If you feel the need to do something, I'd use
b) nylon insert nut
c) star washer
over split-ring locknuts. There's a camp that have a theory that they
serve no useful purpose at all
for the NASA Fastener Design Manual).
BTW, for overhead use, malleable wire rope clips are not recommended;
drop forged are ok. For rigging overhead lifts, cable clips aren't
allowed at all, but with the above caveat on type they are allowed for
static overhead loads.
for some other specifics.
They *are* designed for this purpose, are they not?
They didn't come with lock washers.
I'm sure we have nothing against putting them on; but, if they really
needed lock washers, wouldn't they have come with them?
Threadlock isn't a bad idea.
In fact, it's a great idea.
Wish I had thought of that sooner; but we still have the backside of the
big redwood downhill to add the extra wire to, so there's still time yet.
G. Ross wrote, on Sun, 28 Sep 2014 13:39:26 -0400:
We plan on balancing the load.
Maybe that won't work - maybe it will.
If we need to, the turnbuckle can be added (somehow) as a rube goldberg;
but at the moment, the load is supposed to be balanced when we build the
bridge hanging from the cables.
Dan Coby wrote, on Sun, 28 Sep 2014 12:34:27 -0700:
The tree house will be where our cargo net currently is.
That's roughly half way from the uphill pine to the downhill big redwood
(with two little redwoods, side by side, in between).
The steel cables can handle 14,000 pounds each.
That's 28,000 pounds (because we maintain a double cable throughout).
We don't know how much the bridge & treehouse will weigh, but if it's
close to or greater than 28,000 pounds, then we have a problem.
How much do you think a treehouse will weigh?
You also have to consider the geometry of what you are creating. If you
are tensioning the cables for very little sag then the forces in the
cable can be many time the weight of the tree house. Without knowing
exactly what you are creating then I cannot guess. That is why I asked
if you had any ideas of the forces in the cable.
I do not know what you are planning upon building. That was why I asked
you. If you are talking about the tree houses that we built as kids with
a plywood floor and a few boards and a tar paper roof then only a
couple of hundred pounds. If you are talking about some of the multi
story creations that I have seen on TV then many tons.
Have you allowed for a windstorm where the trees may be moving in
opposite directions to each other?
Temperature affects the length of the wire rope, have you allowed for
maximum and minimum temperatures?
You want some sort of shock absorption built in too. Old antennas used
porcelain blocks for joining cables, the porcelain would shatter under
unexpected loads giving the cables a chunk of extra slack to avoid their
collapse by stretching beyond limits.
May I suggest you find an engineer to look over your design? I'm not
one, but can think of a few ways for this to go wrong already including
the clamps failing etc.
Suspension bridges are close to what you are building - read up on the
design criteria for these. Seat of the pants design may give you another
PS, it looks like a lot of fun though!
Yup. 45 foot pounds. Thanks.
I'm relaying all this information to the neighbor as I'm just a helping
hand. I jokingly refer to myself as the "union worker" because I make
jokes about OSHA getting on their case every time I have to climb one
of those ladders!
I do apologize that updates are slow, as I can't snap a picture unless
I'm there, and the treehouse is only worked on during the weekends, and
I'm not always there to help, but I will try to snap pictures as we
Dunno if I should append all to the same thread, as the way "I" read this
newsgroup is that I only look at the threads from the last day or three.
Dunno how others look at older threads, 'cuz this could take a few months
Dan Coby wrote, on Sun, 28 Sep 2014 20:32:48 -0700:
We "tensioned" the cables, by hand.
What we literally did was put a broomstick through the 60 pound wooden
spool of 250 feet of 3/8" steel cable and we mounted that on two chairs
about 15 feet downhill of a big pine tree.
Then we went uphill to that pine tree at a point about 15 feet off the
ground and then back to the chairs with the spool of wire.
At that point, we tied a rope to the end of the wire, and we walked the
wire downhill a little less than about 100 feet to a big redwood.
At that redwood, we climbed up to the same height as the pine (which,
since it's downhill, is about 40 or so feet up in the air) and we pulled
the rope with the wire cable attached.
Then we pulled the rope which pulled the cable back up the hill back to
the point on the path 15 feet below the pine, where we pulled it tight by
hand, and then clamped the 8 clamps on.
Then, we simply slid the cable around the big redwood and slid it around
the pine, until the cable clamps were symmetric around the pine, as shown
in the last set of pictures.
I won't mention the fact that we accidentally crossed the cables because
we went around the big redwood the wrong way, as that's embarrassing to
mention. Nor will I mention how many times we got hung up in the branches
between trees, necessitating mid-air precarious surgery on the trees.
