Aluminium beer kegs have long been a favourite ornamental vessel to use as a gas tank for "hot rodders." The sturdy aluminium beer keg polishes up like chrome, and they often can be found at salvage yards or junk shops, making the cost quite reasonable. Some kegs are now made from stainless steel, which also shines up like chrome when polished. Keg gas tanks also can be found on old trucks where the original gas tank rusted out. There are a few modifications needed to make the beer keg suitable for a vehicle's gas tank.
Remove the keg bung on the side of the keg (some of the older kegs had a cork installed for the bung). Use a large pipe tap to tap threads into the bung opening. The bung size will vary with different models and year of manufacture.
Insert a pipe nipple three inches long that matches the threads cut into the bung opening. Apply a small amount of pipe thread sealer to the threads on the pipe nipple before threading it in and tightening it with a pipe wrench. This nipple will be the tank filler tube. Place a female pipe cap on top of the 3-inch nipple to be used as a gas cap.
Drill an 11/16-inch hole in the keg next to the newly installed pipe nipple. The hole should except a half-inch pipe thread. Tap the 11/16-inch hole with a 1/2-inch National Pipe Tapered (NPT) thread from the tap and die set. Also drill a 5/16-inch hole on the other side of the extended nipple, tap it with 3/8-inch threads and thread in a 3/8-brass hose nipple.
Drill a 3/8-inch hole in the centre of a forged steel, male pipe plug. Be sure the plug is not galvanised because it will require brazing.
Thread the drilled pipe plug into the 1/2-inch tapped hole. Cut both flanges and remove the threaded line fitting from a 3/8-inch brake line that is about 6 inches longer than the diameter of the beer keg. Slide the brake line into the newly drilled 3/8-inch drilled hole in the pipe plug. Mark a line flush with the top of the 1/2-inch pipe plug. Leave the brake line in the plug and unscrew the plug from the keg.
Align the mark on the brake line with the top of the pipe plug and braze or solder it to the plug so it cannot leak. It is acceptable to braze the line on the top and bottom as long as the braze does not interfere with the pipe plug threads. This will become the fuel pick line.
Trim a quarter inch off the bottom of the brake line that goes into the keg. This will prevent the pickup from drawing sediment from the bottom of the tank. Apply pipe thread sealer to the threads and thread the pickup line into the threaded hole in the keg. Bend the line that extends out of the top of the keg as needed and attach the 3/8-inch neoprene gas line to the pickup.
Remove the female pipe cap that is now the gas cap and clean the keg tank thoroughly.
Use metal straps to mount the keg tank. The tank will now mount horizontal with the nipple and gas line fittings on top.
Use the 3/8-inch neoprene hose nipple to attach a return gas line for venting, or attach a neoprene hose that is run downward with a gas filter, and a small snowmobile-ball-style check valve attached to the other end of the gas filter. If the material around the holes to be drilled is to thin it may require a block of material welded to the keg as reinforcement prior to drilling.
Always wear safety glasses when using a drill or other power tools. Use caution when brazing or soldering. Take care to store all combustibles away from the welding area.