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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