We started the 100-foot long 10-foot wide deck high up in the California redwoods

[Danny D.]

Just to keep you informed, and to get your advice on better ways to
tackle the engineering problems:
https://c4.staticflickr.com/4/3943/15315306567_5e25779b8b_b.jpg

After a lot of initial setup of ladders strapped to the trees:
https://c3.staticflickr.com/3/2948/15314802989_a57dd072da_c.jpg

And setup of the many utillity ropes, and tree-to-tree netting:
https://c4.staticflickr.com/4/3928/15501340972_e31032dcd7_c.jpg

We've finally got the 100-foot-long 3/8" steel cables hung well:
https://c4.staticflickr.com/4/3948/15314983930_3c606db7b4_b.jpg

The next step, was building the first 16-foot long set of the 10-foot-
wide decking from the top of the hill, which will eventually connect over
100 feet downslope to the gnarly big redwood at the bottom of the hill:
https://c2.staticflickr.com/6/5607/15498557171_df86936bcb_b.jpg

It's amazingly ungainly tying all the 16-foot long 10-inch wide boards to
the 100-foot long swinging 3/8-inch cables as we try to build the bridge:
https://c4.staticflickr.com/4/3949/15314983180_78420114c9_b.jpg

It took two people and a lot of rope to get things squared up at first:
https://c4.staticflickr.com/4/3944/15314801909_48b46268b6_b.jpg

In fact, it was so ungainly, that we put in temporary crossbeams, just to
hold the bridge square as we were assembling it on the hillside:
https://c4.staticflickr.com/4/3940/15314801829_a3eeb9395e_b.jpg

Even steps as simple as screwing in the self-tapping screws is difficult
when the entire 16-foot long 10-foot wide bridge-like structure is
swinging freely and nowhere bolted to the ground:
https://c4.staticflickr.com/4/3942/15315124677_c121c8def1_b.jpg

But, eventually, we managed to assemble the first 16-foot long 10-foot
wide lengths from the cables between the groups of redwood trees:
https://c4.staticflickr.com/4/3943/15315306567_5e25779b8b_b.jpg

[hrho...@sbcglobal.net]

What are the two vertical posts made of, and how are they secured into the ground/stone??

[Arfa Daily]

"Danny D." <dannyd...@gmail.com> wrote in message
news:m1ahhg$qr2$2...@dont-email.me...

I wish I had that much spare time on my hands ... :-)

Arfa

[Danny D.]

Arfa Daily wrote, on Tue, 14 Oct 2014 11:35:38 +0100:

> I wish I had that much spare time on my hands ...

It's going to be a nice, 100-foot long, 10 foot wide, treehouse strung
between the redwood trees on a steep slope when it's done.

Here's the varnished decking laid in place but not attached yet:
https://c2.staticflickr.com/6/5604/15558189375_03e664d327_b.jpg

Right now, we just "hung" the first 16-foot section.
https://c2.staticflickr.com/6/5598/15372553580_9751d293de_b.jpg

It's 17 feet on the left and 18 feet on the right to the next straddling
set of redwood trees, which is too bad, given our beams are 16 feet long:
https://c2.staticflickr.com/6/5608/14937422664_148d70ba58_b.jpg

After the straddling redwoods, it's 20 feet to the big fat giant redwood.

So, we're not sure if we'll string four 16-foot lengths, or
maybe change the plan to go for one fewer section but of
a longer section length.

It's a design-as-you-go project, where advice is always welcome!

[Danny D.]

Danny D. wrote, on Fri, 17 Oct 2014 21:28:15 +0000:

> After the straddling redwoods, it's 20 feet to the big fat giant
redwood.

Ooops. It's around 40 feet to the final tree, far downhill.

So, we think, the total length is much less than the length of the 3/8-
inch steel cable, which was 250 feet long (and we had to cut a few feet
off the end).

The bridge itself starts about 15 feet from the end of the cable (simply
because that's a convenient point to get ON the bridge, at the crossing
of the old footpath).

The first section is 15 feet long.
The next set of redwoods is 18 feet away.
The big redwood is another 35 to 45 feet from there.

So, the total length of the bridge is gonna be more like 80 feet or so.
Once the bridge is done, then we can put the building up.

We're told that we don't need any permits for tree structures, so, we can
even put a bathroom, kitchenette, bar, etc., there, and not have to worry
about meeting code requirements.

So, it's probably not 100 feet long, but something like:

[John Robertson]

I love the idea but think there are design issues that need serious
attention.

I always thought that most code requirements were to prevent people from
building structures that would kill them or their guests...

I still don't like the cinched cables as shown in the pictures earlier,
those are stress points and the wire rope is quite a bit weaker now for
them. Have you never looked at how cables are secured when done by
professionals? Clevis hitches, or good splices are best for securing the
rope end. Found a nice page on splices you may want to look at:

http://stoneycreeker.com/knots/knots.htm

I know you aren't the designer (you are one of the helpers), and I am no
expert on wire rope, but I do have a lot of respect for the people who
make it and when they say to follow certain rules I would think they are
the better adviser.

