Just to update this thread, we completed the 250 feet of steel cabling
today by lashing the two ends together using these cable clamps:
https://c3.staticflickr.com/3/2942/1...845164f7_c.jpg

To keep the cables from cutting into the trees, and to allow the trees to
grow outward, we put up a series of these wooden standoff blocks:
https://c3.staticflickr.com/3/2945/1...94070f9b_b.jpg

You'll notice that we doubled the cables as they wrapped around the trees
so that the strength is always two time 14,000 pounds, at all times:
https://c3.staticflickr.com/3/2944/1...3de04150_c.jpg

Here, you can see the two cables, hanging as two catenaries, from which
we will hand the suspension bridge:
https://c3.staticflickr.com/3/2943/1...edf3ba0c_c.jpg

We're starting to get used to working in the heights, as you can see by
this photo of my neighbor coming down from disentangling the lines:
https://c4.staticflickr.com/4/3901/1...7461b64d_c.jpg

As you can imagine, we wear harnesses and we have static lines hanging
from all the trees, as you'd be amazed how many times you need them:
https://c3.staticflickr.com/3/2945/1...61137c64_b.jpg

In fact, my unenviable job today was to stand at the TOP of this ladder
and position the cables, which I did with two hands on the cables so I
had to be wearing a harness or I would have fallen off in no time:
https://c4.staticflickr.com/4/3870/1...f45d19e2_b.jpg

I'll let you know when we drill the redwoods to put in the tree bolts,
which will anchor the house; but first, we're working on the suspension
bridge (you can see our cargo netting in some of the pictures above).

Tomorrow we're putting up WiFi on a neighbor's roof, so we wont' be
working on the treehouse until next week.

OFWW wrote, on Sat, 27 Sep 2014 23:55:45 -0700:

If you installed these without lock washers I would recommend you go
back up and at least put nylock nuts as safety nuts. Heating and
cooling will cause those nuts to walk off the u-bolts.

Thank you for that safety suggestion!
That is a good point. Safety is paramount.

This treehouse 50 feet in the air in the redwoods has to outlast us
and it has be safe at all times.

Since we didn't use lock washers on the steel clamps, I will advise
my neighbor and I will snap a picture of the results for you.

You will notice that we doubled up the two ends of the steel cable
as they wrapped around the tree, so that we'd always have two cables
supporting the bridge.

On the big tree, 125 feet away, we will add a wraparound additional
steel cable, so that the middle also has two cables.

Any other safety ideas are welcome, as we're just at the point now
where we can start hanging the suspension bridge from the two steel
catenaries.

For example, you will notice that we followed the rule as shown he
http://www.pirate4x4.com/tech/billav...dead%20end.jpg

Following that diagram, we put the "saddle" of the clamps on the
"live end" (the mnemonic we used was "don't saddle a dead horse").
http://www.pirate4x4.com/tech/billav...pe%20clips.jpg

Any other tips are welcome, as we're just now at the stage where
we have the ability to build the 125 foot long bridge starting
about 15 feet up in a pine, and then going straight across a
steep slope through the set of two redwoods, and then on to the
really big redwood 125 feet down the slope.

The treehouse will be in the middle of the bridge.

On 09/28/2014 11:50 AM, Danny D. wrote:
OFWW wrote, on Sat, 27 Sep 2014 23:55:45 -0700:

If you installed these without lock washers I would recommend you go
back up and at least put nylock nuts as safety nuts. Heating and
cooling will cause those nuts to walk off the u-bolts.

Thank you for that safety suggestion!
That is a good point. Safety is paramount.

This treehouse 50 feet in the air in the redwoods has to outlast us
and it has be safe at all times.

Since we didn't use lock washers on the steel clamps, I will advise
my neighbor and I will snap a picture of the results for you.
....

I don't believe there's any reason to think the environmental thermal
cycling has any chance of loosening those sufficiently to worry over
from that standpoint.

We've got several miles of cable in feedlot fences with the same style
cable clamps with tension on them sufficient for retaining cattle while
working them. They've been installed w/o lock washers for some 60 yr in
SW KS which is quite extreme in both temperatures and particularly in
changing in extremes over very short time frames relative to CA redwood
country. Not a single one has come loose on its own in that time.

What I'd suggest and use would be

a) at least two/ location, preferably three, and

b) for looped connections (very few in this application; the cables are
terminated at the clamps which are welded to rod)(+), we also used
compression connector at the end to hold the cut end to the running cable.

(+) The rod is then connected via a turnbuckle for takeup tensioning to
a second rod which penetrates the end post/tie.

--

dpb wrote, on Sun, 28 Sep 2014 12:04:29 -0500:

I don't believe there's any reason to think the environmental thermal
cycling has any chance of loosening those sufficiently to worry over
from that standpoint.

