APPLIED MECHANICS- Worm and Worm Wheel Experiment
EXPERIMENT
OBJECTIVE:
To determine the velocity ratio, mechanical advantage and efficiency of a single threaded worm and worm wheel.
APPARATUS REQUIRED:
Worm and worm wheel apparatus, weight, string, scale etc.
THEORY:
Worm and worm wheel consists of a square threaded screw (known as worm) and a toothed wheel (known as worm wheel) geared with each other. A wheel is attached to the worm, over which passes a rope a load is securely mounted on the worm wheel.
Let,
R = Radius of the effort wheel
r = Radius of the load drum
W = Load lifted
P = Effort applied to lift the load
T = Number of teeth on the worm wheel
In the first revolution of wheel, distance moved by effort = 2πr, as worm is single threaded.
The load drum will move through 1/T
Distance, through which the load will move = 2πr/T
VELOCITY RATIO (V.R) = Distance moved by effort/Distance moved by load drum
MECHANICAL ADVANTAGE (M.A) = Load/Effort or W/P
EFFICIENCY = Mechanical Advantage/Velocity Ratio x 100 or M.A/V.R x 100
PROCEDURE:
- Measure the radius of the effort wheel and load drum with the help of string.
- Count the number of teeth on worm wheel.
- Wrap the string over the effort wheel and load drum.
- Suspend some load to the spring passing over the load drum via hanger and go on adding weight in the pan.
- Note the effort in the weight pan.
- Calculate the mechanical advantage and velocity ratio.
- Repeat the experiment with different loads.
OBSERVATION TABLE:
S. No. | Load Drum 2πr (in cm) |
Effort Drum 2πR (in cm) |
No. of teeth on worm wheel (T) |
Load Lifted (W) (in grams) |
Weight of pan (P1) (in grams) |
Weight added in pan (P2) (in grams) |
Total Effort P= P1+P2 (in grams) |
M.A = W/P | V.R = 2πrRT/2πr | Efficiency = M.A/V.R x 100 |
PRECAUTIONS:
- Lubricate the bearings of worm wheel to decrease wheel friction.
- Weight should be gently placed in effort pan.
- String should not overlap on pulley and should not be loose on pulley.
- The pan carrying weight should not be touched.
- There should not be any knot in the string.
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