3/8 inch wire rope is rated at 2440 lb safe load...

http://www.engineeringtoolbox.com/wire-rope-strength-d_1518.html

...using well designed cinching. Now you have two ropes, however each of
them must be able to bear the entire load (if swinging for example) so
you really are limited to around 2500 lbs (a bit over a ton) for the
total weight of the rope, structure, and guests. If I am wrong then the
most safe weight load could only be 4800lbs. I'm not an engineer and
thus don't know how to work out the loading factors, but I can add.

Guests have weight.

Have they made allowances for any people to visit? Looks like you can
put five people in it plus a 1200 lb structure (if 2400 lb safe load),
if the average guest is around 200lb. Ten people and you can only have a
simple wooden platform that weighs 400 lbs...

John :-#(#

--
(Please post followups or tech inquiries to the newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

[Danny D.]

John Robertson wrote, on Fri, 17 Oct 2014 18:29:39 -0700:

> I still don't like the cinched cables as shown in the pictures earlier,
> those are stress points and the wire rope is quite a bit weaker now for
> them.

I see you noticed that the cables are currently bending in a sharp
"V" shape where they are holding up the first gang plank.

We all agree that any sharp bend in the cable is a bad thing, but,
that "V" is supposed to be temporary.

The end result "should" be either a catenary or a parabola (depending
on the amount of force downward per linear distance of cable). If that
weight (i.e., force downward) is evenly distributed, the cables will
form a catenary; otherwise they'll be a parabola.

In our case, the owner has stated that each cable can hold something
like 7,000 pounds (IIRC), so that's 14,000 pounds.

The *original* plan was to have the bridge free swinging, but, we
attached one end of the bridge to posts cemented into the hillside
and, we probably will attach the other end to the big redwood, and,
in the middle, we will probably make use of the two skinny redwoods.

So, exactly how much weight the cables will hold is not really
going to be something we'll be able to calculate on this home
DIY project.

I do know that this lumber is very heavy! I helped carry it, so,
I'd know. We lugged those 16-foot ten-inch wide beams hundreds of
yards into the woods along a narrow foot path, and my hands were
hurting by the time we put them down. Lugging the cement bags
was easier! So, each bridge section is probably something like
500 pounds, and there will be a minimum of four 16-foot sections,
maybe 5, depending on how far it is to the big tree.

We don't actually know the distance because the hillside is steep,
so, you can't just run a 100-foot tape measure, but, it's less
than 100 feet by ten or twenty feet.

[John Robertson]

On 10/17/2014, 8:47 PM, Danny D. wrote:
> John Robertson wrote, on Fri, 17 Oct 2014 18:29:39 -0700:
>
>> I still don't like the cinched cables as shown in the pictures earlier,
>> those are stress points and the wire rope is quite a bit weaker now for
>> them.
>
> I see you noticed that the cables are currently bending in a sharp
> "V" shape where they are holding up the first gang plank.
>
> We all agree that any sharp bend in the cable is a bad thing, but,
> that "V" is supposed to be temporary.
>
> The end result "should" be either a catenary or a parabola (depending
> on the amount of force downward per linear distance of cable). If that
> weight (i.e., force downward) is evenly distributed, the cables will
> form a catenary; otherwise they'll be a parabola.
>
> In our case, the owner has stated that each cable can hold something
> like 7,000 pounds (IIRC), so that's 14,000 pounds.

Better check the specs of the wire rope, the owner may be going by the
rated maximum capacity (12,200 lb for 3/8" wire rope) and only derating
it 50%. Note the manufacturer recommends only a 20% load factor for
safety. I don't think that is so they can sell thicker rope...

It also depends on how the load is distributed on the rope, and any
pressure points, bends etc. All of these are part of the 20% safety
factor, or may derate it further.

Please read this article:

http://www.safetysling.com/wr2.htm

and this:

http://www.thetreehouseguide.com/bridges.htm

note the recommendation that only one person at a time is on the
suspension bridge...

Weight of the wood used...

So, lets say you are using 2 X 6 pressure treated wood that is 10 feet
wide. 2200 lbs equals only 68.75 boards - or about 35 feet if laid side
by side. Check the math yourself:

http://www.engineeringtoolbox.com/green-kiln-dried-pressure-treated-lumber-weights-d_1860.html

All this is based on 3/8 inch wire rope with a safety factor of five.

If these guys can afford to build this, they can afford to get a
qualified engineer to aid in designing it to be safe enough that you
would be willing to risk your children on.

I wouldn't let any kids near this design based on what I've seen so far.
Adults can take their chances...

[Arfa Daily]

>
> We don't actually know the distance because the hillside is steep,
> so, you can't just run a 100-foot tape measure, but, it's less
> than 100 feet by ten or twenty feet.
>

The mind boggles ...

With a design factor that important, wouldn't it make sense to use a laser
measure ? These things are dirt cheap now, and accurate to better than a
half metre. Even if you had to shin up that final tree and pin a white paper
'target' to the trunk ...

Arfa

[Danny D.]

John Robertson wrote, on Fri, 17 Oct 2014 23:46:50 -0700:

> Better check the specs of the wire rope, the owner may be going by the
> rated maximum capacity (12,200 lb for 3/8" wire rope) and only derating
> it 50%. Note the manufacturer recommends only a 20% load factor

I asked the owner about the weight of the deck, where this came back:
https://c2.staticflickr.com/6/5608/14937422664_148d70ba58_b.jpg

Hello Danny:

Thanks for your help last week. I couldn't have done it without you.h

You seemed skeptical about my estimate of the first bridge section.
Given a 2x10 weighs 3.37 lbs per foot.
Given a 2x6 weighs 2.00 lbs per foot.