I don't know. But, safety is cheap, if you know what to do, so I'm not
against the advice at all. This has to handle kids and adults, and has to
outlast us.

They've been installed w/o lock washers for some 60 yr in
SW KS which is quite extreme in both temperatures and particularly in
changing in extremes over very short time frames relative to CA redwood
country. Not a single one has come loose on its own in that time.

This is great information, as your environment is the same as ours!
We're on steep hills in California, in the redwoods.

What I'd suggest and use would be
a) at least two/ location, preferably three, and

You can see that we used *eight* on the connection he
https://c3.staticflickr.com/3/2944/1...3de04150_c.jpg

On 09/28/2014 12:11 PM, Danny D. wrote:
dpb wrote, on Sun, 28 Sep 2014 12:04:29 -0500:

I don't believe there's any reason to think the environmental thermal
cycling has any chance of loosening those sufficiently to worry over
from that standpoint.

I don't know. But, safety is cheap, if you know what to do, so I'm not
against the advice at all. This has to handle kids and adults, and has to
outlast us.
....

If you feel the need to do something, I'd use

a) threadlock

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
(http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19900009424_1990009424.pdf
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.

See

http://blog.uscargocontrol.com/how-to-use-wire-rope-clips/

for some other specifics.

--

dpb wrote:
On 09/28/2014 11:50 AM, Danny D. wrote:
OFWW wrote, on Sat, 27 Sep 2014 23:55:45 -0700:

If you installed these without lock washers I would recommend you go
back up and at least put nylock nuts as safety nuts. Heating and
cooling will cause those nuts to walk off the u-bolts.

Thank you for that safety suggestion!
That is a good point. Safety is paramount.

This treehouse 50 feet in the air in the redwoods has to outlast us
and it has be safe at all times.

Since we didn't use lock washers on the steel clamps, I will advise
my neighbor and I will snap a picture of the results for you.
...

I don't believe there's any reason to think the environmental thermal
cycling has any chance of loosening those sufficiently to worry over
from that standpoint.

We've got several miles of cable in feedlot fences with the same style
cable clamps with tension on them sufficient for retaining cattle while
working them. They've been installed w/o lock washers for some 60 yr in
SW KS which is quite extreme in both temperatures and particularly in
changing in extremes over very short time frames relative to CA redwood
country. Not a single one has come loose on its own in that time.

What I'd suggest and use would be

a) at least two/ location, preferably three, and

b) for looped connections (very few in this application; the cables are
terminated at the clamps which are welded to rod)(+), we also used
compression connector at the end to hold the cut end to the running cable.

(+) The rod is then connected via a turnbuckle for takeup tensioning to
a second rod which penetrates the end post/tie.

--

I agree with the turnbuckle, or some way to adjust the tension in case
the bridge wants to tilt to one side.

--
 GW Ross 

 1st Law of Thermodynamics: Go to 
 class!! 

G. Ross wrote, on Sun, 28 Sep 2014 13:39:26 -0400:

I agree with the turnbuckle, or some way to adjust the tension in case
the bridge wants to tilt to one side.

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.

On 09/28/2014 4:14 PM, Danny D. wrote:
G. Ross wrote, on Sun, 28 Sep 2014 13:39:26 -0400:

I agree with the turnbuckle, or some way to adjust the tension in case
the bridge wants to tilt to one side.

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.

I'd suggest it (balance control) will become mandatory and mayest as
well design it in from the git-go. W/ as much effort as you're
investing, this is a pretty minimal addition.

--

On Sun, 28 Sep 2014 16:50:02 +0000 (UTC), "Danny D."
wrote:

Following that diagram, we put the "saddle" of the clamps on the
"live end" (the mnemonic we used was "don't saddle a dead horse").
http://www.pirate4x4.com/tech/billav...pe%20clips.jpg

Just curious. Is there a torque spec for those clamps? Or ...

On 09/28/2014 12:31 PM, Oren wrote:
On Sun, 28 Sep 2014 16:50:02 +0000 (UTC), "Danny D."
wrote:

Following that diagram, we put the "saddle" of the clamps on the
"live end" (the mnemonic we used was "don't saddle a dead horse").
http://www.pirate4x4.com/tech/billav...pe%20clips.jpg

Just curious. Is there a torque spec for those clamps? Or ...

Yeah...just noticed Danny has referenced the Crosby data so he
undoubtedly has seen the table there...for the 3/8", they recommend 45
ft-lb.

http://www.fdlake.com/wrclips.html

I still think the clips should be used as delivered by the manufacturer
(w/o any additional locknut, that is), with, at most, some threadlock or
perhaps substituting a nylok nut. If were really, really, paranoid,
guess could test the fully-torqued position and then drill and go to
castle nut and pin on a couple.

