Building a low cost chicken tractor doesn’t have to mean that it is flimsy or low quality. In many cases they can be built quite economically using recycled parts. An a frame design (so-called because of its triangular shape like an ‘A’) is probably the simplest tractor to build. The framing could be done with pieces of wood you have lying around or are able to re-use from an old fence, or pallets, or perhaps purchased cheaply from a builders yard or the classified ads of someone wanting their old shed torn down etc. There are many opportunities for free or cheap materials out there if you are on the lookout for them. Even when purchasing 2x4s for the job many find the total cost is often under $50 (depending on size) and cetainly under $100.
Many people just use chicken wire for the run part of an aframe but that is not really strong enough to withstand any serious attempts from predators to get in. The strongest wire is galvanised steel mesh with small holes (so nothing can reach in easily) such as hardwire cloth. You also want there to be an area for them which is totally covered even if your chickens are not going to be living in it over night – this is so that they can feel more secure and can go behind a wall if there is a predator on the other side of the wire, rather than be eyeball to eyeball with it. It also, perhaps more importantly, gives them some shelter from the wind and rain and somewhere to go that is shaded from the sun.
Adding wheels to the base will allow it to be moved more easily although with small chicken tractors, especially if they are made from light-weight materials, they are usually fairly easy to lift and be moved by two people.
Because they are generally lightweight and not fixed to anything you will need to consider strong winds etc. and also how easy it will be for something to dig under into the coop (or have your chickens accidentally dig themselves out when dustbathing!). A wire ‘skirt’ around the base of the coop should help deter things like rats trying to dig in.
The video below shows work on building an A-frame coop on wheels, starting with the ramp for their chickens to come down from the house part (this particular coop has two levels).