I don't know if this is "home improvement" since it is about an item in my garden but it is not about "gardening and landscaping" either so I am going to ask it here in the hope that, since it I think the skillset required to answer questions here probably overlaps so here goes…
I have bought a swing for my child and she loves it but the problem is that it does not swing straight. It is attached to a branch on a tree and as you can see in the photo below, the branch is not straight and, therefore, the ropes connecting either side of the swing are different lengths. Sadly I have no other tree to attach it to.
Try as I might I cannot get a good swing action on it (the seat turns during the swing even if I am very careful and apply an equal pressure push). I have got a spirit level out and the seat is horizontal (as far as the accuracy of that is able to ascertain) but it swings all wonky. I don't know, I have been tightening and re-tieing knots for months now and my wife is getting angry and the child starts to look at me with a concerned experssion every time I sit her on it to "give it one last go."
Is there a technique for fixing this thing? Should I build some sort of triangular wooden structure under it so the ropes are the same length?
Best Answer
A triangular wooden structure as you describe should work if the ropes are the same length and the hooks the ropes are attached to are both hung vertically. Pendulum period depends on rope length, so the set up you currently have couples pendulums having two different periods. That's a recipe for unstable swinging. Also, the angle pictured on the left attachment point will cause wobbling even if you correct the length problem. That's because it causes one rope to oscillate on a different axis* than the other.
For maximal directional stability in swinging, you want the ropes attachment points to the limb to be set a few inches wider than their attachment pints to the seat of the swing
*Actually given the hookup, a different set of axes, but that overcomplicates things. Just work to preserve symmetry between the two ropes and all will be well.