3x16x3.37 = 162 lbs for the three long boards
2x10x3.37 = 68 lbs for the two end boards

2x6 2.00 lbs/ft
10x2x32 = 640 lbs for the decking

870 lbs per 16 foot section.

So if there are 5 sections (80 feet), or 6 sections (96 feet) we have
4,350 lbs or 5,220 lbs for the deck.

The cables can support 28,000 lbs.

That gives us 22,780 lbs for the house and occupants, assuming the only
support is the cable.

If we allow that some of the weight is supported by the posts and the
trees, we have even more leeway.

If the house is 24 feet long and ten feet wide, it will weigh about 8,000
pounds.

Add 4,000 pounds for furnishings and appliances.
That gives us 10,780 pounds of leeway for occupants.

But I plan to have most of the house weight supported by the redwoods,
not by the cable.

[John Robertson]

It again all hinges on the diameter of the cable (wire rope) they are
using and how it is secured. If it is 3/8" then I wouldn't go near it
assuming he is going by the maximum load.

Based on his reasoning (28,000 load spread over two cables) he needs at
least 7/8" (12,900 lb safe load each), but 1" (16,700 lb) would be better.

Attaching the house to the tree will save a lot of weight, however trees
grow larger in diameter so the support must allow for that somehow.

Also his securing of the wire rope must be flawless, and the fact that
he has already stressed the rope in a few places with the clamps has
weakened the original wire rope significantly.

However he doesn't appear to be willing to get an inspector, so I'll
assume I'll read about this upcoming disaster in the newspaper in the
near future (next couple of years).

Just because you are clever doesn't mean you are right. Some of us can
be quite smug...(ducking)

[Lew Hodgett]

"John Robertson" wrote:

> It again all hinges on the diameter of the cable (wire rope) they
> are using and how it is secured. If it is 3/8" then I wouldn't go
> near it assuming he is going by the maximum load.
>
> Based on his reasoning (28,000 load spread over two cables) he needs
> at least 7/8" (12,900 lb safe load each), but 1" (16,700 lb) would
> be better.
>
> Attaching the house to the tree will save a lot of weight, however
> trees grow larger in diameter so the support must allow for that
> somehow.
>
> Also his securing of the wire rope must be flawless, and the fact
> that he has already stressed the rope in a few places with the
> clamps has weakened the original wire rope significantly.
>
> However he doesn't appear to be willing to get an inspector, so I'll
> assume I'll read about this upcoming disaster in the newspaper in
> the near future (next couple of years).
>
> Just because you are clever doesn't mean you are right. Some of us
> can be quite smug...(ducking)

----------------------------------------------------------
You can buy them books, BUT if they eat the covers.

Lew

[Leon]

Now days Lew you buy them books and they eat the Teacher!

[josephkk]

I see a complete failure to account for wind loads. Wind loads on this
tree house will be larger than the dead loads. Ask the owner to calculate
the wind loads as well.

?-)

[Danny D.]

Danny D. wrote, on Tue, 21 Oct 2014 20:10:10 +0000:

> But I plan to have most of the house weight supported by the redwoods,
> not by the cable.

We finished rigging up the second 16 foot section, which missed the
next set of redwood trees by about a foot or two.
https://c2.staticflickr.com/6/5611/15453538738_e049344c53_b.jpg

Unfortunately, those two redwoods straddling the end of the 32-foot
suspended section are just a tad under ten feet apart.

So, we're gonna have to engineer a slight bevel inward, to squeeze
in between those two trees, and then it's on to the next three or
four 16-foot long 10-feet wide sections, all of which is suspended
by ropes and temporary cables, at the moment, as we build it as we
walk out to the edge...
https://c4.staticflickr.com/4/3953/15637200951_f7b58d5ecf_b.jpg

[Danny D.]

josephkk wrote, on Thu, 23 Oct 2014 18:23:37 -0700:

> I see a complete failure to account for wind loads. Wind loads on this
> tree house will be larger than the dead loads. Ask the owner to calculate
> the wind loads as well.

This is a good point so I will mention it to him.

We worked on the second floating 16-foot section today, by the way.
https://c4.staticflickr.com/4/3955/15459997077_b22b960f68_b.jpg

So now we're suspended 32 feet straight out.

Only 60 or so feet to go!

[Danny D.]

dpb wrote, on Thu, 23 Oct 2014 07:36:12 -0500:

> T=W/sin(angle) = (W/2)/sin(11) --> 2500/0.2 --> 12,500 lb

Wow. Those were wonderful calculations.
I forwarded it all to my friend, and will reply back with his response.

Meanwhile, we worked on the second section today, and we ended up stopping
about 2 feet away from redwoods which we need to squeeze through.
https://c4.staticflickr.com/4/3937/15460483990_09bffcce41_b.jpg

[Danny D.]

CRNG wrote, on Thu, 23 Oct 2014 12:40:15 -0500:

> I don't think they are taking heed. They have been successful with
> their little neighborhood projects, and they are starting to get over
> confident.

