FreeRider DIY Documentation v. 1.0

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How to make your own lightweight bicycle trailer,
using simple tools and cheap materials (mostly).

1 Introduction.

Across Africa, bicycles are the basic personal mean of transport in and between villages, among those who cannot afford a motorized vehicle. China made bicycle a token of popular mobility, just before jumping the wagon of personal cars mania. Same holds for the majority of Asia.

Western culture, firmly addicted to oil (and proud of it) made personal car a symbol of status and freedom, with the consequences we all face now. In Europe and North America, bicycles are mostly regarded as a leisure vehicle.

Popularity of bicycles keeps growing in Europe, both in the city and countryside, but they are still underestimated as a cargo transport vehicles.

During Vietnam war, large part of VietCong logistics was done with simple bicycles, pushed by people, loaded up to 180 kG. For a Westerner, it is an extreme example, except for situations of disaster, evacuation or collapse of basic infrastructure (which may become reality also in Europe within years or decades).

However, more and more people do not own a car and use public transport or bicycle to cover their mobility needs. Occasionally they need to transport a load exceeding capacity of their bicycles alone. Be it a dog or child, weekly food shopping at the market, laundry or supplies for a party – this is where a lightweight bike trailer steps in.

We present to you a simple way to build FreeRider, do-it-yourself lightweight bicycle trailer. Cheap in the making, easy to store or transfer (assembled or disassembled), open source appropriate technology design.

With only basic tools (battery drill being the most advanced) you can build it during one weekend day, without breaking sweat.

2 About the construction.

FreeRider is based upon the construction of bamboo trailer, developed by Carry Freedom group. We made some modifications, making it simpler and more suitable for European context.

The DIY version is made mostly of wood. As a standard we use round wood elements, sold as handles for gardening tools (rakes or hoes). Optimally it should be a waterproofed hardwood piece, diameter about 30-35 mm. We do not recommend using wood thinner than 28 mm. Wood thicker than recommended is not a big problem – it will only make trailer heavier than necessary. It should also be medium- to hardwood. We normally use Beech.

Wood has to be sound, without knots, cracks or splits.

The construction consists of three major modules:

  • Main frame, providing stiff chassis for the cargo. Frame is filled with a net, tarp or some other cargo bed, to support the load.
  • Wheel brackets and wheels, supporting frame and make it mobile. As a standard, we use 20” BMX wheels, front ones.
  • Towbar with the hitch, connecting the frame to towing bicycle.

All elements are assembled using carriage bolts, washers and nuts. It makes trailer easy to disassemble (for storage and transport when not on wheels) and reassemble whenever needed.

3 Skills needed.

To build FreeRider based on this documentation, one needs to be able to:

  • Read and understand this documentation. If you have problems at this stage, chances are the documentation needs improvement. Talk to us about it and we will do our best to make it easier to use.
  • Do measurements, calculations and markings using a ruler and measure tape as described here (with 1-2 mm precision).
  • Draw straight lines and right angles with pencil, ruler and angle ruler.
  • Cut wooden elements at a right angle.
  • Drill holes in wooden elements (up to three, stacked together) in the centre and perpendicularly to the surface.
  • Use elastic cable ties, flat or eyelet spanner, pliers, hammer and knife.

4 Tools and materials.

Download PDF with detailed list from here.

Reasonably basic set of tools you will need contains:

  • Battery drill (able to use 12 mm drillbits)
  • Woodworking drill bits: 6 mm and 12 mm
  • Universal pliers
  • 10 mm spanner (flat, eyelet, eyelet with ratchet).
  • Small (300-500 G) hammer.
  • Knife
  • Measurement tape
  • Angle ruler
  • Ruler
  • Marker or carpenter’s pencil.
  • Notepad.
  • Assembly rig plates for frame (4 pcs) and towbar (1 pc). See detailed description below

Carpenter clamps and strong rubber bands may be also useful to keep elements together for drilling.

Parts and materials

  • 2 x 20” BMX front wheels (possibly with smooth tires – less drag resistance).
  • 6 mm carriage bolts with washers and nuts. You can use standard nuts or secure one, with plastic inset. The latter makes (dis)assembling harder and slower.
    • M6 x 25 mm — 1 pcs.
    • M6 x 70 mm — 30 pcs.
    • M6 x 100 mm — 6 pcs.
  • 17 pieces of wood. The length will depend on dimensions of the trailer (and vice-versa). For our standard trailer you will need to cut (colors refer to drawings below):
    • 1 x 140 cm for diagonal beam (burgundy)
    • 2 x 106 cm for front and rear beams (brown)
    • 6 x 97 cm for wheel beams and cargo bed supports (yellow)
    • 2 x 83 cm for towbar junction beams (blue)
    • 1 x 49 cm for towbar front beam (grey)
    • 1 x 46 cm for towbar crossbeam
    • 4 x 15 cm for wheel brackets (red)
  • Elastic cable ties (zip-ties), min 20 cm long. 1 pack.
  • Horseshoe steel clamp, with 6.5 mm holes on both ends, fitting over wood elements you use.
  • One steel ring with 6mm threaded hole in the base plus a 6mm machine bolt to attach it to  the rear rack support in the towing bicycle.

wood-elements.png5 Measurements.

