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.

zipline

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.

ZipLanding

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.

Marston Mat Mudway

Marston Mats, aka perforated steel planking (PSP), were developed by the U.S. before World War II. The idea was to quickly build temporary runways and landing strips. They were first used at Camp Mackall airfield near Marston, North Carolina, in the U.S.

marston

A Curtiss P-40 Warhawk on a Marston Mat runway at Milne Bay, Papua New Guinea in September, 1942. – public domain

marstonmat

 

I honestly don’t remember where or when I acquired four of these heavy metal planks, probably saw them advertised somewhere. I know I didn’t pay much for them. The idea at the time was to see about using them for my bridge deck. I wasn’t able to acquire any more at the time, so opted for the wood deck you see in the photos. One of these days I’ll replace that deck with something metal. I like that the perforations would let air flow through so the bridge would not be as vulnerable to high wind gusts.

Meanwhile during our rainy season, areas where we like to walk get more than a little muddy. The small creeks flood and send water everywhere. I’m always digging ditches to try to control the flow somewhat, but this particular area is low, so it’s always a mucky mess.

mats
So I installed some 2×10 planks I had as well as the four Marston Mats. Nothing much to it, other than first setting out short cross members for everything to rest on. While you could just toss the planks into the mud, raising them up a bit makes them more effective, and you can get them level to some extent. I screwed down the wooden planks, but the mats were heavy enough to be stable without reinforcement.

jeepmud
When finished with the project, we noticed that Jeep the dog appreciated the wooden planks, but not so much the mats. He proved the point that the Marston Mats would not be the best material for a bridge, assuming you want to allow your four legged friends to come across with you. We’ll be watching for other options.

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 2013-2016 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Floating Mantel Shelf

cherry treesOur house has posts, beams, and siding made from Douglas fir milled on our property. I decided to employ another kind of wood for a fireplace mantel. Bitter cherry, also called Oregon cherry (Prunus emarginata) is a native tree that popped up in our woods when it was replanted in 1988. I wondered what the grain and color would look like when it was milled. It has an interesting bark, that much I knew.

So I picked a tree I liked and thinned the woods by one cherry tree. I parked it in the barn to dry for about five months, then had it milled to about a five foot 5-1/2″x7″ with bark edge on the 7″ width. mantle-sawmill

As control against splitting, I scored slices on one side in varying depths, the deepest being the middle cut over the tree center at about 1-1/2″ deep. Then I primed the sawn sides and left it to dry, standing up, for about 3 more months.

frontgrain-joint
I was hoping to preserve the bark, so cutting and fitting the corners was tricky. I sanded down the precautionary slices (which were on the bottom) and cut the pieces. I sanded, splined and glued it all together, then applied a clear finish. The bark is threatening to peel, but underneath looks pretty cool so I really don’t care.

barkless

de-barked Oregon cherry

I used a bracket system to install the 35+ pound mantel. I hollowed out two slot holes at 9/16″ depth on the backside that corresponded with metal brackets that screwed to the wall studs.
wallbrackets

Metal straps, which were recessed so that the mantel would fit flush with the wall, were screwed across the hole slots. Taping their location on the mantel top,  I could line them up with the marked brackets.

backconnection

finetune
hammer

A bit of hammering with someone else holding on, and the mantel was up.

finish2

I have 3″ metal posts that I had intended to install on either side, not for support just for looks, but for now we’re seeing if we like just having a floating mantel. Eventually there will be a wall sculpture underneath. I’m just waiting for my spousal unit to come up with something…
finish

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

Images, diagrams, and text copyright 2016 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

Metal and Wood Computer Desk – DIY

Marvin-DeskLegsI’m not crazy about much of anything we can buy in today’s furniture market, at least in my price range. It’s all badly designed and sloppily made using cheap materials, including a lot of plastic. I feel that even a practical piece of furniture such as a computer desk can be well designed and interesting to look at. And it’s not all that difficult or expensive to make it yourself.