But, thermal expansion is not an issue that's going to cause any
loosening of the fasteners if torqued.

--

On Sun, 28 Sep 2014 13:54:02 -0500, dpb wrote:

On 09/28/2014 12:31 PM, Oren wrote:
On Sun, 28 Sep 2014 16:50:02 +0000 (UTC), "Danny D."
wrote:

Following that diagram, we put the "saddle" of the clamps on the
"live end" (the mnemonic we used was "don't saddle a dead horse").
http://www.pirate4x4.com/tech/billav...pe%20clips.jpg

Just curious. Is there a torque spec for those clamps? Or ...

Yeah...just noticed Danny has referenced the Crosby data so he
undoubtedly has seen the table there...for the 3/8", they recommend 45
ft-lb.

http://www.fdlake.com/wrclips.html

I still think the clips should be used as delivered by the manufacturer
(w/o any additional locknut, that is), with, at most, some threadlock or
perhaps substituting a nylok nut. If were really, really, paranoid,
guess could test the fully-torqued position and then drill and go to
castle nut and pin on a couple.

But, thermal expansion is not an issue that's going to cause any
loosening of the fasteners if torqued.

Good link. Danny should go back an torque the nuts on the clamps. I
would, for sure, now that is important to do so. I'd agree on some
threadlock too.
--
Definition of a camel: A horse designed by a committee

Oren wrote, on Sun, 28 Sep 2014 12:30:52 -0700:

I'd agree on some threadlock too.

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.

dpb wrote, on Sun, 28 Sep 2014 13:54:02 -0500:

I still think the clips should be used as delivered by the manufacturer

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?

On Sun, 28 Sep 2014 21:11:55 +0000 (UTC), "Danny D."
wrote:

dpb wrote, on Sun, 28 Sep 2014 13:54:02 -0500:

I still think the clips should be used as delivered by the manufacturer

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?

Mentioned twice here. Torque the nuts on the cable clamps to specs.

I would.

Danny D. wrote:
dpb wrote, on Sun, 28 Sep 2014 13:54:02 -0500:

I still think the clips should be used as delivered by the
manufacturer

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?

Yes.

--

-Mike-

Oren wrote, on Sun, 28 Sep 2014 10:31:43 -0700:

Just curious. Is there a torque spec for those clamps? Or ...

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.

On Mon, 29 Sep 2014 21:41:56 +0000 (UTC), "Danny D."
wrote:

Oren wrote, on Sun, 28 Sep 2014 10:31:43 -0700:

Just curious. Is there a torque spec for those clamps? Or ...

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.

My point was, if the clamps call for a torque spec, and we now
understand they do - why not follow the details made by the
manufacturers? I'd just feel comfortable doing so. Your friend can do
as he pleases. I get the point of over building something. I've done
hear for a patio cover on my house.

Pick your poison

Oren wrote, on Mon, 29 Sep 2014 15:20:20 -0700:

Your friend can do as he pleases.
I get the point of over building something.

The good news is that, if the whole thing collapses, *he* gets sued, not
me!

On Mon, 29 Sep 2014 21:41:56 +0000 (UTC), "Danny D."
wrote:

Oren wrote, on Sun, 28 Sep 2014 10:31:43 -0700:

Just curious. Is there a torque spec for those clamps? Or ...

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.
I hear that about over engineering stuff. When I was getting ready to
pour the floor for my shop I calculated the concrete thickness for the
various machines and then though about what happens if I move a
machine and then what happens if I buy a heavier machine or one with a
smaller footprint and so on. Then I realized how pointless this was in
my situation, So I had the concrete poured to 7 inch minimum
thickness, had fiber put in the concrete, and I put rebar and wire
mesh in place before the pour. It's a good thing too because I later
bought a lathe that covers 10 square feet with the base and sits on 4
9 square inch pads and weighs 8000 lbs.
Eric

On 09/29/2014 6:42 PM, wrote:
....

... So I had the concrete poured to 7 inch minimum
thickness, had fiber put in the concrete, and I put rebar and wire
mesh in place before the pour. It's a good thing too because I later
bought a lathe that covers 10 square feet with the base and sits on 4
9 square inch pads and weighs 8000 lbs.

8k/4/(9^2) -- 56 psi

Not much load, really.

--

On 9/29/2014 7:42 PM, wrote:
thickness, had fiber put in the concrete, and I put rebar and wire
mesh in place before the pour. It's a good thing too because I later
bought a lathe that covers 10 square feet with the base and sits on 4
9 square inch pads and weighs 8000 lbs.
Eric


Sounds like my elementary school lunch room
monitor woman. We used to call her Bubbles.


..
Christopher A. Young
Learn about Jesus
www.lds.org
..

