Build a homemade rotisserie for your barbecue grill that is motorised and turns the meat at a smooth and even rate to ensure that all sides of the meat get the same amount of exposure to the heat. Rotisseries are also popular because some of the fat melts and runs down the meat into the coals, allowing the proper searing of the meat and reducing the fat content.
Use a grinder to cut the 1/2-inch diameter iron bar stock to the appropriate length so it sticks out 4 inches on either side of the barbecue grill as it rests in the notches on the side that are intended for rotisserie attachments. Sharpen one side on the grinder to make the pointy tip 1 inch long.
Cut the 14 inches of 1/4 inch diameter bar stock into 2-inch segments and use a grinder to sharpen them by grinding down one end.
Get a small steel pipe that just fits over the bar stock with a 1/2-inch internal diameter. Cut 2 inches off of the end of the pipe to use later. Mark off every inch of the remaining pipe with a pencil.
Drill a hole in between every mark with a carbide tipped drill bit that is 1/2-inch in diameter. Weld a nut for a 1/4-inch bolt over every hole, being careful not to obstruct the threads on the nut. Also weld the 2-inch bar stock on the pipe as prongs on opposite sides 90 degrees from each hole in the side of the pipe. Make sure that the prongs are welded on at a 45 degree angle to the original hollow section of the pipe. Cut at every pencil mark with a hacksaw all the way through the pipe. Screw in the bolts.
Take the 2-inch section of pipe and drill a hole 1/2-inch from the end with the same drill bit as before. Weld a 1/4-inch nut over the hole. Screw in the bolt. This piece goes on the tip when it is not needed to skewer the meat as a safety precaution. The other sections of pipe slide into place where you wish to clamp down the meat to the skewer.
Get a large and small motorcycle gear that both accept the motorcycle chain. At the end of the skewer, weld the large motorcycle gear perpendicular to the bar stock. Weld the other (small) motorcycle gear to the motor so that it is perpendicular to the motor axle. Slip on the chain over both gears and weld the motor to the frame of the grill on the legs so that it does not overheat. Add a square piece of metal that you weld to the frame to protect the motor from heat.
Solder up the light dimmer to the motor and drill holes that fit the screws on the light dimmer attach it to a front leg on the grill. Cut the so-called "female" end off of the extension cord and strip the wires for 1/4 inch.
Wire the motor and light dimmer (in series) to the extension cord with the black wire going to the black wire and the red wire to the red wire. Hook up the final wire from the motor as your ground wire. If you do not have a ground wire from the motor, solder the wire to the motor housing. solder all connections and cover all exposed wire with electrical tape.
Plug in the motor with the dimmer in the off position. Slowly increase the speed of the dimmer to the desired speed. Mark this with a sharpie as the maximum speed to use.
Cookbooks are available for rotisserie cooking.
Install a cover for the dimmer if there is any chance that it can get bumped accidentally. High speeds can cause hot parts and grease to be thrown from the grill. Never turn the grill on with the lid in the up position. Always turn off the grill before opening the grill lid. Allow the parts to cool between welding and handling them. Do not touch any part (at all) of the rotisserie when hot and do not let children near the rotisserie or its parts whether in use or not. Keep human bodies away from the sharp parts of the rotisserie. Keep away from the motor when in use and do not let hair, baggy clothes, or anything else that can become caught in the motor or that is flammable near the grill while working. Wear proper protective gear while building and using the grill including safety goggles. Make sure that you follow all laws in your area and that you read/follow all directions/safety information that came with your equipment. Also read safety precautions for equipment similar to the rotisserie that you are building and that you do what you can to keep yourself, others, and property safe. Never operate the motor or plug the device in when wet.