**6.7 Ratchet bar**

The ratchet is used to turn the wheels by the operator. The effort by the operator was determined to be 16.45 N, at the top of the lever assuming the frictionless movements.

**169**

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

bending moment diagram as shown below.

of about 43.17 degrees from the calculations.

**6.9 Designed wide rear wheels**

mended the rear wheel size.

**7. Economic analysis**

made from.

prototype.

stress 180 N*mm*<sup>2</sup>

*Final wide wheel design.*

**6.8 Tipping angle**

N*mm*<sup>2</sup> .

**Figure 14.**

If this results in a reaction on the fulcrum of 789.54 N, the force and bending moment distribution acting in the lever is described by the shear force diagram and

For a bending moment of 7922 Nm, the material for the lever, is designed to be

Designing for a factor of safety of 3, the resulting allowable working stress is 60

The widened rear wheels design was found that it could sustain a tipping angle

**Figure 13** gives the sized views of the resulting design, as well as the recom-

The final 3D view of the resulting wheelchair is given by **Figure 14** below**.**

Some costing was done for components that are going to be manufactured from workshop and others standardized components which are going to be bought. **Table 1** gives the major components the materials they would be

The cost of fabricating a prototype is estimated to be USD 186 including components cost and labor, which is within a maximum cap of USD200. This could vary

The bill of quantities are given by **Table 2** as well as the costing of a

depending on the manufacturer's requirements and specifications.

, yield

mild steel selected from tables to be Fe 310 steel of tensile strength 310 N*mm*<sup>2</sup>

and minimum elongation of 26.

**Figure 13.** *Side and top view of sized design, and the sized rear wheel.*

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

**Figure 14.** *Final wide wheel design.*

*Public Health in Developing Countries - Challenges and Opportunities*

The maximum bending moment was found to be 62.125 MPa.

a lot of a material twists when under pressure.

**6.5 Stress and failure**

**6.6 Shock absorber spring**

**6.7 Ratchet bar**

stresses. On the opposite side the material is compressed by compressive loading.

Shear stress is the stress that attempts to tear something separate. It is characterized as the shear force divided by the area over which the force is acting. In a wheelchair hub, its value is low and is rather higher in the X-brace pivot of a wheelchair. The modulus of elasticity (E) is a material property that tells how much a material make an effort not to distort when it is under stress. Strain is the proportion of how

Looking at the most extreme bending stress in a wheelchair axle with the limit elastic of the material used, it is possible to know whether the hub is sufficiently strong enough to hold up under the individual user's weight and other external forces applied on it. The weight of the person should not exceed 212.33 kg.

The material of the spring should have high fatigue strength, high ductility, high resilience and it should be creep resistant, hence carbon steel was chosen. The free length of 100 mm and the spring wire diameter was determined to be 5 mm.

The ratchet is used to turn the wheels by the operator. The effort by the operator was determined to be 16.45 N, at the top of the lever assuming the frictionless movements.

**168**

**Figure 13.**

*Side and top view of sized design, and the sized rear wheel.*

If this results in a reaction on the fulcrum of 789.54 N, the force and bending moment distribution acting in the lever is described by the shear force diagram and bending moment diagram as shown below.

For a bending moment of 7922 Nm, the material for the lever, is designed to be mild steel selected from tables to be Fe 310 steel of tensile strength 310 N*mm*<sup>2</sup> , yield stress 180 N*mm*<sup>2</sup> and minimum elongation of 26.

Designing for a factor of safety of 3, the resulting allowable working stress is 60 N*mm*<sup>2</sup> .

### **6.8 Tipping angle**

The widened rear wheels design was found that it could sustain a tipping angle of about 43.17 degrees from the calculations.

#### **6.9 Designed wide rear wheels**

**Figure 13** gives the sized views of the resulting design, as well as the recommended the rear wheel size.

The final 3D view of the resulting wheelchair is given by **Figure 14** below**.**

### **7. Economic analysis**

Some costing was done for components that are going to be manufactured from workshop and others standardized components which are going to be bought. **Table 1** gives the major components the materials they would be made from.

The bill of quantities are given by **Table 2** as well as the costing of a prototype.

The cost of fabricating a prototype is estimated to be USD 186 including components cost and labor, which is within a maximum cap of USD200. This could vary depending on the manufacturer's requirements and specifications.

#### *Public Health in Developing Countries - Challenges and Opportunities*


#### **Table 1.**

*Components and material specifications.*


**Table 2.** *Bill of quantities.*

## **8. Recommendations**

The wheelchair design is still limited when it comes to very steep inclines, in which case an incorporation of a motor to assist the hand effort will be required. There is also need to have adjustable rear wheels that can be pushed in or outwards from the chair so that it is not hindered when passing through narrow pathways of the rural terrain.

The operator has to always lock the brakes before getting in and out of the wheelchair. They have to also avoid putting heavy loads on the back of a wheelchair, as this may result in a shift in the position of center of gravity. This could cause the chair to tip over backwards.

The operator of the chair can keep it maintained by being knowledgeable about the wheelchair, and having a handy list of providers that one can rely on for repairs, parts, and maintenance. The user may not be able to perform the basic daily and weekly cleaning and upkeep but can set up a routine that can be followed by caregivers, family members or others to monitor the chair for problems. Assemble and store a set of tools that you will need to have on hand for maintenance and emergencies. There is need to keep the wheelchair clean to help keep the operator healthy and free of infections, this will also make it easier to identify equipment problems as they arise. The casters (front wheels) can present a safety hazard when they are worn out. One has to always check your casters for cracks in the spokes that may eventually cause the caster to collapse.

#### **9. Conclusion**

The chapter investigated the development of a rough terrain wheelchair design which is capable to withstand tipping angles up to 43.17 degrees, which is relatively

**171**

**Author details**

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

**Acknowledgements**

disabled from any injuries.

materials are used for manufacturing of the wheelchair.

Ignatio Madanhire\*, Loice Gudukeya and Roy Mushonga

\*Address all correspondence to: imadanhire@gmail.com

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

University of Zimbabwe, Harare, Zimbabwe

provided the original work is properly cited.

higher as compared to conventional wheelchairs. The wheelchair counters toppling in almost every direction due to the wide wheels and back caster wheels for anti-tipping. This wheelchair is intended to improve the mobility of those operators living in rural uneven terrain by reducing wheelchair related accidents. The incorporation of the spring shock absorber will also contribute to the comfortable sitting of the user. The overall cost of the design was estimated to be USD 186, if local raw

We would like to thank the University of Zimbabwe (UZ), Mechanical Workshop team for working with this team of researchers in fabricating the prototype which gave the study a practical form result. We also acknowledge Danhiko Rehabilitation Centre for allowing us to access their facilities and also their input on wheelchair operator expectations. Also, we do really appreciate the solicited guidance offered by colleagues we work with at the University of Zimbabwe. Finally, we wish to thank all those who are implementing measures that help to protect the

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

higher as compared to conventional wheelchairs. The wheelchair counters toppling in almost every direction due to the wide wheels and back caster wheels for anti-tipping. This wheelchair is intended to improve the mobility of those operators living in rural uneven terrain by reducing wheelchair related accidents. The incorporation of the spring shock absorber will also contribute to the comfortable sitting of the user. The overall cost of the design was estimated to be USD 186, if local raw materials are used for manufacturing of the wheelchair.
