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ABSTRACT

For the growing number of people using personal mobility devices, development of devices that address their unique needs are fundamental to their quality of life. Traditionally those with mobility impairments have used wheelchairs to participate in activities. Two problems with traditional wheelchairs are the stress they put on the user’s upper limbs and their inability to actively engage the lower limbs. In this report we outline our proposal for a mobility device that requires substantially less force to drive by exploiting the mechanical advantage that an engine provides.
The goal of the Tricycle Project is to bring increased mobility to disabled persons. Presently, hand-powered tricycles are used by many of the disabled in this community, but some current users of the hand-powered tricycles do not have the physical strength or coordination to propel themselves on the tricycle with their arms and hands. The aim of this project is to add an internal combustion engine to the current hand-powered tricycle to provide tricycle users with improved levels of mobility, facilitating freedom in travel and contribution to the community. The design objectives required a simple and affordable design, a design that needed to be reliable, sustainable, and functional.
The most important part of the design is the incorporation of the fuel powered system which was added to improve the efficiency of the tricycle and to make life more comfortable for the physically challenged persons. A spark ignition automatic single speed two- stroke engine was chosen for this design and consideration was also given to the weight of the user in which a maximum weight of 70kg was used.


INTRODUCTION
Hand-powered tricycles are presently being used to provide mobility for disabled persons in rural communities. With this project we designed and manufactured a system to convert the hand powered tricycle to an engine version. We essentially created an affordable, rugged tricycle.
We have worked to make our design appropriate to the culture where it will be used. This meant designing for the use of locally available parts and manufacturing capabilities. The result is a system that can be almost entirely replicated, with the exception of an engine with familiar parts, tools, and processes. Using the hand-powered tricycle as the basis for our design made the tricycle more of an appropriate technology because it uses a familiar, locally available platform as a starting point. Hand-powered tricycles are being used like conventional wheelchairs with the motive force coming from a person pushing from behind. This engine powered tricycle which we have designed should enable to be independently mobile.

EXISTING DESIGN
To understand the current devices available in the area of personal mobility devices, the products can be classified in three groups:
(1) Traditional Wheelchairs,
(2) Electric Wheelchairs,
(3) Hand cycles.
The first of these products, the traditional wheelchair, is driven by the rims on two large wheels at the user’s side. This propulsion mechanism can lead to upper body injuries.
The second of these products, the powered wheelchair or scooter, only makes up less than 10% of the mobility device market.
Finally, the third type of product, the hand cycle is driven by a crank with a drive chain used to power the front wheel. These devices have three wheels, positioned like a tricycle. The crank mechanism allows users to obtain faster speeds while putting less stress on their shoulders and back. Furthermore, the tricycle design enables the device to traverse tougher terrain. Hand cycles are available as attachments to traditional wheelchairs, as well as autonomous devices.

DESCRIPTION

The design of the engine powered Tricycle is adaptable to the current hand-powered tricycles with little modification. The design consists of an IC Engine, a drive system. See picture below for design schematic:


Figure 1 - Schematic of Tricycle

The first aspect of our design that was addressed was the drive system or means of power transmission. Power must be transmitted from an IC engine to a rear wheel of the tricycle. The controls for engine speed and braking were incorporated into a simple mechanical system to facilitate operation by users with limited dexterity. The hand-power system was replaced with a steering system that disables the hand-power capability of the tricycle. Third, power is supplied to the rear wheels by means of reduction gears.
All the above components were designed to be able to be installed on the existing hand-powered tricycles with slight modification. Everything necessary to convert a hand-powered tricycle to the engine tricycle is simple to install.

LITERATURE REVIEW
Research was done online as well as in magazine articles in search of presently available solutions to our problem. We found many products that were available for purchase, but they didn’t entirely meet the requirements of our unique problem. The problem has been solved, and in many different ways, but what we found, or rather didn’t find, was a solution to our problem that meets our specific needs of affordability and appropriateness. The advantage of finding these solutions is that we can see what works, what has been tried, and what’s available on the market. Then we can more effectively consider how to design a similar product that meets our unique needs.
The figure shows different ways, very expensive ways, of hand powering a tricycle. This option may or may not allow for a better design for attaching an engine to. We decided that although these are great designs, their purpose was for recreation and would not suit the needs of the people that we are designing the kit for. Their low position doesn’t allow a good seating position for a table or clearance enough for the conditions of the area.