Introduction: Cargo Trailer for Bicycle

Update 4/23/08: I have removed the (removable) backpack frames from the roof and installed a permanent, relatively waterproof, "hardshell" lid. I've added two pictures to the instructable - the large white panels of plastic are a giveaway as to which are updated pics. The lid is lined on the top with garden/hardware mesh (plastic coated steel mesh, not visible in this picture) for placing things on top of the lid. Under the metal mesh is a thin layer of white backsplash plastic material (visible in this picture)- this same material was used to enclose all the sides as well. The hinge is a piano-hinge made of brass. I used a (home) window lock as a latch to keep the lid down and eliminate vibration of th lid at the same time. I used L-stock and flat aluminum once again as structural support across the perimeter and inner field of the lid itself. I found that quality (high in acrylic) construction adhesive ($5 per big tube) works great as an all around waterproof and strong glue for almost any of the materials used - it even sticks pretty well to the plastic - (but don't rely on a plastic bond.) The white plastic sheeting is about 1/16" thick and should be able to be purchased as 4'x8' sheets (<$20?)from most home centers, though I only found it at Lowes. It was best cut with beefy scissors. In general, I attached the plastic it by using 1/16"x1/2"-wide aluminum strips on all edges - glueing them with construction adhesive while using little stainless steel bolts every 16" or so. Sometimes I sandwiched the plastic (edges) between aluminum L-stock and flatstock - always using construction adhesive to seal all joints - to keep vibration down and seal water out. Note that the plastic is neither really light or heavy - it seemed well suited for my beefy trailer in terms of weight. As with all aspects of my trailer, this took a long time - probably 20 hours - a lot of it trial and error - testing and scrounging for parts. I guess the main thing I want to convey is that the combination of aluminum stock, steel hardware mesh (gardening section of store) and plastic sheeting can be made into a nice waterproof lid for a cargo trailer, provided you have the patience of dealing with attaching it with little bolts and construction adhesive. Once more thing - I used thick, tough, tubular (with a flat section for attaching) weather stripping as a sort of anti-vibration / water seal / drip-edge on the underside lid perimeter (visible in pic).

This is a description of how to make a cargo trailer that attaches to the rear hub of a typical bicycle. The two main parts are the trailer itself and the hitch which is permanently attached to the bicycle. The relatively heavy "core" (near the axle) of the trailer was made from wood and common steel bracing and mechanical fasteners. Attached to the core is a system of aluminum pieces that comprise the main "basket" of the trailer. Most all the aluminum can be joined with woodscrews (to the core) and stainless bolts and nuts (for aluminum-only joints). I finished the wood with polyurethane and filled annoying gaps with epoxy paste filler. All the above parts can be found at a typical hardware store.

I also used certain recycled materials and added optional features using special new materials. I used a piece of tubular steel from an old ironing board (leg) as the angled connection between the bicycle hitch and the trailer core. I used a steel bar from an old exercise machine in the hitch, but that could be purchase easily. Also, I left space open in the lower portion of the core for a set of three batteries since I would connect my trailer to my electric bike. I see electric assist as a luxury, not a necessity. The wheels are 20" diameter (from recycled BMX bikes), but can really be any size you like, since the main body can be built to conform to any size wheel you have laying around. Two recycled backpack frames and some stretch-cords were used as a cargo lids, but these, like the batteries, are optional. I found a $10 grill cover that can be used as a stataionary cover as well as adapted to be used as a cover while using.

The aluminum was the most expensive part of this project and also added to the difficulty in assembly since it requires the drilling of many holes, some preferrably with a small drill press. Other that that, only typical hand tools are needed.

