As I turned 82, several years ago, I began thinking of a more comfortable bicycle to ride. Since I wasn't ready to quit bicycling I set out to convert my old aluminum-frame Specialized bicycle into a front wheel drive recumbent (aka bent). There expensive commercially available bents and conversion kits that offer similar configurations but I really wanted to build my own. Just to add a little challenge to the effort three goals had to be met: all fabrication done without welding, total cost less than $100, and overall weight within 35 lbs. With a little ingenuity, I met the first two goals, however the overall weight is approximately 38 lbs. I’d like to share my solutions to the problems I encountered that resulted in a rather simple functional design. Over time I was able to make adjustments to the design geometry to help improve riding characteristics to my liking. In the attached clip I am riding an earlier iteration of design with a straight handle bar and a stiffer back rest.
Step 1: The steering column and handle bars
1) Used MTB - aluminum frame, suspension fork, wheels
2) Road bike frame – sacrificed frame: chain stay and bottom bracket assembly, drivetrain
3) Razor scooter – sacrificed aluminum tubes, steering column
4) Aluminum walker
5) Miscellaneous bike parts, metal brackets, pvc pipe cut-offs, sturdy mesh, nuts and bolts.
Step 2: Swapping the front and rear wheels
To enable the front wheel drive configuration the front and rear wheels had to be swapped. Brackets to provide a wide enough (5 5/16") opening for mounting the drive wheel in front were designed, fabricated, and mounted with carriage bolts to the front fork dropouts. The fork was left in the normal position rather than turned backwards as is the design of some conversion kits. This allowed me to mount the front brakes without any modifications. With this fork configuration, a short bracket, and close tolerances I was able to keep enough of a trail for good handling. To fit the front wheel between the rear drop-outs I used an axle of appropriate length with spacers, taking care to use matching cones and ball bearings in the wheel hub.
Step 3: The bottom bracket triangle
The bottom bracket triangle was designed to have pivoting at all tree vertices to utilize the spring action of the suspension fork. The chain stays with the bottom bracket from a the sacrificed bicycle frame makes up one side of the triangle; the suspension fork is its second side; and the third upper side is made from the inside tube steering column of an old Razor scooter. The front end of the triangle is pivoted at the bottom bracket and the trailing end is pivoted at a bracket hammered into proper shape from a piece of tubing. This bracket is rigidly mounted inside the top of the fork with a bolt and a conical nut that is jammed inside against the steering column's butted end by tightening the bolt.
Step 4: The steering column and handle bars
The outer tube of the Razor scooter steering column turned out a good fit for extending the height of the handle bar, providing enough clearing for the knees while pedaling. That tube is bolted to the fork's steering tube in a usual threadless manner. The handle bar stem needed a sleeve to tightly fit it inside the top of steering tube.
Step 5: The drivetrain
The drivie wheel with 8-speed cassett5 and the derailleur are used up front without modifications. This worked out perfectly. I had to abandon my earlier attempt of using a wheel with a three speed hub because it needed a tension idler complicating the design. Changing gears and braking is done similar to a normal bicycle with shifters and brake levers.
Step 6: The Seat
A bigger wider seat with a good spring suspension is used. It is mounted on an appropriately shaped piece of PVC pipe of suitable diameter and then on the top tube of the bike with round clamps. This arrangement allows positioning along the top tube with relative ease.
Step 7: The back rest
A U shaped aluminum pipe from a walker is clamped into a handle bar stem. Halves of a steel tubing are used as sleeves to prevent damage to the aluminum pipe. An additional supporting strip is used to strengthen the arrangement. The handlebar stem is anchored inside the seat tube by utilizing additional sleeves to match various tubes' diameters. A heavy duty screen is wrapped on the U shaped pipe and stretched by inserting a properly shaped PVC pipe on top of the U shaped back rest pipe.
Step 8: Accessories
My bent includes other features including a handlebar-mounted rear-view mirror, bicycle computer, bottle cage, and bright orange colored safety visibility tape installed on the seat rest.