Bike Trailer -- Tough and Light




Instructions on how to build a tough and light bicycle trailer out of standard light gauge angle iron found at the hardware store. This design is tough, relatively light, easy to build and easy to customize.

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Step 1: Collect Tools

Tools required for this job include --

Hack saw
Adjustable wrench (two)
Ratchet with 5/16 socket
Drill with phillips bit
Tape measure
Combination square

If you have a circular saw, it may be easier than using the hammer and chisel. Eventually I got sick of using the hack saw and borrowed a friend's angle grinder with a cutting disk.

Step 2: Collect Materials

These photos are just to show you what the materials look like. Below is a more or less thorough bill of materials. Costs maybe $100, but well worth it as a cargo trailer at a bike shop is about $300.

6 each conduit straps, two-hole kind, sized for 1/2 inch conduit
About 19 linear feet light gauge angle stock (find at hardware store or local big box store)
4 washers, 1/2 inside diameter
38 washers, 5/16 inside diameter
8 wood screws, 1 inch long
8 bumper washers that fit the wood screws
24 bolts, 5/16 diameter by 3/4 inch long, hex head
2 bolts, 5/16 diameter by 1 1/2 inch long, hex head
24 nuts, 5/16
24 washers, split ring, to fit 5/16 bolts
3 foot 1/2 inch threaded rod
2 each 20 inch diameter wheels, plastic spokes
3 feet 1x3 nominal lumber
2 feet 2x6 nominal lumber
6 each nylon washer, 1/2 inside diameter, about 1/2 inch deep
12 feet rope, about 1/4 inch diameter
4 machine screws, no. 10 diameter by 1 1/2 inch long, phillips head
4 nuts, no. 10, with nylon locking inserts
1 caster wheel with removable wheel and ball bearings at its base
1 1/4 bolt with pin, to be used as a quick release between tongue and receiver

Step 3: Cut and Assemble Chassis Frame

The basic chassis frame consists of a 2 foot by 3 foot rectangle of angle iron, reinforced with two 2 foot long pieces in the center.

Cut 2 each 3 foot pieces and 4 each 2 foot pieces of the angle iron. Bolt together using the 5/16 hex bolts with 1 split ring and 1 cut washer each. The frame will have some weakness in twisting, but we'll make it more rigid in the next steps.

Step 4: Assemble the Axle

The axle, axle support, and straps are attached to the chassis frame in one giant step.

Cut the 1x3 to about 26 inches long and position in the middle of the chassis frame. There should be about a 1 inch overhang on each side.

Bolt the 1x3 to the frame with a 1 1/2 inch long 5/16 hex bolt. I used a cut washer and a nut with nylon insert, since this is a crucial connection. You'll have to counter sink the hex head so that it doesn't interfere with the axle.

Before attaching the axle, spin a 1/2 inch nut onto the threaded rod first, then two nylon washers (bushings). Spin two more nuts onto the threaded rod and position next to the conduit straps as shown.

Pre-drill through the wood and angle iron and bolt the conduit straps onto the chassis frame.

Step 5: Construct Center Support

Cut the 2x6 nominal lumber to 24 inches long. The piece should fit snugly between the two intermediate angle supports, directly over the 1x3.

Notch out the ends of the 2x6 to accommodate the bolts that are securing the axle assembly. You can use a hammer and chisel and cut away wood until if fits, basically trial and error. I actually used a circular saw and curf-cut the end and bashed out the loose bits.

Secure the 2x6 into place using wood screws and bumper washers. Use four screws each side, two in the ends and two on the bottom. Be careful here, I split the first 2x6 doing this, so I recommend pre-drilling and not torquing it down a lot.

After the 2x6 is secured, the frame becomes much more rigid without any twisting action. The 2x6 also supports the cargo and resists bending of the axle under heavy load.

Step 6: Assemble the Tongue

Cut a length of angle iron to 31 inches long. At about 19 inches down, cut a vee notch to allow the piece to bend about 40 to 45 degrees. The short end of this piece becomes the connection to the read axle on your bicycle, so you need to check the length of your bicycle wheel first. The dimensions here are probably fine for most mountain bikes, since that's what I tow the trailer with.

Once your satisfied with the length and bend angle, cut two pieces of angle iron to reinforce the tongue. The lower one is about 10 1/2 inches and upper one is about 12 inches. Bolt these to the tongue to form a C in section.

Cut two more piece of angle iron, each 7 1/2 inches long. Bolt these to reinforce the bend in the tongue.

Fashion a clip that will reinforce the connection between the tongue and chassis frame. Its made from three pieces, two 2 1/4 inches long and one 1 1/2 inches long. They all bolt together with one bolt, then bolt them to the tongue and frame.

In early models of this trailer, the weakest part was the tongue, which flexed so much during riding that it permanently bent and twisted and caused the trailer to sit crooked. So if there seems like a lot of reinforcing on the tongue, it for good reason.

Step 7: Build the Receiver

Remove the rubber wheel from the caster wheel.

Cut a length of angle iron about 4 inches long. Grind or cut down one edge so that its no more than 3/4 inches. Grind or cut the corners of the short leg as well.

Bolt the caster wheel to the angle iron in such as way that will allow you to skewer the angle iron with the wheel axle skewer and tighten down.

Step 8: Build and Attach Coupler

Cut two lengths of angle iron to 3 1/2 inches. Chop or grind down one edge of each piece so that there's no more than 3/4 inch left of the leg.

Nest these two pieces together and bolt to the end of the tongue. Jam cut washers between tongue and coupler so that the coupler fits inside the caster wheel receiver, but not tightly, as a little play is good here. This should take about 14 cut washers total, but it depends on the side of your caster wheel and washers.

