Custom bike trailer
I mentioned a couple of months ago that I was looking for a new flatbed trailer to augment my BOB Yak for use in the city. Armed with my requirements, I headed down to Urbane Cyclist, fully expecting to ride away from the store with a new Burley Flatbed or equivalent. But after considering the options and talking to the staff about my needs, they recommended that I either get a DIY trailer kit from Wike and build my own trailer, or call Wike and get a custom trailer built to my specifications. I opted for the former, and am really happy with the result.
It’s done duty twice so far: its inaugural trip was ably carrying three Rubbermaid totes crammed full with much of the equipment and materials required for the Ward 29 Bikes meeting two weeks ago, and it pulled 80 lb of cat litter home last weekend. It’s big enough to be used for flats of flowers, bags of soil, and many other large or awkward loads that would have overwhelmed or overflowed my Yak.
Read below the fold for more details about the construction.
Requirements
My requirements were actually fairly simple: I wanted a large flatbed trailer that could take virtually any odd-sized load that I’d want to throw on it. The two specific applications I had in mind were carting home a rain barrel from one of the city’s Community Environment Days, and hauling a good-sized load to the local Goodwill. A larger trailer would also be handy for many other regular tasks: fetching bags of cat litter, bringing home flowers and plants at the beginning of gardening season, and carrying most large purchases that I’d otherwise have delivered. My BOB Yak can do some of those things, but it’s better suited to long-haul riding rather than carrying random loads of stuff around the city.
All of the flatbeds I saw at Urbane were smaller than I would have liked. The Burley Flatbed was closest, but it still wasn’t quite what I was after. So I ordered the Wike DIY kit the next day and started work.
Design
I considered a few layouts before picking my final size: 2′ x 4′. That’s big enough to hold three of those ubiquitous Rubbermaid Roughneck totes. I’d originally hoped for a trailer big enough to hold four totes, but it would have been huge and far less practical for smaller loads.
Materials
In addition to the Wike kit, I used the following materials:
1″ square aluminum tubes:
- 3x 48″ for the sides
- 1x 53″ for the side piece that connects to the tow bar
- 3x 24″ for the crosspieces
5x Red oak slats, each roughly 5/8″ x 3″ x 48″
3x Red oak crosspieces, each roughly 3/4″ x 1″ x 20″
50x pop rivets (could also have used bolts or self-tapping screws)
6x #10×1-1/2″ self-tapping screws
7x end caps for the aluminum bars
4x 160mm aluminum bar handles for front and rear tiedowns
Tools
Power driver (optional, but it’ll make your life much easier)
Drill press (optional)
Screwdriver, rivet tool, and/or wrench to drive your chosen fasteners
Gotchas
Building the kit is fairly straight-forward, but I’ll offer tips based on my experience:
- The documentation with the kit recommends making the arm that connects to the tow bar 8-12″ longer than the others. About 3-5″ in addition to the supplied tow bar is more reasonable. Do a dry fit and make sure that your rear wheel has adequate clearance.
- If you don’t have a drill press, just use #8 or #10 self-tapping screws instead of pop rivets. I wanted the cleaner look of rivets, but I’m not sure about how durable they’ll be. If they start shearing, I’ll replace them with self-tapping screws.
- I had to grind down the tang on the tow bar supplied with the kit so that it would fit into the tubes that I bought.
- 1″ square aluminum tubes should be available at any halfway decent hardware store. I got mine at my semi-local Metal Supermarket. They cut your order to length for free and I didn’t need to make any adjustments to their cuts.
Depending on the material and finishing touches you use, you can have a large custom cargo trailer for under $200. The kit saved me many hours I would have needed to spend in the shop if I was building the trailer from scratch.
Here’s a partial gallery showing the building process and result.
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- Two quick-release wheels came with the Wike DIY trailer kit
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- The rest of the kit contained six connectors to help construct the trailer, a bike hitch and pin, and a tow bar to connect the trailer to the hitch. It seems minimal, but this the kit contains basically everything you need to build a trailer, including all of the hard parts. With this kit, you can finish a trailer without any specialized tools beyond maybe a drill.
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- Start with seven lengths of aluminum tubing
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- You need to drill holes in the brackets for both the top and bottom tubes that run the length of each side of the trailer. If you use self-tapping screws rather than pop rivets, you don't need to drill.
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- The brackets are already drilled to secure the crosspieces. I drilled out the crosspieces for pop rivets, but if you're using self-tapping screws, you won't need to drill at all.
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- Insert a pop rivet into each hole in the bracket and tube.
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- Use the pop rivet tool to, uh, pop each rivet into place, securing the joint.
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- Two pop rivets have been installed here.
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- I chose red oak for the trailer bed, largely because I had some lying around from a previous project. I planed it down to 5/8" to keep it light. If you‘re using a softer wood, you should keep it a bit thicker. Here, the slats are drying after a second coat of Varathane. Cedar would also be a good choice for the bed, as would a plain old sheet of exterior plywood. If you don't have a saw, you can take your trailer to Home Depot, have them cut a piece to size, and you can carry it home on your trailer to finish assembly. You can use pretty much any hard-wearing exterior finish here, including paint or tung oil. If you really want shine and a bullet-proof finish, try marine spar varnish. But it‘ll cost you.
