1. V Belt & Rope Drive Problems

2. Selection of v-belt from manufacturer catalogue
The data is available :-
power to be transmitted
Input and output speed
2. Select the service factor or load correction factor for the
given application
Select type of v-belt cross section
calculate the design power
select the standard pulley
calculate pitch length of the belt
Select nearest standard pitch length of the belt from manufacturer catalogue and calculate the exact centre distance

3. Selection of v-belt from manufacturer catalogue
8. Find the power rating of the selected v- belt from
manufacturer catalogue
Calculate arc of contact for the smaller pulley and find arc of contact correction factor
Find belt length correction factor
Calculate the modified power rating of the v-belt
Find the number of belt required

4. Creep In Belt
When the belt moves over the pulleys to transmit the power, the tension Ft1 in the right side is more than the tension Ft2 in the slack side.
As the belt material is elastic, it elongates more on the tight side than on the slack side, resulting in unequal stretching on two sides of the drive.
Therefore the length of the belt received by the driving pulley is more than the length of the belt that moves off the driving pulley.
On the other hand length of the belt received by the driven pulley is less than the length of the belt that moves off the driven pulley. Hence, the belt must creep forward slightly relative to the driven pulley rim.

5. Creep In Belt

6. Creep In Belt
This motion of the belt relative to drive and driven pulley due to unequal stretching of two sides of the drive is known as creep.
The effect of creep back on the driving pulley is to slow down the speed of the belt with respect to driving pulley and the effect of creep forward on the driven pulley is to slow down the speed of the driven pulley with respect to the belt.
It is important to note that, the creep which is due to the elastic property of the belt is totally different than the conventional slip, which is due to insufficient frictional grip between the belt and pulley.

7. Method of belt tensioning
In order to transmit the power, the belt must be provided with the sufficient initial tension. The power transmitting capacity of the belt drive also depends upon the initial tension.
Some of the method use to adjust the belt tensions are as follows:-
Manual adjustment
Pivoted overhung motor
Weighted idler pulley

8. Manual adjustment
The position of motor and hence the initial tension can be adjusted manually with the help of the screw and nut adjustment.

9. Pivoted overhung motor
The belt tension is due to the product of the weight of the motor and the moment arm.

10. Weighted Idler Pulley
The idler pulley is held against the belt by its own weight and the adjustable weight.
By changing the position of the adjustable weight, the required belt tension can be achieved.

11. Inroduction to chain drive
Chain drive is a way of transmitting mechanical power from one place to another. It is often used to convey power to the wheels of a vehicle, particularly bicycles and motorcycles. It is also used in a wide variety of machines besides vehicles.
Most often, the power is conveyed by a roller chain known as the drive chain or transmission chain, passing over a sprocket gear, with the teeth of the gear meshing with the holes in the links of the chain.

12. Advantages of chain drive
As no slip takes place during chain drive, hence perfect velocity ratio is obtained.
Since the chains are made of metal, therefore they occupy less space in width than a belt or rope drive.
It may be used for both long as well as short distances.
It gives a high transmission efficiency (upto 98 percent).
It gives less load on the shafts.
It has the ability to transmit motion to several shafts by one chain only.
It transmits more power than belts.
It permits high speed ratio of 8 to 10 in one step.
It can be operated under adverse temperature and atmospheric conditions.

13. Limitations of chain drive
The production cost of chains is relatively high.
The chain drive needs accurate mounting and careful maintenance, particularly lubrication and slack adjustment.
The chain drive has velocity fluctuations especially when unduly stretched.

14. Types of power transmission chain
Roller chain
Large reduction ratio (usually up to 1:7)
Chains can be used with long shaft center distances (normally up to 4m). By changing the number of links it is possible to freely adjust the shaft center distance.
The chain can be used on both sides and drive multiple shafts at the same time.
Easy installation and replacement (easy to cut and connect chains).
If the distance between shafts is short, it can be used vertically.
The sprocket diameter of a chain drive could be smaller than a belt pulley while transmitting the same torque.
Transmitting power by meshing many teeth results in less wear of sprocket teeth than gears.
Chain drives have greater shock absorption than gear drives.

15. Roller chain drive

16. Inverted tooth drive chains
Inverted tooth drive chain are the optimal solution for requirements exceeding those met by other chains (e. g. roller chains). They allow for low-backlash drives with exact positioning. They are also highly effective, inured to vibration and have minimal noise emission.

17. Inverted tooth chain drive

18. Lubrication of chain
It is very important for the effective and durable functioning of chains.
The chains are lubricated by light or medium mineral oils like SAE30.SAE40,SAE50
Methods of lubrication
Manual
Drip
Oil bath
Oil stream