DecadentLinuxUserNumeroUno wrote, on Mon, 16 Feb 2015 19:24:43 +0000:
Right now, the two 16-foot boards to the side of the tree are unattached at the tree (they're screwed into the floating bridge only).
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At the moment, the bridge is wholly supported by the cables and, at the low end, by the posts we first cemented into the ground, when we started this project in the untrampled woods.
It is time for those attachment pins you speak of though...
What we are thinking is that they sell these $100 treehouse attachment bolts, designed specifically for trees (but they're expensive since we'd use probably use four or six of them overall).
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We can't find anything larger than one-inch wide bolts at our local Home Depot, so, we have to order our bolts online, at any measure.
We're debating right now the feasibility of 1 inch or 2 inch bolts, which are about twenty bucks each, versus the treehouse attachment bolts which are five times as expensive.
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So, that's our next question. What kind of bolts make the most sense, keeping cost in the equation (if cost were no object, the treehouse bolts would do quite well).
Thanks for your well wishing. It is one of a kind, so, we're learning as we go. In the end, it will be pretty neat though, don't you think?
It a 10-foot wide suspension bridge, which starts at ground level on a path in the redwoods about a thousand feet (or so) from the nearest anything, and then goes for about 70 feet to a large second-growth redwood, where the deck expands to 16 feet wide.
Sitting on the wide decking, about 40 feet above the ground, will be a two story treehouse, with a bathroom, kitchen, electricity, gas heating, and WiFi Internet (which is something we're experts at by now, given that we all maintain our own radio antennas).
We're thinking of suspending the treehouse with 1/2 inch cable wrapped from the big tree to the two smaller trees cradling the bridge at about the half-way point that you see to the right in this picture.
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So, that way, the treehouse and the suspension bridge would be, in effect, supported separately (or we might make the support mutual and redundant). We're also thinking of adding downward hanging support cables, again from the smaller redwoods to the decking, to add redundancy once the treehouse weight goes up.
One problem we have been having is we have had to constantly adjust the tilt and leveling of the bridge, as weight was added to the end. We ended up buying a dozen cable winches, which are what is holding the bridge up now, one of which can be seen in the left in this photo below.
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We also may erect a few more nets so that we can walk out to the neighboring trees. In fact, if you look closely, you can see two different nets in the picture above. One is to the top left of the picture, and the other is in the center right, in the big redwood tree itself, where someone spent months sleeping in and writing a book, many years ago (his net is still there, 40 feet up in the tree; but we would replace it as it's not safe to use probably, being fifty years old).
Interestingly, that dog is fantastically protective!
When the mountain lion came by, and we didn't know it, he was barking and yelping like crazy and growling, which is not his normal nature. It was only later, when one of the animals got killed, during the storm, where the dog was locked inside, that we had realized what he was making all that commotion about.
So, now, the dog stays outside, with the rest of the animals, to protect them, even during the storms (which may have abated until next winter, by now).
That'd be cheap if it fails with somebody on it...
There's bound to be a local Fastenal outfit nearby or similar but it's not clear what you're comparing.
Those are a constant-diameter shank equivalent of a heavy-thread screw in a hardened material supplied with an integral bolster. I see no reason why one couldn't use any compatible compression sleeve; machining that is undoubtedly a large component of the cost of these.
There's a link to an engineer's report at the site that says ultimate capacity of these in shear is roughly 8500 lb in Doug fir; and Appendix is referenced that compares material properties of other species including redwood but it is, unfortunately not available. I'm quite certain redwood will derate that performance by a pretty sizable chunk but don't know a specific figure otomh.
Plus, again you need at _least_ a 2X (preferably imo 3X) safety factor.
I also noted the recommendation on one of these sites that before using these to get a qualified arborist and engineer involved...methinks we've been over that ploughed ground before that there's little heavy-lifting on the engineering side going on first...
I don't know what kind of bolt you will use, but here is my experience with bolts in a living tree: I fastened some wooden squirrel feeders to trees using lag bolts and washers. In a year the tree grew AROUND the bolt, pulling it through the plank of the feeder. I learned to put a spring between the bolt head and the washer to allow for this.
A threaded SS bar through the tree might be a better option, making it longer than needed so you could back off the nut as the tree grows. Of course you would want a jam nut so that it would not back off by itself.
Redundant would be good. Bridges without redundant support fall down, e.g. the one in Minnesota--see e.g.
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We're also thinking of adding downward
You can't wrap the cables round the trunks, or you'll kill the trees in a few years. Nice big eye bolts are the ticket, I expect, provided you don't put any torque on them (i.e. you have to drill the pilot hole in the direction of the pull). The tree can easily grow around them, unlike wraparound cables. The problem with wood fasteners is that they aren't load rated, unlike machine bolts.
Sure beats turnbuckles.
I think George Dyson probably published construction details of his famous tree house.
A one inch hole drilled through the center meat of a Redwood? Hardly. The stainless bar finishes the task. The tree would have no problem growing around the bar, and even if it did not, it would not weaken the tree ANY significant amount.
If the tree could take a 30 ton tornado force before, now it can only take a 29.8 ton force.
Pretty much negligible, is the point.
You'd break the gear you hang on the pins before you'd break the pins or the tree.
They can easily bring down a full-sized buck, so, a puny human "should" be easy prey. Given that they're experienced hunters, I doubt the human would have much time to see the mountain lion that gets him.
Given that, the mountain lion should "win" against a puny human, particularly with the claws and teeth of the mountain lion wrapped around a puny human's head, neck, and throat.
So, given that, why aren't there far more mountain lion attacks than statistics show?
Clearly, where I hike alone (almost daily), mountain lions abound. We have dead deer, dead goats and sheep, and even videos of a mountain lion dragging a buck taken by a dash cam on our winding road.
The enigma is that there aren't really a whole lot of documented attacks on humans. Sure, humans aren't their standard fare; but how do "they" know that?
I'm not worried, but, I do hike in these here hills almost every day, and, I haven't yet "seen" a mountain lion (although I've seen plenty of dead deer).
Phil Hobbs wrote, on Mon, 16 Feb 2015 17:45:37 -0500:
Actually, if you saw the first pictures, the cables don't actually "touch" any tree (this is the smallest pine at the low end):
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What we did was attach two-by fours to the tree, and then wrap the cables around the two by fours.
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Dunno if that will "protect" the tree or not; but that's why we did it that way (in theory).
You'll notice we doubled the cable at *both* ends also, so that there are always *two* cables at all points, even around the big tree where there is no cable joint at all.
Actually a bolt through the tree is the least damaging way to attach something. The comparison with woodpeckers nests is not valid - they make large holes that greatly interfere with sap flow. Methods wrapping around a trunk can do enormous damage as the tree grows, including effectively ring-barking (hence killing) the tree.
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