I made my trailer for under 20 bucks. I had to buy a couple cans of paint, a sheet of sandpaper, a spring for the hitch, and a replacement bolt & knob for the hitch. I already had some wire panel. Those are about $15 each, so you should be able to build this trailer for under $100 easily, even if you need a replacement hitch or something. I'm going to add a reflective sign or panel on the back for going can collecting and fishing.
I suggest a steel frame trailer with 16 or 20" wheels, quick-detach wheels, quick-clamp hitch, and folding capability. The Safety First model is easy to find for less than $50 even in good condition. I got one from the trash for free!
UPDATE: This trailer is still in use, and working well. The rubber/plastidip on the clamp has come off, so I carefully padded the clamp with Gorilla Tape. This held up all day in 100+F heat, and did not scratch the bike frame. Make sure the corners of the clamp are protected or they will 'bite" the frame.
Step 1: What you will need
2. Wire "hog panel" from feed store or hardware store (about $15 each, will have enough for 2 or more trailers)
3. Probably a set of tires and/or heavy duty tubes, I suggest www.niagaracycle.com for budget replacements
4. Possibly a replacement hitch or parts. I will discuss that more in this article
A. Need a hacksaw, or bolt cutters, or a cutoff saw, to remove unneeded metal from trailer, and cut wire panel. I used a hacksaw, but it was slow.
B. Vice Grip pliers, to bend the wires on the panel
C. Appropriate screw drivers, allen wrenches, or wrenches as needed to remove buttons, reflectors (save them), etc while removing the fabric and seat. A sharp knife and/or box cutter can help in removing the fabric parts.
D. measuring tape and a Magic Marker/Sharpie
E. A small crescent wrench or two, to remove the pivot bolts from the side hoops of the frame (keep the hardware and hoops) F. 60 grit sandpaper, to remove rust and old paint or chrome. If it is chromed and not in bad shape, you might want to leave it that way. To paint over chrome, scuff the surface up to take primer.
6. Paint and reflective devices
Note: if you don't want to mess with paint, or live in an apartment, you can buy colored Duct Tape, even in camouflage patterns!
A. 1 can of black or red/brown primer. 1 can of each color you wish to use. I used Krylon Ruddy Brown Primer and Krylon Satin Hunter Green paint. I highly recommend the specialty Krylon camo coordinated primer+paint combo colors, about $5-7 a can. they are non-reflective, and very durable. I painted a car once with them. It lasted for years (the paint).
B. Reflectors (sometimes they come on the wheels and trailer. Save them if you can. You can obtain them from bicycle shops, junkyards, scrapyards, usually in take-off bins or on old kids bikes. You can use rubber shims to make them fit the tubes on the frame, or epoxy them. You can find a million free pedal reflectors in white and yellow colors, along bicycle trails in the woods. haha They fall off of cheap pedals. You can tape or glue them on.
I suggest Reflective Tape from trailer accessories depts at auto parts or hardware/ag stores. This can be wrapped around any tube and will shine brightly when hit with lights.
C. Flags, reflective panels, blinking lights, or extension wands. Bike trailers often come with flags and poles, usually an orange triangle flag. This is cool, and replacements are cheap. You can make one from a piece of PVC pipe or broom handle, and attaching a flag you like (such as your country or state flag, or an orange warning flag. These help especially in hilly areas. I highly recommend battery powered red blinkers and white headlights, on the trailer as well as your bike. Dealtime Extreme, Lazerpoint, Amazon and bulk battery stores have them straight from China and Taiwan for $2-5 each, like this http://www.lazerpoint.com/p-5-led-6-mode-multifunction-bicycle-taillight-with-bracket_7945414 You can make extension warning wands (to discourage close passes) by zip-tying a foam pool toy ("noodle") onto the rear bumper bar of the trailer, or to your bike's rear rack.
7. Baskets and cargo bins, rope, and straps.
A. I highly recommend common laundry baskets, milk crates, and discarded picnic coolers. You can tie them to the trailer frame or wire grid with climbing rope, clothesline rope, or motorcycle straps (cheap cargo straps are available in the "king tools" bargain bins at hardware stores, in the big stores such as Big Lots or Harbor Freight, and Walmart.
You can bolt down picnic coolers or Action Packer boxes with j-hook bolts, washer and nut combos.