I think the owner is taking heed, it's just that he's a third party
to this conversation (he doesn't know Usenet). :)

BTW, here's a view from below today, when I dropped my glasses
and had to climb down the steep hill to retrieve them.

https://c4.staticflickr.com/4/3943/15645979325_89a8481615_b.jpg

[Danny D.]

dpb wrote, on Thu, 23 Oct 2014 13:35:20 -0500:

> Of course, if the droop angles are significantly larger than the assumed
> 10 degree or so, then they gain a fair amount by there being a larger
> vertical component but it's too spooky by far as described and shown

I'm sorry I haven't responded in a while. I hurt my back and was laid
up but hopefully I'm better now ...

The whole thing is supposed to hang from the cables, but we did anchor
one end because we needed a way for people to get "on" the decking.

Here's where we left it today...
https://c4.staticflickr.com/4/3945/15459995717_3722bf0914_b.jpg

[Danny D.]

CRNG wrote, on Thu, 23 Oct 2014 08:05:45 -0500:

> Good analysis. Unfortunately Danny D and Friends just don't seem to
> understand what the effect of the catenary configuration has in
> increasing the tension in the cable. I really hope someone convinces
> them to have a engineer look at their exact config and do some simple
> calcs as you have done above.

I'm sorry I haven't been able to respond lately.

We had to readjust all the cables today, with a set of 5 winches, as
we had to re-balance everything once the second 16-foot section was
planked.

Unfortunately, I ruined my clothing, as I hadn't expected the oil
to still be soaking wet ... even though it was drying outside for
a day ...

https://c2.staticflickr.com/6/5616/15645979935_55c2665284_b.jpg

[Danny D.]

VinnyB wrote, on Wed, 22 Oct 2014 05:58:58 -0500:

> The lawyers are going to love it. Everyone from the wire rope
> manufacturer to the water-boy will be sued.

You forgot the screw manufacturers!
https://c4.staticflickr.com/4/3935/15025811753_8de1cc2650_b.jpg

Notice we gave up on the lower screw (the one with the longer thread).

It was just too hard to drive into the wood.

Even with this nice pile driver thing from Harbor Freight!
https://c4.staticflickr.com/4/3934/15459836048_8f3a566c90_b.jpg

The screw on top, with the shorter thread, goes in without pounding!

[Ian Malcolm]

"Danny D." <dannyd...@gmail.com> wrote in

news:m2mk88$c0c$5...@dont-email.me:

See <http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)>
The chances of your bridge deck fluttering in a blow are fairly high.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
[at]=@, [dash]=- & [dot]=. *Warning* HTML & >32K emails --> NUL

[Danny D.]

Ian Malcolm wrote, on Tue, 28 Oct 2014 00:21:08 +0000:

> See <http://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge_(1940)>
> The chances of your bridge deck fluttering in a blow are fairly high.

We actually joked, a few times, about the Tacoma Narrows bridge, and,
yes, I think just about everyone has seen that video of the car on
the bridge and the person getting out and making it just in time.

This bridge isn't nearly as long.

It's only about 100 feet long, by 10 feet wide, supported on one end
on the ground and on the far end about 40 or 50 feet up in a tree on
a (very) steep slope.

Here's what the first two 16-foot-long sections looked like today,
when we ran out of oiled wood:
https://c4.staticflickr.com/4/3945/15459995717_3722bf0914_b.jpg

I'm currently learning how to wash good clothes to get the oil
out! :(

[Arfa Daily]

"Danny D." <dannyd...@gmail.com> wrote in message

news:m2mkq5$c0c$7...@dont-email.me...

Pardon me for a silly suggestion but ...

... in view of the - how shall we put it - challenging ? - nature of the
site, wouldn't it be a good idea to have your specs on one of those strings
around your neck ? And tools like hammers, roped to your belt ?

Arfa

[Danny D.]

dpb wrote, on Thu, 23 Oct 2014 08:13:06 -0500:

> ERRATUM: I forgot to divide the cable limit by the two above
> -- the actual limit per cable is (optimistically) as used by
> your friend 14000, not 28000.

Here's the response from the neighbor building the deck...
https://c4.staticflickr.com/4/3953/15460990220_5b1f28763d_b.jpg

The 3/8" steel suspension cable is a good deal higher than 10 feet above
the deck at the ends. Currently that 3/8" steel cable is anchored at a
tree about 25 feet above the deck at the beginning end of the deck.

Also, the 100 foot final length of the deck was a guess that is probably
a bit high, where perhaps 80 feet might be closer to the final length. So
the 11 degrees may no longer still be the result of the calculations.

Looking at the photos, the angle of the cable looks like around 30
degrees to me. If the height of the suspension cable above the deck is 25
feet, and the length of the deck is 80 feet, we now have 32 degrees.

Using his tension formula, we get a tension of 4,718 pounds.
So, I believe, that means the 3/8" suspension cable can support almost
six times what we are assuming.

While the deck was originally supposed to be free floating, since we
decided to anchor the close end of the deck on the dirt path (so that
people could just step onto the deck from the path), that end of the deck
is now supported by the two fence posts, so half of its weight goes away.

If, additionally, we add another fence post, in a "T" shape support, at
the end of the first 16-foot-long section, then the weight of that first
16-foot-long section goes away completely, as does half the weight of the
next 16-foot-long section. And we still have the option of supporting the
other half by attaching it to the small redwood trees, along with half of
the third section.

