What size timber for Monkey Bars?

[jmsgld]

Kids 5 & 7 years old, want some monkey bars from their play house ( built of 4" x 4" posts, approx 5m tall to ridge). Monkey bars to be 4m long ( so that they can climb into a tree from there), one end fixed to the playhouse, the other with free standing uprights, braced.

I have a load of timber left over from re-roof.

I am concerned about the span, not so much for the kids as the 7 year old is only 22kg, but should an adult have a go. I guess if I put the braces at 45 degrees, I could easily knock 1m off each end of the span.

The timber I have left over (all C24) is 2 x 4", 3 x 4", or 3 x 7".

I am guessing that the 2 x 4" would need an additional support in the centre to half the span. The 3 x 7" would surely be overkill?
Could I get away with the 3 x 4" ?

Thoughts? thanks

[biggiles]

The "Sagulator" (online tool) will show you whether it will be ok or not. Very handy tool, probably best to assume it's just one "side" so it's always strong enough.

[TA14]

One quick observation: for that span 7" x 2" C16 would be a floor joist size but here you don't have the lateral stability from the floor boards so 7" x 3" C24 does not look crazy / mad-oversized.

[Vincecj]

We built these for a job near Exeter. 4" rounds, 12' long

[paulrockliffe]

TA14 said:

One quick observation: for that span 7" x 2" C16 would be a floor joist size but here you don't have the lateral stability from the floor boards so 7" x 3" C24 does not look crazy / mad-oversized.

Yeah but in reality 4" x 2" is going to have a bit of flex in it when I'm swinging in the middle of it, but it's miles off breaking. 3" would be fine for the kids while an occasional adult might struggle to keep a good rhythm because of the bounce, it's not going to snap.

Housing standards for this are primarily concerned with the ceiling underneath not cracking and falling off rather than taking the weight above because that will become a problem before anything else.

[jmsgld]

Many thanks, your 4" rounds look great, but I have spare timber.

From a quick look at the sagulator, 4 x 3" (selected white spruce, no option for C24) should be absolutely fine, there will be a bit of bounce as suggested with adult weights, but static centre load of 80kg on a single piece only produces 4mm of sag.

[squicky]

Out of interest, what are you using for bars? I'm currently pondering building some for my daughter too.

[Vincecj]

squicky said:

Out of interest, what are you using for bars? I'm currently pondering building some for my daughter too.

We use QuickClamp handrail. 27mm dia. Then two or three lengths of threaded bar to stop them separating.