How and why to build one.

9 Febbraio 2022

The concept behind Polisfonia is that of a mobile and participatory lab where sound explorations and political dialogue intertwine in public space. In other words, a series of practical activities using sound and music as tools to trigger a dialogue on politically relevant issues together with the people participating.

Carrying out workshop activities often requires the use of bulky materials, and activating public space requires mobility and adaptability. For these reasons we decided to build a bicycle cart.

But why a cart?

Why building it yourself?

And how could you do it?

Why a bicycle cart?

One of the main reasons why building a cart is a good idea has to do with the vehicle to which it is attached, the bicycle. The bicycle is an excellent means of locomotion, especially for city dwellers. It is simple, affordable, environmentally friendly, lean and fast. It can reach any public place on the road, on the ground and on grass, it is a practical object, a symbol of freedom, conviviality and health. Expanding the possibilities of this vehicle can therefore be an excellent way of reinforcing or expanding its values.

Many people in Bozen (where Polisfonia was born), as well as in other European cities, own or have access to a bicycle, but use it mainly for personal transport. To transport objects of significant volume or weight, however, an ordinary bicycle may not be enough, and many people choose to use cars or other motorised vehicles to overcome this problem. In reality however, with some exceptions, the weight and volume of objects that are commonly transported (e.g. groceries, small pieces of furniture, musical instruments, sports equipment, books, games, tools, and materials of different kind) is not so great as to require a car, even a more 'capacious' bicycle would suffice.

To address these problems and needs, therefore, both in the past and in recent years, many people and companies have devoted their energies to building cargo bicycles. Although this type of bike is exceptionally useful, it has a number of significant limitations, including its high purchase price, its large size and the fact that it may be necessary to own a second general-purpose bike in addition to the transport bike for more agile riding, or to replace one's usual bike entirely if available space is not enough.

A good solution to get the advantages of a cargo bike while circumventing its limitations could be the use of a cart. The concept is simple, it can be attached to any existing bike without requiring replacement, it takes up proportionally less space and is therefore easier to store than an entire cargo bike when not in use, it is much cheaper and therefore more accessible, and above all it can be built by oneself with a few simple tools.

photo: WS / Claudia Corrent

Why building it yourself?

Buying a ready-made cart is already a good idea, but building one yourself is even better for several reasons:

  • The process is much simpler than you might think
  • The size can be adjusted to suit your needs
  • It's a fun and enjoyable experience that can be done in company
  • It is a way of adding value to an object you own
  • Easily reusable or recyclable materials can be used

There are many methods for building carts, but one in particular requires commonly available tools and easy-to-find materials. This method is inspired by the construction technique used by the XYZ CARGO BIKES project adapted for a cart instead of a whole bicycle, and is the same method we used to build the cart for Polisfonia.


Building a cart and using it is a simple and generally safe process, but there can be risks in both of these phases that should be borne in mind.

As far as construction is concerned, it is important to:

  • Wear personal protective equipment such as goggles and gloves when necessary
  • Work in a safe and spacious place
  • Supervise the work carefully, especially if children are involved

Concerning the use of the cart it is important to:

  • Check that the dimensions comply with local bicycle regulations (ask your municipality)
  • Respect traffic regulations and common sense when driving
  • Periodically check that the components of the cart are mounted solidly and correctly
  • Check that the cart is firmly attached to the bike
  • Make sure to have several practice sessions with different types of load in a safe and spacious place to ensure proper handling of the cart

The construction of the cart and its use remains a process entirely at the discretion and responsibility of the individuals who wish to undertake it.

photo: WS / Claudia Corrent

Which tools are necessary?

Tool list

  • 1 Pencil
  • 1 Measuring tape (or other measuring tools you have at home)
  • 1 Saw for metal
  • 1 Saw for wood (only if you'll not be able to buy wood in the correct measurement)
  • 1 Electric or manual drill
  • 1 A drill bit for metals 6,5mm in diameter (if you cannot fin it, 7mm would do just fine)
  • 1 Sandpaper (120 or 180 grid)
  • 2 Wrenches number 10 (alternatively pliers or adjustable wrenches will work)

Materials list

  • Hollow square aluminium tubes, 25mm in diameter and 2mm thick, or wooden strips with a square profile and no less than 25mm in diameter (details of specific measurements in the description below)
  • 2 x 21" bicycle wheels
  • 60 M6 bolts 60mm long (ideally stainless steel, alternatively galvanised steel)
  • 60 M6 nuts (ideally stainless steel, alternatively galvanised steel)
  • 120 12mm flat washers with M6 hole (ideally stainless steel, alternatively galvanised steel)
  • 1 plywood measuring 90X55cm and at least 6mm thick (other materials can also be used as an alternative to wood)
  • 1 perforated steel plate 20X20cm with a thickness of 2mm
  • 1 fixing hook for carts (alternatively 1 rope of 1m length and with a diameter not exceeding 6mm)

Getting the required materials

The first thing to do is to find the tools and materials. The necessary tools are very common and if you do not have them yourself, they can be borrowed from neighbours or acquaintances without having to be bought. You could also turn to a social workshop or fablab which usually have all these tools available. The construction materials are all easily available at a hardware store or DIY shop, but there are a few tricks you might want to follow to limit costs, especially for the slats/tubes and wheels which are the most expensive part of the cart.


