DIY Suspension Bridge - 54' Span

How to build a suspension bridge. Cost: approx. $500. Time to complete: 40 hours. Built across a creek in the woods by one person.

- a complete Materials List for a 54' DIY Suspension Bridge with quantities and image references,
- How To Determine If Your Location Will Work,
- and a BONUS section on how I spent only $500 building my own 54' suspension bridge.

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[WVmedic]

Yes sir, very creative. I'm not writing this to criticize, but to inform. I am not an engineer and I'm sure some will read this and could offer more specific suggestions for the next one. I lived in the country in West Virginia and 'swinging bridges' were common. I concur as Ted mentioned about the I-bolts...not passing through the pipe. This reminds me of the skywalk collapsed in KC. (I'm an old firefighter/paramedic). I also was trained in high-angle rope rescue, so was familiar with the tension put on static lines and anchors (bottom cable, I-bolts, pipes). It will probably do you fine in your garden, but I wouldn't allow more than one person on it at a time. I'll share why. Your bridge, not counting the cable, has a standing load of about 460 pounds (wood). Add two 150 lb. adults brings load to 760 lbs. The tension placed on the anchors would be calculated based on the angle created by the load on the cable(s). If your cables are so tight there is very little deflection when the additional load is applied, the force on the anchor (and cables) can be estimated as follows: 170 degree vector angle increases tension force 574% on each anchor, or an adjusted load of 5144 lbs. 140 degree internal angle increases tension by 145%. Take that into account when chosing your support cables and calculating the 'sag'. The recommended safe working load on 1/4 inch steel cable 1100 lbs. static, while 3/8 is 2440, and 1/2 inch is 4280 lbs. The in-line working load limit on a split eye I-bolt (wire turned)...for 3/8 inch is 125 lbs, for 1/2 is 200 lbs. (4:1 safety factor...should NEVER be used). In contrast, forged I-bolts are 1200 and 2200 lbs. respectively (5:1 safety factor). These numbers are just some examples I learned dealing with rope rescue and safety considerations and don't include force changes with acceleration (bouncing). Again, your bridge is really cool, and will likely serve you well, but I just wanted to mention these things so others may want to go 'heavier' to increase their safety margins. It is just important to calculate these forces and assure your 'weakest link' will meet the test. Sorry for rambling....

[tompate]

Watched this video cause I need to build one very similar length but over a deeper ravine.

Can't lie, some the components and practices used gave me heartburn, there's just no way I'd get on that bridge.

I just hope everything has worked out ok so far and nobody has gotten hurt on it.

[aliastagami]

This video is 10 yrs old now. I'm curious if you've updated the bridge or if it is still functional/standing. I won't repeat the engineering comments previously made, but I see many design choices that might not last over time.

[cadavatar]

I think this is awesome, I'll just say that outright, it is. I do, however have an important critique with safety in mind.

Where your eye bolts are installed, you should always use an eye bolt that goes through the pipe entirely, 2 holes not just one, and there should be two, thick galvanized washers, one on each side of the pipe. This only increases the build cost very slightly, but it increases the structural integrity of the bridge significantly.

Installing a nut inside of a pipe and using one hole means the force exerted on the cable is creating the pull on the inside of the pipe against a small concave steel surface area. Since the shape is concave, it invites deformation of the hole under load and the nut can possibly pull through.

Installing an eye without using washers means the nut, even if it is on the opposite side of the pipe, can possibly deform the hole and if it pulls through the first side, there may be enough energy for it to pull through the other in the event of a failure.

I'm just putting this out there, of course do as you like but you may want to do a little research on how to improve your already impressive design.

[brentderksen]

Thats awesome! At least there are still some people out there who like to try cool stuff.

[kayakerodie]

there is no redundant (backup) safety system on the support cables at the ends of the bridge in case of a cable break due to the clamps slipping or turnbuckle failure. The free end of the cable should have been turned back and reclamped at the source before the turnbucke.

[skyelinepark]

Thank you very much for sharing. Good on you for starting it and putting it out there to share and also to allow others to make suggestions to improve it.
I love people giving stuff a go.
I have been putting shade sails up around my place using similar steel rope on a mountain top where the winds are crazy. The shades over lap and are in uneven places so it is quite the adventure with improvements happening every time. I trust my brain is gaining much from the exercise as yours must too from the bridge. One day I will give the suspension bridge a go having learnt from here. When people mention problems with hardware I am wondering if Stainless steel is a must.
Thank you again.

[hogwilder]

Amazing! Great Craftsmanship, you do neat work. It's so cool to see someone do great work and also figure out how to save some $$$. Great Video and Great Bridge!

[franksnb]

a rough calc. assuming a 5ft sag in the middle, a load of 185lbs in the middle and the load is divide over 2 bolts the maximum tension will be 250lbs on each bolts. if the sag is less the force goes up! whats the shear strength of the thread/bolt?

btw thats static, jump up and down and expect a large increase.

[zoelo]

Good job for one-man work like this. For the bridge to last longer, I would use PT#2 deck boards and 6x6 PT timber. The galvanized conduits will rust after a couple of year.

[ronaldj]

I googled for a suspension bridge and came across your video. You've done a fantastic job and the result is impressive. Some folks have a good eyeball for what's good some folks don't. Obviously you have the touch!

[damiansar]

Does the creek have flash flooding? I want to do a similar bridge, but I need to keep the bridge high due to fast moving water in winter at my place.

[MichaelBrown-znfc]

how deep did you make the post holes for the concrete? What diameter was the concrete? And how has the bridge held up so far? Thx.

[PeterRatsch]

Question, wondering if the screwed in metal strapping under the boards securing the cable slips at all? Considering the same for a treehouse but mine will be more sloped so worried they might slide?

[DandyDi]

I really like your bridge and my husband and I are thinking about building something very much like it.  Is there another video that completes the process, since this one just gets as far as the attachment of the planks to the cable and then ends?  Thanks for posting such a helpful video.

[VaranusVideos]

Talk about creativity love it man im building a bridge accros my 14 foot stream, might do something similar

[jamieshotter]

Good bit of simple engineering. For securing the deck to the support cables, I would recommend u-bolts through deck or passing two bolts right through the deck with plates top and bottom. Bottom plate holding cable to deck on underside and the top plate to stop bolts pulling through timber deck.

[williamblacksmith]

Great bridge. You did a very nice job of constructing it. It would be interesting to have James Crane expand on his comments that you should have your home owners insurance up to date and you should expect to have a lot of problems with your hardware. Anyway, I hope to begin construction on my own suspension bridge soon. Essentially I will be using your basic design premise to build my bridge. It may be a little longer span. Between 50 to 60 ft. Thanks again for sharing the video. I have watched it many times as I think it is probably the best DIY suspension bridge on you tube. Also, I am curious how your bridge is performing. Do you suggest any changes or modifications? Thanks again.

[crayyzgames]

How is it holding up all this time later?

[matthewdavis]

That's tight, thanks for sharing, totally going to implement this design thank you!