If you're handy and want to save some money, you can build a homemade treadmill. A treadmill must hold your body weight and withstand vigorous movement, so consider your safety when constructing a homemade treadmill. You can also save energy with a homemade treadmill, if you design a ramp that depends on your efforts rather than electricity to keep it moving.
A treadmill may include these parts: motor with a 1.5 to 3 horsepower to provide power to the treadmill belt; a flywheel to regulate the belt under the impact of your weight and moving feet; a frame to hold the parts of the treadmill together; rollers to keep the treadmill belt running smoothly; a deck to support the running surface; a belt or possibly two belts; and an electronic display console. On a homemade treadmill, you could skip the motor and display console. Consider your weight and workout intensity when choosing material for the frame -- aluminum holds more weight than steel. Rollers with larger diameters may keep the treadmill running more smoothly.
An alternative to building a homemade treadmill entirely from scratch is purchasing a manufactured treadmill in need of repair. You can purchase one inexpensively at a garage sale and replace parts as needed.
You can build a homemade dog treadmill, sometimes called a carpet mill, similar to the one you design for yourself. You may wish to include a motor on the treadmill for your dog to encourage proper use, but you could train your pet to operate a manual treadmill. The dog treadmill should include a slight incline. Design a walking board long enough to accommodate your dog's stride.
If you like to multitask, you could outfit your homemade treadmill with a detachable desk. Don't use this during a vigorous run, but you could get some work done while walking on your treadmill. If you want to work and work out at the same time, keep your pace between 1 and 2 miles per hour. You can burn 150 calories an hour working at your desk and walking on the treadmill. If you enjoy wireless Internet access and add a hands-free headset to the arrangement, you will net a fully functional work and workout space.