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Design of chain drive mechanism 2

Selection method for low speed case

At a low chain speed of 50m/min or less, it is hardly necessary to consider stretching due to chain friction, and lifespan will be mainly determined by fatigue strength. In this case, selection of a low speed setting method is permitted rather than the “general case selection method”. The low-speed selection method is used for the case of a smooth transmission with few starts and stops, and the atmosphere, placement and lubrication etc all comply with the general case.

（Table 1）（Table 4）

**Table 4. Speed factor table**
Roller chain speed	Speed factor
0～15 m/min	1.0
15～30	1.2
30～50	1.4
50～70	1.6

(1) Grasp of usage conditions
Same as [General case selection method].
(2) Selection of chain and no. of small sprocket teeth
From Table 3 Simple Selection Table choose a slightly smaller chain and sprocket from the rotational speed (r/min) and motor (kW).
(3) Calculation of chain speed

V

: Chain speed (m/min)

P

: Chain pitch (mm)

N

: No. of sprocket teeth

n

: Sprocket rotational speed (r/min)
(4) Calculation of chain maximum acting load
Finds the maximum load acting on the chain.

F

: Load on the chain (kN)

V

: Chain speed (m/min)

kW

: Power transmission (kW)
(5) Decision on used factors
The used factors are found from the Used factors table (Table 1).
(6) Decision on speed factors
Finds the speed factor from the chain speed calculated in (3).
(7) Study of maximum allowable tension of the chain
Substitute the values found in (4) - (6) in the selected formula, compare the result with the maximum allowable tension of the chain selected in (2) and consider if it satisfies the selection formula.
If not satisfied, change the chain and sprocket and consider again.
(8) Check of the no. of teeth and shaft diameter of the large sprocket, and calculate the chain length
The selection below is the same as “General case selection method”.

Selection method when impact load acts at low speed

Under conditions where there are many sudden start/stops, or reverse braking or braking, and the action of many impact loads, the inertia (GD2) of the motor or non-motor must be taken into account.
Compared with the general transmission case, sufficient care is required because a rather large load is acting on the chain.

Select the chain according to the following method.

（Table 5）（Table 4）

Impact factor
The constants determined by the inertia ratio (GD2 ratio) of the motor and the driven machinery and the size of the motor play are shown in (Table 5). Note that where the play is extremely large, an impact larger than that value may be acting.

Table 5. Impact factor table

Selection method of the stainless steel roller chain (CHES)

Please used the low speed selection method as the stainless steel roller chain selection method.

1) Maximum allowable tension is lower for CHES (stainless steel type) compared to the CHE (steel type) roller chain.
2) Please avoid use of the offset link as far as possible.

Temperature selection method

Roller chain temperature selection method
This is the size selection method anticipating reduction in strength due to temperature.

1) Problems with roller chain transmission at high temperatures
(1) Increased friction due to decline in hardness
(2) Increased stretch due to hardening
(3) Oiling defects and flex defects due to oil deterioration and carbonization, increased friction
(4) Increased friction and flex defects due to occurrence of scale
2) Problems with roller chain transmission at low temperatures
(1) Decline in impact strength due to low temperature brittleness
(2) Coagulation in the lubricant oil
(3) Faulty flex due to snow or ice attached

**Roller chain power transmission guidance at high and low temperatures**
Temperature	CHE Roller chain
Temperature	Less than CHE60	Greater than CHE80
Less than −60℃	−	−
Greater than -60℃ to -50℃	−	−
Greater than -50℃ to -40℃	−	Not used
Greater than -40℃ to -30℃	Not used	Catalog value × 1/4
Greater than -30℃ to -20℃	Catalog value × 1/4	Catalog value × 1/3
Greater than -20℃ to -10℃	Catalog value × 1/3	Catalog value × 1/2
Greater than -10℃ to 60℃	Catalog value	Catalog value
Greater than 60℃ to 150℃	Catalog value	Catalog value
Greater than 150℃ to 200℃	Catalog value × 3/4	Catalog value × 3/4
Greater than 200℃ to 250℃	Catalog value × 1/2	Catalog value × 1/2
Above 250℃	Not used	Not used

Selection method at high temperature of stainless steel roller chain
(1) Up to 400℃ use the low speed selection method. (General selection method cannot be used.)
(2) Above 400℃ use the temperature factor shown in the table below.
(3) Selection method