I was light and the grass in front of the swing was thick and deep, so I managed not to break anything. The swing's seats were solid wooden two by sixes, which, though capable of giving you a broken nose or concussion, were really easy to jump out of. Sadly, insurers these days require us to use those rubber, butt-hugging flexi-seats on the grounds that they won't knock children unconscious who walk in front of them. I believe this leads to children being less careful about what they walk in front of, but I do understand the safety people's concerns.
That said, here's how to make a nice two seater swing. Make it a little wider and give yourself about five feet of clearance between the swing and the posts and you can play a nifty game with the kids called "Cut the Butter". (I'll describe how that's played sometime in a later post, in case you missed it growing up).
Dig the bottom of the hole wider than the top. Do this by angling the attack of the post hole digger so that you cut out a bell shaped bottom for each hole as shown in the drawing to the left.
Insert the posts in the holes. Turn them so they are squared with one another. The posts should be six by six posts and 10 to 12 feet long or longer depending on how tall you want your swings. Buy pressure treated posts. You want this swing to last a long time and be safe for the kids to use. Always over-engineer where playground equipment is concerned.
Lift the posts and pour pea gravel around the base - about 2 inches below the bottom of the post so each sits on top of a layer of gravel and then another 4 inches around the base as shown at the left.
Allow the whole thing to sit for at least 24 hours for the concrete to thoroughly cure. Fill the rest of the hole with dirt and pack it down tightly.
Clamp a 2 by 8 inch pressure treated board to one side of the two support posts as shown on the right. Get a couple of large Vice Grips (TM) clamps. You'll be so glad you have them. They are well worth buying just for this project. Another way to do it is to hold them in place with a nail on either end till you drill the bolt holes.
Drill 5/8 inch holes through the ends of the cross-members and the posts. Insert a ten inch long 5/8 inch carriage bolt and flat washer through the holes and bolt them in place with a flat washer, lock washer and nut.
You can also use a three foot long 6 by 6 instead of two shorter ones. It makes it easier to place the support bolts and vertical eyes through the blocks without drilling them too close to each other. For an even sturdier solution run a 6x6 the length of the gap between the cross members. That sucker ain't goin' nowhere. Space the long carriage bolts between the vertical eye-bolts for the swing. Costs a little more with that much lumber up top, but then, peace of mind always costs a bit more!
Drill a half inch hole vertically through chain support blocks. Offset the hole an inch from the carriage bolt through the chain support blocks. Push each ten inch long, half inch carriage bolt through a flat washer and through the vertical holes in the blocks and screw a half inch screw-on threaded eye bolt onto the end of the carriage bolts.
You are ready to go. Simply add kids.
P.S.: I forgot to include a materials list. This bad boy will look nice and last nearly forever, but the materials can add up. I scrounged a lot of my timbers. I used some long scrap timbers I found from a demolition project on an old building. I got them cheap and they gave us a rustic look. I had to sand the splinters away and seal with a heavy clearcoat because it was on a children's playground, but it looked good and still saved me money. Anyway, here's the list -
2 treated timbers, 6 by 6 inches by 12 feet
5 bags concrete mix
2 treated boards, 2 by 8 by 16 feet You can use
4 pieces of treated timber, 6 by 6 inches by 8 inch or two three foot long six by sixes
1 Box 16d nails
6 Carriage bolts, 5/8 by 10 inches long
12 flat washers, 5/8
6 nuts, 5/8
4 Screw-on half inch threaded eyes with half inch carriage bolts, 10 inches long
2 Swing, chain and hook assemblies
Post hole diggers
Wheelbarrow, shovel and water hose
Large Vice- Grip (tm) C-clamps
Drill and bits
When I built this thing, I over-engineered the heck out of it because it was going up on a day care center playground. That makes it more expensive, but also longer lasting and sturdier. My license rep was skeptical that I could pass safety inspection with a homemade wooden swing, but I did. I recessed all the bolt heads for added safety. You can do that with a paddle bit to avoid people catching themselves on the bolt heads, but for this swing, the bolt heads are out of reach so unless you want to do it for aesthetic purposes, it really isn't necessary. My license rep was impressed anyway.
The swing chains and seats can be purchased complete. You can get the cheap ones at Wal-Mart for not very much and just hang them when you've finished building your swing - easy peasy. If you want the heavy rubber belted industrial strength swing seats, you can order those on-line from a playground supply company and they do get pricey. If you want to go traditional, you can cut a seat out of a 2 by 6 or 2 by 8, bolt U-bolts into the ends and hang it from chains with "S" hooks. Just bend the U-bolts in the center to make a sharp "V" shape so the seat doesn't slip and dump the rider.
Caution: I like the wood seats, but with kids around you have to be very careful with them. Wooden seats can whack the little ones in the heads and cause concussions, lost teeth, black eyes and all manner of head trauma. I waited till mine got older before I put in a wooden seat. I went to wood mainly because their mama loves to swing and doesn't like the rubber sling seats (too constricting). I would never put wooden swing seats on a playground where kids are unsupervised or only minimally watched.
With scrounged material I spent about $100 building this one back in 1987. With careful shopping you should be able to do it for a little more than twice that nowadays if you shop carefully. The big cost will be the six by sixes. You can do it with 4 by 4 uprights, but they will tend to flex more and can work themselves loose in the ground, so you'd best dig a larger base hole and put in more concrete if you use smaller timbers. I stuck with the larger timbers because my family are very large Texans and we like to swing high!
With costs for building materials skyrocketing, the best way to figure the costs for this is to carry the materials list down to Lowes and check prices. Also check old downtown building demolition projects. They sometimes tear out big old solid beams that have been cured indoors for ages. If you know someone involved in the project, they might give them to you for a good price. You can treat recycled beams yourself with outdoor wood treatment and spray on water seal. If you have time, you might want to hold off on your project a few months till you find the right wood for the project. I love aged wood anyway and for outdoor garden projects, it can really give you a stunning effect.
Hope this helps. Good luck with your project. It's worth the effort and cost, I promise.
A backyard swing is good for the soul. There have been scientific studies.
Here's a diagram for how to recess the bolts and nuts to prevent injury to the kids. Once the bolts are tight, cut off any excess even with the top of the nut or bolt head. Use a hacksaw or saws-all with a metal cutting blade to cut off the bolt. Use a file to smooth any jagged edges.