If we really did get to 28,000 pounds of tension, the trees would pull
closer together, reducing the distance, and making the angle steeper. It
thus gets asymptotically harder to actually put that much tension on the
cable.

The treehouse itself, when it's built, will be supported mostly by the
redwood trees.

[Danny D.]

Arfa Daily wrote, on Tue, 28 Oct 2014 02:05:05 +0000:

> ... in view of the - how shall we put it - challenging ? - nature of the
> site, wouldn't it be a good idea to have your specs on one of those
> strings around your neck ? And tools like hammers, roped to your belt ?

That's a good suggestion, as we have tools all over the place!
https://c4.staticflickr.com/4/3948/15647694665_4bc6370a50_c.jpg

Usually, we tie in when we're out on the cable, with no firm footing:
https://c4.staticflickr.com/4/3947/15461051649_0ffee9cb37_b.jpg

And, we tie in when we're working on the steep slope below the deck:
https://c4.staticflickr.com/4/3950/15461715927_30b042e8a8_b.jpg

The harnesses we use are the same ones we use for climbing the hills:
https://c2.staticflickr.com/6/5602/15026942014_d22eb1ee32_b.jpg

Here's my setup, for example, as I was digging the fence post holes:
https://c4.staticflickr.com/4/3950/15461715927_30b042e8a8_b.jpg

And, here's what I used when I had to double-line rappel downslope:
https://c4.staticflickr.com/4/3932/15648510152_b903b1b22c_c.jpg

Even so, we've had a few of the typical gotchas, from dropping the
spool of wire (where it rolled a hundred or so feet downhill before
getting wedge under a fallen tree) to the inevitable search for missing
glasses and hammers.

Such is the nature of working in the trees...

[Danny D.]

dpb wrote, on Mon, 27 Oct 2014 21:06:58 -0500:

>> https://c4.staticflickr.com/4/3943/15645979325_89a8481615_b.jpg
> Where are the supporting cables in the picture--on top or
> just hidden by the view?

All the supporting cables are above the deck.

It's a bit hard to see in that picture from below today, but the 3/8"
steel cable is glinting in the sunlight a few feet *above* the deck.
https://c4.staticflickr.com/4/3943/15645979325_89a8481615_b.jpg

The deck is not attached to *anything* other than the cable on the free-
floating end, as we build it out. In fact, while it's hard to tell from
the angle of this picture, but the end of the second 16-foot-long section
is still shy of the leftmost redwood by about a foot, and maybe it's two
feet shy of the right-most redwood tree:
https://c2.staticflickr.com/6/5600/15648508432_8ea7136264_c.jpg

Here is a picture taken earlier in the day, before we planked the second
16-foot-long section, showing how the 10-foot-wide deck is suspended from
the steel cables (this is the second of the two 16-foot-long sections):
https://c2.staticflickr.com/6/5601/15026940484_8853aa5e3e_c.jpg

[Danny D.]

dpb wrote, on Mon, 27 Oct 2014 21:06:58 -0500:

> You also need to consider how much side load this is putting on those
> trees and how large they are at that point to handle the lateral load
> plus how well their root systems are capable of that additional
> continuous load, particularly when the ground gets saturated when it
> finally does rain again...

This is a good point, in that sometimes it pours out here, and this is a
steep slope, so the runoff could be great.

We just had a half inch of rain over the weekend, and this is a shot of
the cables and the people on the decking (the dog won't go on the deck):
https://c4.staticflickr.com/4/3953/15460990220_5b1f28763d_b.jpg

We're still about a foot from the left-most redwood here, and about two
feet from the right-most redwood, so we "can" attach to them (if decided)
with the third 16-foot deck section:
https://c2.staticflickr.com/6/5600/15648508432_8ea7136264_c.jpg

[Arfa Daily]

"Danny D." <dannyd...@gmail.com> wrote in message

news:m2n5iq$c0c$2...@dont-email.me...

> Arfa Daily wrote, on Tue, 28 Oct 2014 02:05:05 +0000:
>
>> ... in view of the - how shall we put it - challenging ? - nature of the
>> site, wouldn't it be a good idea to have your specs on one of those
>> strings around your neck ? And tools like hammers, roped to your belt ?
>
> That's a good suggestion, as we have tools all over the place!
> https://c4.staticflickr.com/4/3948/15647694665_4bc6370a50_c.jpg

Boy oh boy ... I thought I was making a bit of a silly suggestion there ...

>
> Usually, we tie in when we're out on the cable, with no firm footing:
> https://c4.staticflickr.com/4/3947/15461051649_0ffee9cb37_b.jpg

Work clothes ?

>
> And, we tie in when we're working on the steep slope below the deck:
> https://c4.staticflickr.com/4/3950/15461715927_30b042e8a8_b.jpg

That's concrete, yes ? Looks a little lean on the mix ... ?

>
> The harnesses we use are the same ones we use for climbing the hills:
> https://c2.staticflickr.com/6/5602/15026942014_d22eb1ee32_b.jpg
>
> Here's my setup, for example, as I was digging the fence post holes:
> https://c4.staticflickr.com/4/3950/15461715927_30b042e8a8_b.jpg
>
> And, here's what I used when I had to double-line rappel downslope:
> https://c4.staticflickr.com/4/3932/15648510152_b903b1b22c_c.jpg
>
> Even so, we've had a few of the typical gotchas, from dropping the
> spool of wire (where it rolled a hundred or so feet downhill before
> getting wedge under a fallen tree) to the inevitable search for missing
> glasses and hammers.
>
> Such is the nature of working in the trees...

