1. Chapter 9 Transmission of Chains
Key Terms:
chain drives
pitch
number of links
chain plate
sprocket
efficiency of polygon

2. 9.1 Characteristics and Application of Chain Drives
1.Construction
1—driven sprocket 2—chain 3—driving sprocket

3. Sprocket

4. 2.Characteristic Advantages: 1) A wide range of center distance;
2) Average velocity ratio is positive;
3) High efficiency =98%;
4) Can operate under an adverse environment. Disadvantages:
1)The instantaneous velocity and speed ratio of chain are not constant, which lead to impact and noise of chain drives;
2)Wear of joints result in the faulty engagement;
3)More accurate assembly and more complicated service are required.

5. 3.Application Good for low speed & high torque;
v<15m/s, P100kW, i 8
amax=10m

6. 9.2 Types of Chain Drivers Lifting chains Hauling chains
Power transmission chains
a. Roller chains
b. Silent chains

7. 1. Roller chains 1——inner side plate 4——bushing 2——outer side plate
3——pin

8. Strand number: single, double, multiple strands, 4

9. 2. Pitch P
1)Pitch P is the linear distance between the centers of rollers.
2) Pitch is a critical parameter of roller chain drives, the more the pitch is,
the larger the size of the chain parts and the greater the power transmitted is.

10. 2. Number of links Lp 1) Even number of links 2) Odd number of links
Best!
1) Even number of links
2) Odd number of links
offset links

11. 3. Standard roller chain (GB1243.1—83)
Table 9.1: A series roller chain
Mark of roller chain:
08A-187 GB

12. 9.3 Moving Characteristics of Chain Drives
1. The average velocity of chain

13. 2. The instantaneous velocity of chain

14. Variation of a Chain Velocity

15. 3. The instantaneous speed ratio of chain drives

16. Conclusion The instantaneous velocity of the chain varies;
The larger the pitch is, the less the number of teeth of sprocket is, the larger the variation of the chain speed will be;
The instantaneous speed ratio varies;
The uneven moving features of chain drives is named the efficiency of polygon

17. 9.4 Appended Dynamic Loads of Chain Drives
It is necessary to apply
less chain pitch
and much number
of teeth of the sprocket.

18. 9.6 Design of Chain Drives 1. Failure Type
1）Fatigue failure of the plates;
2）Wear in joints lead to elongation of the chain and its faulty engagement;
3）Veneer
4）Impact damage;
5）Wear of the sprocket;
6）Static break failure (v<0.6m/s).

20. 2. Load-carry Capacity of Roller Chains
1) Limiting Power Curves, Fig. 9.10
1—good lubrication;
2—limited by fatigue failure of plates;
3—limited by impact fatigue
failure of bushings and rollers;
4—limited by veneer failure
of the pins and bushings;
5—applicable area;
6—bad operating condition.

21. 2) Rated Power Curves P0, Fig.9-11
Experiment Conditions:
z1=19; Lp=100; single-strand; steady load;
service life=15000h;
Recommended lubrication ways: Fig.9.12

22. Recommended Lubrication
1—artificial regular lubrication
2—drop lubrication
3—oil-bath or splash lubrication
4—pressure spay lubrication

23. modified power in real working conditions:
P—name transmitted power;
KA—working condition factor, table 9.2;
Kz, K'z —factor of the number of
teeth of small sprocket, table 9.3;
Km—multiple-strand chain factor, table 9.4
KL—chain length factor, Fig.9.13;

24. 3. Design Criteria
1)For general chain velocity (v0.6m/s): Rated Power Curves
2)For low chain velocity (v<0.6m/s): static strength
FQ—limiting tensile load, table 9.1;
m—the number of strand;
Fc—centrifugal force;
Ff—sagging force.
KA—working condition factor, table 9.2;

25. 4. Design Calculations and Parameter Selection2 1 a w2 w1 D2 D1

26. Number of teeth of sprocket and speed ratio
uneven number is best!

27. 2) Types of chain, pitch and strand number p, P0, Fd ,v;
Type of the chain: Fig.9.11

28. 3) Distance between the sprocket axles and the chain length
The number of links Lp:
even number is best!

30. the more the
number of teeth z,
the much possible
for the chain to
shift outward
upon the sprocket teeth 。

31. The end Thanks!