From Handyman USA Wikiplanz
A Basic Design for Two Swings
- 4 each 4 x 4 x 10' Pressure Treated
- 1 each 4 x 4 x 8' Pressure Treated
- 3 each 2 x 4 x 8' Pressure Treated
- 2 Pair Swing Hangers
- 4 each 1/2-13UNC x 6" Long, Galvanized Bolts
- 2 each 1/2-13UNC x 10" Long, Galvanized Bolts
- 4 each 1/2" X 5" Hex-Head, Galvanized Lag Screws
- 4 each 1/2" X 3" Hex-Head, Galvanized Lag Screws
- 20 each 1/2" Washers
- 6 each 1/2-13UNC Hex Nuts
- 1/4" Nylon Rope
- Cut the notch at the top of each leg. To do this, cut a 1-1/2" by 3-5/32" slice off the top of the 4x4x10s. Set your circular saw to a 1" depth, and chop out the notch. Break off the slices with a screwdriver, and clean out the smaller pieces with a chisel and hammer.
- Next, assemble the top joint. To do this, drill first through the top beam (the 4x4x8). Then set the top beam on each leg, and drill thru the leg as shown in the picture. Once a hole is drilled thru all three pieces, assemble one of the joints with a 10" bolt.
- Fit up and cut the brace between the two legs. Drill and attach with two 6" bolts. Note that this brace goes on the inside of the legs.
- Along the top of the top beam, mark a distance 19" from the edge. Use a square to ensure that the legs are square to the top beam. Cut a 2x4 close to, but slightly longer than needed. Template the notch on the corner brace. Cut the notch, and fit up. Trace a line for the top angled cut. Cut the board, and check the fit. Pre drill a hole for the upper lag screw, then attach with one of the 5" long lag screws. Leave the screw one or two turns loose.
- Unless you have a high platform to work off, you'll find it easier to disassemble the legs to the top beam, and then assemble the legs on the other side. Repeat steps 2, 3 & 4.
- Drill holes for, and attach, the swing hangers at 19" and 43" from each end.
- Reassemble the second pair of legs. This will require a ladder and two people. Drill holes for, and install the 3" Lag screws from the leg brace to the corner brace.
- Give a final tightening of all of your bolts, and tighten down the corner brace lag bolts. Hang your swings - base your rope length off of the user's height.
- Some sort of soft ground material at the site is recommended such as pea gravel or mulch.
- Pay attention to weight capacities when you purchase your swing hangers and your seats. Higher weight loads will accommodate kids getting older, and will probably last longer.
- Attempting to use this device in a circus will void your warranty. .
- I built this for my niece, who is still tiny (see picture). When her 160-lb uncle used this, the legs jumped off the ground. Various sources I looked at prior to building this recommended attaching 2x4 stakes on each leg, and sinking them approximately 18" into the ground.