Step 1: Make the Hitch Part That Will Permanently Attach to the Bike

Use common flat, 90-degree and "L" shaped steel mending plates that you find at the store. Use gaps in the area around the frame near the hub nut as places to route nylon-insert lock-nuts and bolts for the steel plate parts in the first picture. Use a linch pin as a quick release connection between this permanent hitch and the steel trailer arm. I used tubular steel and aluminum to make a straight, adjustable length, connection between the bike hitch and the white tubular steel of the trailer. This puts the second pivot point (sort of a universal joint - I'll call it the U-joint) as far back as the back of bike (at the tire). This U-joint provided two degrees of freedom for rotation. The linch pin (gold color) functions as the another, extra joint that allows the tubular steel extention to angle down so that the pivot point (U-joint) is at the height of the trailer. This is the third (of 3) degrees that are needed for a real U-joint. Note that the key to the linch pin hinge is that you need a wide-channed piece of steel in which to route the gold linch pin, so that it can still move up and down in, without being able to move left and right (which would let the tubular steel to be able to rotate into the wheel, which would be bad).

The U-joint is to the left of the end of the white tube in the second picture. It consists of a flat steel hardware piece bent into a "U" shape to fit around the steel tube. This allows the trailer to pivot left and right at the point near the back of the bicycle. It gets the added feature of rotation (needed when turning while the bike is not in line with the trailer, say at the bottom of a hill) by being connected to the triagular steel support by a relatively loose-fitting special single nut and bolt that screws together to form a small shaft (I'll update with a closeup soon). The white tube pivots side to side using a silver clevis pin connection.

In my case, the reasoning for using the steel tube that slids inside the aluminum tube (to form a variable-length extension) was to accommodate use with bikes with smaller-diameter tires, assuming you want the pivot point to still be at the back of the bike. Note that putting the pivot point at the rear of the bike is not necessary, but it keeps the bike from rubbing against the trailer in really sharp turns when using the relatively short(white) trailer-arm length that I chose. I liked the idea of having a minimal amount of distance between the bike and the trialer, thus reducing the over length of the bike-trailer unit. You can choose a longer trailer arm with more angle as a replacement - this is what typical retail trailers use.

Note the use of thick gauge electrical cord (with coiled plastic protection) for the optional batteries - this reduced the voltage drop.

So, you may be concerned that the hitch may get torqued off the bike frame in sharp turns. Well, that depends on how lucky you are in being able to use strong bolts in enought key areas in the area around the frame of your bike. I was lucky. I may add a closeup showing the exact bolt areas for my bike, but yours will likely be different. The idea is to bolt the hitch tightly to the frame, as close to the hub as possible. I was lucky in that I can still accommodate an old-fashioned bike rack/hub connection. I still need to remove two small bolts to change my back wheel though - a little hassle, but not a big deal.

Step 2: Build the Trailer

I need to include more closeup if one is to duplicate what I did. The pictures here show the finished product only. The basic idea is to use 1x6 pine or other available wood to make the two side walls of the trailer. Attach these to a flat base of thin plywood and use two 1/8"-thick, strong steel L-brace to connect these three panels together. The key is to leave some of the L brace sticking up above the side panels so that he wheel can attach directly to the L brace via the inner nuts of the wheel. The outer nuts of the wheel connect to 1"x3" wood bracing that surrounds the outer portion of the wheels and attaches to the sidewalls and floor. Using a file, angle grinder and/or hacksaw to kollow out a notch in the top of the L-braces to fit the shaft of the wheels. The wheels attach into the notch from above, so you need to make the notch deep enough so ther is leftover metal at the top to bend slightly. This bend keeps the wheel shaft (using a washer) in place so the wheel can't slip out of the notch under heavy load (the washer will hit the bent metal). This connection is somewhat visible in the second and especially the third pictures. These three panels are then "boxed in" to form a sturdy box-like structure using more wood, screws and epoxy paste to keep the water out. Polyurethane then covers the wood for waterproofing. I added an arm to secure the batteries (wood, hinges and typical latch hardware). I also added a plywood lid to cover the battery. Make sure to leave some sort of slots or hole open on the bottom to let water drain out of the trailer.

I spent several days adding the aluminum basket. This is just a case of using 1/8" and 1/16" thick barstock and anglestock to get the shape and size you like. I used just stainless bolts and locknuts to put it together. Make sure to use crossbracing to get a super firm, unshakably strong basket.

