Now we use the bicycle hubs, its structure more than two kinds, one is represented by the beads shimano file structure is no doubt of its smooth, compact in design and technology of surface hardening conditions, is guaranteed under certain conditions normal time. Second, a long margin, represented by the bearing bearing, so that is very awkward, because the bearing itself is bearing the meaning, then is the "bearings" in this industry on the general structure of the connection as a relatively rotating parts, but not so called , because only the middle of the ring is the real bearings, the outside part of the bearing can only say that, we said, hub or skin. So I suggest that you call them after the beads file hubs, bearing hubs.
Beads files I do not say, we just open a permanent, Phoenix hub, you can see, has not seen, and quickly to dismantle. Some people think that beads file hubs, strong, durable, and to his life than the old shimano hub of high-margin an example, may be part of the truth, the other part of the fact that he may be fitted for a long time margins of the car to DH, shimano car in the city with the work, this is immeasurably, there may be shimano surface craft and precision better than better than a long margin bearing land. But from the perspective of industrial design, said bead profile is not as good as bearing too, or else industrial machinery, automobiles, and so they've been using this ball plus the design of the iron. a point of contact of the surface pressure of the force is too large, b ball ball gap is too large irregular movement momentum, c the hardness of a bad ball handling, too hard upon impact, the surface will be crushed, or internal premature fatigue too soft easily deformed. However, bearing hubs do not think that is a line we are exposed, most of the bearings such as deep groove ball bearing 6001 is, in fact it is a small round face contact, the misconception may stick shaft and bearing are in contact on line In addition, needle roller bearings line contact.
We are concerned that the selection of the bearing hub bearing type, why should so choose, what kind of car should choose what bearing, our car may also have bearing on what is upgrade.
First, there is a common bearing
Deep groove ball bearings, angular contact ball bearings, self aligning ball bearings Cylindrical roller bearings
, Needle roller bearings, spherical roller bearings, tapered roller bearings.
Omitted here because they can not map 5000 words ... ... while others have thrust bearings, many types, but because the main force is axial, Electric Bikes do not need, so do not introduce more, and generally have a corresponding radial bearings axial thrust models.
Has thrust the ball, angular contact thrust ball bearings, cylindrical roller thrust ball bearings, needle roller thrust bearings, tapered roller thrust bearings.

Suitable for use on the bike, the best is the deep groove ball bearings, no seals and no dust cover, the most quiet, least resistance.
We take a look at this bearing parameters. (Parameters to the company's products skf 6001, for example)
Diameter d = 12 (mm)
Diameter D = 28 (mm)
Width B = 8 (mm) dynamic pressure C = 5.4 (kN) static pressure C0 = 2.36 (kN) fatigue limit load Pu = 0.1 (kN) rated speed of 60000 r / min
Limit speed 38000 r / min
Weight of 0,022 kg C, C0, Pu is the three key data, determined that we can not use the bearings.
"Basic dynamic load rating C" is used to calculate the dynamic stress in the bearing, that is a rotation by the bearing load conditions. The value that according to ISO 281:1990 standard, providing 100 million transfer basic rating life of the bearing load. Assumed direction of the same size and load, in terms of the radial bearing radial load, in terms of thrust bearings for the axial load acting on the center. This means that if we want to turn bearing turn 1 million, then regardless of lubrication, speed, pollutants can be factors bearing exercise should not exceed the pressure.

ISO 76:1987 standard defines the basic static load rating as follows: with the heaviest load rolling element / raceway contact center contact stress calculation of the corresponding static load, the stress will cause the rolling elements and raceways overall permanent deformation, rolling diameter of about one ten-thousandth. Self-aligning ball bearings for the 4 600 MPa;
All other ball bearings for the 4 200 MPa;
All roller bearings for the 4 000 MPa.

Fatigue load limit is a good design, excellent materials, fine workmanship and install the correct bearing, as long as its easy enough to withstand the load, then the bearing material will never fatigue damage, a feature that the bearing value is easily fatigue limit load.

Suppose a person's weight is 70 kg, with weight 10 kg, a total of 80 kg, then the front and rear weight distribution is assumed 4:6, under the rear axle in normal driving pressure is 80 * 0.6 * 9.8/1000 = 0.47 ( kN) and so far less than C C0, but greater than Pu, so sooner or later we still have a bad bearing, but we can have a long bearing it, this is a difficult question, because too many factors to consider, and if We stole a lazy, with some assumptions and ideal state, then we can get a rough reference, let's calculate.
L10 = (C / P) p
p = index of life formula: 3 refers to the ball bearing 10 / 3 roller bearings
L10 = (5.4/0.47) 3 = 1516 (millions of revolutions), if it is uniform, then, assuming a second four laps (about 30 kilometers per hour) is lap n = 30 * 1000 / (3.14 * 28 * 2.54/100) / 60 = 224 (r / min), then the work hours is L10 h = 106 / (60n) L10 = 1000000 / (60 * 224) * 1516 = 112849 (h) you must be very happy, and I can so the shaft long? 110,000 hours A day, 3 hours, also with 100 years.
But calm down, this is not considered friction lubrication, that this value is only theoretical reference value, in order to obtain the actual reference value, we need to trouble about.
Rated life Lnm = a1 * * L10 life reliability coefficient a1 of which is that you would like to ask them how much the value of a reliability (which is the amount of random mathematical behalf of tolerance, tolerance means, we check it online, You can be interpreted as confidence), we want to add the correct parameter values.
Reliability
The probability of failure SKF rating life
Coefficient

