The TurtleDog stand

[le_butters]

Love this thread. I'm going to have to get on this ASAP. I hate my bed and this is perfect.

[gregwoodwalker]

I have read this thread with interest. Elegant design. I will build one.

One idea strikes me, that I wondered if anyone had comments on. As designed, if I understand the forces involved, the hammock is attached to the ridge pole, thus the ridge pole needs to be strong enough to withstand the force of the loaded hammock. The tripods basically keep the pole and whatever is hanging off the pole, suspended. You could hang the ridge pole from anything, doesn't have to be tripods, it is the pole that holds the hammock, not the tripods.

This is what makes this design so elegant. The tripods simply have to resist a downward force. The pole is the part that sees an angle force, resulting from two components, the weight pulling the hammock down plus the force trying to pull the ends of the hammock together.

Now consider an alternative way of dealing with the forces, sort of a divide and conquer way. Suppose you hooked the hammock to the tripods directly. For the moment, envision this without the ridge pole. Of course, this won't work, because the tripods will be pulled toward the center and capsize. But they will resist the downward pulling fine. The only thing stopping this from working is the lack of a pole, so yes, you need the pole.

But now suppose, instead of attaching the hammock to the pole, you leave it attached to the tripods. Now think about what else is needed...only a way to stop the tension from pulling the tripods together, since the downward force is already taken care of by the tripods. I would expect that this force pulling the tripods together is relatively small part of the total force withstood in the typical TD stand, where the ridge pole has to withstand both forces.

So now, suppose we add a ridge pole that has only one force to contend with, that of withstanding the hammock pulling the tripods together. This pole would be attached to the top of the tripods, and independent of the hammock attachment. Now the ridger pole merely needs to withstand a straight, compressive force, with no angular component (for practical purposes anyway). The top of the tripod can push against the ridge pole, independent of the downward force.

My expectaions is that in this arrangment, the ridge pole can be a relatively light weight pole. All it has to do is withstand compression. Does this sound like it would work? I am still pondering how to attach the ridge pole to the top of the tripods...

By the way, for any of those that would like to know how to calculate the spread of the legs, based on the length of the tripod baords and the angle use to cut the top parts of the legs, assuming you are using the design with the boards being stopped from spreading by the tapered ends above the hinge, the formula is as follows.

The horizontal distance from the center line to the bottom of the pole is equal to the length of the pole times the Sin of the angle. for example, a 72 inch leg, cut to a 15 degree angle, would be 72*0.2588=18.6 inches. to get the total width of the feet, multiply that by 2, for 37.2 inches (18.6 x 2).

To calcualte this for other angles, you simply need a lookup table or calculator that will do trigonometry. For the sin of 10 degrees, use 0.1736 and for the sin of 20 degrees, use 0.3420

To look up other angles, here is one resource:

http://myhandbook.info/table_sin.html

Cheers!

greg

[hppyfngy]

Greg,

We all like thinkin' folks around here.

There are a couple of thoughts that come to mind. Is what you want to accomplish with this alteration the use of a smaller, lighter ridge pole? I'm not sure how much smaller or lighter you could get. The reason the chain link fence rail is popular is because it's off the shelf easy, just whack it in half and the swaged ends make it just fit together. It's strong enough and inexpensive and one of the only ways we've come up with to have a ridge pole that readily comes apart into two relatively small pieces.

And it's doing more work than you might think opposing these forces.



My concern with your idea is how you're going to attach to the tripods without introducing forces that will compromise it as well. Also a reason the 2x2" uprights are popular is they are cheap and light weight. And there strength is in opposing the compressive downward force as you point out.

But don't let me dissuade you! Give it a go or draw it up and let's see what happens!

That's how we got this far in the first place...

[samsara]

I have read this thread with interest. Elegant design. I will build one.

One idea strikes me, that I wondered if anyone had comments on. As designed, if I understand the forces involved, the hammock is attached to the ridge pole, thus the ridge pole needs to be strong enough to withstand the force of the loaded hammock. The tripods basically keep the pole and whatever is hanging off the pole, suspended. You could hang the ridge pole from anything, doesn't have to be tripods, it is the pole that holds the hammock, not the tripods.

This is what makes this design so elegant. The tripods simply have to resist a downward force. The pole is the part that sees an angle force, resulting from two components, the weight pulling the hammock down plus the force trying to pull the ends of the hammock together.

