Title : Belt Friction
Aim: To determine the coefficient of static friction (μ) between the given flat belt and drum.
Apparatus: The belt friction apparatus consists of a drum with well polished surface and is fixed on wooden board which acts as a protractor. The belt passes over the groove, provided on rim of drum. A small smooth pulley is fixed eccentric to the wooden board which is used to adjust contact angle of belt on the drum.
Theory: Consider belt passing over fixed drum. When the belt is about to slip towards the side of greater
tension 'T'. The relation between these two tensions is given as :
Knowing T1 and T2 and keeping angle of lap (Β) constant ; value of μ called as coefficient of static friction can be worked out for belt by using equation
Procedure:
-
A) β constant
- With the help variable pulley position the angle of lap (β) is fixed and recorded in radians.
- The belt is allowed to pass over the drum and pulley.
- One side of belt (Slack Side) is loaded with weight W1(T1= W1).
- The other side of belt (Tight Side) is loaded gradually in small increments until this side just starts slipping. The corresponding load is W2(T2= W2)
- Steps 3 to 4 are repeated for various values of T1 giving different sets of T1 and T1
-
B) T1 constant
- One side of the belt is loaded with a weight W1(T1= W1) and T1 is recorded.
- With the help of variable pulley position, the angle of lap (β) is adjusted to a convenient value and recorded in radians.
- The other side of belt (Tight Side) is loaded gradually in small increments until this side just slipping. The corresponding load is W2(T2 = W2 ) which is also recorded.
- Steps 3 to 4 are repeated for more values of β giving different sets of β and T2
Observation Table :
A) β constant| Sr. No. | Tight side Tension (T2) | slacked side Tension (T1 ) | β | μ |
|---|---|---|---|---|
| 1 | 456 | 100 | 3.14 | 0.48 |
| 2 | 556 | 150 | 3.14 | 0.41 |
| 3 | 776 | 200 | 3.14 | 0.43 |
| 4 | 256 | 50 | 3.14 | 0.52 |
| Sr. No. | Tight side Tension (T2) | slacked side Tension (T1 ) | β | μ |
|---|---|---|---|---|
| 1 | 456 | 100 | 3.14 | 0.48 |
| 2 | 806 | 100 | 4.71 | 0.48 |
| 3 | 1506 | 100 | 4.88 | 0.55 |
| 4 | 806 | 100 | 3.14 | 0.68 |
Result: The observed value of coefficient of static friction between the given flat belt and the drum is μ = 0.49