# How Much Weight Will a Lag Bolt Take ???



## NorPlan (Jul 21, 2014)

:help:  Came across an idea to Hang a DIY Hammock Bed from the Ceiling in the Backdeck Sunroom.... We've looked at various sizes and ideas on Pinterest.. The idea is taking a Super Single Mattress , 2x4 frame and plywood..4 chains and appropriate hooks top and bottom..Then  screw hook lag bolts into 2 / 2x4's placed across from truss to truss which the chains will be hanging from.. Pictures can be deceiving and some ideas are a double bed hanging on chains...Hence my Query, Will a Lag Bolt hold the Weight and if so How a much Weight..:hide:


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## Chris (Jul 21, 2014)

It all depends on size, material and material it is going into. That said I have eye bolts into a single 4" x 6" to hang my hammock on my patio.

You can always drill through and nut and washer the a bolt through the wood and I believe that way will hold more than just threads into wood. Also green wood will bite better than an old piece.


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## bud16415 (Jul 21, 2014)

There is a huge difference in fasteners these days. I&#8217;m just finishing up the deck and I used lags to attach the rail posts. I bought some junk bolts at tractor supply and I would pre-drill holes and snap the heads off barely tightening them. Don&#8217;t use this junk that&#8217;s coming from China. With a good quality bolt you won&#8217;t need that big of bolts at all. If you do want to calculate it figure area of the minor dia of the threads X 10,000 to get the pounds it will safely hold. 10,000 would have a safety factor already in it of 2 or 3 :1 would be my guess. 
.25-20     300 lbs per
.312-18   500 lbs per
.375-16    750 lbs per

The screws you use to hold these 2x4 up should be deck type screws not drywall screws and go a good inch and a half into the joists. The 2x4 idea is good because you will be spreading the load across many joists. Two screws into each joist. 

Then all you need is a sign (If the sunrooms a rocking don&#8217;t come a knocking!)


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## Wuzzat? (Jul 21, 2014)

A 200 lb person in a hammock where the support chains are 30 degrees below the horizontal will have 200 lb tension in each of two support ropes.  
A tighter hammock at 15 degrees will have 400 lbs tension and a saggy hammock at 45 degrees will have 140 lbs.

Assuming a tensile strength of 70,000 PSI, a 0.3" dia. bolt could hold 70,000 x 3.14 x (0.3^2)/4 = ~5000 lbs.

5000/200 = 25, a way big safety factor.


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## nealtw (Jul 21, 2014)

"I" bolt with nuts and washers, in a sun room you could have people using it as a sofa, best over do it.


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## NorPlan (Jul 22, 2014)

bud16415 said:


> There is a huge difference in fasteners these days.
> The screws you use to hold these 2x4 up should be deck type screws not drywall screws and go a good inch and a half into the joists. The 2x4 idea is good because you will be spreading the load across many joists. Two screws into each joist.
> 
> Then all you need is a sign (If the sunrooms a rocking dont come a knocking!)




  10-4 on a Deck Screw stronger than a Drywall Screw...The Plan is to use  lag bolts to screw the 2x4 cross member into the Trusses.. Having browsed Pinterest for ideas, a few were Double Bed size hanging by chains from the ceiling...And not the bolt & nut theory either as some were older homes or Verandas, doubt  if they took the time to pull the ceiling down.. That's where we are , this idea came along later, I have v-joint closing off the ceiling...

 @ bud16415. This Senior Citizen don't need Warning Signs...Got a couple High Energy Grand Kiddies is the concern..:hide:


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## kok328 (Jul 22, 2014)

I would go to the local nut & bolt guy (not a big box store, not a hardware) and they will help you with bolt hardness and sheer strength.
I would also recommend the threaded eye bolt w/a washer and 2 nuts (jamb nut).
In my neck of the woods, I have a nut & bolt store that is their specialty.  They provide hardware for Cedar Point, OH roller coasters.


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## NorPlan (Jul 23, 2014)

kok328 said:


> I would go to the local nut & bolt guy (not a big box store, not a hardware) and they will help you with bolt hardness and sheer strength.
> I would also recommend the threaded eye bolt w/a washer and 2 nuts (jamb nut).
> In my neck of the woods, I have a nut & bolt store that is their specialty.  They provide hardware for Cedar Point, OH roller coasters.



:beer: @ kok328... I hear yah !! We got one of those Nut,Bolt,Fasteners Specialty Stores  close by too...Amazing what you find if you keep digging :hide: Can you believe if I could drill a hole wide enough, a collapsible wing thingamajig just got to coordinate the wings opening up blindly


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## slownsteady (Jul 23, 2014)

> In my neck of the woods, I have a nut & bolt store that is their specialty. They provide hardware for Cedar Point, OH roller coasters.



I would trust those guys with my life......oh wait....I already do.


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## bud16415 (Jul 24, 2014)

Last year at Cedar Point waiting in 2 hour long lines I wasn&#8217;t as concerned with the fasteners as the hydraulic lines.


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## Wuzzat? (Jul 25, 2014)

It'd be good if you can get the Ultimate Strength and Working Load for your components.  With the UPCs the supplier's website may help with this.


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## bud16415 (Jul 25, 2014)

Wuzzat? said:


> It'd be good if you can get the Ultimate Strength and Working Load for your components. With the UPCs the supplier's website may help with this.


 

A few posts back you threw out a number of 70,000 PSI as a tensile strength number. That IMHO is close to double of any normal hardware you are likely to find. You would never want to design close to that margin. You correctly pointed out a huge safety factor and it would still be huge but not as huge. In my line of work we generally look at 3 or 4 to 1 and in the case of life on the line we go to 10:1. 

Your information was correct about factoring in the angle if the load is not pulling straight down. A real world example is my Dog I built a run for using .25 steel cable and I strung it from the house to a big tree a couple hundred feet away I used a huge lag eye bolt into the houses framing and another in the tree with a turnbuckle. I had the cable quite tight and the Dog could run on a cable that would roll along the long cable. Well a rabbit came thru the yard and caused the dog to go full out 90 degrees to the main cable. Of course in theory the angle was zero as the cable deflected it was only a couple degrees and the force that dog exerted thru the toggle mechanism of that linkage was huge. Huge enough a smallish lab could rip the framing and the door frame out of a strongly built farm house. The solution after repairing the house was to leave the cable much looser and add a big spring into the turnbuckle end. 

So yes always be concerned with the force vector.


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## Wuzzat? (Jul 25, 2014)

bud16415 said:


> and add a big spring into the turnbuckle end.



Which may prevent internal injuries to your dog from sudden deceleration.  The ripped out framing might have done that the first time.


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## stadry (Sep 16, 2014)

there are only 3 strengths i consider & tensile's 3rd,,, pullout & shear are the numbers we watch mostly closely,,, we rarely consider labradors in our calculations


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## slownsteady (Sep 16, 2014)

> we rarely consider labradors in our calculations



most products are subject to "lab tests"


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## nealtw (Sep 16, 2014)

Never mind the lab, the Zorba test would be better
http://mostextreme.org/biggest_dog.php


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