On 9/28/2014 9:50 AM, Danny D. wrote:
.... snip


On the big tree, 125 feet away, we will add a wraparound additional
steel cable, so that the middle also has two cables.

.... snip


Any other tips are welcome, as we're just now at the stage where
we have the ability to build the 125 foot long bridge starting
about 15 feet up in a pine, and then going straight across a
steep slope through the set of two redwoods, and then on to the
really big redwood 125 feet down the slope.

The treehouse will be in the middle of the bridge.


Are you saying that the tree house will be in the middle of a 125 foot
suspension bridge. How much will the tree house weigh when fully loaded
and do you have any idea of the forces that may be in the cables?


Dan

Dan Coby wrote, on Sun, 28 Sep 2014 12:34:27 -0700:

Are you saying that the tree house will be in the middle of a 125 foot
suspension bridge. How much will the tree house weigh when fully loaded
and do you have any idea of the forces that may be in the cables?

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?

On 9/28/2014 2:18 PM, Danny D. wrote:
Dan Coby wrote, on Sun, 28 Sep 2014 12:34:27 -0700:

Are you saying that the tree house will be in the middle of a 125 foot
suspension bridge. How much will the tree house weigh when fully loaded
and do you have any idea of the forces that may be in the cables?

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).


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.


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?

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.


Dan

Dan Coby wrote, on Sun, 28 Sep 2014 20:32:48 -0700:

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.

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
feet maybe?

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.

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.

"Dan Coby" wrote

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.


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?

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.

I agree with Dan's concern. Someone with good trig math skills needs to
figure this for them. I would "eyeball" calculate that the load on the
cables would be at least 3 to 5 times the weight of the structure and the
added weight of the occupants and furnishings. It could be much higher than
that.

It would appear to me that you are beginning to cross into the zone of
pushing the design strength of the cable.

Another engineering principle here would also be involved. That of safety
design limits. A totally dependant system such as this, where failure of
one system could and would probably cause loss of life would be designed
with a 150% safety factor.

That means that a structure weighing 4200 pounds would be the maximum, if
you used the figure of the tension increased by the geometry from the load
by five times.

You seriously, seriously need to get a structural engineer involved before
you proceed. I believe you are playing with fire, that could get someone
baldy hurt, or worse.
--
Jim in NC


---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com

On 09/28/2014, 2:18 PM, Danny D. wrote:
Dan Coby wrote, on Sun, 28 Sep 2014 12:34:27 -0700:

Are you saying that the tree house will be in the middle of a 125 foot
suspension bridge. How much will the tree house weigh when fully loaded
and do you have any idea of the forces that may be in the cables?

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?


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
Tacoma bridge...

John :-#)#

PS, it looks like a lot of fun though!

John Robertson wrote, on Mon, 29 Sep 2014 09:54:57 -0700:

Have you allowed for a windstorm where the trees may be moving in
opposite directions to each other?
Have you allowed for maximum and minimum temperatures?

Only that each cable supports 14,000 pounds!

You want some sort of shock absorption built in too.

Hmmmmmm.... The cables don't "give" a little when you walk on the bridge
that would be hanging below it?

May I suggest you find an engineer to look over your design?

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.

Suspension bridges are close to what you are building

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
spend there.

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).

On Sun, 28 Sep 2014 12:34:27 -0700, Dan Coby wrote:

On 9/28/2014 9:50 AM, Danny D. wrote:
... snip


On the big tree, 125 feet away, we will add a wraparound additional
steel cable, so that the middle also has two cables.

... snip


Any other tips are welcome, as we're just now at the stage where
we have the ability to build the 125 foot long bridge starting
about 15 feet up in a pine, and then going straight across a
steep slope through the set of two redwoods, and then on to the
really big redwood 125 feet down the slope.

The treehouse will be in the middle of the bridge.


Are you saying that the tree house will be in the middle of a 125 foot
suspension bridge. How much will the tree house weigh when fully loaded
and do you have any idea of the forces that may be in the cables?


Dan

You better check it. Wind loads can exceed the dead loads by many times.
Wind loads may be the real issue.

?-)

OFWW wrote, on Sat, 27 Sep 2014 23:55:45 -0700:

I hate ladders like these, seen the two by's pull off after a
short while especially if your shouldering a load going up or
down. The rungs should be in notches.

This is a good point.

We have so many ladders, most of which are roped end-to-end to the trees
for height, that we just made them as simply as we could.

You can see that we have cargo netting, to allow us to cross from tree to
tree once we climb up the ladders:
https://c4.staticflickr.com/4/3865/1...e8c93589_c.jpg

But, we also usually wear safety harnesses and ascenders whenever we work
more than 15 or 20 feet up (which is almost always since it's a steep
slope so what is 15 feet up at the uphill end of the cables is something
like 50 or 70 feet up at the downhill end.