LumberJocks

Reply by Canuckfarmgirl

  • Advertise with us

Posted on wobbly bridge,rope bridge suggestions,

View Canuckfarmgirl's profile

Canuckfarmgirl

1 post in 2727 days


#1 posted 08-30-2012 05:31 PM

We’re just setting up to build a rope and plank suspension bridge from a “tree house” (loft on our garden shed) to a low tree fort in a large maple across the yard. The bridge will be fun but on a practical level will help keep the kids out of the garden I’m trying to establish. I’ve done some reading but haven’t found any good, suitable build plans/designs. There are a couple of sites you might find helpful to design your own:

http://www.thetreehouseguide.com/forum/forum.php?req=thread&id=52 – this one has a description of a public suspension bridge built by a local community. Some very good pointers for load bearing, tension and safety – and bonus, a nice set of pictures to show how to attach the planks to the suspension chain and a attractive way to tie the handrails.

http://www.thetreehouseguide.com/bridges.htm
This one doesn’t have plans but has some good pointers for design and safety for different types of suspension bridges as well as taking into consideration what type of bridge suits what ages.

And for some fantastic esthetic ideas check out Barbara Butler’s playground design website (I can’t even imagine how much this stuff costs):
http://barbarabutler.com/tree%20house%20slideshow/7.1000_1294202719.html

My partner is a engineer so when we get a plan laid out and built (and tested) I’ll post what we’ve come up with.
From the safety point of view there are a few items that keep popping up on websites:

- Your anchors and the material the anchors are attached to (4×4 or 6×6 posts; trees; decking) must be able to support the load you expect on the bridge. There will be a great deal of tension/load on these attachment points. You can calculate this – (http://answers.yahoo.com/question/index?qid=20060810124024AAEeIEZ) or (http://www.ehow.com/how_12164343_calculate-effect-point-loads-catenary.html) and buy the appropriate materials. You can reduce the load on individual points by increasing the number of anchors for each cable (i.e. using a screw carabiner to branch one chain into a Y shape). For climbing we use 2 anchor points per rope as the minimal safe requirement for a dynamic load (i.e. falling), 3 anchor points is better. One website suggested 2 sets of posts (one behind the other, outside one shorter) to distribute load or tension cable anchoring in the main post into the ground or a tree.

- Your main “cables” also need to be able to bear the load on the bridge. Heavy aircraft cable or steel chain (galvinized) ideally but I’ve also seen static climbing rope (not dynamic rope) >10mm diameter listed (expensive option). The cable also needs to be taught when you attach it, it will ease on its own over time.

- Hand rails should be between 3-5’ high and the design/spacing of gaps should be determined by the age of the kids using the bridge. If you want nice colours you could pick up a couple of different weight climbing ropes (i.e. 8 – 10mm for main lines and 6mm for the weaving) but white nautical line looks nice (well, at least for the first season).

- It appears the easiest overall construction is 1×6” decking boards bolted (washers & nuts on underside) to 2 galvinized steel chains and anchored into 4×4” or 6×6” posts or a tree.


DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com