Now consider an alternative way of dealing with the forces, sort of a divide and conquer way. Suppose you hooked the hammock to the tripods directly. For the moment, envision this without the ridge pole. Of course, this won't work, because the tripods will be pulled toward the center and capsize. But they will resist the downward pulling fine. The only thing stopping this from working is the lack of a pole, so yes, you need the pole.

But now suppose, instead of attaching the hammock to the pole, you leave it attached to the tripods. Now think about what else is needed...only a way to stop the tension from pulling the tripods together, since the downward force is already taken care of by the tripods. I would expect that this force pulling the tripods together is relatively small part of the total force withstood in the typical TD stand, where the ridge pole has to withstand both forces.

So now, suppose we add a ridge pole that has only one force to contend with, that of withstanding the hammock pulling the tripods together. This pole would be attached to the top of the tripods, and independent of the hammock attachment. Now the ridger pole merely needs to withstand a straight, compressive force, with no angular component (for practical purposes anyway). The top of the tripod can push against the ridge pole, independent of the downward force.

My expectaions is that in this arrangment, the ridge pole can be a relatively light weight pole. All it has to do is withstand compression. Does this sound like it would work? I am still pondering how to attach the ridge pole to the top of the tripods...

By the way, for any of those that would like to know how to calculate the spread of the legs, based on the length of the tripod baords and the angle use to cut the top parts of the legs, assuming you are using the design with the boards being stopped from spreading by the tapered ends above the hinge, the formula is as follows.

The horizontal distance from the center line to the bottom of the pole is equal to the length of the pole times the Sin of the angle. for example, a 72 inch leg, cut to a 15 degree angle, would be 72*0.2588=18.6 inches. to get the total width of the feet, multiply that by 2, for 37.2 inches (18.6 x 2).

To calcualte this for other angles, you simply need a lookup table or calculator that will do trigonometry. For the sin of 10 degrees, use 0.1736 and for the sin of 20 degrees, use 0.3420

To look up other angles, here is one resource:

http://myhandbook.info/table_sin.html

Cheers!

greg

It seems like it should work fine... just put a pad under you and wear some football gear until you are sure that it won't come crashing down on top of you

The beauty of the turtlelady and turtledog stands is that they actually do divide and conquer the two forces (compression and gravity). Keeping the discussion on the TD side of things, if you make it with the hppyfngy eyebolt (which I consider the latest greatest version mod) and hang your hammock the way he shows in pics then the pole takes all of the compression and the weight is transferred to the tripods (you won't see any bowing in the pole). The way that I did it in the original version for this post also worked too but only because I used the prussik wrap for attaching my hammock.

My TD 2.0 (with the pole sitting on top of the tripods) also does the same thing as long as the attachment is right where the pole rests on the tripod. If I move it just a little bit away from that spot then it is obvious that you start getting away from transferring all of the gravity to the tripods because the pole bows like crazy and looks like it could snap (which is also why you need something solid just to be safe).

The other points by hppyfngy are also important (relatively inexpensive and easy to acquire and build) and why we have done things the way that we have but really as long as you divide and conquer (and test carefully ) then you should be fine. The previous versions have done the divide and conquer, now we continue to divide and conquer in the way that best suits us. That's what I'm most thankful for... turtlelady helped me to understand the two forces that need to be addressed and gave me a way to solve the problem and the knowledge of how I can apply it in other situations.

Dave

[olddog]

gww, interesting first post and welcome to the forum. Not much for the mathamatics and physics of the hang, I'm still pushing the limits on my SLS( single line suspension). Those I'll leave up to the experts, I just have a tendency to throw something togeather and see if it works. What I'm mentally visualizing sounds interesting and just working out the physical means of accomplishing your goal. What I'm visualizing is an attachment of the hammock to the tripods with the toprail used only to keep the tripods from collapsing inward. Looking forward to seeing how this progressses. As you will find some of us thrive off of feeding off of the input of others. Again welcome aboard.

[Whiskeyjack]

Just a thought an Greg's post. If the pole is simply keeping the tripods apart, would you be able to simply tie off the tripods to another structure to hold them out? Possibly even stake them out to the ground? Not being a math person, I don't know if the structure would have to be as strong as supports required for a normally hung hammock.

