An Adjustable Bike Trailer for a Craft Booth

I have a small craft booth at the local farmer's market which is only about a mile from my apartment. After about a year of schlepping all of the sundry bits back and forth in my car, I'd finally had enough of the downtown parking mayhem and decided I should start running my booth from my bike. The road between here and there is mostly flat, and I'm not selling really heavy items like candles or beverages.

I kept an eye out for a used bike trailer, and, when one became available, I was finally able to go car-free for my market booth. I'm really happy with how it turned out, and I'm really excited because I was able to do it without making any permanent modifications to the base trailer. If we have kids in the future or I get a cargo bike and decide to sell the trailer, I can still revert it to its original kid-hauling purpose. Hopefully, some of what I did here will be useful for you in your own bike hauling endeavors!

• A bike trailer
• 4x U-bolts (1/4" rod x 2-3/4" tall x 1-3/8" diameter for the 1-1/4" Al tubes I used)
• 4x Wingnuts (optional)
• 8 inches vinyl tubing (optional)
• 4x Pipe strap (1" worked best for the 1-1/4" Al tubes I used)
• 2x Al tubes (6' long x 1-1/4" diameter in my case)

• Miter box and hand saw
• Drill and bits
• Adjustable wrench
• Philips screwdriver
• Tape measure

Since my primary purpose for this project was to transport all the parts of my craft booth for the farmer's market in town, I had a pretty solid set of constraints. The trailer needed to transport my 10'x10' canopy tent, two folding tables, and two plastic totes of merchandise and fixtures. After several failed attempts to pick up a used trailer on Craigslist, I rode straight to my local bike kitchen when I saw they had two recently-donated trailers. While both trailers were were in great shape, when I checked the weight ratings, the choice was easy. One trailer was rated for 100 lbs while the other was only safe for 50 lbs.

When in its case, the tent is 5' long which became the critical dimension for the modifications. Without it, I probably could have fit everything onto the trailer in its stock form. Since the trailer is almost touching the rear fender of my bike, there was nowhere to go but back for adding length. The nylon sides were attached to the trailer tubes by a series of elastic loops and one sleeve that went around a support tube on the upper back of the trailer. I removed the support tube since it would prevent the tables from fitting in the trailer, and the elastic loops easily slid off of the upright side tubing of the trailer. Since the sides are sewn into the bottom of the trailer enclosure, I just folded them down into the inside of the trailer so I could keep the bottom as a catch-all for bungees and other small items I would need for the show. I left the front of the enclosure situated so it could still be upright to prevent items from sliding forward when braking.

After getting the trailer canopy out of the way, the next step is to add the tubes for the extended platform to the trailer. I had a couple of 1-1/4" aluminum tubes that I salvaged from a scrap metal dumpster that were perfect for the job. Plenty big enough to be strong, and since they're aluminum they won't rust on me. The U-bolts, wingnuts, and vinyl tubing were from the farm supply store, but any hardware store should have them too.

To keep things from sliding around, I slipped a 2" piece of vinyl tubing around the U-bolts and placed it in the center of the U. I wanted to be able to adjust the length of the overhang out the back, so that's why I went with wingnuts instead of the regular hex nuts that came with the U-bolts. If you are planning on having a fixed length trailer, then save yourself a couple bucks and skip the wingnuts. I almost always go for the more flexible solution, so I like that I can make the trailer longer or shorter as needed.

Once the tubes were in place, I pulled out my tape measure and checked to see how wide I needed to make the boards for the extended platform. I made sure to leave enough room on the ends for mounting the clamps, which came to 27". I had some scrap pallet slats from an earlier project (9 years earlier - I'm not a hoarder, promise!) and cut them down with my handy-dandy miter saw.

If you haven't worked with pallet wood before, you should know that it is extremely brittle. I usually drill pilot holes when putting screws into wood, but it is absolutely imperative when working with pallet wood. I used a 3/32" drill bit for the screws from these clamps after the 1/16" hole I started with was making some lovely cracking noises when I started screwing down the clamp. I didn't screw the clamps all the way down into the slat right away so I could slide them down the tubes. This meant I could do all the drilling and screwdriving without having to also maneuver around the trailer and the tubes.

I put the two cross pieces on 16" centers because I figured if it's good enough for framing a house, it's good enough for a bike trailer. I left a bit of a gap at the end so I could also use the trailer as a hand cart if I swap the tubes around to the front of the trailer instead of the back. Like I said, I like to keep my designs flexible.

At this point, you can start loading up the trailer and seeing how everything fits. I put everything together with the tubing fully extended, but now I was able to shorten the trailer by 1' to fit the 5' long tent which had the added bonus of reducing the overhang in the back. This was also the time where I was able to play with weight distribution to make sure the trailer didn't try to tip up in front and drag its tail. The tent came with sandbags to weigh it down when it's windy, so I was able to move those around to keep the nose weighted down appropriately.

Since the farmer's market is only about a mile away from my apartment, and most of my projects take longer than I expect they will, the first shakedown was a real-world test of taking all my gear down the street and setting up shop. I don't have a good way to check the weight of the fully-loaded rig, but I suspect it was far more than 50 lbs. There aren't any big hills between here and the market, but the weight was definitely noticeable. Stopping and starting were a little trickier than normal, and going over large bumps is interesting since the hitch for this trailer includes a large spring for damping.

Overall, the trailer turned out pretty well for about 4 hours worth of work. It definitely has a lot of room for fine tuning, but for less than $100 in parts I have a pretty usable rig that should help me save money and time running my craft booth at the farmers market. I'm hoping someday to get a cargo bike, but until then, I think this trailer will be flexible enough to help me do a lot more with my bike.

For future improvements, I've identified a few key areas for improvement:

• Lights - Now that we're coming into fall, setup for the market happens in the dark. I have lights on my bike, but I'm going to add some rear-facing lights to the trailer so my land barge is visible to approaching traffic.
• The hitch - As I mentioned this bike trailer uses a large spring as part of the hitch mechanism. I assume this is to help isolate the bike from bumps the trailer experiences, but it also results in some interesting resonances being translated back to the bike when going over large bumps. I'm not really a huge fan, so redesigning the hitch will probably be my next project for the rig after lights.
• Tie-downs - I was able to wrap a ratchet strap around the tubes for strapping things down, but I'd like to add some actual tie-downs to help better secure the load. As it is currently, things can shift around a bit which results in some interesting effects on handling while riding.
• Better tires - since I bought this trailer used, it turns out it has a mismatched set of tires. One side says to inflate to 35 PSI and the other says 40-60 PSI. With the loads I'm carrying, I think I need to get a matching set of higher PSI tires to help bear the load. 40 PSI, while probably providing some shock absorption, looked pretty sad when loaded down.
• Less vinyl - I'm going to remove the vinyl tubing from one U-bolt on each side of the trailer. The tubing kept things from moving around a little too well, so that adjustments were overly-difficult with the Al tubes binding when I tried to slide them fore or aft. I think one set will hold things tightly enough without severely impeding the adjustability of the design.