Hmmmm ...

Arfa
>

[Arfa Daily]

"Danny D." <dannyd...@gmail.com> wrote in message

news:m2n6ir$c0c$2...@dont-email.me...

> dpb wrote, on Mon, 27 Oct 2014 21:06:58 -0500:
>
>> You also need to consider how much side load this is putting on those
>> trees and how large they are at that point to handle the lateral load
>> plus how well their root systems are capable of that additional
>> continuous load, particularly when the ground gets saturated when it
>> finally does rain again...
>
> This is a good point, in that sometimes it pours out here, and this is a
> steep slope, so the runoff could be great.
>
> We just had a half inch of rain over the weekend, and this is a shot of
> the cables and the people on the decking (the dog won't go on the deck):

Animals have a sort of 'sixth sense' about this sort of thing. Perhaps this
should tell you something ... d:-}

Arfa

[John Robertson]

The dog is the only one paying attention to load factors.

[Danny D.]

Arfa Daily wrote, on Tue, 28 Oct 2014 09:53:11 +0000:

>> https://c4.staticflickr.com/4/3947/15461051649_0ffee9cb37_b.jpg
> Work clothes ?

We're all retired, and, getting a bit complacent, so, we tend
not to own (real) work clothes.... :)

But, we're getting real good at buying army surplus static line!
https://c4.staticflickr.com/8/7474/15627944646_f7aaff11cc_b.jpg

Maybe we should pick up a pair of these Ghillies as fitting
work clothes, since we're always hanging around in the trees:
https://c4.staticflickr.com/4/3943/15465541258_e2d8aa3fd1_b.jpg

[Oren]

On Mon, 27 Oct 2014 23:46:30 +0000 (UTC), "Danny D."
<dannyd...@gmail.com> wrote:

> https://c4.staticflickr.com/4/3935/15025811753_8de1cc2650_b.jpg
>
>Notice we gave up on the lower screw (the one with the longer thread).

Those screws are from GRK Fasteners...

<http://www.grkfasteners.com/index.php/en/>

Videos on Youtube:

<http://www.youtube.com/user/grkfasteners/videos>

[Danny D.]

dpb wrote, on Tue, 28 Oct 2014 09:21:42 -0500:

> While it is true that the end that is resting on the ground does have
> that support, it's not necessarily so that the remaining load on the
> cable is only half; it depends on the actual geometry of the
> configuration. It _might_ be half; could be more, could even be less.

Thanks for all the insight.
Below is the owner's response to your concerns.

BTW, I created an animated GIF of the entire process, as I see it,
but I can't get Flickr to show the animations since Flickr turns
an animated GIF into a static JPG.

I'll post the animation separately, if I can figure out how to
preserve the animation, but here is the starting point static JPG:
https://c2.staticflickr.com/6/5605/15466740929_084969faac_z.jpg

Here is where we are right now:
https://c4.staticflickr.com/8/7575/15629669196_d8ed414ac3_z.jpg

And here is the penultimate ending point static JPG:
https://c2.staticflickr.com/6/5600/15466738719_4866bb66b1_z.jpg

Here's the owners response to your valid concerns ...

I wonder if they realize how huge the final redwood tree is?
The tree probably weighs in excess of 2,000 tons, and has a 30 foot
circumference.
The smaller set of redwood trees I would estimate weighs 15 tons.
In a wind of 50 mph, the small tree experiences 200,000 pounds of force
due to the wind.
The idea that 28,000 pounds of tension on a cable is more than it
encounters in a light wind does not seem tenable.
The root structures of both trees routinely handle much larger forces
during a typical day.

A wind blowing at 100 miles per hour generates 25 pounds of force per
square foot.
If that wind were blowing straight down on 800 square feet of deck, we'd
have 20,000 pounds of force.
I consider that unlikely. :-)

Edge-on, we have 67 square feet, or 1,666 pounds of force. But that is
also somewhat unlikely.

Sideways forces will add a little to the cable tension, but will mostly
be taken up pushing against the trees and the support posts.

The deck will weigh in the neighborhood of 5,000 pounds, and has 800
square feet of maximum surface area. Lifting that, requires 6.25 pounds
per square foot, or a wind speed straight up of 50 miles per hour. But
the deck is held down at the ends and in the middle by either trees or
posts, which also limit the amount it can tilt or twist. The surrounding
trees limit the wind considerably.

The assumption that the engineering is "seat of the pants", or that the
mathematics have not been done is incorrect, but the ideas are all good
because I don't want to miss something, by not thinking about it at least.

Let them know that I appreciate their advice!
(Please invite them to lunch on Wednesdays in Redwood City if they're
local.)

[Danny D.]

Oren wrote, on Tue, 28 Oct 2014 10:37:43 -0700:

> Those screws are from GRK Fasteners...

The ones with the longer threads were really stinky because
you needed four hands, while suspended on the cable, to
screw them in.

The ones with the shorter threads only take 3 hands.

Here's an animated GIF, I just made, of the suspension bridge...
http://i62.tinypic.com/ieeakx.gif

[Danny D.]