%
n%

Lnm

a1
90
10
L10m

195
5
L5m

0,62 96
4
L4m

0,53 97
3
L3m

0,44 98
2
L2m

0,33 99
1
L1m

0,21
Because they are not precision instruments, less demanding of reliability, the reliability of our right to take 90% of a1 = 1
Skf's calculation is correct parameters, they have their own set of theories, and is said to be very accurate, then we used, this coefficient represents the fatigue load limit ratio (Pu / P), lubrication (viscosity ratio) and bearing the degree of pollution (ηc) the relationship between, as shown below k
Is the viscosity ratio = v/v1 v is the lubrication index, depends on our use of oil, this aside, set to 32, is a good lubricant.
V1 is the use of the bearing mean diameter dm = (D + d) / 2 (mm) and bearing speed (r / min) to calculate these two values, (specific calculation to use function table, because they can not map, it is omitted).
       This diagram is based on the latest rolling tribology research made the appropriate changes, if the speed is 224, then we can obtain V1 = 98.9, thus k = 0.324, then in front of a map, can be roughly
= 0.342,
So Lnm = a1 aSKF L10 L10m = 1 * 0.342 * 1516 = 518 (million revolutions)
L10mh = 518 * 1000000/60/224 = 38576 (h) = 38576 / (3 * 365) = 35 years! ! ! ! ! .
       This figure is still pretty good, but it really is the actual situation? We know, of bearing the greatest damage from accidental impact strength of the random weight, such as washed down from the hills, stairs or landing. Here we have to look at the momentum under the impact of your bearing to go very far.
     As time goes on, the load bearing strength and direction with the velocity, temperature, lubrication conditions and pollution levels change applications, bearing life can not be directly calculated, need to work with variable operating conditions related to the equivalent load of the intermediate calculation steps. However, considering the complexity of the system, the intermediate parameters is not easy to determine, it will not simplify the calculations.
     Therefore, fluctuations in operating conditions, the need to apply the load range or duty cycle, reducing the load to a more simple case of a limited number. In the continuously variable load, can be accumulated for each different load levels, load range can be simplified to a constant load of the rectangular area of ​​each histogram describes the application to run a certain percentage or time percentage. Therefore, the load diagram shows the full impact of load and peak load are important, even if the load is relatively rare occurrence, but only a few turn.

In each load cycle, or the short term, bearing loads and working conditions can be an average of a certain constant value. Also, each load cycle, the expected number of hours worked or number of revolutions, that the conditions required for that particular load of the life of the percentage. Thus, for example, N1 P1 load conditions, said the number of revolutions required, the application of N that the entire life cycle, the life of the percentage of load conditions P1 U1 = N1 / N, the calculation of life L10m1. In the variable operating conditions, bearing life can be predicted using the following formula:

Among
L10m
=
SKF rating life (90% reliability), millions of revolutions

L10m1, L10 m2, ...
=
Constant conditions 1, 2, ... under the SKF rating life (90% reliability) million transfer
U1, U2, ...
=
Conditions 1, 2, ... life under the percentage.
Description: U1 + U2 + ..... Un = 1 the calculation method used depends largely on whether the application representative load diagrams required.
Assumed that the process of moving mini electric scooter only two cases, a normal driving, by the pressure of 0.47kN, 2 bumpy momentum C2, let's calculate c2
Assumption goes down, the front wheel touch the ground, the rear wheels from a 30 cm high rock fell on the ground,
Because the body forward, we adjusted the front and rear wheel bearing ratio of 50:50, the front and rear wheels to the static pressure is C '= 80 * 50% * 9.8 *= 0.39kN, set the rear wheels touch the ground time of 0.05 seconds, the momentum for the
V =
F = mV / s = m
/ S = 40 * 2.42/0.05 = 1.94kN C2 = C '+ F = 2.33kN,
518,
= 97.5% (once every two seconds, shock)
3, = 2.5% = 98, converted to hours of work L10mh = 98 * 1000000/60/224 = 7291 (h) = 6 years.
       Up to six years of life. It seems we still have to take care of his car, but this is working life, for most bikers, in the life of the bearing did not meet the time may no longer be able to endure the wear and tear caused by the main power, noise , and have a vibration in advance for bearing the defects.
       Finally, to explain, for bearing lubrication is extremely important, without changing the conditions of other factors, just use good special bearing lubricants, can greatly enhance the life of the bearing, such as SKF's LGEP-2 synthesis of lithium-based fat (expensive 200 g / 155 million), but the viscosity of 200, high load, high water, high corrosion, high earthquake. In this lubrication, the
,
, Improved to 9950,11, and
Up to 421,
L10mh = 31384 (h) = 31384 / (3 * 365) = 28 years. That is for the high-end bearing oil can be used to ensure that the bearing life, but 28 years of bearing oil royalties is also very substantial.