Suspension Bridge VS Big Tree: Bridge Wins!

February 25, 2019 was not a good day for our suspension bridge. A snowstorm hit that weekend with 8-12 inches of wet, heavy snow, and trees started falling everywhere. Power was out all over the state, including here (which isn’t that unusual given our rural location). But alas, one big alder tree snapped and landed on one of the bridge posts, breaking it in half. Here’s what we were faced with when we cleared out the mess on the our side:

The cable-locking system held up as did all the stringers. We can’t see the other end of the main cable but assume it is also okay. Just nothing there to hold it up anymore!

Since the creek is still too high/freezing cold to cross, we can’t easily assess all the damage. But the bridge is “hanging in there” until help can arrive. Hopefully our spring won’t need any maintenance in the meantime.

Once we cut away the mess, we’ll need to dig out the old post (three feet), get another post across the creek and in place, tamped in with gravel, and then all the hardware re-attached. The decking will have to be removed so the structure can be lifted up more easily. As for the dead man, we’ll have to find out how it fared the blow.

You can see the tree that did the deed just uphill from the bridge. Nice aim, tree!

Ah well, it was time to replace the decking anyway. We’re looking for metal paneling of some kind (that we can afford). I’ll post photos of the fix later in the spring! Onward. P.S.: We’re getting too old for this sh*t.

UPDATE: So far we replaced the post, reattached the main cable and cranked the bridge back into place. You can see how those things happened here and here. We also built new new sets of stairs, and how to do that is here and also is a featured Instructable.

Book-inspired Suspension Bridge in Virginia

We were delighted to finally receive photos of a suspension bridge that was inspired by our book, Building a Small Cable Suspension Bridge With the Cable Locking System.

According to the builder, Mo Goldman, the bridge is just under 40′ feet in length and 4′ wide (basically half the length of our bridge) and is located in Virginia just outside of Charlottesville.

The posts are aluminum, 13′ in length, 6″ round with 1/4″ thick side walls, easy for two guys to carry. The post holes are 3′ deep and about 2′ around; the posts are placed on a concrete footer prior to pouring around them. Everything was hand-dug and poured because they were limited to access with a Polaris on one side.

It was fun to see that Mo set up a temporary cable to move materials across. That’s how we moved our gravel for the opposite side, one bucket at a time. But Mo took it further and carried the posts, other materials, plus wheelbarrow and even himself across their “zip line.”

Mo also followed the idea of setting up the catenary curve between two trees/structures located away from the creek to plan and build the cables and stringers on dry ground.

Mo didn’t use our cable-locking system, but instead used a system often used for this type bridge – an appropriate length “eye” bolt placed in a drilled hole in the beam. The suspenders were then connected with a chain connecting link, which uses a threaded portion mating to a free spinning nut to open or close it.

He wrote to us about the bounce in his bridge which was more than he expected, though not a big deal. I noticed that he paid attention to harmonic resonance in the arrangement of the stringers so they were assumed off the “nodes,” so wondered if the decking material he used could be partly responsible (a suspension bridge is going to bounce, that’s a given). He used a material called Trex, which is a deck material made from recycled plastic and wood fiber. Trex tends to flex more than standard lumber does. We concluded that he needed to stiffen the deck, so now he is working on some ideas.

Mo even put up a sign on his bridge similar to ours and inspired us to remake our sign so that it names the creek, too. We hope others who build a bridge based on what we did will also send us photos and notes about their building experience.

Meanwhile our book is available in paperback and as an ebook via Amazon.com.

 

How to Build a Small Cable Suspension Bridge

As mentioned, we built this bridge and wrote a “how we did it” book about the process a few years ago. Recently, I thought it would be fun to share the basics of this design as an Instructable for people who have enough skill to be able to take the information and work with it. And as we do in our book, we recommend having your specific design approved by an engineer just to be on the safe side.

Here is the link: Building a Small Cable Suspension Bridge – the Basics Plus a Video Demo

I entered their “Outdoor” contest and you can kindly vote if you like by clicking the little vote button at the top of the instructable page. Thanks! I need a t-shirt.

UPDATE: Thank you for your votes – were a winner! We won a t-shirt and a waycool  Campstove 2 from BioLite Energy!

Adjusting a Suspension Bridge Deck

One of the hazards of building a bridge in the woods is that there are trees in the woods. And trees sometimes fall. It was only a couple of weeks after my bridge was completed that a tree fell on it. It bounced off without causing damage other than a dent in a deck board.

