This simple trailer is light, cheap, and can hold two 5-gallon buckets containing whatever you like. It can attach to any normal bike, and can be built with basic tools. A rope may be used in place of the bike, turning this into a 2-wheeled wagon. We built it for a group project for our Introduction to Permaculture (sustainable design) course at NCSU.
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Step 1: Materials and Tools
Two 16-inch wheels, with bearings and 1/2" axle holes (Available here and in various hardware stores.
24" or longer piece of 1/2" threaded rod
Two 1/2" lock washers
Four 1/2" nuts
One box 3" decking screws
Two carabiners or locking steel rings
One 2"x4"x48" (as clear and straight as possible)
One 2"x4"x30" (as clear and straight as possible)
Six 2"x4"X3.5" blocks (Or 2 blocks for the axle suport, and enough L-brackets to secure each corner)
Dozens of pieces of bamboo, 30" long
One or two rolls of twine
Two 5-gallon buckets
Total cost of all materials: $50-65
A friend (at least for part of it, but it makes things go better in general)
Circular saw (or handsaw and miter box)
Drillbit (to drive pilot holes for screws)
1/2 inch drillbit
Square & measuring tape
Safety glasses and ear protection
Step 2: Frame and Axle
The 30" long 2"x4" piece , and 48" piece will form the sides of the frame. They should be as straight, clear, and free from defects as possible, to maintain the strength of the trailer. The longer board will be on the left side of the trailer frame. This will connect the trailer to the bike, and since most bikes have gears on the right side and are mounted from the left, it is better to connect on the left side than the right.
Drill a 1/2" hole 15" from the end of each board on-center. This will be for the main axle, so be sure that there are no knots or structural defects in this area. A drill press is ideal for this task.
Drill a centered hole in two of the 3.5" blocks. These will support the main axle.
Thread the axle rod through the four holes before screwing the blocks to the frame sides. Threaded rod is very picky, and won't like it if you try to push it through holes that aren't completely in line. Leave the threaded rod in until the frame is complete, to ensure that the holes line up.
Attach the two 12" pieces of 2"x4"to the axle support blocks. These give the trailer some support against twisting forces.
Attach the remaining two 12" pieces to form a large rectangle, using the 3.5" blocks (or L-brackets if you opted for them). This rectangle will be the base of the trailer.
Put both wheels on the axle, and check to make sure that they are on straight and run true. Adjust the length of the axle as needed to ensure that the wheel, inner and outer nut, and lock washer all fit on each side. Use a permanent marker to mark the length, and remove the wheels.
Cut the axle to length using a hacksaw, rotary tool, or whatever tool you prefer.
Step 3: Sides and Floor
Cut each upright at about 20 inches. If you used blocks, use two uprights in each corner, (one for the side panel, and and one for the front or rear panel). If you used L-brackets instead of blocks in the corners, you will need only one upright per corner. Lash the uprights to the frame at each corner. (For instructions on lashing, we used the Boy Scout Handbook, but most knot books will show you how to do this. It's worth the research to learn to tie clove hitches, wraps, fraps, etc., but for the truly desperate, screws, brackets, or zip-ties could be used. As long as you start and end with a clove hitch, it should turn out alright.)
Line up enough pieces of bamboo to cover the floor of the cart, between the uprights. Cut the ends of the pieces on each side as needed to fit between the uprights. Cut 4 pieces of a small-diameter piece of bamboo to serve as cross-braces, and lash together like a raft. Place the completed floor between uprights.
Each side needs a minimum of 1 side piece, but 5 seems optimal. Lash each of the side pieces to the uprights, as pictured. For the top pieces, lash the corners to each other to keep the sides from wobbling.
Step 4: Hitch
Note: We're still working on the best way to design the hitch, to ensure that it doesn't scrape the bike and allows for a full range of motion. The following hitch works, but the wood at the end of the hitch may wear. It's based off the hitch found in PVC bike trailer. It's more elegant and probably works better, but we had carabiners available.
Cut the end of the trailer frame at a 45 degree angle, as shown.
Take the 11" block and cut a 45 degree angle on one end, as shown.
Measure, from the side with the 45 degree angle, along the centerline, 10 and 9/16 inches. This will be along the very center of the trailer, and will be if you used 1.5" thick 2"x4"s and 12" struts.
Drill a hole at this point, the same diameter as the eyebolt shank.
Cut off the two corners of the block at the end with the eyebolt. This will allow it to turn a little more smoothly.
Place the block on the frame, so that the angles match. Place the 2"x4"x6.5" block underneath, and mark the edges to be cut at a 45 degree angle. It helps to have a second person for this step.
Cut the 6.5" block, line it up so the angles match, and screw it to the frame.
Place the modified 11" block on top of the frame and 6.5" support block, and screw it to them.
Add the eyebolt, upside down. This keeps the trailer from banging into the bike's spokes.
Use two carabiners or steel clips to attach the eyebolt to the rear supports on the bike.
Step 5: Use and Maintenance
The clips can be removed from the eyebolt, and replaced with a rope, allowing the trailer to be pulled by hand like a wagon. You can use a tarp to cover the cargo during wet weather, but make sure to thoroughly dry the trailer to avoid rust or rot. Periodically spraying the axle with waterproofing agent should extend its life, and the wood may be preserved using a sealant.
You can use a woodburning tool, paint, or bumper stickers to spiff it up. We added a thin piece of bamboo with a wetland delineation flag as a warning to automobiles. Enjoy!