A Hand-Powered, Hand-Controlled Tricycle

KENNETH KOZOLE, B.S.M.E. MARY ANN BUSH, MA., O.T.R.


Introduction

A tricycle, designed and constructed for a 3-year-old client with bilateral proximal phocometia, resulted from the unavailability of a marketed tricycle solely powered by the hands. The tricycle was engineered on the premise that the design should be simple and durable, and should resemble that of a conventional tricycle, yet be hand-powered. The considerations and design for the tricycle are unique for this client. However, similar applications may be appropriate for a variety of other persons with lower-limb involvements. In this article we present the plan for constructing a hand-powered, hand-controlled tricycle.

Case Presentation

A female, was born on April 4, 1974, following an uneventful pregnancy and delivery. She was diagnosed as having bilateral proximal phocomelia (femoral deficiency with tiny femoral remnants present). An X-ray of the femoral anomalies is shown in Figure 1 . Both legs are in external rotation, with movement at the hips and ankles. Upper-limb function appears normal, as does mentation. S.S. has had speech delays as a result of a cleft palate.

S.S. mastered developmental motor milestones with few exceptions, even though some were delayed. At an early age she was fitted with numerous devices, such as a pelvic bucket, followed by a pelvic bucket mounted on a platform with sway walker feet, followed by orthopedic shoes. None of these was reported to have been used for any length of time. S.S. started rolling, sitting, pulling to standing, creeping on all fours, and later taking a few steps sideways without any equipment. She was then fitted with a pair of orthopedic shoes with Wright cuffs. She currently wears this type of shoe, with lifts added routinely to increase height.

S.S. continued to pass developmental milestones until she attempted to ride a conventional foot-powered tricycle. She attempted to peddle a toddler-sized tricycle using her feet. No functional forward or backward propulsion was possible since movement occurred only at the hips. Her shoes limited movement at the ankles. Analysis of the problem resulted in a tricycle which was hand-powered, hand-steered, and hand-braked.

Design, Construction, and Operation of Tricycle

The following factors were considered in the design, construction, and operation of the tricycle.

Design

Stability: Once on a tricycle seat, S.S. could not touch the ground with her feet. This condition suggested provision for foot supports, a firm seat, and firm hand grips within S.S.'s available range of motion. Another consideration was the prevention of sideways tipping during mounting, propulsion, and dismounting of the tricycle.

Hand Power: The conventional tricycle is designed for cyclic leg propulsion. However, S.S.'s most functional power source is her arms. The arm strength and endurance required to propel, steer, and brake the tricycle had to be considered. Accessibility: The tricycle had to allow for easy mounting and dismounting, since S.S. is shorter than most children her age using a toddler-sized tricycle.

Socially Acceptable Design: The tricycle design was to remain as similar as possible to the conventional design and not have a "handicapped" connotation. This consideration would minimize any difference from the tricycles of her peers.

Use of Marketed Parts: Since the authors did not have access to special machining equipment (except a welder, electric drill, grinder, and hacksaw), custom machining of parts was limited. Most parts were obtained from a 40-cm (16-in.) child's bicycle and fitted to the tricycle. A bicycle shop could provide the necessary components for this tricycle.

Construction

The final design resulted in a conventional toddler-sized tricycle (AMF Junior Model) with the following modifications (Figure 2 and Figure 3 ).

Foot Supports: A piece of band steel was bent into a "V" shape and welded onto the tricycle frame for foot placement. Wooden foot blocks were attached to the foot support to allow for adjustment as 5.5. grows. The foot supports provided stability for 5.5. as she propelled and steered the tricycle with her arms.

Hand-Crank Assembly: A hand crank was welded onto the gooseneck of the tricycle where the original handlebars were located. The crank assembly was obtained from a child's 40-cm( 16-in.) bicycle (cut off the bicycle with a hacksaw). A 14-tooth sprocket was welded to the crank in place of the original sprocket (this sprocket provided a one-to-one, crank-to-wheel power ratio).

Front Wheel: The front wheel chosen for the tricycle was a 40-cm (16-in.) bicycle tire and rim. This tire was the rear tire from a bicycle and was chosen because it provided a chain sprocket and a coaster brake. This tire also lifted the front of the tricycle and shifted the weight concentration more toward the rear wheels. This factor improved the tricycle stability during mounting, propulsion. and dismounting.

Idler Assembly: Since the chain would scrape on the fork during propulsion. it had to be directed away from the fork, using an idler assembly (Figure 4 ). The idler housing was made from band steel, and the small idler gear was obtained from a 10-speed bicycle, rear Dcrailleur assembly. A similar idler assembly may be obtained from a lawnmower shop.

Chain: Once the wheel was attached to the fork and the crank assembly was fastened in place, one end of the chain was threaded through the idler assembly', then around the wheel sprocket and up over the crank sprocket. l-lere it was linked to the beginning of the chain (Figure 3 and Figure 4 ).

Chain Guard: A chain guard was titted and fabricated to cover the chain for safety. It was cut from sheet metal using tin shears. The sheet-metal parts were welded together to form the guard, and were attached to the tricycle at the crank assembly and at the front-wheel axle.

Hand Grips: These were made from a 2.5-cm (I-in.) diameter wooden dowel. A hole drilled through the axis center allowed them to slip over the crank grip bolts.

Operation

The tricycle was easy to operate. Forward cranking resulted in forward propulsion, and coasting in the forward direction was possible if S.S.'s arms became tired. A reverse direction of the crank engaged the coaster brake, and the tricycle stopped. Steering was controlled like that of the conventional tricycle. To mount the tricycle, S.S. stood at the rear of the tricycle. She then reached over the seat and grasped the gooseneck just below the crank assembly and pulled herself onto the seat (Figure 5 ). By reversing the process. S.S. could dismount.

Summary

Some children are incapable of propelling a conventional tricycle because of lower-limb involvement. These children usually sit passively on their tricycles or in wagons, while someone pushes or pulls them. Many are often restricted to wheelchairs for both ambulation and play activities. These children should be given the opportunity to explore and control their play environment through active participation.

An unsuccessful search for a commercially available conventional tricycle, powered and controlled solely by use of a child's hands, resulted in this original tricycle design. The concept of using a cranking motion to propel a tricycle is not new. However, to crank, steer, and brake a conventional-looking tricycle using only the hands as a power source is unique. The originality of this project resides not only in the design and function, but also in the feasibility of building other similar tricycles with a minimum of special equipment (most parts are commercially available) and at a low cost.

S.S. quickly adapted to the tricycle, maneuvering it forward, turning, and braking (Figure 6 ). From the home driveway she ventured onto the neighborhood sidewalks and driveways. After one year of use, there are no reported complications. However, adjustment for leg growth has been necessary. These adjustments for S.S.'s growth are possible since the seat height, foot-support blocks, and hand-crank position are adjustable.

This hand-powered and hand-controlled tricycle allowed S.S. to master one more developmental milestone. S.S. also derives satisfaction not only from the physical mastery of the activity, but also from being able to do what other children do at this age ride a tricycle.