The tricycle is designed primarily for disabled people. Our design is to envision and explore the solutions to the acutest of problems. The immense possibilities in the simplest of mechanism and workability of abundant materials have bound us in this field of innovation and creativity. However the tricycle design is also meant for disabled people. The tricycle is suitable for disabled people who cannot walk but can use both arms. These users may have lost their mobility by an accident and have a leg amputation or are paralyzed. With the tricycle they have the possibility to travel independently and seek work. The measurements (seat, footrest adjustment and reciprocating mechanism). For users who do not fit into this group the measurements should be checked and, if necessary, adjusted.
“The Hand-Powered Tricycle for the Paraplegic”
The hand-powered tricycle is a vehicle that provides physical therapy and recreation for but not limited to paraplegic people. The objective is to create a vehicle that is fun to ride and gives disabled people the joy and freedom of riding a tricycle as well as providing encouragement for them to participate in physical therapy. This vehicle will require the rider to have moderated upper body strength and control.
TRICYCLE CONCEPT
The hand-powered tricycle is a fully mechanical system. The vehicle is powered when the rider perform a bench press motion that drives the chainattached at the lower section of the handlebars down tube (this section is contained within the frame). This pushing motion pulls the chain that goes around the sprocket attached to the rear wheel to create a forward motion of the vehicle. The chain will freewheel backwards due to a tension spring located at the other free end of the chain; this spring is anchored inside the frame. The design of the steering mechanism allows the rider to steer regardless of the position of the forward stroke. This is accomplished by having the cable mounting points of the steering arms concentric to the pivot location of the handlebars down tube. The steering motion is actuated by cable attached to the spindles and routed throughout the frame. If 6061 aluminum was used to fabricate the entire frame then it has high strength and light weight. Some of the tricycle’s features include Ackerman steering geometry for a better turning radius and vehicle control, disc brakes for all weather braking conditions and outstanding braking modulation, and a racing bucket seat for a secure and comfortable seating.
BASIC TRIKE FRAME DESIGN:
Weight Distribution
The weight distribution of a trike dictates how well it handles. The more weight on the forward wheels, the better the cornering and less over-steer. However, too much weight on the front wheel causes the rear wheel to be too light. This can lead to the rear wheel to wash-out during hard cornering or cause the trike to end-over during braking. Too much weight in the rear of the trike causes it to capsize even during mild handling as the single wheel has the majority of weight. A trike with 70/30-weight distribution is optimum.
Centre of Gravity
Forget what I said about weight distribution. If all the weight is placed well below the axle, the trike is going to have excellent handling regardless of weight distribution. Obviously, a low slung vehicle does have several disadvantages including visibility, safety and comfort.
Wheelbase
The effect of the wheelbase on a trike influences the steering, weight distribution and overall comfort. The wheelbase is the length between the rear wheel axle and front wheel(s) axle. A short wheelbase makes the turning radius of a trike much smaller while a long wheelbase makes the turning circle larger. Additionally, a trike with a short wheelbase exhibits faster steering than a trike with a long wheelbase. A short wheelbase trike generally places more of the payload weight on the front wheels. On the other hand, a longer wheelbase trike offers a much smoother ride, as the rider is not placed on top of the wheels. Obviously, a happy medium is needed. For the Thunderbolt and Zephyr, I used a 43-inch wheelbase. If tighter turn radius, faster steering and convenience is required, a much smaller wheelbase should be used.
A reduced wheelbase is compromised (limited) by two factors; the rear wheel size and the seat angle. Obviously a trike with a short wheelbase, steep seat angle, and large rear wheel cannot exist. This statement is repeated when I discuss wheel size and seat angle, so remember it.
Wheel Track
The wheel track is the width between the two front wheels. The wider the wheel track the less susceptible the vehicle is to capsizing during cornering. However, if too wide, the vehicle becomes impractical on most bike lanes. A 32-inch wheel track offers excellent handling and is practical for all bike roads, too. Lately, several manufacturers have released compact trikes that have reduced wheel tracks. The overall widths of these trikes allow them to pass through a standard doorway. On the Hell-Bent Spitfire RS, the wheels can have a negative camber (we'll discuss camber later) that allow a wider wheel track but the overall width compact enough to fit through a door way.
Driving Control
This design consists of Reciprocating Mechanism for controlling the vehicle. This reciprocating mechanism dictates direction to the trike.
Frame Design
The last element in basic trike technology is the frame design. There are several issues here that affect efficiency and handling. The most important issues of the frame are weight and rigidity. Along with rigidity comes stability, as any frame or wheel flex is always undesirable especially at high speed. Beyond these basic requirements are other elements that should be equally noted. Reliability, cost, ergonomic and convenience are but a few requirements that the designer must consider.
An excellent frame configuration is a 3-dimensional space frame as the design is both extremely strong and lightweight.However, the lowest weight, lowest cost, and least rigid of any vehicle would be a two-dimensional frame without seat.
Summary
The success of a recumbent tricycle design is a careful mixture of Weight Distribution, Low Centre-of-Gravity, Wheelbase, Wheel-Track, Driving control and frame configuration. In most cases the design will be a compromise of all these attributes.
