Made from 3/4" conduit and other common hardware store items. No salvage parts, other than 16" kids bike wheels. Simple, sturdy, tested.
For more information, check out Bike Walk Wichita (BikeWalkWichita.org/grocery-getter-trailer, or https://www.facebook.com/BikeWalkWichita/)
Step 1: Bend Frame
The frame and tow arm are a single piece of conduit. Easy and solid. A bolt at the joint secures it.
This is for a roughly 26” square body trailer, perfect to hold a plastic tub.
Mark conduit for proper corner bends. I found it easiest to mark the length of the trailer for the three key bends.
Starting at what will be the bolted corner, measure and mark 19”, 42”, 64”. There’s usually a line down one side of pipe, use that to help keep the orientation straight. Place arrow of bender on 19” mark, and bend to 45°, bending towards long end of conduit. Continue with mark at 42, 64. Basically bring frame around on itself. You should end up with about 30” left, which is the hitch arm.
Step 2: Bend Hitch Arm
The hitch arm needs to end up near the center of the frame; bend should end up about 2” short of center to allow for the flex piece
Mark 14” from end of conduit. Place star, not arrow, on mark and slowly bend until close to center. You can move star point forward and back to shape the bend of the arm. The exact bend isn’t critical, as long as it ends 2” short of center.
Step 3: Cut and Attach Inner Wheel Frame
You will need 2 pieces of conduit cut to length to act as the inner wheel frames.
On mine, they measure 26”. Make sure your frame is square before measuring, these should be identical length. After cutting, use the mallet and steel pipe to flatten the ends. The idea is to make the conduit sit snugly on the frame, with a slight bend to fit.
Step 4: Create Wheel Mounts
You will need 4 wheel mounts, made from metal outlet covers
Using a steel piece of conduit to act as form, clamp plate and conduit into vise. Hammer to bend to shape. It should fit snugly around the top of the conduit.
Once they are shaped, cut U-shaped slots to accept the wheel axles. Measure the axles you plan to use, as they vary.
Drill a 3/8" hole at the top of the slot, and then use jigsaw to cut to the hole. Cut the slot twice the height of the axle dimension to allow a bit of adjustment room. Be sure the slot is cut in the same location on each plate. Use oil when cutting and drilling metal.
Step 5: Drill and Assemble
Frame - both wheel frame pieces need bolt holes at each end, as well as the frame where it meets the tow arm. The inner wheel frame pieces need to be placed so the wheels you are using fit, on mine they are 4” apart. It might be different if using rear wheels or larger hubs. Take care to keep all parts square as you drill and bolt them using 1/4" x 2" bolts, washers and plasti-nuts.
Wheel mounts - center wheel mounts on the frame and mark the location. Mark spot for two bolt holes. Drill from the inside of the curved section, use a point chisel to mark the hole
Mark the frame through these bolt holes and drill through the conduit, taking care to keep drill plumb. The wheel mounts are flexible enough that you can bend to fit a variety of axle widths.
Step 6: Hitch Arm Flex Mount
In order to allow the trailer to flex (ie flip!) without disturbing the bike you need a flexible hitch.
This is modeled after the Burley flex hitch, but costs less than $1 for both hitch and flex piece!
Use 2 4-5” lengths of hose; one ordinary garden hose and the other pneumatic hose (found at most hardware stores, sold by the foot). Lube (I used dish soap) the pneumatic hose and force into the garden hose. Lube garden hose and force into conduit at least 2”.
In trailer arm drill ¼” hole and run bolt through to fix to trailer arm.
Drill another ¼” hole, slightly oversized, about ¾” from end. Round this end if needed to allow clearance in hitch.
Step 7: Hitch Plate for Bike
This trailer design is for Burley hitches. Use a 4” electrical box cover, folded in half. Use vise and small sledge hammer to bend. The technique I used was to mark the plate with line at 2". Place the plate so the 2" line sits at the top of the vise, then hammer to a 90 degree angle. Open vise up to fit plate in, with edges in center of jaw. Close vise to bring two sides together. When they are about halfway there, remove from vise and use sledge mallet to flatten by striking right along crease line.
Using design in photo, create a template on plastic or cardboard. I used a carryout container top. Trace template onto metal plate and use jigsaw to cut, bench grinder to smooth curves. Bend tabs by clamping in vise and hammering, it takes some work to get tabs parallel. The gap between tabs should be just over 3/4" inch, this one is a bit too wide.
Cut holes - ⅜” for axle hole, ¼” on tabs. I found it easiest to shim using 3/4" scrap wood between tabs as I drilled the top hole to keep it from bending down. Remove wood when top tab drilled, then keeping drill plumb drill bottom hole.
Step 8: Secure Tub to Trailer
Measure your frame to make sure the tub you are planning to use will fit. The one I used is more rectangular, so it was a snug fit. Other tubs are more narrow at base, so will need to be secured to the frame.
I used short lengths of rope to secure the tub to the trailer, to make it easy to remove the tub. There’s lots of ways to do this, though - bungie, bolts, up to you!
For a narrower bottom tub, use several pieces of rope tied across both front and sides, I overlapped them so they make a loose net, then secured the tub using length of rope tied through two holes I drilled in handle area of tub.