This page describes the final design our team arrived at and the prototype we built this semester.
The project will be continuing, with two students traveling to workshops in Vietnam, Kenya and Tanzania. They will continue prototyping and testing - so check back for updated designs.
Tricycle Attachment (Homepage)
Our project was right on schedule so on May 15th 2008 we were able to present the first tricycle attachment prototype.
The attachment can be split into two main areas of focus, the drive sections (wheel, petals, gears, etc.) and the attachment method (pivot mechanism and attachment points).
The front section was made entirely out of one bicycle, utilizing the front fork, a 20 inch wheel, the back petals with gears as handles, and even the front break was reused in this application. It attaches to a bar between the petals to be easily accessible while riding.
The only adjustment that must be made to the original wheel chair is that a bar must be inserted behind the foot rest. This serves as the attachment point for the bottom two vise grips. It must be free to rotate so that the tricycle attachment functions. This can be achieved by inserting one long bar through the entire wheelchair, or separate bars on either side, which have plates welded onto the edges so that they don't fall out. Although the latter is more complicated, it allows the wheelchair to be folded without removing any parts.
Vise grips were our chosen method of attachment. This was because of their simplicity and the speed at which they can then be used. Any other clamp can replace these, with the only draw back being the attachment and removal speed.
Step 1: The vise grips are attached to the bottom bar before there is any weight on the tricycle wheel.
Step 2: The handles are pushed away from the user, which pivots the bar in the wheelchair and raises the casters off the ground.
Step 3: The attachment is stabilized with a third bar. This bar is in compression, so that the vise grip only supports weight while traveling over bumps or in other uncharacteristic situations.
Here is a video of the attachment in use:
In the video a member of the group rides up to the attachment on the ground and is able to complete the three step and ride off in 20 seconds.