Danny D. wrote, on Tue, 28 Oct 2014 20:48:36 +0000:

> BTW, I created an animated GIF of the entire process, as I see it, but I
> can't get Flickr to show the animations since Flickr turns an animated
> GIF into a static JPG.

Flickr turned the animated GIF into a JPG but tinypic seems to keep
it as an animated GIF ...

Here's my rendition, as I understand the plans so far ...
http://i62.tinypic.com/ieeakx.gif

I am omitting the actual building structure, but what you see here
are the following:

1. The starting point, on a steep slope, with a path near the top:
https://c2.staticflickr.com/6/5605/15466740929_084969faac_z.jpg

2. All brown lines are 16-foot long lengths of lumber:
https://c2.staticflickr.com/6/5610/15467815060_5471646329_z.jpg

3. This approximates the "ladder network" you've seen in the photos:
https://c4.staticflickr.com/8/7580/15467423737_a9ec2183b7_z.jpg

4. This was the first (thin) cable that went from tree to tree:
https://c4.staticflickr.com/8/7572/15654210442_007a87f618_z.jpg

5. From that thin cable, we hung two large safety cargo nets:
https://c2.staticflickr.com/6/5614/15467236098_ffe03d5577_z.jpg

6. Then we hung the thick cable, which was initially 250 feet long:
https://c4.staticflickr.com/8/7554/15650701911_a8bc487651_z.jpg

7. We sunk two fenceposts, so that the platform rested on the ground:
https://c2.staticflickr.com/6/5611/15467814730_6b9ae30e5e_z.jpg

8. Then we built & suspended the first 16-foot by 10-foot section:
https://c4.staticflickr.com/8/7583/15653383255_8ab43e6304_z.jpg

9. Yesterday, we hung the second 16-foot-long section which is a
foot or two shy of the smaller redwood pair of trees:
https://c4.staticflickr.com/8/7575/15629669196_d8ed414ac3_z.jpg

10. The plan is to add successive 16-foot sections, one by one:
https://c4.staticflickr.com/4/3955/15654209272_22de5c06a0_z.jpg

11. We keep that up until we finally reach the big redwood tree:
https://c2.staticflickr.com/6/5600/15466738719_4866bb66b1_z.jpg

12. And, finally, we'll add 8'x4' sheets of plywood as a railing:
https://c4.staticflickr.com/8/7467/15653381675_a674bb6d59_z.jpg

After that, we begin to build the actual treehouse, complete with
WiFi, refrigerator, bar, running water, and heating (no kidding).

It will take time, of course, so, I'm not sure if I should continue
to update this thread, but, since we've never done this before, any
and all advice is welcome.

PS: Jeff Liebermann and SMS are both welcome to attend the Internet
WiFI setup party since they both live in the area!
https://c4.staticflickr.com/4/3953/15460990220_5b1f28763d_b.jpg

[Oren]

On Tue, 28 Oct 2014 20:57:49 +0000 (UTC), "Danny D."
<dannyd...@gmail.com> wrote:

>Oren wrote, on Tue, 28 Oct 2014 10:37:43 -0700:
>
>> Those screws are from GRK Fasteners...
>
>The ones with the longer threads were really stinky because
>you needed four hands, while suspended on the cable, to
>screw them in.
>
>The ones with the shorter threads only take 3 hands.
>

The GRK screws are self-tapping, self-pulling and self-counter
sinking. From videos they will drive into a wood knot - generally with
just a hand held impact drill/driver.

_Screws that Practically Drive Themselves _

<http://www.youtube.com/watch?v=tWFf4IOuAnI&list=PL1szv0FP8dUthzyAv88t3sQzhxFLWMXRF>

<https://tinyurl.com/mza8hmp>

[Oren]

On Tue, 28 Oct 2014 21:18:32 +0000 (UTC), "Danny D."
<dannyd...@gmail.com> wrote:

>Danny D. wrote, on Tue, 28 Oct 2014 20:48:36 +0000:
>
>> BTW, I created an animated GIF of the entire process, as I see it, but I
>> can't get Flickr to show the animations since Flickr turns an animated
>> GIF into a static JPG.
>
>Flickr turned the animated GIF into a JPG but tinypic seems to keep
>it as an animated GIF ...
>

Tinypic showed it just fine:

<http://tinypic.com/view.php?pic=ieeakx&s=8#.VFAWF2dqE2N>

What software did you use to make it?

[Danny D.]

Oren wrote, on Tue, 28 Oct 2014 15:22:29 -0700:

> What software did you use to make it?

> http://i62.tinypic.com/ieeakx.gif

I drew it, by hand, with Kolourpaint, on Linux, which,
according to Wikipedia, is a Microsoft-Paint like drawing app:
http://en.wikipedia.org/wiki/KolourPaint

After drawing each line, I just saved the file to a new name,
e.g., drawing01.jpg, drawing02.jpg, drawing03.jpg, etc.

Then, I slapped it all together with this Linux command:
$ convert -delay 50 -loop 0 *.jpg animatedplans.gif

That created this:
http://i62.tinypic.com/ieeakx.gif

The "loop 0" just means loop forever; and the delay is something
like 50 milliseconds between images, I think.

I use this method only because it's trivially simple to do,
so, I'm sure there are *better* ways to make animated drawings.

