Age group: Venturers/DFs

How long it will take: several weeks

What materials you will need: various

The aim of the activity: To build bike trailers as a sustainable form of transport

What to do:
Bike trailers proved useful and popular at International Camp - using pedal power to transport goods as well as people around the camp site. You might want to build one to use on future camps or at home in your neighbourhood for shopping, picnics or other activities.

Hints & Tips
1. What do you need to transport with your trailer? The weight and size of the load are the key areas. The weight needs to be kept as low as possible in the design while still offering enough ground clearance for the terrain that it will be used on. If the trailer is too narrow then it will have a tendency to turn over when cornering. A long trailer will need higher ground clearance to cope with rough terrain.

2. The choice of wheels could well be the force that leads the design of your trailer. They are relatively expensive to buy new. One of the best sources of wheels is off second hand bikes. Tips and recycling centres often have bikes for very little money. There are two types of wheel, the normal bike wheel supported from both sides of the wheel and the wheel chair type that are supported from one side only. There are also pram type wheels, which are connected by an axle. If two similar wheels can be found that are connected by an axle this makes the whole process much simpler.

3. There needs to be some kind of flexible joint between the bike and the trailer so that when the bike turns or leans the trailer stays with both wheels on the ground. There are a variety of things that could be bought to do this job. A simple and affective joint can be made using a length of hosepipe. The hose is then held onto the frame by jubilee clips. This gives all the necessary movements very cheaply.

4. There are a number of things to bear in mind when designing a trailer. Safety is the main concern. The rider of the bike still needs to be able to stop in a reasonable distance, this limits the weight that can be carried on the trailer it will rely on the brakes of the bike. Of prime concern on camp are the children so it is important to smooth all external edges as mush as possible. Pipe insulation is very useful for this.

5. The definitive guide to a bike trailer does not exist, but here is a possible design for a platform to which a box could be attached. Two bicycle wheels are used, together with a metal frame, which could be welded or bolted together. It is also possible to make frames out of wood, plastics, plumbing pipes and plastic boxes.

Examples
Here are some examples to inspire you:

A trailer design
First construct 2 rectangular frames to support the two wheels. These will determine the size of trailer you can have.

The basic frame is detailed below. In essence it is just 2 boxes that surround the wheels joined together. The proportions of the frame will depend on the size of wheel and the cargo to be carried. One possible way to construct the frame is out of Dexian, commonly used for shelving units, it is basically bent metal with a large number of holes drilled in it so that it can be bolted together.

Now a linkage is needed between the trailer and the bike. It must be kept in mind that the linkage must not foul on the rear wheel of the bike while turning. This is why it is bent up at an angle. It is hard to give a definitive design for the connection onto the bike, since it depends on the bike involved. The easiest way is to use a flat strip of metal bent into a U shape around the seat post, with a bolt going through the free ends. When tightened, this will grip the seat post. Bike inner tubes are a good material to sandwich between the clamp and the seat post to protect the bike.

Four slots need to be made to locate the wheel axles and these can either be attached as extras or they can be cut into the frame. The profile required is similar to that found on the forks of a bike. The slot needs to slope backwards so that the axle is pushed back up into the slot when the trailer is used.

The main thing to bear in mind is that a bike trailer needs to fit your needs and can be as flexible and diverse as you like. This is, as the title suggests, a compilation of hints and tips, which we hope will spark interest and enthusiasm.

Web sites that may be of interest:
Tim Smith - Recumbant Cycle enthusiast
The Green Culture
International Bicycle Fund