Ergonomics:
1. Introduction:
The word Egronomics comes from the Greek word "Ergo"-Work
and "nomos" -Law.
Wojciech Jastrzebowski used it first.
Ergonomics deals with:
1. Recognition and analysis a variety of problems and suggest design
solutions.
2. The problems can be related to:
Noise and vibration.
Heat and cold.
Work-rest cycle.
Organizational factors.
2. Anthropometric measures:
1. HRP: Hip Reference Point.
In designing of cars it is common to start with the hip joint
or HRP and then laying out the rest of the body going up to the head
2. ARP: Accelerator Reference Point
In designing of racing cars it is common to start with the ARP
and then lay out the rest of the body going upwards
3. HARP: Hand Reference Point
For manual jobs hand should be about 20cm below elbow height.
For precision jobs with supported underarms,
the hand should be 5 cm above elbow height.
For worstation design the most convenient hand height is
determined and the rest of the body is layed out
,3. Hand Tool Design:
Guidelines for handtool design:
1. For precision grip:
Grip between thumb and finger.
Grip thickness 8-13mm.
Grip length minimum 100mm.
Tool weight maximum 1.75 kg.
Trigger activated by distal phalanges of fingers,
with fast release locking mechanism.
2. For power grip:
Grip with entire hand
Grip thickness 50-60mm.
Minimum grip length is 125mm.
Grip force maximum 100N.
grip shape non cylindrical.
Preferably trianguar with 110mm periphery.
Maximum tool weight 2.3kg( 1.2 kg preferable)
trigger activated by thumb with locking mechanism.
3. General Guidelines:
Grip surface smooth, slightly compressible & non conductive
Avoid Vibration particularly in the range of 50 - 100 hz.
Design handles for use by either hand.
Keep wrist straight in handshake orientation
Tool weight balanced about grip axis
Eliminate pinching hazards
Types of grips:
Power Grip:
Hand makes a fist with the fore fingers on one side and thumb reaching
around.
1. Force Parallel to Fore-arm. E.g. saw
2. Force at an angle to forearm. E.g. Hammer
3. Torque about forearm: E.g. Screw-driver
, Precision Grip:
1. Internal Precision Grip: Tool is held inside the hand. E.g. Table knife
2. External Presicion Grip: Tool is pinched by the thumb against the index
finger and middle finger. E.g. pen
Bennet’s Bend:
1. The bending of handles of different tools(hammer/ knife/ broom handles)
at an angle (19+-5) degrees was patented by John Bennet and are called Bennet
bends.
2. It has been verified that bend hammer handle reduced ulnar deviation
and did not hamper performance.
3. However there is skepticism about the 19 degree angle.
4. Manual lifting:
The so called correct lifting technique:
The straight back bent knee movement.
It reduces disc compressive forces.
Limitations:
1. Applies only to small compact objects that can be held
between the legs while lifting. No large objects.
2. In some cases(according to experiments) there too much
force on the leg muscles andstoop lifing is better than
squat lifting.
, 5. Noise:
There are two types of hearing protectors:
1. Ear-plugs.
Made of rubber, neoprene, plastics.
Designed to ocllude the ear canal.
2. Ear-muffs. Designed to cover the entire external ear.
Consists of ear cushions made of soft spongy material.
Plugs and muffs can be worn together in intense noise
situations.
Contrary to popular belief cotton provies no protection.
6. Physical Work and heat stress:
1. Thermal Balance Equation:
M-W=C+R+E+S
M-Metabolic power
W-Effective Mechanical Power
C-Heat Exchange by convection
R-Heat Flow by radiatio at skin surface
E-Heat Floew by evaporation at skin surface
S-Heat Storage.
2. Metabolism:
1. The process of conversion of foodstuffs
into mechanical work and heat.