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- Connect the wooden crosspieces to the aluminum crosspieces with #10 self-tapping screws.
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- The wooden crosspieces have been mounted to the frame and are ready for the slats to be fastened. I chose this design rather than attaching the slats directly to the aluminum crosspieces because it means that the entire bed is attached to the trailer frame with only six screws, greatly easing any future replacement or maintenance.
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- The oak slats, dry after a third coat of Varathane, get a dry fit before being secured to the trailer frame.
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- With the addition of some cabinet handles from Lee Valley Tools to provide front and back bungee tiedowns and some resistance against items rolling off the trailer, we're done.
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- The new trailer easily carries two 40lb boxes of cat litter, twice what I would usually carry on my BOB Yak. I could easily have carried a third without approaching the load limit.
Cycling, In the shop | Val Dodge | 
July 4, 2009
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Essentially, this project seems to be for the benefit of your feline companion(s?). Hauling litter features prominently.
Inquiring minds want to know how many two-fours of beer this baby could handle.
BTW, those are very good photo instructions. Even a ham-donny like me could follow them.
Well, big boxes of cat litter are something I buy regularly that I can’t just lug home on foot or bungee onto my bike rack. After Pet Valu moved from 30 lb boxes to 40 lb boxes last year, I was only able to carry one box at a time on my Yak, which made it less practical to use a trailer rather than pop over with the car. It was definitely one of the primary requirements that convinced me to consider getting a bigger trailer.
As for the beer, Wike gives their kit a carrying capacity of 150 lb. If a 2-4 weighs about 25 lb, that would be six cases. Perhaps more importantly, it can carry at least a two-month supply of Haagen Dazs.
It looks to be sturdier than the Burly trailer too
I’m adding this to my cargo bike (Kona Ute). See any modifications that would need to be made given the different dimensions of longtails? Perhaps just tweak the tow bar?
Because it connects to the bike at the rear axle, the length of the tow bar is determined primarily by the size of your rear wheel. Looking at the Kona Ute, you may want a bit of extra clearance because of how far back the rear rack extends. The best approach is to do a dry fit and see what you prefer.
I like that trailer, it looks like you could do some serious carrying with it.
ttp://picasaweb.google.com/EDixon250/NewBoldGoldTrunk?feat=directlink
Check this out.
Hello Val,
Very nice trailer, I don’t see where the cross members are. I understand where they are under the long slats U just can’t see them in any of the pictures.
What do you think it weighs?
Scott
The crosspieces are shown in two of the pictures toward the end (numbers 10 & 11), before the oak slats are fastened to them. The wooden pieces are attached to the aluminum bars with self-tapping screws.
The whole thing weighs about 30 pounds. That’s a bit more than twice the weight of my BOB Yak trailer.
Hi, Val:
Thanks for all the helpful information you’ve provided on your Wike. I just received my DIY kit and am now planning my construction, but would like to ask you a few questions first:
1. What’s the thickness of your aluminum square tubing? Wike told me that the 150 lb. capacity is what the axles/wheels can withstand, not about the framing. Still, I wonder whether 1/16″ will do or whether I should get the stronger (and heavier) 1/8″ tubing. I want the option to carry very heavy loads but I don’t want the thing to weigh a ton.
2. Did you consider other materials/options for the trailer bed? My plan is to use a single piece of either aluminum tread brite or a suitable thick piece of all-weather plastic and mount it with the connectors turned “upside down” so that I have one large 2′ x 4′ flatbed with no gaps on the sides. Then I’m thinking of adding some more tubing and plastic connectors (such as those sold by Esto: http://www.estoconnectors.com/) onto the flatbed to create a fence to keep my cargo contained. (Again, I’m trying to keep overall weight in mind.)
Speaking of Esto, their 1-inch “hexagon connector” (http://www.estoconnectors.com/index.php/connectors/detail/pn-532306/) could serve as a nice mount on the front of the trailer for a removable pull handle using another piece of aluminum tube bent at 135 degrees of about 30-36″ (like a longer version of the trailer arm).
3. Have your ridden in the rain with your trailer? If so, has not having fenders on it posed a problem with excessive spray? Any other weather-related issues you’ve encountered?
Hope you’re still enjoying your Wike; I’m looking forward to getting mine completed and on the road.
George P.
I used 1/16″ wall tubing; it’s plenty strong enough. In my informal and basic testing, a 4-foot tube supported at the ends was able to support my weight (a lot more than 150 lb) in the middle. It flexed, but didn’t buckle or permanently deform. I figure that the three short transverse tubes that carry the bed and the four lengthwise tubes that transfer the load to the wheels are more than strong enough to carry anything I’d realistically want to pull. It’s also worth noting that the tongue assembly supplied with the Wike kit probably won’t fit into 1″ tubing with a 1/8″ wall.
I considered all kinds of materials for the bed, ranging from plywood to aluminum grill. I went with oak primarily because I had some extra lying around and really like the way it looks.
My very first loaded ride with the trailer was in the rain and I had no problems with spray at all. The wheels are far enough back and out to the side that neither I nor the cargo is in the spray zone. If it was a problem, I’m sure it wouldn’t be too hard to mount a couple of fenders from the side tubes.