Everything comes from the great priority number system.
Renault, a French engineer, saw that the wire ropes on the hot air balloon had various specifications, so he thought of a way to raise 10 to the 5th power to get a number 1.6, and then multiplied them repeatedly to get 5 priority numbers as follows: 1.0, 1.6, 2.5 , 4.0, 6.3
This is a geometric sequence, the last number is 1.6 times of the first number, then there are only 5 types of steel wire ropes below 10, and there are only 5 types of steel wire ropes from 10 to 100, namely 10, 16, 25, 40, 63
But this division method is too sparse, so Mr. Lei made persistent efforts to raise 10 to the 10th power, and obtained the R10 priority number system as follows: 1.0, 1.25, 1.6, 2.0, 2.5, 3.15, 4.0, 5.0, 6.3, 8.0
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The common ratio is 1.25, so there are only 10 types of steel wire ropes within 10, and only 10 types of wire ropes from 10 to 100, which is more reasonable. At this time, some people must say that the numbers in front of this series seem to have little difference, such as 1.0 and 1.25. There is no difference. I usually round up, but the interval between 6.3 and 8.0 is large. Is this reasonable?
Reasonable or unreasonable, for example. For example, the natural numbers 1, 2, 3, 4, 5, 6, 7, 8, and 9 are very smooth. We use this sequence to pay wages. We give Zhang San 1000 and Li Si 2000. Both of them are convinced. Sudden inflation, 8000 to Zhang San and 9000 to Li Si. In the past, Li Si's salary was twice that of Zhang San's, but now it has become 1.12 times. Do you think Li Si can be willing? He is the supervisor, and it is about the same to send him 16,000. Zhang San will not complain that the supervisor has 8,000 more than him.
There are two ways to compare things in nature, namely "relative" and "absolute"! The priority number system is relative.
Some people say that his product specifications are 10 tons, 20 tons, 30 tons, and 40 tons. Now it seems unreasonable? If you take twice as much, it should be 10 tons, 20 tons, 40 tons, 80 tons, Or keep the head and tail, it should be 10 tons, 16 tons, 25 tons, 40 tons, and the common ratio is 1.6 to be reasonable.
This is "standardization". I often see people say "standardization" on forums, but they actually mean "standard parts". The work they do is just sorting out the standard parts of the whole machine, which is called standardization. In fact, it is not like this. . For true standardization, you need to serialize all the parameters of your product according to the priority number system, and then serialize the functional parameters and dimensions of all parts and components with the priority number system.
Natural numbers are infinite, but in the eyes of mechanical designers, there are only 10 numbers in the world, and it is the priority number R10. Moreover, these 10 numbers are multiplied, divided, squared, and square rooted, and the result is still in these 10 numbers, how wonderful! When you design, when you don’t know what size to choose, just use these 10 How convenient it is to choose from the number!
1.0 N0, 1.12 N2, 1.25 N4, 1.4 N6, 1.6 N8, 1.8 N10, 2.0 N12, 2.24 N14, 2.5 N16, 2.8 N18, 3.15 N20, 3.55 N22, 4.0 N24, 4.5 N26, 5.0 N28, 5.6 N30, 6.3 N32 , 7.1 N34, 8.0 N36, 9.0 N38
Two priority numbers, such as 4 and 2, whose serial numbers are N24 and N12 respectively, multiply them and add their serial numbers, and the result is equal to N36, that is, 8;
Divide and subtract the serial number, which is equal to N12, which is 2; for the cube of 2, multiply its serial number N12 by 3 to get N36, which is 8;
For the root of 4, divide its serial number N24 by 2 to get N12, which is 2. What if you want to find the fourth power of 2? N12*4=N48, there is no such thing here, what should I do? The above list does not write a number, it is 10. Its serial number is N40. If the serial number is greater than 40, only look at the part greater than 40.
Such as N48, look at N8, which is 1.6, and then multiply by 10 to get 16. If the serial number is N88, look at N8 to get 1.6, then multiply it by 100 to get 160, because the serial number of 100 is N80, the serial number of 1000 is N120, and so on
For mechanical design, these 20 numbers are enough for a lifetime. But sometimes the R40 number system is needed. If there are 40 numbers, it will be more perfect. If it is not enough, there is also the R80 series. I have memorized the R40 number system backwards, and I don't need a calculator for general calculations.
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Simply speaking, to calculate the torsional capacity of 45 steel with a diameter of 40, the torsion coefficient is 0.5*π*R^3, the torsional stress is selected to be half of the yield point 360, which is 180MPa, and the pi is selected to be 3.15. Come out in a while. Some people say that you don't add a safety factor? Tell me, is it 1.25, 1.5, or 2? Ha ha.
The golden section is 0.618, which is 1.618, and there is also 1.6 here. The square root number sequence is the root number 1, the root number 2, and the root number 3. It is easy to find it? (The serial number of 3 is N19)
What is the square of π equal to? It is equal to 10. Is it convenient for you to calculate the stability of the pressure bar? The torsion coefficient of the round bar is about 0.1*D^3. Now you can calculate the torsion coefficient by mouth, right?
Why do big screws jump directly from M36 to M40?
Why is the transmission ratio of the gears 6.3 or 7.1?
Why does the channel steel have a 12.6 size that is rarely seen in the market?
Why did the outsourcing factory call and say that there is no 140 square tube, but there are 120 and 160?
Because the R5 number system has priority over the R20 number system.
Why do the parameters of standard parts have a first sequence and a second sequence? Generally speaking, the first sequence is the R5 sequence.
Why does Inventor have M11.2 in the list of screw holes? Now you know it is not a nonsense number, right?
There are also steel plate thickness, section steel type, gear modulus, all standard parts, functional parameters, dimensional parameters, standard tolerance tables on all industrial product samples, and so on. Their sources are slowly becoming clear in our hearts at this moment. . It can be said that we have understood half of the mechanical design manual, as well as those industrial products that have not yet been made.
Then, when designing a product, a series can be designed at the same time, instead of the so-called "standardization" after the design is completed; furthermore, if the product is destined to be serialized, then we can even design it without changing the actual working conditions. Design the product with a good understanding, because the priority number system has included all models.
The applications of the priority number system, listed above, can be described as a drop in the ocean, and endless applications are waiting for us to develop ourselves. Memorize the priority number system, it's a once-for-all job.