If you decide to build your cart with aluminium tubing, the best way to reduce the cost is to buy it directly from the manufacturers. A simple online search should be enough to find metal tubing manufacturers in your area, but it is often useful to ask people who work with metal (blacksmiths, mechanics, etc.) for information, they usually know where to find it.

These companies usually sell rods up to 6m in length, which needs to be bought whole but can fortunately be cut on site. Ideally, you should bring a tape measurer, a pencil and a sheet of paper with the measurements of the individual pieces with you when you buy the material, so that you can cut them on site in the correct measurements. If the company does not offer a cutting service, the cuts can usually be made by hand in proximity of the manufacturing place (there is practically always some space to do this), but in this case you need to consider about 1 extra hour to get the job done.

Square aluminum tubing

2 rods of 6m are enough to build the whole cart and at the time this article was written (December 2021) they cost about €20 each, considering a diameter of 25mm and a thickness of 2mm. Larger diameters and thicknesses can also be used, but the cost increases considerably, as does the final weight of the cart. The 25 mm diameter and 2 mm thickness is a good compromise between solidity and lightness.

If you decide to build your cart with wooden slats and want to limit the cost of materials, you could ask a local sawmill or try to find used ones, although the latter option is more difficult. Wood is a possible alternative to aluminium but it is not the ideal choice for a cart, as it can carry less load and is much more vulnerable to weathering. In any case, to make it more resilient it would be ideal to increase the diameter of the slats to 30mm and weather seal it with paint once it's completed.

Measurements and quantities of the aluminum tubing

  • 25mm diameter and 2mm thickness
  • 5 pieces of 100cm length
  • 6 pieces of 60cm length
  • 6 pieces of 30cm length

With these tubing measurements you will obtain a cart with external dimensions of approximately 100X80X50cm. If these measurements (especially the 80cm width) should conflict with local regulations concerning bicycle carts (check your local municipality), you should adapt them accordingly.


The wheels we have used to build our cart have a diameter of 21''. They are very common on folding bikes and BMXs, and can often be found used online or at flea markets. If you want to reduce the purchase cost a good solution is therefore to buy them used. We have chosen to use BMX wheels because they have a larger number of spokes and a more robust construction, which makes them more suitable for carrying heavy loads. Another advantage of BMX wheels is that they often have a longer axle compared to other wheels, which makes them easier to attach to the cart.
If you decide to buy wheels whose axle is not long enough to attach them to the tube frame, you can buy 2 x 12cm long M10 or M12 bolts (depending on the diameter of the wheel axle) with 2 x nuts and 4 x washers, ideally made of stainless steel or galvanised steel, to replace the original wheel axle.


The hook for attaching the cart to the bike is certainly the most difficult part to get because it is not a very common component. It can be found online, in some bicycle shops or, with a bit of luck, in DIY shops. This component can also be built by yourself (we will not go into this in detail here, however) and possibly, if you cannot find better alternatives, replaced by a rope.

Additional elements

Bolts, nuts, washers, perforated plates and plywood can all be easily found at a hardware shop or DIY shop.

Nuts and bolts necessary


The final cost of the cart can vary greatly depending on the condition of the materials used, and the place/time of purchase. As a guide, the total cost will be between €100 and €300. The biggest impact on the final cost is given in particular by the laths and wheels. For example, to buy a complete pair of new bmx wheels can easily cost around ~100€.


Once the tubes have been cut according to the above measurements, it is time to drill and assemble them. To make the process easier you can download this pdf, which you will also find at the end of this article.
To drill the tubes you can use a hand drill/screwdriver with a 6.5mm or 7mm metal drill bit. The holes should be slightly wider than the screws to allow a minimum of clearance and ease of assembly. It is a bit complicated to describe in words how and where exactly the holes should be drilled and how the tubes should be combined, but you can follow the pictures below which are explanatory.

Cart drawing
Detail of the 3 axis connection
Detail of the holes' placement
photo: WS / claudia corrent
photo: WS / claudia corrent