Coup d'Etat
General Description
Coup d'Etat is a chiken tractor that I recently built for my 4 year old daughter (right). She personally selected the colors (purple on purple !).
The coop features 40 square feet of “grazing” area, 15 sq. ft. of enclosed coop, and 4 sq. ft. of nesting boxes. It is suitable for 8 to 12 chickens provided it is moved regularly. The coop can easily be moved by one person. Here are the girls lifting the coop on its wheels:
The overall length of the coop is about 13'6”, which includes 18” of protruding handles, 8 feet of cage, 3' of house, and 1' of nesting boxes.
Special design features
The coop features “space frame” construction with a pair of 2x6's forming the lift-handles of the coop and running it's entire length. These members form the “backbone” of the coop and carry the weight of the other members. Most other members are 2x2 to minimize weight.
The most unique feature of the coup is a pair of retractable 10 inch neumatic casters. These casters pivot on a 4x4 pivot-axle. In the “up” position, the cage section rests flatly on the ground, allowing the chickens to scratch and graze.
In the “down” position, the casters lift the front end of the coop about 3 inches off the ground. The castor and pivot-axle assembly is attached to the bottom of the 2x6 mainframe.
The axle is positioned so that, in the “down” position, the weight of the house section counterbalances the weight of the cage section. Therefore, only about 25 lbs. of lifting force is required to pick the cage end up by the handles, making the coop easy to lift. When in the “down” position, the pivot-axle is slightly “over-square” so that the casters will stay in the down position as the coop is moved.
The casters are raised and lowered via a handle connected to the pivot-axle on the “port side” of the house. The lifting action is assisted by a pair of stiff springs that provide their maximum force when it is most needed (the initial lifting phase). The springs are not required, but do decrease the effort required to deploy the casters, and also help stabilize the coop by maintaining a constant down-force on the wheels when they are in the “up” position, thereby shifting the center of gravity towards the “bow” of the the coop house.
The coop also features a storage bin, between the 2x6 members and just under the nesting boxes, where removable panels and windows can be stored when not in use.
The Cage Section
The first section is a wire covered cage 5 feet wide at the base, tapering to 30” wide at the top. This section is 8' long. Clear height inside the cage is approximately 5' 10”, which makes it possible for children and most adults to stand up inside. The end of the cage section is fitted with a full height door with spring closure for easy access (removed for photo).
The entire cage section is covered in 1/2” square hardware cloth to resist snakes and other predators. The floor of the cage section is covered with 2”x4” square welded wire so that the chickens can easily scratch and forage. The 2x6 mainframe members run the full length of the cage section at knee height. They carry the weight of the 2x2 framing members, and provide perches for the chickens.
The House Section
The house section sits on top of the 2x6 mainframe members. It is 4' high in the “stern”, and 3' high in the “bow”. The house is designed to be “tight” in the winter, while providing ample ventilation in the summer. The entire house section is sheathed in plywood.
The chickens access the house section via a chiken ladder which extends into the cage section. The chicken ladder also has an integral hatch that closes off the house from the cage section. It is hinged so that the hatch can be closed, and the ladder stowed, in one motion.
The house also has a large ventilation port near the roof and facing into the cage section, which can be closed off with a removable panel in winter. In addition, the house has a large triangular 1/4” plexiglass window on each side of the house. These windows can be removed and stowed in the summer.
The “starboard side” of the house includes a large access door which extends almost the whole width and height of the side, facilitating easy cleaning.
The interior of the house is painted white to protect the wood surfaces, increase visibility, and making cleaning easier. The floor is covered with vinyl flooring to aid in easy cleaning. Perches are positioned above the entries to the nesting boxes to encourage the chickens to roost in the house rather than in the boxes.
The roof is composed of plywood decking, covered by tar-paper, covered by tin. The tin extends approximately 6” beyond the house on all sides, except the “bow”, where it extends 13” in order to shelter the nesting boxes.
The Nesting Boxes
The coop includes 4 nesting boxes on its “bow.” These boxes are positioned approximately 6” off the floor of the house, and feature a entry “porch” made from a 2x4, and oval cutouts in the rear of the house to make the nesting boxes more private and cozy (and to prevent nesting material from falling into the house). Each box is about 12” by 12” square, with a height sloping from 16” to 12”. The nesting boxes can be checked for eggs via a “roof” that is piano hinged, and securely fastened with a bungee.
Design Details
The coop was designed in QCAD community edition, an open source CAD software package. The CAD design includes the main structural elements. Of course, I had to tweak things a little and add some elements (such as the doors, etc.) when I got into the actual construction. So, the CAD drawings are merely a guide.
Here is the all elements view:
The Door Frame forms the "stern" end of the coop. Unlike most other structural elements, it is composed of 2x4 material for extra strength.
The following diagram shows the repeating cage frame sections in white, with the "mainframe" elements (2x6's at knee height, and 2x4's at top) shown in yellow. The outside "square" dimensions of each cage frame section match the door frame so that everything will line up right. They are just made of 2x2 instead of 2x4.
Here is a side view of the door frame, cage frame, and mainframe elements:
Finally, here is a top view of the same elements.
Here is the framing and plywood members for the house wall that faces the cage.
Here is a side view of the house framing @ Plywood
Here is the framing for the bottom of the coop (looking from the top down). The framing consists of 2x4's that sit on top of the 2x6 mainframe members.
The following diagram shows how the wheel assembly and nesting boxes integrate into the design. I didn't do detailed drawings for these elements. I just experimented to get them right during the construction phase.
What I would do Differently
I guess time will tell. Right now, there is not much that I would change.
I think I might make the bottom runner and upright supports of the very last cage frame section (next to the house) out of 2x4 instead of 2x2. This would provide a little extra support for that big house hanging off the end.
Also, I would probably come up with a better plan for the spring assist using stronger springs with more leverage. The springs were an afterthought and I just had to work with what I had at that point.
It would also be nice to integrate a feeder & water system in from the beginning. I really like some of the nipple designs that I have seen on this website for a watering system.