For example, on Windows, I'd just draw using "Paint.NET" or even
Microsoft Paint. Then, I'd slap it together using one of the
programs described here:
How to make animated GIFs, by PC Magazine
http://www.pcmag.com/article2/0,2817,2392701,00.asp

[Danny D.]

Danny D. wrote, on Wed, 29 Oct 2014 05:04:53 +0000:

> There's almost no way you would have known how absolutely huge the big
> redwood tree is downslope.

I found only one picture of the big redwood, but it doesn't show
how massive the trunk is (measured at 30 feet in circumference).
https://c2.staticflickr.com/6/5607/15498557171_df86936bcb_b.jpg

There's actually a person, close to the tree trunk up there, in
the cargo net, setting up the blocks of wood for the cable to go
around (this picture was taken a few weeks ago).

[malua mada!]

Looking at the animated sequence,
the uphill end of the carrying wire is tied to a tree, not anchored in the ground otherwise? That tree is going to bend over.

Likewise, no matter how huge the downhill tree may be, watch the roots on the downhill side for signs of popping.

Good luck with the parade ground in the sky!

[Tom Miller]

"Danny D." <dannyd...@gmail.com> wrote in message

news:m2n459$c0c$2...@dont-email.me...

Here are a few things that come to mind:

Has the owner checked with his insurance provider to see if he is protected
from liability? Things like this are known as an attractive nuisance and
everyone involved might be at risk should anyone get hurt.

Have you considered corrosion of the cable? Is it steel, galvanized, or
stainless?

Do you have an inspection plan in effect to detect future failure
conditions?

You might apply some paint to the cable clamps to serve as a witness mark to
see if anything slips.

It is pretty neat and will have all the kids in the area interested.


Regards

[josephkk]

It never was a question about the strength of the trees. It has always
been about the cables and the load.

?-)

[Danny D.]

josephkk wrote, on Wed, 29 Oct 2014 21:11:45 -0700:

> It never was a question about the strength of the trees. It has always
> been about the cables and the load.

I would tend to agree, as the big redwood is massive (30 feet in
circumference).
https://c2.staticflickr.com/6/5607/15498557171_df86936bcb_b.jpg

For scale, there's actually a person, wearing blue, in the cargo net
right next to the tree, fixing the blocks for the cable that we later
wrapped around that tree.

BTW, even the little redwoods are not all that little:
https://c4.staticflickr.com/4/3910/15279581646_2753fa993e_c.jpg

[Danny D.]

Tom Miller wrote, on Wed, 29 Oct 2014 15:56:20 -0400:

> Things like this are known as an attractive nuisance and
> everyone involved might be at risk should anyone get hurt.

The owner is an ex Google executive, so, he has the disposition to have
lots (and lots) of "attractive nuisances" on his property! For example,
you can travel in another part of his property, high up, from tree to
tree to tree to tree (etc) by cargo net, for HUNDREDS of feet!

I always find a way to take my grandkids to his place for fun stuff.

> Have you considered corrosion of the cable?
> Is it steel, galvanized, or stainless?

Steel. When I asked, he said there's plenty of zinc fittings, so, he
wasn't worried about rust.

> Do you have an inspection plan in effect to detect future failure
> conditions?

Good question. I'll ask.

> You might apply some paint to the cable clamps to serve as a witness
> mark to see if anything slips.

This is a GREAT idea!
I will suggest that to the owner!

> It is pretty neat and will have all the kids in the area interested.

Kids love his place. I can't count the number of "attractive nuisances"
he has on his rather large (scores of acres) property.

[Danny D.]

dpb wrote, on Thu, 30 Oct 2014 08:13:07 -0500:

> I don't need a picture of the big redwood; I'm perfectly willing to
> allow as how they can and do get big; I've been through redwood country
> a number of times. I was simply noting from the pictures posted near
> that point in the thread there didn't seem to be much of any real size
> and was more concerned of potential on the root system with the load
> than whether the tree itself was sufficient presuming it was.

I apologize that most of my pictures were from the uphill side (where
the suspension bridge is currently forming), where those trees are puny
in comparison to "General Sherman" (which is what we call the big one).

The only time I climbed down the 100 feet to General Sherman was when we
were setting up the cables around it, and I was the gaffer who passed up
tools and supplies.

So my only pictures of General Sherman are the ones I showed, which don't
quite show the massive girth of the thing, especially at the bottom,
because what you see above is already split in two.

> When the response to the question regarding angles for trying to
> estimate tension needed to provide a given vertical force component
> includes the justification that the angle will increase owing to the
> tree flexure doesn't lend itself to thinking they're terribly big,
> either. Just a "devil's advocate" position raising the question...

I agree with you, that when I first saw the angle stuff, I too wondered
about bending a tree that much to make *any* difference. I'll forward
your comments above on to the owner to see what he makes of that.

> From a diagram such as that with a few measurements one could get at
> least a reasonable approximation using simple-enough analyses as
> outlined in the following (beginning at 7-30ff)--
>
> <http://isdl.cau.ac.kr/education.data/statics/ch7.pdf>

I will forward that "Chapter 7: Forces in Beams and Cables" PDF to the
owner, who, while he isn't an engineer, he has multiple graduate degrees
and can handle almost anything we throw at him (he was an early Google
exec).