I bought a length of 1-1/2″ square metal tubing (wall thickness roughly 1/16″) and enough steel angle to build a nice, sturdy structure that could hold up a heavy wooden top. I cut and bent the angle steel so that it formed a three-sided structure, allowing for a chair to fit underneath.
tablestructure2
I made wooden feet from some ipe (that’s a hardwood) that I had. I cut out blocks, then cut a little off each of the four sides of each block so that they fit snugly inside the metal tubing, leaving about 1/2″ for a foot. A nice look and a way to protect the floor.

tablefeet

For the top, I had several 2″ thick slabs of rough-sawn wood that I got from a local sawmill last summer. I knew the seller well and got a great price on some beautiful big leaf maple as well as Lebanon cedar he’d cut down in someone’s yard. The slabs had been drying for about ten months and looked good. I decided to use the cedar for this project.

tablestructure6

The tricky part was picking out the part of the cedar I wanted to use for the table. It wouldn’t be deep enough so a second piece would have to be glued to the first and they’d want to match or at least, go well together.

top-cut

finishtable-2A lot of cutting and sanding later, I had pieces that worked. I splined and glued the pieces, removed the bark, then finished with clear Sitkens stain, one of my favorite finish products. I also added holes for the computer cords, etc.

finishtable

I added more angle steel to hold a shelf for the keyboard, and my new computer desk was ready to use.

MarvinOfficeYou won’t find this at Ikea, or anywhere else for that matter. It’s not a design everyone will love, but suits me. That’s the beauty of building your own stuff.

I didn’t include a lot of detailed instructions here, as most of it is self-explanatory. Please ask questions if you have any about this project or any others included on this blog.

And 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

Images, diagrams, and text copyright 2016 by Marvin Denmark unless otherwise noted. Please do not copy and post my content anywhere without my permission. Thank you.

 

DIY Radiant Floor Heating System

This is about installing radiant floor heating in a slab floor system. While it was done as a new house was being built, in my last house I poured a concrete floor on top of a wood framed floor system and could have put radiant heat in that as well.

Pex-Plan

I obtained a design for the entire system from Supply House where I bought all the parts. They will provide, free, a layout according to your specs and also give you a list of parts you’ll need for the heating system. You can also download a free program from Uponor and also read more information than I will include here.

I opted for a single pump, single zone system for our 980 square foot little house, but opted to have each room a separate system zone that could be controlled by shutting down the water supply. For larger spaces, they would recommend more than one zone with a pump and thermostat for each.

First step was to install a vapor barrier and then insulate. I used extra (rigid) insulation – R15 – to encourage the heat to go up, not down into the dirt.

Pex4

Next I added 6×6 welded wire fabric (WWF) aka concrete reinforcement wire and used that to tie down the pipe. I bought a 1,000 foot roll of 1/2” pex pipe. You can get smaller rolls, but no way did I want any connections under the concrete floor. The pipe is very unwieldy especially in a coil that long, so I built a big spool for it and added dolly wheels so it could follow me around as I unwound pipe. The same contraption came in handy later when I wired the house.

Pex8

I used zip-ties to tie down the pex pipe. Here are a few photos of the process. We took a lot more photos so we could remember exactly where all those pipes fell. I did not want to be nailing down a plate for a closet and poking a hole in my heating system.

Pex9

Pex5

Then I installed concrete doobies and tied down rebar, just standard practice for a concrete floor.

Pex3

Pex-1

I also tied all the pipes together and pressurized them. I wanted to make sure there were no leaks before that 4 inch thick concrete was poured on top of them.

Pex-2

After the floor was poured, I moved on to building the house. Since I worked pretty much alone and at my own pace, it was a couple of years before it was time to set up the heating system. I built a large utility core with plenty of room for two water heaters as the one designated for the floor would be set low, and space for me to get in and make adjustments. The option for an instant-flow water heater was there, but I didn’t want to spend that kind of money. I just got a standard 40 gallon hot water heater for a couple hundred dollars.

