**5.2 Extended front caster wheels concept**

The user propels the wheelchair forward by pushing the rear wheels to the front. A back-caster wheel is fitted to prevent the wheelchair from tipping backwards.

**Figure 5.** *Cambered rear wheels.*

*Public Health in Developing Countries - Challenges and Opportunities*

**Figure 6.** *Extended front caster wheels.*

#### **Figure 7.** *Widened rear wheels [12].*

Forward stability is affected by the size and position of the front castor wheel in relation to the operator's center of gravity. The front caster wheels of the above wheelchair in **Figure 6** are extended to the front to provide forward stability.

The wheelchair resists tipping forward when the castor wheels are stopped suddenly by an object they cannot roll over. Less weight on the front wheels will reduce the rolling resistance of the front wheels, allowing the wheelchair to roll more easily. More of the user's weight on the rear wheels will provide more traction on

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**Figure 8.**

*Detailed design assembly.*

*Development of a Rough Terrain Wheelchair Design DOI: http://dx.doi.org/10.5772/intechopen.91267*

**5.3 Widened rear wheels concept**

remains on the ground (**Figure 7**).

**6. Detailed wheelchair design**

the rear wheels to drive through soft ground. On the downside, overall wheelchair

Sideways stability is affected by wheelchair width, thus the need for wide rear wheels. A ratchet arm assembly is operatively connected to each of the rear wheels to enable the operator to propel the wheelchair by that method, should the person so choose. Shock absorbers are fitted to the rear wheels to provide independent wheel articulation, such that if one wheel is to go over an obstacle the other one

The further out to the side of the wheelchair the front and rear wheels touch the ground, the more the chair will resist tipping over sideways. The width of the rear wheels increases their bearing ability such that when utilized in sandy, loose or unstable terrain they do not sink into the underlying terrain and loose traction resulting in the occupant being left stuck. The wheelchair becomes easy to push and there is increased stability. On the downside a wide wheelchair is more difficult to get through narrow pathways. Side way stability is limited due to vertical wheels. Using the binary dominance matrix method, widened rear wheels concept was chosen for further development. The mechanical design of this concept was devel-

The widened rear wheels design concept was further designed in detail. The parts making up the system were sized and materials for the parts selected according to the design standards for mechanical parts. The designed parts were tested to configure if they could withstand the operating stresses and adjustments if any were taken in order to minimize failure of the parts during operation. The main parts are the widened rear wheels, ratchet bar, spring shock absorbers, rear caster

length is longer, making it harder to maneuver in confined spaces.

oped into the final design in the next section of this chapter.

wheels and front caster wheels given in **Figure 8**.

the rear wheels to drive through soft ground. On the downside, overall wheelchair length is longer, making it harder to maneuver in confined spaces.
