanket and secure it around the perimeter with a hammer and 30-40 mm nails so that the blanket was as close as possible and collected the springs, not allowing them to fall in different directions. This removes the main cause of breakage or excessive stretching of the cushion springs - their asynchronous work.
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