Step 2: Check trailer function and safe operation
Check out the wheel bearings and wheel shapes. The bearings should be ok, because most of these don't get a lot of use before being discarded or sold. You may need to service the bearings (grease bearings, adjust cones, etc). If the wheels are not fine, you may be able to order replacements from the manufacturer, or a bike shop. If the frame uses 100mm axles and QR or bolt-on hubs, you can source front wheels from kids bikes or BMX bikes.
Check out the hitch arm and hitch clamp. The hitch may be missing the rubber pad for the frame, the spring may be stretched, the internal plastic connector (inside the spring, acts as a damper to prevent trailer surge) may be broken from age. The safety catch strap may be damaged or missing. You may be able to make one from an old belt or from something like a camera bag strap.
You can order a new hitch if needed, from Amazon, for about $15, with the safety strap. It is a bolt-on item.
Mine had a busted plastic connector and the weak spring was not enough. I just used a heavier "utility spring" from Lowes, about 65lb working capacity. This bends well in turns and supports plenty of cargo. I didn't need a plastic connector, but I did beef up the safety strap by replacing it with a section of old leather belt.
Here is what the hitch part looks like. This one is $30 from Cruizer. It is best that your existing hitch works well. There are other trailer hitch options available. Message me if you need help.
Look for rust damage on the trailer. If it's steel, you can spray cooking oil in the frame after your build, to prevent rust.
Step 3: Prepare the trailer, remove old fabric components
This Safety 1st brand trailer (I think Walmart sells them), had a weather damaged fabric cover and no top cover/window.
If the side panels and top are good, you might not want to remove/destroy them. If they are good, you can leave the side panels intact and remove the side hoops from the frame with a small crescent wrench and pliers or duplicate wrench. Save the hardware and reinstall after completing the wire floor.
On this trailer, I completely removed all the buttons, snaps, screws, straps, and fabric with a sharp kitchen knife, a razor blade box cutter, screwdrivers.
I hacksawed off the seat and the brackets it attached to, and recycled it with my cans and scrap.
The wheels were in great shape, with good tires and tubes. Niagara Cycle sells a lot of tires for $7-15 each, and extra thick "thorn proof" tubes that are great for cargo trailers, for less than tubes at most Walmarts.
Step 4: Sand and paint the trailer
Step 5: Measure and mark the wire
I recommend putting the trailer on top of the panel to confirm your measurements, and using a magic marker to make your marks before cutting.
Make sure the wires extend over the ends of the frame enough to wrap around the main frame tubes, and avoid spacing them where they will conflict with wheel brackets or the trailer hitch bracket.
Step 6: Cut and bend the wire
Use your hacksaw or sawzall, cutoff wheel, or bolt cutters to cut the wire panel where you marked it.
I used vice grip pliers to clamp onto the wires and just hook them about 90 degrees bend over the frame tubes, all the way around, to check for fit. Then I used it to clamp onto each wire and hook it around as much as I could, going front to back and side to side. Finally, I used the wide open jaws and the adjustment knob to incrementally crimp the wire against itself making a "u" shape to hook it well around the tubes and closing each as much as possible. This wire is hard to bend, but this will be permanent, so it's worth the effort.
Step 7: Final touches and notes
I recommend painting with light coats of primer, then waiting for the sun to cure it, and the next day doing the paint. If you use the 1 step primer-paint, you can do several thin coats (don't make it drip or run!) and let it cure for 2 days before use.
If you bought the colored duct tape, you can wind it or wrap it as you wish, using a knife or scissors to cut pieces to length or cut the roll loose. That takes about 20 minutes and any torn up piece can simply be replaced.
Enjoy your cargo trailer! Do not use ratchet straps too tightly against the wire grid, or you can break the welds and bend the wires. You can pull down pretty firmly against the frame main tubes though. Be careful that your load is well secured or it could shift and contact your bicycle, causing a crash.
I recommend strapping down 2 laundry baskets, which gives a lot of room for collected cans, grocery purchases, or small dense items like potted flower plants, scrap metal, UPS boxes.
You can ziptie the flag to the roll bar somewhere, since you don't have the fabric to hold it anymore.
You can remove the side tubes (roll bar) if you do not need it, but it comes in handy for tying to fishing poles, or tying fabric grocery bags to it. You can put the blinkers or reflectors on it also.