I used more linch pins to connect a few old backpacks as lids. These open like clam shells and can be bungi-corded down over any size bulky load.

I haven't weighed it, but, without the batteries, I'd say it weighs at least 35-40 pounds. Goulet!


CameronSS made it!(author)2007-09-26

+1 for now, but I would recommend adding more steps to better show the construction process. That looks like a very well-built, very strong trailer!

Ian01 made it!(author)2017-06-11

> +1

Wow, that brings me back… I had nearly forgotten that Instructables used to have a +1/-1 rating system… and a 5-star rating system too, though I forget which one was the earlier one.

clothbot made it!(author)2007-09-27

Ditto. Very clean looking build (+1) but the instructable does need breaking up into more steps, annotated photos, etc.

Iconoclastic+Technocrat made it!(author)2007-09-27

yep, I'd like to work on this entry more - as the weather gets worse I think

xsmurf made it!(author)2008-03-09

Is the weather still too nice? Hehe ;) I'd really love a remake on this instructables. You're trailer looks awesome. I see you take it cyclo-touring (the old school backpack mount!) I went touring a few times and am seriously contemplating a trailer. It would be awesome for doing the groceries too. Could you pleeeease finish this article?

Iconoclastic+Technocrat made it!(author)2008-03-14

I've been lazy about this, sorry. I have to say that I posted this more to show off the general idea, not to be able to give step by step instructions. This really took a long time - we're talking at least 15 or more 8 hour days, drawn out over 4 months or so of weekends. In hindsight, I'm hesistant to encourage someone else to start on the same unending path. If I want this to be a realistic project that others could duplicate, I need to simplify the design - basically redesign it so that there is less need for precise measuring/cutting, especially with all that aluminum. This thing is more like an art project that got out of hand. This is another reason why I can't really go back and describe exactly what I did - the end product is the cumulative result of many small additions - of me staring at it, staring at my available materials and deciding what I could add on that given afternoon or weekend. Also, I already changed the design, removing the backpacks and replacing it with a solid hatch. Also, I have two electric hub motors (front and rear wheels of the bicycle) which baically allow this thing to be driven like a car -with no pedaling at all. All I can promise is that I'll look over the instructable again, perhaps add new pictures if necessary, but I'm sticking with the idea of trying to keep people from exactly duplicating it, bolt by bolt. I have to say, I often find I have problems sorting/uploading/inserting my pictures in the instructables site - another reason I dread editing my entry. Thanks for your interest in my bike trailer. I have to say that I like using it - though I wish that bike racks were more accessible to it - that is, I can't get this thing up over a curb easily. Other than that, I find it a very useful device, especially for groceries. I'm not a touring cyclist - just a on/off commuter cyclist who occasionally decides to build some off the wall stuff.

CameronSS made it!(author)2008-03-14

Possibly re-publishing it as a Slideshow might alleviate some criticism, since a Slideshow does not need full instructions. We could all pitch in and copy our comments over there...

xsmurf made it!(author)2008-03-14

I understand... maybe you could re-open it as a collective?

Iconoclastic+Technocrat made it!(author)2007-09-27

thanks, I suspect I can hold 500 pounds or so without it breaking. I can certainly get into it fine - and I'm 220 lbs

stephenniall made it!(author)2009-03-14

Hi using This sorta layout If i used Thicker wheels (Or two Bicycle wheels parallel either side) And steel instead of aluminium What weight do u think i could hold I have this Mad idea to create a bicycle pulled caravan And if it works ill make a recumbent Bicycle Built in so its like a motorhome lol

xsmurf made it!(author)2007-12-31

Same as above, +1 cause it looks damn nice! But the instructable needs some polishing. This looks like the best trailer I've seen (and there's been a lot on this site alone)! What's with the electronics? You have some break lights?

PC.FREAK made it!(author)2007-10-13

can you please post a detailed list of what you used? i would like to build one, but i need to know the sizes (on the metals, woods) .... the number of screws .... etc. thank you in advance.

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