tractor seat design

8/3/2019 Tractor Seat Design

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Tractor seat design

A tractor seat design must take into account human/ biomechanics perspectives which are

energy and vibration absorbing and which do not disrupt the spinal configuration and the

spinal geometry. The biomechanical and engineering factors such as ride vibration, pressuredistribution at the seatoperator interface and the body posture play an important role in the

tractor seat design. With a constant need to improve tractor operator comfort and safety under

dynamic condition, progress has been made in attenuating ride vibration levels Functions of

tractor seats

The requirements for a comfortable tractor seat are as follows:

(1) The seat should provide a comfortable and controlled seating posture.

(2) It should reduce mechanical shock and vibration transmitted to the operator.

(3) It should position the operator to provide easy and non-fatiguing access to machine

controls.

(4) It should position the operator relative to the tractor to provide adequate vision for

allowing him to perform all works safely and effectively.

(5) The seat should support the weight of the thighs and upper body.

(6) A good-seated posture should support the spine to approximate the correct curvature. The

backrest should not be soft and over padded to prevent back ailments.

(7) The seat cushion underneath knee muscles should be soft and rounded off to change his

position from time to time to relieve pressure and rotate muscle groups under tension.

(8) The tractor seat must support the body during many continuous hours of operation,

especially to the lower back and thighs. This requires adjustability in the seat to

accommodate all people in the percentile range that has been chosen.

Fig. 1 Physiologically favourable position of upper

body and arms when handling tractor steering

wheel


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Fig. 2 Seat adjustment for comfort (all dimension in mm)

OWPD in relation to s

The safety feat

Fig. 3


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1.Control

A control is a device that allows you to 'communicate' with objects and to manipulate them.

Controls can enable you to direct equipment or machinery that can help you to generate more

power, more reach and to reduce effort and risk. In some cases, the control also provides the

force to make an action happen, for example, a foot pump pedal.

The controls on your mobile phone allow you to make calls, send text messages and set your

favourite ring tone. The keys on your keyboard and your mouse buttons are all controls that

enable you to view this page!

The main function of a control is to transmit information to an object. When you use a

control, information is flowing from you to the object (brain signals pass to the muscles in

your hands which move to activate the control). You gather information from the object via

feedback, for example, in the form of a change in a visual display when you press a key on

your keyboard, or illumination of a room when you operate the light switch, etc.

2. Types of controls

The type of information that is transmitted by a control can be discrete (separate) or

continuous. Discrete controls use a limited number of conditions, for example, a light switch,

which is either on or off. Continuous controls use any value between the outer limits, for

example, the gas control knob on a cooker hob can regulate the flow of gas anywhere

between the minimum and maximum flows.

Controls often have an associated display to provide you with information about the results of

your control actions. These displays can also show discrete or continuous information.

3. Human factors considerations for control panels

3.1 Placement of Controls

The placement of controls seems to be the most important ergonomic factor which ensures

safe and efficient operation. Controls should be arranged in such a way to minimize the

requirement for operators to change their position solely to operate a control. All controls

should be positioned so that, in manipulating them, operators do not appreciably move their

nominal eye reference and possibly miss seeing important events occurring outside or on the

principal internal display. All controls in the tractor cab which required accurate

manipulation must be grouped on the right hand side of the operator, leaving his left handavailable for steering at all times.


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3.2 Control Labelling

Control labelling is an important issue for operators working with any control layout. The

identification of controls is essentially a coding problem. Labels and symbols (or icons) are

common methods of identifying controls. Labels are probably the most common method of

identifying controls and should be considered the minimum coding required for any control.

They demonstrated that labels should be placed above the control so that the hand will not

cover them when the operator is reaching for the control. Also, the label should be visible to

the operator before reaching for the control.

3.3 Functional Reach

Important components must be placed in convenient locations so that they can be reached

without undue arm exertion

3.4 Control compatibility

The control should operate in the way that people expect it to operate. There are certain

directions of control movement which are expected by the majority of people. They are called

population stereotypes and control movements which conform to these stereotypes are said to

be compatible. In western Europe, for example, a movement to the right, a movement

forwards and away from the body, or a clockwise rotation, instinctively suggests a start orincrease in operation.

People learn how to use controls more quickly if compatible control movements are used.

Compatible controls are safer to use in emergencies. When people are under stress, they tend

to use the 'expected' direction of movement. Control movements that seem 'natural' to the

operator are more efficient and less tiring because there is less need for thought and

assessment, and therefore operation is faster.

4. Coding of controls

Controls that are different (coded) in terms of either shape, size, mode of operation, labelling,

or colour are easier to identify than controls which are similar in these respects.

4.1 Shape coding - the use of a unique shape for controls improves their visual and tactile

(touch) identification. Standardised shapes should be used and sharp edges should be avoided

on the parts of the control that are to be hold.

4.2 Size coding - where size is used to distinguish controls (usually control knobs), the largercontrol should always be at least 20% larger than the smaller one for controls ranging from

15-150mm in diameter, in order to avoid confusion in selection.


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4.3 Colour coding - colour should not be used as the sole method of coding of the control. It

is more effective when combined with other methods. Use red, orange, yellow, green and

blue as they are the only colours that are effectively identified and recognised. However

about 7% of men and under 1% of women suffer from red-green colour blindness - they are

unable to differentiate reds and greens and tend to see these colours as shades of greyish-

yellow. Therefore, in situations where colour coding and recognition are vital, you should

check that all operators can distinguish the colours used.

4.4 Labelling

If controls are to be labelled, adequate space and lighting must be provided to enable the

labels to be clearly visible. Labels should be either on the control or immediately adjacent to

it. Letters and numbers used should be standard.

5. Effective controls Design

To be effective, controls must be accessible, identifiable and usable.

5.1 Accessibility - since almost all controls require physical contact to be operated, they must

be able to be reached comfortably and efficiently. You must consider the body size of the

user - it's no use putting an emergency button out of reach!

5.2 Identifiability - a control needs to be able to be identified in terms of what it does in

order to operate (twist, lift etc.), what it controls and what state it is in (on, off, partially open,

etc.). This is especially true for groups of controls that may have similar functions. For

example, the controls on the cooker at home probably look almost identical, but the labelling,

and often the position of the control, enable you to tell them apart. The controls on a cooker

rotate when operated to give you an idea of their state. Feedback is given by the oven, grill,

burners or plates as they produce heat. Feedback is an important element of controls, giving

you confirmation of your actions.

5.3 Usability - a control must be able to be used! You should be able to operate it with the

required force, speed and accuracy. For example, it would be difficult to operate a foot pump

with your hand because you need a lot of force to push air into a tyre. Using your foot for this

enables you to put your weight behind it and use the large leg muscles to push. However, you

don't need to be precise, unlike setting a rotary central heating control. The control knob is

designed to be operated with the fingers and does not require force.

tractor seat design

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