Notes from Windward: #67
Building a Rabbit Tractor
getting the buns out to where the grass is
Our rabbit population is getting to the point were the Vermadise cages don't have enough room to hold them all, so it's time to add to our rabbit housing options by building a Rabbit Tractor.
In animal husbandry terms, a "tractor" is a portable housing unit that is dragged a few feet every couple of days so that the animals can have access to pasture and enrich a patch of grassland before they're moved a few feet to do the same thing on the next patch of grass. This is actually the start of a program of grass management which will play an ever greater role in Windward's sustainability work--for more on the relationship of grass management to sustainability, a great resource is Michael Pollan's The Omnivore's Delimma.
One of the reasons for raising rabbits and chickens in Vermadise is that they give off carbon dioxide and heat--critical resources for our plants in winter. Come the end of May, we take off Vermadise's plastic covering and replace it with shade cloth since in summer the need is to let the heat out rather than keep it in.
Last year we found that even under the shade cloth, the rabbits tended to become over heated, so this year we'll be moving the main pens out into the heavily wooded area just south of Vermadise. Then we'll move them regularly so that their manure will be evenly distributed and enhance an area that we'll be using to grow mushrooms in the years to come. We could keep the pens in one place and haul the manure, but it's just so much more pleasant to move the cages three feet, and leave the manure where it falls.
This tractor will be eight feet long and four feet wide, and separated into two compartments. The first step was to create the 4'x8' frame and cover it with rabbit wire--that's a type of "hardware cloth" that has rectangular holes a half-inch wide by an inch long. It's small enough to give the rabbits support for their feet, but large enough to let the manure pellets fall through.
With the hardware cloth secured to the deck, the next step was to form the ends using 1/2" plywood. The wrap-around design on the ends was used in order to increase the rigidity of the joints since the tractor is desiged to be lifted by one end and drug over uneven ground.
A more closeup view of the way the ends are glued and screwed together.
Now that the tractor has the front mesh in place and the roof screwed on, it's time to mount the wheels. The point of a critter tractor is that it can be easily moved a few feet so that the critters contained can munch on new grass and manure a new area every day or so--and to do that, it helps to have wheels.
I picked up a set of wheels that fit on an non-rotating 5/8" axle at Harbor Frieght. In order to make the mount, a 5/8" rod connector was welded to a nine inch length of angle iron, and then screwed to the bottom of the tractor.
The wheel was mounted by screwing the 5/8" bolt into the rod connector until it was tight, backing it out a half turn and then tightening the jamb nut to keep the bolt from vibrating loose.
A pair of legs was added to the other end of the tractor to hold it level off the ground.
The last task that needed doing was to create access doors for each of the two 4'x4' compartments. The trick there was to cut out 12" by 12" squares in the center of each end, but to stop the cuts just short of connecting.
By leaving just a bit of wood at each of the corners, it was easy to screw on the hinges and latch since you didn't have to struggle to keep the door aligned with the hole. Once the hinges and latch were attached, it was easy to take a saw and cut through the little bit of wood remaining.
Notes From Windward - Index - Vol. 67