A couple of years ago during a flood, a tree next to the bridge came down, and while not actually falling on the bridge, parts leaned heavily on the suspension cable. I cut off the branches that were in our way and let the rest stay for now since I was busy with other projects. This spring I finally cut the rest of the tree that was affecting the bridge cable. I knew that the deck had sagged a bit and would need to be adjusted at some point.

That’s why I have turnbuckles installed on all the deadman-to-post cable connections as shown in my book, Building a Small Cable Suspension Bridge. I could just turn them to pull the posts back and level out the deck again.

I used  what was handy to provide a resistance (something to work against) to turning the turnbuckle – in this case a big stick and a metal pipe.

WD40 oil worked to loosen up the connections. They weren’t rusty having been protected under the cover of those white tubes all these years, but they didn’t want to break loose easily.

I used a small bar for turning, but a longer one could have made things easier.

I used a pencil mark to verify if I was tightening or loosening.

Once they broke loose, each turnbuckle turned easily.

Jeep seemed amused that one side was now lower than the other. But that’s just part of the process!

I worked on all four turnbuckles, using line of sight to achieve the results I wanted.

All done, until the next tree takes a dive into the creek and the bridge is in its way.

This all only took about 30 minutes. Here’s a movie of the process if you’ve never seen a turnbuckle in action.

Thanks for stopping by! Be sure to check out our suspension bridge book. Here is the link:

Building a Small Cable Suspension Bridge with the Cable Locking System

Images, diagrams, and text copyright 2013-2017 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Zip Line Challenge

My spousal unit, who actually writes this blog, is an author and illustrator of books for kids. She ran across this website for aspiring engineers, and thought it would be interesting to some of my readers. DiscoverE (formerly the National Engineers Week Foundation) helps to unite, mobilize, and support engineering and technology volunteer communities. They hope to increase the collaborative footprint in K-12 education and celebrate with the public as it discovers the value of engineering education and careers.

I was especially intrigued by their Zip Line Challenge for kids. It’s actually a model that challenges kids to transport a ping-pong ball down a zip line from start to finish in 4 seconds or less. The activity discusses many of the considerations when designing and building a zip line. I’ve uploaded the PDF so you can download it from here, or you can get it from the website listed above. There are a lot of other creative engineering related activities there, all free to download and use in your classroom, home, summer camp, whatever.

Check it out: zip-line-challenge_091316

One of these years I hope to finish my zip line. All is ready, but now the brush has grown up so much I have to hire a tree climber to clear the 420 foot long pathway.

View from the zip line tower to the landing 420 feet down the hill.

Thanks for stopping by! Be sure to check out our bridge book if you’re thinking about a DIY suspension bridge. Here is the link: Building a Small Cable Suspension Bridge with the Cable Locking System.

And if you’re curious about Robin Koontz’s books, look her up on Amazon as well: Books by Robin Koontz

Images, diagrams, and text copyright 2013-2017 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Photographic Journaling

I’m not exactly someone who keeps a formal journal, but I keep a lot of records. They are for reference or just as a way to look back and remember what I did that day, that month, that year.

One of the many helpful advantages of digital photography is the ability to take and store photographic records. It’s easy and virtually free, once you have the device, to document and store the process for any project. Publishing the book Building a Small Cable Suspension Bridge was an afterthought after I finished building my bridge, but luckily my spousal unit had recorded most of the steps, using our first digital camera. That old beast used 3-1/2 inch floppy disks (remember those?) and the photos were low resolution. But with some computer magic, we had enough photos to chronicle the steps I used to construct the bridge. Many photos were taken just for fun and our own life journal, but others were for reference.

Since my first bridge was a “Golden Gate” style suspension bridge, the stringers were of varying lengths with obvious repeats on each side. I installed the connection “eyes” to the stringers and organized them using a numbering system. That way, when I attached them to the two main cables, it was an easy chore to sort and install, using cable clamps.

I assembled everything on dry land. Then I just attached the two cables (with stringers attached) to the four posts. I could then easily install the cable locking system components and the decking.

My more recent project is our house. I put in a lot of blocking so that there were plenty of places to connect cabinets, towel racks, grab bars, whatever. Then I photographed all the walls before covering them. That way, when it was time to hang cabinets, I referred back to the photos to recall just where I put the blocking.

This photo shows the backside of the kitchen wall with blocking for the cabinets. My only regret was that I didn’t write exactly how far the blocks were from the ceiling or floor – large lettering would be easy to read in a photo – but I was able to locate them pretty accurately using my electrical boxes for reference.