Step 9: Install Wheels

Wheel installation is easy, just follow the order in the photo.

You could put some thread lock on the outside nut, but with the end cap, its probably not going to work itself off, especially if you tighten it down to the other nut.

Before putting on the end cap, cut the end off the threaded rod leaving about a 1/2 inch extension beyond the outside nut. The cap will cover this.

Don't tighten the nuts onto the washer because it binds up the bearing and the wheel doesn't rotate smoothly. Instead make it snug and tighten the bolts to each other.

Step 10: Thread Cargo Net

Thread a rope across the chassis frame with 1/4 nylon rope to form a net to hold cargo. This can be done in any kind of creative pattern, shown here is basic chain link pattern.

Step 11: Final Trailer

This is how the trailer looks completed. I can carry at least 100 pounds of cargo on this with no problem. At only 20 pounds, this is also pretty light weight for its class. You could really pimp it out with reflectors, a good paint job and a flashy rope net.

1 Person Made This Project!


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51 Discussions


1 year ago

When you add weight on to the trailer how much weight goes on the rear wheel of the bike? Wondering as looking to make one but depends on bolt strength I can hold up to 200kg but rear wheel on bike holds 70kg max as of current tyre

1 reply

Reply 1 year ago

I loaded everything over the axle as much as I could. Fully loaded, I did not notice significant downward load on the rear wheel, but I can totally see what you're getting at. I would venture to guess that the trailer takes about 90 to 05 percent of the load due to the transfer of the weight from the netting to the frame, and then to the axle. I'd bet not very much actually gets to the trailer tongue, as long as its long enough. With this design, I actually did overload the trailer, but it the weak point was the threaded rod axle itself, which will allow the wheels to splay out due to bending of the axle.


Question 1 year ago on Introduction

I want to make a trailer for my bike, but am confused about all the various types/styles of tow-bars I see being made/ does the curve/bend of the tow-bar affect whether the trailer will track correctly behind the bike? If the trailer does not track correctly behind the bike then the tires will be ruined over time, and it will cause more 'drag' (harder to pull). So how does someone determine the correct angle/curve of the tow-bar, besides trial and error and possibly wasted materials?
Thank you for our time and assistance.

1 answer

Reply 1 year ago

I did not spend much time thinking about this, mostly because I'm a poor engineer. I made my best guess as to the alignment of the tow bar so that the center line of the trailer would align with the center line of the bike. I also hoped that the trailer would find its own line, even if its not exactly aligned with the bike. The attachment method I decided on had enough swivel and play in it that it seemed the trailer would take the easier and most direct path, that being more behind the bike than not. In practice, I didn't make exact measurements of how this turned out. The trailer did not show any ill effects of not being aligned directly behind the bike and I suppose the play in the tires, axle, and attachment to the bike frame just took up the slack.

If I really wanted some exactness, I would model this in SketchUp to determine the correct angles. But honestly, it didn't seem to be a factor in my experience, as long as the attachment method was flexible.

One problem with this design that should be fairly easy to rectify. there isn't a rotational degree of freedom about the in-plane axis; i.e. you cannot lean your bike in a turn, as required for any substantial amount of momentum. Other than that a great build. Just be careful around those bends.

11 replies

Yes, that is a problem I'm aware of. There's been enough play in the coupler/receive for this not to be a big problem. However, I haven't had to pedal "out of the saddle" yet with the trailer (for going over hill or sprinting). I'm interested in anyone's solution, though I prefer not to have to completely redesign the connection yet again.


Reply 2 years ago

Look at the connections for Off Rod trailers that people use behind 4x4 motors..
thats the way to can go left to right...up and down and 360degrees...and they are very strong...thats what we want.


Reply 10 years ago on Introduction

What about a hinge type of setup between the caster and the bike? The hinge would be at a right angle when the bike is upright, with the caster below it, so that in a turn the hinge could go up or down depending on the direction of the lean. I'm sure someone would be able to figure it out


Reply 10 years ago on Introduction

Good idea -- sketch attached, comments welcome. (no, I do not work for Perkins + Will) I'm wondering if there will be too much back and forth movement in such a design.


You might catch the spokes in the rear wheel. What about another caster in line with the support arm and 90 degrees "out" from the 1st caster.

I was thinking more along the lines of the hinge being horizontal, or bent at a 90 degree angle, so that when leaning the bike right, the hinge will open downward, and when leaning left, it would close upward. This might avoid the problem of the spokes catching, but i'm not entirely sure. i'm just thinking conceptually


Reply 10 years ago on Introduction

I was about to suggest some sort of universal joint near the point of attachment to the bike, myself. If you just have it attached with a bolt, the tires would drag and screech on a sharp turn, and wear out too fast.


Reply 10 years ago on Introduction

How about a heavy duty spring? The connection on my store-bought trailer that our kid sits in has a simple rigid post-and-hole connection but a section of the tow bar is actually a heavy spring. It makes turning quite easy and provides much needed flexibility between bike and trailer. Just a thought.


What I did when I needed a light-duty universal joint was to take two fairly heavy threaded eye-bolts, get one red-hot with a torch so I could open it up and put the opened end through the other eye and closed it up again. Worked just fine.


3 years ago

My bicycle trailer hops from side to side and I have to ether slow down or stop, it only happens when I go fast, is the trailer to light? Do have any idea why it hops from side to side???

1 reply

Reply 3 years ago

Might be because the axel of the trailer is on the middle of the length. It has to be 60% more to the thonghue. I guess


4 years ago on Step 11

Nice build, and a great starting point for the trailer I need. Thanks.

1 reply