Tractor Seat Design

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, pressure distribution at the seat–operator 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

Fig. 2 Seat adjustment for comfort (all dimension in mm) OWPD in relation to s The safety feat

Fig. 3

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 hand available for steering at all times.

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 or increase 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 larger control 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.

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 greyishyellow. 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.