How I made my own Cougar springs...
(Technical/legal remark: this is an article about home metallurgical works. When done properly everything can be perfectly safe. Despite of it I shall not bear any responsibility for direct/indirect damages, skin/property losses etc. you will potentially suffer by application of it. Everything you do you will do on your own.)

        When I got a brand new Hotas Cougar some two years ago, it brought to me a completely new dimension of my virtual flying. HC is metal solid, sympatically hard piece of hardware, able to firmly stand on a desktop while you are trying to withstand all furious maneuvers, attacks and counterattacks in usual dogfight. Anyway in calm periods of flying I realized one of few oddities of this device. Original springs in X-Y axes were too hard for me, after while of holding of slow turn I felt quite strong tiredness in muscles of my hand. So I decided to make a new pair of springs. Believe or not, this can be made at home very simply. My father many years ago tought me the fundamentals of the "black craft" so I know how to do it. It's even not difficult if you have the basic knowledges of works with metal materials.

First of all we have to get a proper spring wire. It must be a steel, not an iron. Steel material is able to be hardened by quenching. Quenching is a process of thermal treating of steel, in which the metal will recrystallize and become harder and more brittle. The process consists of heating over eutectoid point of material (about 720 ºC) and rapid cooling down through this point.

The most available material will be some finished spring with proper diameter of wire. The original springs in joystick are made from 2,1 mm diameter wire (see picture, original spring is left one). Despite of that it depends also on common material constants of used wire, I estimated the proper wire diameter for the softer spring around 1,8 mm. Happily I found a spring for accelerator pedal in an old model Skoda car which is quite common in my country. I purchased more for experimenting...
To make a proper shape of the spring we must soften the wire. It can be done by annealing (heating) of the wire and slow cooling. The material will recrystallize at high temperature and by slow decrease of temperature it will retain the forgeability and elasticity. The main purpose is to make the wire soft and flexible enough to form into a desired shape.

Purchased spring we can heat on the gas range in the kitchen. For more massive gas flame you can take off the top of the burner (eventually with distancer), the flame will come out directly from the pipe. From this moment be carefull, the flame can be sometimes "sucked" into the burner pipe (in fact a venturi tube), in such case IMMEDIATELY close the valve, as the burning continues in the tube and it will heat. Also keep in mind such using of range is not recommended by the manufacturer nor the fire department.

Grip the original (purchased, not the one from Cougar :-)) spring with the proper pliers (they shoud not be plunged into the flame) and start heating. The temperature can be judged according to a color of glowing. The proper color is from orange to darker yellow. Try to heat progressively all parts of the spring and keep the needed temperature at least 0,5 to 1 min. In the next step you will see how uniformly you annealed the wire. After annealing let the spring cool down holding it in the pliers. Again be carefull, 400 ºC hot spring look like the cold one. If you will not be satisfied with the smoothness of the wire, the annealing process can be repeated. Anyway too much annealing is not desirable as during every heating above 500 ºC the surface of material burns and oxidizes and it can change a material properties.

Now after cooling we have a flexible wire which can be shaped into desired form. We will start with flattening the wire. Be patient and don't try to "use" bolts of the original spring for the shape of the new one. The best way is to flatten the adequate part of wire as straight as possible. That's the point when we can consider the regularity of annealing. When it's needed return to the range and soften the more rigid parts of wire. Don't burn yourself :-).

We can simply enumerate that we need about 145 mm of flatten wire for each spring. Don't cut it yet! The excess of length will help with shaping. The inner diameter of the bolts should be no less than 12,5 mm. The straight parts of a spring are 25 mm long. For nice rounded shape of bolts we will do a trick with winding over proper rod in the jaw vice. You can use any pipe or back part of a drill of diameter 12 mm. We can stilly decrease the diameter because the bolts will stretch after winding.
According to pictures catch one end (about 25 mm) of wire perpendicular to a rod at the very end of a vice jaw. Wind two bolts out of jaws as closely each other as possible. You must count a resilience of a wire and wind it a bit more then two bolts. After you will finish you should have more-less parallel ends of a spring, which resemble "uncompleted" two bolts shape better than "over completed".

If you make the angle more than 180 º, the joystick should play around the center. The less the angle the more the preload you will have around the center position. Straight parts of the spring should be as flatten as possible to avoid additional play on the joystick (see an article about sources of play on joystick - will be soon). After shaping cut the rest of the wire to let flatten part 25 mm long.
Now will come another metallurgical operation, hardening by quench. The matter is to heat the material above eutectoid point (about 720 °C) to recrystallize it and then "freeze" the new crystallic structure through fast cooling down. It will be done by throwing it to the water or oil. With my spring material I tried first the water with negative result but common food oil for frying worked well. Before quenching take some file and try to make a little scratch to the spring, or simply try to bend it a little with your hands. After hardening repeat it again and if you will see the difference, that's it.

For quenching prepare a glass with some oil or water near of range, take a spring and put it in the flame. Try to heat it uniformly at the temperature about 750 °C. It can be judged again after glowing colour, that temperature responds the dark orange colour. I heated it for sure to the lighter tone. You have to hold this temperature for at least 20 seconds for releasing the inner stresses after shaping. Then plunge the spring into the oil as fast as possible, simply throw it there. As the oil removes the heat very quickly, you can check the result after few seconds. Try to scratch the spring with file and if you can feel the file like to be „slipping" on the surface your spring is hardened. Be carefull when trying to bend it, by quenching it will become brittle and it's no problem to break it.

To remove the fragility we have to tempere the spring. The first springs I made did their job quite well until after few sharp moves of joystick they broke.

So we will soften them by tempering. Take some metal sheet or iron plate usually used for heat dissipation on the range. Clean the springs with abrasive cloth or paper to get a silver metal surface. It is important for guessing of tempering temperature. Put the cleaned springs on the plate and start to heat on the middle flame. It will take few minutes and you will notice a change in surface colour of the metal. It will change gradually from yellow, orange, violet to blue, brown and black. The colour change is caused by surface oxidization of the metal. For our purposes is suitable colour from violet to blue.

Now let it cool down, mount into Cougar and enjoy...
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