Do you know why the thread size is 6, 8, 10, 12, 14, 16?
Do you know why the roughness is 0.8, 1.6, 3.2, 6.3, 12.5?
Do you know why the cylinder bore is 63, 80, 100, 125?
Do you know why the cylinder pressure is 6.3, 16, 25, 31.5?
Do you know the innumerable tables in the mechanical design manual, and how do the parameter tables on all product samples come from?
Everything comes from the great priority system.
French engineer Renault saw a lot of wire ropes on the hot air balloon. He thought of a way to get 10 times 5 times, get a number of 1.6, and then multiply and multiply, and get 5 priority numbers as follows:
1.0
1.6
2.5
4.0
6.3
This is a series of equal ratios, the number of which is 1.6 times the number of the first few, then there are only 5 kinds of wire ropes below 10, and only 5 kinds of wire ropes of 10 to 100, namely 10, 16, 25, 40, 63.
However, this method is too sparse, Mr. Lei will continue to work hard, will open 10 times 10 times, the R10 priority number is as follows:
1.0
1.25
1.6
2.0
2.5
3.15
4.0
5.0
6.3
8.0
The common ratio is 1.25, so there are only 10 kinds of wire ropes within 10, and only 10 types of 10 to 100, which is more reasonable.
At this time, some people must say that this series, the previous figures seem to be similar, such as 1.0 and 1.25, there is no difference, usually I am rounded off, but the interval between 6.3 and 8.0 is big, is this reasonable? Reasonable and unreasonable, let us make an analogy.
For example, natural numbers . 1, 2, 3, 4, 5, 6, 7, 8, 9 seem to be very smooth, we use this series to pay wages, give Zhang Sanfa 1000, give Li Sifa 2000, both are convinced. Sudden inflation, gave Zhang Sanfa 8000, and Li Sifa 9000. In the past, Li Si’s salary was twice that of Zhang San, and now it’s 1.12 times. Do you say that Li Si can be willing? He is the supervisor, and it is almost the same to send him 16,000. Zhang San will not complain that the supervisor is 8,000 more than him.
There are two ways to compare this natural thing, "relative" and "absolute"! The priority number is relative.
Some people say that his product specifications are 10 tons, 20 tons, 30 tons, 40 tons. Now it seems unreasonable? If you take twice, 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, the ratio is 1.6.
This is "standardization". We will often see people saying "standardization". Actually, they are talking about "standard parts". The work done is only to sort out the standard parts of the whole machine. It is called standardization. Actually it is not like this. .
For true standardization, you need to serialize all the parameters of your product according to the priority number, and then serialize the functional parameters and dimensions of all components with the priority number.
Natural numbers are endless, but in the eyes of mechanical designers, there are only 10 numbers in the world, which is the R10 priority number. Moreover, the 10 numbers are multiplied, divided, multiplied, squared, and the result is still in these 10 numbers, which is wonderful! When you design, don't know how big the size is, just choose among the 10 numbers. What is convenient?
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 numbers are N24 and N12, respectively, are multiplied, and their sequence numbers are added, and the result is equal to N36 or 8;
Divide, the serial number is subtracted, equal to N12 or 2 is;
2 cube, multiply its serial number N12 by 3 to get N36 or 8 is;
The square of 4, divide its serial number N24 by 2 to get N12 or 2 is the fourth power of 2? N12*4=N48, not here, what should I do? The above list, does not write a number, is 10, its serial number is N40, where the serial number is greater than 40, only look at the part greater than 40, such as N48, look at N8, that is, 1.6, then multiply by 10 to get 16 . If the serial number is N88, look at N8 to get 1.6, then multiply by 100 to get 160, because the serial number of 100 is N80, the serial number of 1000 is N120, and so on.
Do mechanical design, it is enough to use these 20 numbers for a lifetime. But sometimes you need to use the R40 number system, there are 40 numbers, it is more perfect, if not enough, there are R80 series. I have turned the R40 number back down, and I don't need a calculator for general calculations.
To put it simply, the torsion resistance of the 45-diameter 45 steel is 0.5*Ï€*R^3, and the torsional stress is half of the 360, that is, 180 MPa, and the pi is 3.15. The left and right hand pinch the decimal point. I will come out in a minute. Some people say that you don't add a safety factor? Say, is it 1.25, or 1.5, or 2? Ha ha.
The golden section is 0.618, which is 1.618, and there are also 1.6. The square root series is the root number 1, the root number 2, and the root number 3. Is it easy to find out? (The serial number of 3 is N19)
What is the square of π equal to? Equal to 10. Is it convenient when you have a stable pressure bar? The torsion coefficient of the round rod is about 0.1*D^3. Now you can calculate the torsion coefficient.
Why does the big screw jump directly from the M36 to the M40?
Why is the gear ratio of the gears 6.3 or 7.1?
Why does channel steel have a number 12.6 that is rarely seen on the market?
Why does the outsourcing factory call to say that the 140 square tube is not, but there are 120 and 160?
Because the R5 number is preferred over the R20 number.
Why does the standard component have a first sequence and a second sequence? In general, the first sequence is the R5 sequence.
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