When doing major construction products at home involving concrete, it's handy to have a cement mixer around to keep the cement in a pliable state and to save your arms from constantly stirring the concoction. You can rent a cement mixer from someone, but if you do many home improvements involving concrete, that can get expensive. An easier and less expensive option is build your own cement mixer from scratch and save both money and manpower.
Measure the depth and width of the barrel. Snip four paddle shaped pieces from sheet metal using tin snips that are a little less than the width of the barrel and 6 inches long. The paddles will be the device that actually stirs the cement mixture.
Bend each mixing paddle into a right triangle. This shape is ideal for mixing and churning the concrete. Place the paddles into the barrel so they are spaced evenly apart and cover most of the bottom of the barrel. Secure them to the barrel with duct tape and make note of their position.
Drill holes in the side of the barrel and through the paddles on the other side. Drill three holes for each paddle and then, using bolts and nuts, secure them permanently to the barrel with a wrench.
Pour the water and cement into the barrel and secure the lid. Mix the concrete by turning the barrel onto its side and rolling it back and forth. The motion of the rolling along with the paddles on the bottom of the barrel mixes the cement.