[olddog]

D.a.m.n. Greg now I'll be going to the hammock tonight trying to reduce the material in a TL/TD stand. No worry this is how I go to the hammock every night.

[Acer]

The simplicity of the tripod stand is to set it up without staking it down. If you wanted to stake it down, then do a Almosa Stand which is 1 pole at each end, and staked down each with 2-3 boom stakes, and each upright single pole is tied together with a single strand of amsteel. In its simplicity, the Almosa Stand works perfect until you either try to pitch this stand on solid rock or sandy ground vs the tripod stand working absolutely anywhere. Having built a Almosa Stand, I built 2 stands from Army Surplus 4' poles for me and the wife to car camp with when we can't or don't have permission to go to trees if that ever arises and can hang virtually anywhere we have the space with or without trees.

https://www.hammockforums.net/forum/...=Alamosa+Stand

[gmcttr]

I think you'll find that the forces don't divide up as you're thinking.

Keep in mind I'll be making some broad statements ignoring small, fairly inconsequential forces as well as dynamic loading

The downward force that each end of the ridgepole/tripod sees, is 50% of your weight. Properly rigged, the ridgepole only has to resist the crushing force, across it's diameter, of this weight as it is transferred through to the tripod.

The compressive force applied to the ridgepole is dependent on the hang angle. The shallower the angle, the higher the force. At 30*, the pulling force on each strap equals your body weight. The ridgepole will see compressive forces well above your body weight which is applied to both ends of it.

Whether the ridgepole has the hammock directly attached or not, the forces on it will be close to the same.

Some reduction in compressive loading of the ridgepole could be accomplished by having it mounted to the tripods well above the hammock mounting points. Some of the compressive load would then be transferred through the tripods to the ground. As the base of the tripods would be pulled inward, they would need to be staked down in this scenario and complicate the entire system.

[samsara]

The simplicity of the tripod stand is to set it up without staking it down. If you wanted to stake it down, then do a Almosa Stand which is 1 pole at each end, and staked down each with 2-3 boom stakes, and each upright single pole is tied together with a single strand of amsteel. In its simplicity, the Almosa Stand works perfect until you either try to pitch this stand on solid rock or sandy ground vs the tripod stand working absolutely anywhere. Having built a Almosa Stand, I built 2 stands from Army Surplus 4' poles for me and the wife to car camp with when we can't or don't have permission to go to trees if that ever arises and can hang virtually anywhere we have the space with or without trees.

https://www.hammockforums.net/forum/...=Alamosa+Stand

Yup, what he said (I was typing up something similar but thought I would see if anyone responded already)

I think you'll find that the forces don't divide up as you're thinking.

Keep in mind I'll be making some broad statements ignoring small, fairly inconsequential forces as well as dynamic loading

The downward force that each end of the ridgepole/tripod sees, is 50% of your weight. Properly rigged, the ridgepole only has to resist the crushing force, across it's diameter, of this weight as it is transferred through to the tripod.

The compressive force applied to the ridgepole is dependent on the hang angle. The shallower the angle, the higher the force. At 30*, the pulling force on each strap equals your body weight. The ridgepole will see compressive forces well above your body weight which is applied to both ends of it.

Whether the ridgepole has the hammock directly attached or not, the forces on it will be close to the same.

Some reduction in compressive loading of the ridgepole could be accomplished by having it mounted to the tripods well above the hammock mounting points. Some of the compressive load would then be transferred through the tripods to the ground. As the base of the tripods would be pulled inward, they would need to be staked down in this scenario and complicate the entire system.

Again, yup I think if you keep the attachment point very close to the tripod/pole attachment then there won't be much compressive load transferred to the tripods and could pass on staking it out. I guess I could take one for the team and put my fencerail between the two legs towards the middle and butted up against the back leg (it would take two seconds to do since I'm using my sit on top TD 2.0) and then attach my hammock to the hinge... nah, I'll pass (if it ain't broke... and it ain't broke me... then I'm not going to fix it )

This is why I like the TL/TD system because it does such a great job of dealing with those forces and I don't see the fundamental way of doing it being improved upon (but I would be happy to be wrong). You can change materials and do a few tweaks but if you fundamentally change it and improve it then you really are probably talking about something that is no longer a TL/TD stand.

There's my $.02 and now I'm off to my hammock in my TD stand to watch the rest of the FGCU/UF game (go Eagles!!)

Dave