Instruction - Drafting Vehicles
Drafting, or activities where dogs pull some sort of vehicle, is an enormously
broad topic. I tend to broadly categorize the vehicles used into ones
that are designed to have a human occupant and those that are designed
to carry cargo. My discussion here will be limited to vehicles designed
to carry cargo and/or enter in drafting competitions. If you are interested
in a sulky, sacco, sled or other vehicle designed for passengers, you
may want to go to http://www.cartingwithyourdog.com/
and check out some of their links.
Two wheeled vehicles, known as "carts", are the most common type seen in drafting competitions. This is because their smaller size make them more maneuverable and their lighter weight makes them easy to pull. Another feature of carts that is very important to some people is that they are smaller and can usually be partially disassembled for easy transport or shipping.
The main disadvantage of carts is that adding weight can easily upset the balance of the cart - especially if the weight is not well secured and can "shift around". If the weight is too far forward, the shafts will press down on the dog's shoulders much more than they should. If the weight is too far back, the shafts will "pop up" and will actually create a lifting action on the harness. The heavier the weight, the more critical balancing becomes.
One other point I would like to make about cart balance is that the higher the weight is above the axle, the more severe the balance problems will be on uphill or downhill slopes. This is purely the laws of physics and how a high center of gravity will exagerate imbalance when tilting forward or backward. The carts that will have the best balance are those where the weight is closest to the axle. In other words, the distance between the "floor" of the cart and the axle should be as small as possible.
Four-wheeled vehicles, usually known as wagons, are extremely versatile. They are great for parades as you can do a lot to decorate them. They are also great for carrying heavy or bulky loads as the four wheels support the cargo weight while the weight of the shafts on your dog always remains constant. The wagon does not tilt forward or backward as on a single axle cart.
The main disadvantage of a wagon is that it is heavier and bulkier to transport so you typically need a truck or van to haul it around. Also, due to it's size, it is not as maneuverable in tight spaces. However, you can enter drafting competitions with one and I have seen a dog/handler team earn a drafting title using a wagon!
Two key things to look for in a wagon are "automotive"
type steering and a pin that will lock the front wheels in a straight
position. Locking the front wheels straight will make backing up in a
straight line much easier and is important if you enter draft tests.
Automotive style steering is an arrangement where the front wheels of
the wagon turn to the sides when going around a corner but still remain
in relatively the same spot at the front corners of the wagon. This is
a very important feature to keep the wagon from tiping over when turning
sharply. Wagons with a "single pivot" front axle can be prone
to instability because the front wheels get out of their normal position.
The following diagrams can help you see the difference.