Given all that, I wouldn't call the tension all that tight. You can see
the sag in the photos. Maybe it sags, oh, I don't know, about 5 to 10
I think we're talking just a plywood box, with a deck. I should mention
that there will be anchors on the two little redwoods, so, the treehouse
won't actually be floating on all sides. The bridge *will* be floating
though. It should be fun once it's done and wired for Internet. It has a
great view once you're up in the redwoods.
John Robertson wrote, on Mon, 29 Sep 2014 09:54:57 -0700:
Only that each cable supports 14,000 pounds! :)
Hmmmmmm.... The cables don't "give" a little when you walk on the bridge
that would be hanging below it?
The neighbors are all owners of companies and people with graduate
degrees, so, they *are* engineers (of all types). The one having the most
fun with the design is the retired carrier fighter pilot. :)
Yes. I'm told the catenary will turn into a parabola once we hang the
bridge off of it. Since the bridge starts uphill about 15 feet above the
trail, it will be fun to just step onto the bridge, at the level of the
trail, and then walk "downhill" level but going higher and higher above
the steeply sloping ground, to get to the two smaller redwoods in the
middle of the span.
At that point, we will be in the "treehouse" which will have a deck and
WiFi and a great open view of the mountains.
Then, if we want, we can walk further to the *big* redwood, which will
have sleeping quarters (hammocks and cargo nets) for the nights we'll
It should be fun, once done, and I'll try to keep you guys informed; but
I personally am not designing or building it; I'm just the free help (we
all have Spanish nicknames when we do free labor. I'm "Rodruigo", and my
wife's nom-de-labor is "Marisol", for example).
I keep threatening that I'm gonna call OSHA on them if I fall or if they
don't provide cold soda (the free soda has been warm, to date).
Hmm, well with two separate cables your power requirements are fine,
just run them on 24VAC @ 50A (120VAC @ 10A equivalent) and then use step
up transformer or AC to DC regulators to power everything in the tree
house. No unsightly wires!
(Please post followups or tech inquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
Speaking of doublechecking my work ... notice this picture:
It's how I *finally* learned how to hook up the ascender so that when I
climb the precarious ladders, the ascender just slides *up* the rope,
with effortless ease, but, it *locks* into place instantly if/when I fall.
You won't notice, but, there are *two* mistakes that I didn't make in
*that* picture, but which I had made when I *first* hooked up:
The amber carabiner placement is critical:
1. It goes AROUND the rope (not outside the rope).
2. It goes on the TOP (not the bottom of the ascender).
I learned both those tidbits the hard but gentle way.
At first, I had hooked the carabiner on the bottom of the ascender,
thinking that the top hole was already *busy* with the rope, but, what
happened when I tried climbing up the ladder was that the ascender, which
is clipped to my waist by a locking carabiner, flipped upside down as I
went up the ladder.
Then, I tried hooking the amber carabiner to the top hole, which
prevented the flip, but which actually hindered the rope movement if it
was outside the rope.
So then I hooked the amber carabiner *around* the rope, and then
everything worked smoothly, as it should.
As I climb the ladder, the ascender just slips on the rope, causing no
problems whatsoever; but the moment I descend, it locks instantly in
Trial and error ... but it works nicely now that I know how to set it up.
I had forwarded this thread to the owner of the treehouse in the redwoods, who replied with the following ...
People worry too much.
I simply design for 10 times the expected load, and pay the premium.
Trying to finely engineer the solution where torque and special fasteners are important
is a way to save money, and I'd rather spend the money and not waste my time.
I've never seen a malleable cable clamp. Drop forged ones are cheap, and I use more than
normal anyway, not because I think they are needed, but because they help keep the cable
from slipping out of place on the wood block spacers.
The reason for keeping the U-bolt on the dead end of the cable is because the saddle has
a lot more surface area, and thus does not reduce the strength of the cable as much as the
U-bolt does. But they make dual-saddle cable clamps, for those who don't use the over-engineering
approach I do.
Each cable can support 7 tons, so the total weight of treehouse and occupants can be 14 tons.
(Although there will be other supports besides the cable -- one end will rest on the ground, and
another end will be anchored to the tree, and there may be other support cables used just to
make installation and leveling easier.)
If half of the weight is treehouse and the other half is people, we have 7 tons of treehouse
possible (although the actual treehouse will probably weigh less than 1.4 tons fully furnished),
and 7 tons of people (70 people, if they are all 200 pounds). I doubt we will ever have 70 people
in the treehouse -- they'd be shoulder-to-shoulder.
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