Whenever I provide any measurement here, there are the following conventions I use:
“D” always means diameter (or, for squares, side) of the element.

When giving distance between elements, we always mean distance between their sides facing measured gap (so you need to take their thickness into consideration as well).

We always recommend that the holes in elements should be no closer than 1 D from the end. It prevents splitting and cracking in use.

If you see a hole to be drilled and there is no distance given, it should be understood that the hole is central in this dimension.

5.1 Frame dimensions

In many countries the law regulates maximum dimensions of bicycles and trailers. Consult your local regulations, if you care to comply.

On technical level, there are two factors that have to be considered.

The minimal width and length of the trailer has to include space for wheels. Wheels we use (BMX 20” front wheels) need 115 mm space between brackets and 55 cm width of wheel bay. The wheel bay needs also to accommodate diagonal beam (at 45* angle), which takes another 23 cm. This makes minimal space between front and rear beam 78 cm. So minimal length of side beams will be 78 + 4D.

Theoretically, the width of the trailer can be as small as 2*115 mm + 6*D, but this leaves no usable cargo space. Instead, the builders should consider typical size of cargo they plan to transport (bags, crates, boxes and such) and calculate dimensions accordingly.

Our standard design is suitable to carry 4 crates of beer bottles, 30*40 cm each. With some space to manoeuvre it makes the cargo bed 85 cm long and 65 cm wide.

5.2 Towbar is important!

Towbar triangle is essential for stability of the whole trailer. Towbar itself carries all load of he trailer and cargo, transferring it (via hitch) to he towing bicycle. It has to be straight and rigid and the triangle provides both features. To make assembling it easier, there is a separate rig for this purpose (see section below for description).

5.3 Wheel brackets

Wheel brackets are simple pieces of wood, 15 cm long, with three holes in them. One hole is of 12 mm diameter (the size of wheel axle). Two others, drilled while mounting the wheel for the first time, are 6 mm bolt holes.

6 Assembling process.

6.1 Work area

You will need a space with some kind of table, no less than 1 x 1 m (optimally 1 x 1.5 m) for assembling the frame. You will need a place to put your tools and materials close, without the need to search for them every time (looking for pencil again and again can spoil the fun totally).

Ideally, you will also need a smaller bench, approximately 1 x 0.6 m, to put the frame on, while mounting wheels for the first time.

The first and fundamental goal of your work is to get through it unscathed. Thus: safety.

Make sure there is enough floor space around the table, so you can move without tripping or knocking things. Make yourself familiar with safety rules concerning use of electric drill.

Sharpen your knife (dull knife is more dangerous at work, as you need to press harder which means less precise control).

Get rested, sober and in positive mood.

Print this documentation, or otherwise make it handy (but out of the main workspace).

6.2 Assembling rig plates.

Assembling rigs are essential for proper shape of the trailer. You can make a very good trailer without them, but it will take more adjusting and triple-checking. On the other hand, making proper rigs takes time and effort as well. So, the choice (as usual) is yours.

Rigs have to be done from any plate of rigid material (wood, plastic, even metal), strong enough to hold 6 mm bolts and soft enough to be easily drilled. You will need four frame rigs and one towbar rig. Dimensions given here are relevant to our standard construction. For different sizes and materials you need to change them respectively. In standard version, the rig plate is 15 mm thick (or thicker, up to 28 mm). We also use standard carriage bolts, 6 x 70 mm, with nuts and washers.

Frame rig

Frame rig is needed to assure that the corner of frame is straight and all elements are in place. You will need four such rigs to complete the frame.

The rigs need not to be fixed to the table. Proper sizing of frame comes from precisely sized elements (beams).

You will need 16 bolts in total to make the rig set. There is no need to buy extra bolts, if that makes a problem. After you assembly the frame, you can remove bolts and reuse them for towbar rig and to assemble towbar. Finally, bolts from towbar rig will go to wheel brackets.

Frame rig plate
This is exact drawing of your frame rig plate.

 

How to make frame assembling rig:

  • Cut four, exactly rectangular, piece of plates, sized 175 mm by 210 mm.
  • On the A4 paper, print four copies of the frame rig template and put them on the plates you just cut, so the edges match. Use glue or tape to affix the template to the plate. Make sure dimensions match.
  • Drill 6 mm holes as shown on the picture. Be precise. Triplecheck the higlighted dimensions, they are essential.
  • Install bolts from the bottom and tighten nuts from the top of the rig.
  • When installing bolts, if you use square or rectangular elements to build the frame, use 12 mm drill bit to “sink” nuts, so the surface around the bolt is flat.
  • Note that the rig is asymmetric. Each corner needs different rig plate position.

Towbar assembling rig

Towbar is the hardest working part of your trailer. All power, needed to haul the cargo, transfers through this structure. All bumps and holes on the road, all changes of speed and direction, make it stretch, compress, twist and bend. Both geometry and fitting must be perfect here, so your trailer can go hundreds and thousands of kilometers without failure. Using a rig to assemble it is the simplest way secure proper alignment of elements.

