The new diy bigbridge sent me to ground rapidly and unceremoniously tonight. Was gonna try to stay te night to try it out. About the time I got stretched out I heard snap crackle pop and hello earth. Very unpleasant 4 weeks after back surgery. Both spreader bars which are te larger .75 from dutch, snapped where they joined. My triangles are about 83% of the spreader length. I don't understand what went wrong. The prior two times I laid in it no issues. 20160513_211047.jpg20160513_211457.jpg
That is indeed alarming. Sometimes a bridge hammock is pulled pretty tight to make it flat enough. Do you have an idea what the sag angle was? Did you use a structural ridge line, and if so, what was it's length? What was the length of the hammock, including the suspension triangles? What were the spreader bar lengths and the width of the hammock where they attached? How did they attach (any torque exerted on the tip)? I'm not giving you the third degree, here, just trying to think of all the factors that could have contributed to the failure. Perhaps the most worrying thing is that they both broke. You have probably already contacted Dutch. If not, do so. He'll inevitably make it right, but more importantly he'll want to figure out what happened. Lastly, how's your back? Which end broke first? That is, which part of you hit the ground first? If you're not sure, they may have gone simultaneously.
both ends snapped pretty much at the same time. It wasnt a slow bend then fail either the head end snapped with some force. one side hit me in the back of the head leaving a sizable knot. lol. Im sore but since both ends snapped at same time I hit pretty flat and I did have an inflatable mattress under me so all in all I was lucky I think.
My spreader bars were 44 and the body width is 52. Total length of the body is 82 Ill have to go measure with the triangles. the other 2 sides of the triangles is right at 83% of the spreader bar width 37. Im not sure about the angle but I did pull it tighter because I had an issue the prior time with shoulder squeeze so I lowered down my straps and moved one end out to another tree about 3 feet further than the 2 I normally use.20160513_213716.jpg photo where spreader bar whacked my head when it snapped.
Those spreader bar ends where they join, look pretty short. The spreader bar is under a large compression force. That is why the suspension triangle length is important. The Ridgerunner bridge from Warbonnet Outdoors is made in a similar fashion (ratio of spreader bar length to fabric width is close to 1:1). The stock suspension triangle length is also much longer than the length of the spreader bar to reduce the compression force on the spreader bar.
For your bridge hammock, I would increase the length of the suspension triangle so it is closer to the length of the spreader bar.
Cheers
Brian
Good judgment comes from experience, and often experience comes from bad judgment. - Unknown
I am a BIG boy and when i built my diy grizzbridge i wanted to avoid things like this from happening to me
1The length of your triangle suspention pieces should be equel to the length of the spreader bar..
2 What i did was to use .742 poles from Quest and then i took one of the poles with me to home depot and found the pvc pipe that i could slide my bar into that would fit it snug,, i then bought 2 lengths that i slid my bars into for reinforcement leaving about an inch short on each end.
I was around 440 lbs at the time and i could bounce around in my bridge all day long without worry about the bars snapping, it works, if you are a very heavy guy then i strongly suggest this, much better for the back than the sudden smack of the ground!
This ratio of a spreader bar on a bridge is often 70%-75% of the body width. Your ratio is over 80%. Just as decreased hang angle increases tension on the system in the main axis, increased spreader bar ratios are going to increase the stress on the lateral axis. And with the increase ratio comes a more acute angle torquing the spreader bars, aside from the purely compressive forces.Originally Posted by bigsig11010
that is a great idea zilla. This is my first ever bridge and I thought that by going with the 742 poles i was going strong enough. Im about 299 1/2 . it is all about learning as we go. As my old football coach use to tell me.... "son if you gonna be dumb, and you are.. you gotta be tough."
Last edited by bigsig11010; 05-14-2016 at 13:33.
After i cut my white pvc to the size's needed i then wraped them in camo duct tape so they would match my bridge, it just looks better,,, good luck and let us know how it works out..
Also you could double check with Grizzly Adams but i'm sure he will tell you the same, - the triangles must be equel lengths, the cordage and the spreader bars should match, the smaller the cords are compared to the bars increases the likelyhood of tipping over.
I suffered the consequences of not understanding all the physics involved. I was trying to stay close to the sizes that v allen had used on his xxl bridges. I left the spreader bars a little long to start with thinking I could shorten them a little if I needed to but I couldnt really put length back on after I cut them.
They say a person can learn something new everyday of his/hers life, live and learn.
Your bridge will not only be very enjoyable once it's done but you will have learned quite abit by then.
And don't forget that it's really okay to learn from others mistakes as well as your own, in fact it's easier on the back..!!...
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