The hardest part of making a bar scale has been done. Wang Tian used rattan to thread a string of soil lumps and weigh them back to the cave.

Find Wu and get a hand drill and start making a rod scale.

The principle of making a rod scale is the principle of leverage. Specifically, it is moment balancing.

The rod scale is divided into two sections from the connection of the rope point, which can be regarded as the support point of the lever. In this way, when the two ends of the rod scale are balanced, the moment acting on the rod and the object acting on the disc is equal.

Power × power arm = resistance × resistance arm. The weight of the rod brace is known, (Wang Tian does not know here) the balance of the rod scale is the force distance at both ends (the vertical distance from the stone to the lifting point and the object to the lifting point) can be seen intuitively. Therefore, for a balance formula, it is easy to find one of the 3 parameters (that is, the weight of the matter).

The scale on the rod scale is the parameter table of the weight of this object, which can be read directly.

Wang Tianxian used a hand drill to turn out a rope hole in the center of the scale rod at five centimeters from the big end of the scale rod, which was used to install the weighing pan.

Wang Tian took out a bamboo basket that was only half the height of an ordinary basket and used it as a weighing pan. This is a weighing pan used to weigh small weights.

We call it a small weighing pan, and the depth of the weighing pan is not high, so that it is easy to take the things that are weighed.

Tie two thick ropes on both sides of the small weighing pan basket. The rope is thick enough to support twice the weight in the basket.

The hole used to thread the scale hook on the scale rod must be large enough because it must bear more than 100 pounds of weight. to be able to wear a thick enough rope.

The diameter of the drill bit drilled by Wang Tian hand obviously does not meet the requirements. It has to be drilled several times and then trimmed out.

After the weighing hole is done, Wang Tian has to select the material used as the scale hook.

He found a wooden hook with a diameter of five centimeters, cut off the bark on the surface with a knife, drilled holes on both sides of the rope position several times to make the rope holes, and then carbonized it on the fire.

Then choose a strong straw rope, pass through the weighing plate hole and the scale hook hole respectively, adjust to the appropriate length and tie a dead knot.

Adjust the knot end of the dead knot at the upper third of the scale hook, hide one end of the straw rope in the middle of the straw rope loop, tie a knot with yourself after the other end is close to the weighing hook, and then wrap the two lanyards and the other end of the rope in the middle.

Wrap it all the way to close to the hole of the weighing plate, tie the knot again with the two terminals, and then hide the knot in the middle of the rope and arrange it, and a beautiful weighing hook is installed.

Wang Tian is a perfectionist, otherwise it would have been solved with a dead knot.

Primitive society has not yet required the exchange behavior to be accurate to "two", but when the scale is made, it must be guaranteed to be accurate to two.

Wang Tian has never weighed it, and the reason why he chose to make a pole scale with a length of one meter from the beginning. It is for a lift (a scale generally has two gears, and the lighter weight of the rope is called "one lift") when weighing things, it can be accurate to two, and the weight that can be weighed is as large as possible.

And if the length of the scale from zero to one pound is only one centimeter in total, the diameter of the straw rope of the weighing stone reaches two millimeters, and there is no way to read it.

In order to be able to read two on the rod scale, the distance from the zero scale mark to the one pound scale mark must be at least two centimeters.

The total length of the rod scale is one meter, and the tail is minus 5 centimeters as the tail. The head came in 5 cm and installed a small weighing plate, minus the 20 cm rope lifting position, and the effective scale was about 70 cm.

In order to be accurate to two, the scale interval between each two catties must be two centimeters. 70 cm effective scale. The effective weight of "one mention" can only be 70/2, that is, 35 catties.

According to the formula: resistance (35 kg) X resistance arm (20cm) = power (weighing weight) X power arm (70cm)

It can be calculated that the weight of the scale is ten catties.

According to the formula, it can be seen that in order to make a rod scale that can be accurate to two, the effective maximum weight of "one mention" can only be 35 catties, and the position is 20cm away from the small scale plate hole.

The position of "one mention" was determined, and Wang Tian drilled holes on both sides many times with his hand to make a "one mention" hole position, and put on the lifting rope.

Before the tribesmen did not democratically elect the standard parts weighing one catty, the production of rod scales could only be temporarily suspended.

Without reference weights, there is no way to determine the spacing of each weight, and there is no way to continue the follow-up work.

In fact, Wang Tian can also dictatorically decide how much a pound weighs, but the pole is said to serve the tribe. If this weight does not reflect their will. Then it makes no sense to make this name.

In order to more intuitively represent how big a fish is, or how many fish are in it, and how much of a fish can provide food for an adult in the tribe for a day, the best way is of course to vote for everyone's approval.

Next, Wang Tian wants to make a simple balance, which is needed to check whether the bar scale is accurate.

The making of the balance is very simple, just like when Wang Tian explained to the sunspot why he wanted to make a scale, he could build one temporarily. But it needs to be used, and it's always good to be more formal.

Wang Tian looked up at the sky, it was time to call it a day, and the second brother of King Kong returned to the tribe after collecting enough forage to make grass ropes.

The second brother is not so much to mow the grass, but to use an axe to cut the grass. No way, just such a metal tool.

Seeing the second brother come back, Wang Tian asked the second brother to cut out a wooden board 70 centimeters long, 10 centimeters wide, and 2 centimeters thick as a crossbar for the balance. Two discs with a diameter of 30 cm are used as pallets, and a triangular balance base with a bottom, height and length of 30 cm.

In fact, the length does not need to be this long. Because the width of the crossbar is only ten centimeters. Do it so long in order to be able to place it smoothly. You won't overturn when you touch it.

This production requirement is much simpler, as long as the ridge line at the apex of the triangle is straight and horizontal, drill a whole groove one centimeter deep with a hand drill on the center line of the bottom surface of the crossbar, and put the balance crossbar on the contact surface of the ridge line at the vertex of the triangle base flat.

The reason why you want to make a groove is when you take things from both ends of the scale. The balance bar will not slip off.

Place the crossbar on the triangular base and place two trays so that the balance is level. (Use a knife to cut off some wood from the crossbar or pallet with a knife)

After determining the level, two holes are drilled at both ends of the crossbar and the tray, and the tray and the crossbar are connected into a whole with a thin straw rope.

Place on the base again, test the level, and then turn the position of the left and right trays until you place them no matter what. Both trays are always level.

It's easy to say, but it's also laborious to do, and after the balance is completed, the gathering team and the brick-making team have also returned to the tribe one after another.

All the adults of the tribe have returned, and Wang Tian began to organize everyone to vote for the first democratic vote in history.