2. In order to be useful to the body,
the foodstuff is converted into a high energy
compund called ATP(Adenosine Tri Phosphate)
1. Introduction:
The word Egronomics comes from the Greek word "Ergo"-Work
and "nomos" -Law.
Wojciech Jastrzebowski used it first.
Ergonomics deals with:
1. Recognition and analysis a variety of problems and suggest design
solutions.
2. The problems can be related to:
Noise and vibration.
Heat and cold.
Work-rest cycle.
Organizational factors.
2. Anthropometric measures:
1. HRP: Hip Reference Point.
In designing of cars it is common to start with the hip joint
or HRP and then laying out the rest of the body going up to the head
2. ARP: Accelerator Reference Point
In designing of racing cars it is common to start with the ARP
and then lay out the rest of the body going upwards
3. HARP: Hand Reference Point
For manual jobs hand should be about 20cm below elbow height.
For precision jobs with supported underarms,
the hand should be 5 cm above elbow height.
For worstation design the most convenient hand height is
determined and the rest of the body is layed out
,3. Hand Tool Design:
Guidelines for handtool design:
1. For precision grip:
Grip between thumb and finger.
Grip thickness 8-13mm.
Grip length minimum 100mm.
Tool weight maximum 1.75 kg.
Trigger activated by distal phalanges of fingers,
with fast release locking mechanism.
2. For power grip:
Grip with entire hand
Grip thickness 50-60mm.
Minimum grip length is 125mm.
Grip force maximum 100N.
grip shape non cylindrical.
Preferably trianguar with 110mm periphery.
Maximum tool weight 2.3kg( 1.2 kg preferable)
trigger activated by thumb with locking mechanism.
3. General Guidelines:
Grip surface smooth, slightly compressible & non conductive
Avoid Vibration particularly in the range of 50 - 100 hz.
Design handles for use by either hand.
Keep wrist straight in handshake orientation
Tool weight balanced about grip axis
Eliminate pinching hazards
Types of grips:
Power Grip:
Hand makes a fist with the fore fingers on one side and thumb reaching
around.
1. Force Parallel to Fore-arm. E.g. saw
2. Force at an angle to forearm. E.g. Hammer
3. Torque about forearm: E.g. Screw-driver
, Precision Grip:
1. Internal Precision Grip: Tool is held inside the hand. E.g. Table knife
2. External Presicion Grip: Tool is pinched by the thumb against the index
finger and middle finger. E.g. pen
Bennet’s Bend:
1. The bending of handles of different tools(hammer/ knife/ broom handles)
at an angle (19+-5) degrees was patented by John Bennet and are called Bennet
bends.
2. It has been verified that bend hammer handle reduced ulnar deviation
and did not hamper performance.
3. However there is skepticism about the 19 degree angle.
4. Manual lifting:
The so called correct lifting technique:
The straight back bent knee movement.
It reduces disc compressive forces.
Limitations:
1. Applies only to small compact objects that can be held
between the legs while lifting. No large objects.
2. In some cases(according to experiments) there too much
force on the leg muscles andstoop lifing is better than
squat lifting.
, 5. Noise:
There are two types of hearing protectors:
1. Ear-plugs.
Made of rubber, neoprene, plastics.
Designed to ocllude the ear canal.
2. Ear-muffs. Designed to cover the entire external ear.
Consists of ear cushions made of soft spongy material.
Plugs and muffs can be worn together in intense noise
situations.
Contrary to popular belief cotton provies no protection.
6. Physical Work and heat stress:
1. Thermal Balance Equation:
M-W=C+R+E+S
M-Metabolic power
W-Effective Mechanical Power
C-Heat Exchange by convection
R-Heat Flow by radiatio at skin surface
E-Heat Floew by evaporation at skin surface
S-Heat Storage.
2. Metabolism:
1. The process of conversion of foodstuffs
into mechanical work and heat.
2. In order to be useful to the body,
the foodstuff is converted into a high energy
compund called ATP(Adenosine Tri Phosphate)
