I picked up two decent 20" bikes at a local flea market for $35 and purchased $65 worth of metal from a local supplier. This included 20' of 1.5x1.5 square tubing, 12' of 1x1 square tubing, 4' of ½ x ½ square tubing, 6' of 1" black pipe and 4' of 2" wide 3/16th flat stock steel. The remaining odds and ends for the project (nuts, bolts, upholstery material and primer) were things I had in my shop and would probably add up to about $10 or $15 if they had to be purchased.
I would rate this project as “moderately difficult” since it requires a good bit of welding as well as cutting and shaping some metal parts. It may also require some design work since the old bikes you find to make your trike might be quite different from the ones I happened to get. You also need a basic understanding how a bike is assembled and taken apart as well as a decent grasp of how a derailleur works and how it is adjusted. Most of this information can be found on the web if you lack hands-on experience. Derailleurs were a mystery to me when I started this project. So thank you internet.
Step 1: Front Wheel and Steering
I began with this Huffy Roadmaster 20" frame and 6 speed sprocket set. (Photo 1) I used a 4" angle grinder to cut away unneeded pieces of the frame. (Photo 2) Next I marked and cut a “birds mouth” in the seat tube so that the tube will point forward 18 degrees from vertical rather than to the rear as it did originally. (Photo 3) The seat tube is then bent forward and welded. (Photo 4) The seat tube is strengthened with a steel gusset. I first made a patten using heavy paper (Photo 5) and then cut the gusset from 1/8" flat stock and welded it in place. (Photo 5) Cut off the balance of the lower support bar. (Photo 7)
The steering head is cut away from the down tube. (Photo 8) Cut a length of 1.5 x 1.5 square tubing one inch shorter than the head tube. (Photo 9). Cut away one of the four sides of the square tubing making it into a U-shaped channel. (Photo 10). Fit the channel around the head tube. (Photo 11) and weld it in place filling in the gaps on the top and the bottom with small pieces of flat stock. (Photo 12)
Cut the top portion of the steering tube away from the front fork assembly. (Photo 13) Remove the seat post from the saddle. Butt weld the seat post to the steering tube. Make sure the tube and post are straight and aligned by inserting appropriately sized tubing into the inside of the tube and post. I used a 13 mm socket to slide inside the steering tube and then found a leftover length of thin wall tubing from a solar light set which slipped inside the seat post tube AND fit snuggly over the 13 mm socket. (Photo 14) These parts are clamped together to hold them tight and straight and then the butt joint is welded (note: the 13 mm socket is sacrificed to the cause). (Photo 15) Cut away the remaining “ears” of the fork attachment points. (Photo 16) This is now the new steering tube. (Photo 17)
Step 2: Main Frame
Step 3: Front Forks
The front forks are attached to the existing mounting holes from the Huffy. (Photo 2) Cut a 1 ½" x 2" piece of 3/16 flat stock, drill holes to match the mounting points and screw the flat stock to the drop out. (Photo 3) Cut a slit in the end of a 3' section of 1" black pipe and place it over the flat stock. (Photo 4) Drill a 3/8" hole through the steering stem. (Photo 5) Put the stem in place in the steering tube. Line up the top end of the black pipe with this hole in the stem and then tack weld the bottom of the black pipe to the flat stock mounting tab. Remove the black pipe and finish welding the mounting tabs. Cut off any excess portions of the 3/16 flat stock. (Photo 6)
Attach the lower end of the black pipe to the drop out and then drill a 3/8" hole in the top end of the black pipe to match the hole through the steering stem. Use a bolt or threaded rod to secure the top end of the black pipe to the steering stem. (Photo 7) The front forks are now complete. (Photo 8)
Step 4: Rear Frame
Step 5: Brakes
Cable guides for brakes and derailleurs can be purchased but you can also make your own using #10-24 x 3/4" coupling nuts from Home Depot. (Photo 6) Clamp the nut in a drill press vise and bore out one end large enough for the ferrule. The bit should only go about ½" deep into the nut leaving enough metal at the bottom or the nut to prevent the ferrule from slipping through. (Photo 7) Put the nut in a vise and slit it lengthwise with a 4" angle grinder. (Photo 8 and 9)
Step 6: Derailleur
The derailleur must be installed upside down in order to operate properly. The mounting point must also be moved 2 1/4" forward and about 1/16" higher than the original axle mounting point. A bracket to do this is made by welding together two pieces of 3/16" flat stock. (Photo 1) Holes are drilled to mount the bracket on the axle and to mount the derailleur to the bracket. Note the smaller hole which is used to keep the derailleur from spinning out of position. (Photo 2) The bracket is mounted on the axle (photo 3) and the derailleur is attached (Photo 4)
Step 7: Adjustable Recumbent Seat
The sections are “hinged” to each other by welding 1"x2" pieces of 3/16" flat stock to the outside of the frame rails for the top and bottom section of the seat. The hinges extend toward the center section of the seat and holes are drilled through the hinge section and the side rails of the seats center section. (Photo 2) The sections are then bolted together. (Photo 3 and 4) The seat sections can be moved to an unlimited number of positions relative to each other and then the hinge bolts can be tightened to hold the seat in place. (Photo 5) Addition support for the seat is provided by two small braces on the back side of the seat which are also fully adjustable. (Photo 6)
The seat cushions are made using ½" strand board as a base. (Photo 7) Holes are drilled through the metal frame and wooden seat base and tee nuts (Photo 8) are used to secure the seat base. (Photo 9) To secure the seat to the main frame of the trike, metal tabs are welded to the bottom of the seat frame and holes are drilled through the tabs. (Photo 10) The seat frame is flipped over and can be slid forward and backward along the center rib of the trike’s main frame. When a comfortable pedaling position is found, the seat bolts are tightened in place. (Photo 11)
The cushion padding consists of 4 layers of 1/4" closed cell foam glued together on top of the wooden seat base. The edges of the foam and base are sanded to provide a smooth and even surface. (Photo 12) The upholstery for each seat section consists of three pieces. The seat top, the seat side, and a strip of welting. (Photo 13) The three pieces are sewn together inside out. (Photo 14) The upholstery is then turned right-side-out, stretched over the foam, and stapled to the bottom of the wooden seat base. (Photo 15)
Step 8: Ready to Ride.
The finished trike (Photo 1 and 2) Also a short video of Louie taking an early cruise.
The trike has been on the road for a number of months. In fact, Louie has lost about 10 lbs due in part to the great exercise he gets running along with the trike. I recently tore the trike down, however, to apply a paint job AND to install an electric motor. The Instructable for making the trike electric (dual powered) can be seen here.