Thanks for stopping by! If you want more information about my bridge, you can view a video and also read through the archives of this blog. If that’s not enough, be sure to buy my book! Here is the link:

Building a Small Cable Suspension Bridge with the Cable Locking System

Images, diagrams, and text copyright 2013-2014 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Evolution of the Cable Locking System and an Alternative Plan

When the idea of the cable locking system first came to me, it was to assemble and disassemble the means of holding the beams for the deck of a suspension bridge. How it was to be produced and what that might cost were of secondary consideration then. After working out just how I would have it made, I found a manufacturer that would do the job, and it was a reasonable cost.

It was a long process getting the patent for the cable locking system, but once that was accomplished we set about writing a book – Building a Small Cable Suspension Bridge with the Cable Locking System. The book was meant to promote the cable locking system and talk about all the steps we took to build the bridge.

I never thought there was much of a market for small suspension bridges, after all, how many people have a creek or ravine that they need to cross on their property? But after we published the book, there was a fair amount of interest in the cable locking system, mostly in the United States, but also from around the globe. And we had put in the book, and on our website, “contact us if you are interested in the CLS.”

About a year later, some people were asking about purchasing CLS components. We had three companies that could do the job, but we were only considering about 50 “units.” After some waiting they gave quotes on 100 or 300 units. The prices seemed expensive, and after informing the interested buyers, we heard no more from them.

The cost of production seemed to be a problem and we weren’t willing to buy and store parts in case someone ordered them. So I wondered: Can I simplify the CLS so that it could be produced more cheaply, and by just about anyone, with a minimum of tools? I came up with a possible answer.

The “inverse” CLS employs the cable locking system but places it somewhat in reverse of the
original application. It eliminates some of the materials and simplifies the manufacturing process while still using the patented cable locking system. Here’s a drawing:

The new system has some drawbacks, in that it has to be placed beneath the beam during assembly as opposed to slipping the beam into the original CLS. Also, the beam has to be pre-drilled and a PVC tubing should be inserted to protect the cable from corrosion. But overall, assembly is not all that different from the original cable locking system design.

Picture a swing: hung by two ropes (chains, cables, etc) one on each side. To assemble the “inverse” system, while cradling the beam in your lap, grasp the first of the two suspender cables, push it through the pre-drilled hole ( with tube protector) such that the cable can be inserted through the “inverse” CLS. Pull tight. Proceed to other side and repeat. A screw through the side of the inverse will lock it to the beam so that it can’t move about. I actually use a screw in my original design, if you noticed in the book.

Hopefully this design will be something more affordable and something that people can have made locally without a lot of hassle. I prefer the original set-up for ease of assembling “on the fly” and less intrusion to the beam, but this is an option for you to consider.

Thanks for stopping by! Be sure to check out the book. It includes some cool ideas that apply to other projects, like how to put a really tall post into a deep hole when you aren’t that tall. Amazon has the book on sale for about $12.00 right now. Here is the link:

Building a Small Cable Suspension Bridge with the Cable Locking System

Images, diagrams, and text copyright 2013 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Zip Line!

When I created this blog I promised something would be posted about zip lines aka ziplines. So, here is the first post about all that.

I visited Costa Rica a few years ago and rode on my first wild zip line. That is, it wasn’t a carnival ride or a rope in someone’s yard. It was down a mountain, in the rainforest, and attached to trees, and pretty freeking amazing. When I got home, my spousal unit said, “You’re going to build one of these, aren’t you?” And I said “Of course!”

I set up a a 420 foot zipline on our property. So far I’ve built the tower and ladder, which is a great treehouse getaway:

and I built the lower platform:

and have installed and tested a temporary (smaller diameter) cable. Here is a fun movie of a sandbag wearing my spousal unit’s blouse slamming into the platform:
Zip Line Test with Fake Spousal Unit Getting Seriously Hurt.

While I was pleased at the 32 MPH speed, this test proved that I need to raise the final cable a bit on the tower tree and on the base post as well when I finalize everything.

There are more photos of the building process on my website: Zipline Photos.

The full size cable is up on the hill ready to install but at this point the path down the mountain needs to be cleared (again) before we continue with the construction. For now, I’m working to finish building our house, so this project is on hold for the moment, but will be completed at some point.

What’s funny about this particular project is that when my spousal unit’s elderly relative heard about it, she wrote us out of her will, telling another relative in private (which of course didn’t remain private) that “Building a zip line is pure Tom Foolery! These people have time to burn!” Well, building a zip line is what I do on the weekends rather than watch football. Just don’t call me Tom.

Thanks for stopping by! Be sure to check out my book about building a bridge. It includes some cool ideas that apply to other projects, like how to put a really tall post into a deep hole when you aren’t that tall. Amazon has the book on sale for about $12.00 right now. Here is the link:

Building a Small Cable Suspension Bridge with the Cable Locking System

Images, diagrams, and text copyright 2013 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.