You will need four M6 carriage bolts with nuts. They can be reused from frame rig, after you finish putting the frame together. Once the towbar is done, you can use them again, for one of wheel bracket sets.

Towbar rig plate
This is exact drawing of your towbar rig plate

How to make towbar assembling rig.

  • Cut exactly rectangular piece of plate, sized 115 by 210 mm. The orientation of the rig will be vertical (top/bottom edges are the short ones).
  • On the A4 paper, print the towbar rig template and put it on the plates you just cut, so the edges match. Use glue or tape to affix the template to the plate. Make sure dimensions match.
  • Drill holes and mount bolts as shown on the drawing, applying the same advices as given for frame rig plates.

6.3 Assembling the towbar.

Follow the step-by-step pictures. Pay attention to dimensions shown on each picture – they are crucial at given stage. Double and triple check all dimensions, especially before cutting and drilling elements.

  1.  Put the rig plate on the table, as shown on the picture.
  2.  Zip-tie junction beams to both sides of the plate.
  3.  Zip-tie towbar front beam on top of the plate.
  4.  Cut towbar crossbeam at an angle, so it fits as shown on the drawing.
  5.  Drill holes and bolt towbar together.
  6.  Drill holes for the hitch and frame junction.
  7.  Remove and disassemble the rig plate.

Congratulations! Your towbar is assembled. Put is safely aside – you will need it soon.

6.4 Assembling the frame.

We will be assembling the frame on top of the table, upside-down compared to its normal position. Please pay attention to dimensions shown on pictures.
There is no need to affix rig plates to the worktable. If plates are made properly, proper geometry will emerge from precisely cut elements.

Follow the step-by-step pictures. Pay attention to dimensions shown on each picture – they are crucial at given stage. Double and triple check all dimensions, especially before cutting and drilling elements.

  1. Zip-tie the rear beam to the rig plate.
  2. Add two wheel beams.
  3. Add second corner and beams for the other wheel.
  4. Add third corner and front beam.
  5. Add last corner and check geometry. Both diagonals should be equal (1-2 cm difference is not a tragedy).
  6. If everything is ok, add the diagonal beam and fix it with rubber bands (not shown).
  7. Drill, baby, drill – and bolt it all together. Leave out bottom-left corner – we will add towbar there.
  8. Now you can cut zip-ties and remove three rig plates. The fourth one will be removed once the towbar is in place.
  9. Add two cargo bed supports, drill holes and bolt them to the frame.

Congratulations! Your frame is assembled!

6.5 Joining the frame and the towbar. Mounting wheels.

  1. Put towbar on top of (upside-down) frame, as shown on the picture. Pay attention to beam alignment and position of holes you drilled in towbar beams.
    Use clamps or zip-ties to fix it temporarily (not shown).
  2. Through the holes in towbar, drill holes to join towbar with the frame. Bolt them together and remove the rig plate.
  3. Prepare four wheel brackets.
  4. Drill holes in wheel beams using wheel brackets as templates.
  5. Mount the wheels and bolt brackets to the frame.
  6. Turn the trailer to working position. VOILA!

6.6 Hitch.

Currently, we have tested two versions of hitch. For lightweight trailers, the construction is simple.

Sports Camera

Shackle is used for quick mounting/dismounting. It fits around the rack support, just above rear axle. The downside is that it scratches the paint. Thus we are now testing the alternate approach. A steel ring is bolted to rear rack support, and mounting/dismounting is done by removing the bolt in the towbar beam.

Sports Camera

For heavier versions, the hitch is made of steel cable and shackle. The latter can be also replaced by a ring, but it will not be so easy to attach/detach quickly.

Sports Camera

Loose ends of the cable are buried in specially drilled holes, to improve grip and protect from rust or scratching.

6.7 Cargo bed.

The basic version has a simple cargo bed made of heavy tarp (320 g.sqm) with eyelets along the edges, matching positions of bolts on the frame.
Another option is a piece of tarp, lashed to beams. This solution creates some problems when we need to dis/assemble trailer quickly.

In both cases the cargo bed is supported by two additional (lengthwise) beams and the diagonal beam.

All kinds of lightweight stiff material can also be used for this purpose. In further editions we will be describing best proven solutions.

6.8 Lights & visibility.

There are two basic reasons we need the trailer to be more visible:

  1. It is low platform and may be easily overlooked by drivers, especially when it is dark.
  2. Pile of cargo may obstruct the rear light of the towing bicycle.

So, our recommendations for lights and visibility are:

  • Put passive reflectors all around the frame, as shown on the picture. If you have hi-viz tape, it will be even better (cheaper)
  • Put at least one red and one white blinking lamps (rubber clip-on type is the best) as shown.
  • If you can, mount a vertical antenna whip, no less than 60 cm long, at the left rear corner, with a lightweight ball or a pennant at the end, in visible color.

Frame-ligts