Pex12

 

The heating system consists of a thermostat which is wired into a relay transfer switch. I located the thermostat in the living room, which in our house is a central location. Since I was building the house from scratch, I could easily run the wire in the walls and over to the utility core. The relay tells the system when to start up. A pump kicks on and water runs from the water heater and into the floors. Water from the floors runs back into the water heater. If you can see the numbers on the gauges in the photo, the water going out is about 100 degrees and the water coming back is about 80 degrees.

Pex11

The first issue once everything is connected up is getting the air out. If you troubleshoot a radiant floor system by googling, “air in the lines” comes up as the #1 issue. I futzed with it until the air was gone. The second issue was the size of the pump. I trusted the supply house to provide me with a pump adequate for the system they designed, but that didn’t happen. The pump has to be strong enough to deal with the resistance in over 900 feet of 1/2” pipe. You can determine the needs by calculating the feet of head, which I did and the pump came up short. I ordered two sizes up and the system is now working beautifully. The pump doesn’t kick on very often and the house stays evenly heated, ranging from 69-72. I use a Cen-Tech infrared thermometer to see what’s going on.

Pex13

Meanwhile, the pets have figured out where the supply pipes are and love to lay down on the nice warm floor.

Pex14

With me doing all the work, the total cost including everything involved was about $1,700. We haven’t got an electric bill yet, but considering that the house is so warm and the water heater is well insulated, plus the water going back in is almost as hot as it needs to be anyway, we suspect we’re not using very much energy for this system. It is a wonder that at least in Oregon, there are no Energy Credits for putting in this efficient system. I hope to change their minds about that.

Happy winter!

 

 

Lichen and Moss, Green but not always Mean

What’s that green stuff? People, including house inspectors, don’t like to see anything green on house siding, decking or roofing. As we learned last year, even the FHA has a hissy fit over the color green, and will demand eradication, cleaning and painting, even if the green stuff is not damaging anything.
lichen-HouseIn our case, our 35-year-old house’s cedar siding had a few areas with tiny little hairy lichens happily blowing in the breeze along with a few patches of algae. There were no signs of damage after three and a half decades.

But even though the FHA regulations clearly stated that cedar siding was exempt from the rules regarding wood siding, we still had to provide the funds to pressure-wash and stain the house before we could sell it.

The deed was done and the sale went through. We just hope they were careful, as pressure-washing can be much harder on cedar siding than any amount of lichen.

Lichens are a “plantlike” hybrid of fungus and algae that grow all over the world. The self-sufficient stuff can flourish anywhere as long as it gets a little bit of moisture on occasion. It doesn’t retain much of that moisture and it doesn’t take root, making it easy to remove and control. Lichens don’t bother trees and shrubs unless their growth blocks light to the leaves. But people freak out about lichens anyway.

Moss, on the other hand, is a real plant, and even though anything green growing on a roof is often called moss, this is the real bad guy. Mosses are generally found in shady, wet places. That’s why we see mosses in the woods, especially in wetter climates such as western Oregon. We also see them on roofs, decks, and other structures where debris and water can collect and provide a foothold for it to grow and spread. Mosses break down whatever they attach to, providing a surface cover and moist soil environment for other plants. It’s great stuff, but not if it’s chomping on your house or your bridge!
MossyBridge

This is one of our small trail bridges, in sad need of a good cleaning. It is obviously located deep in the woods, and is victim to leaves, fir needles, vines, sticks, and of course, moss.

My spousal unit came up with an easy way to clean the leaves and other debris that collect on all our bridges. A long-handled squeegee for washing windows makes quick work of the task. But alas, this bridge decking has been adopted by moss mostly because of our neglect. For now, we plan to carefully chip the rest of the green stuff away with a knife, as the decking appears to be secure enough for another year or two anyway.

The under-structure is pressure-treated and so far oblivious to the spongy, green, wood sucking plant. Lichen would have been welcome!

MossyBridge2MossyBridge3

 

 

 

 

 

 

 

 

Thanks for stopping by! Be sure to check out our bridge 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 $13.00 right now. Here is the link: Building a Small Cable Suspension Bridge with the Cable Locking System
Images, diagrams, and text copyright 2015 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.

OLYMPUS DIGITAL CAMERASince 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.
StringersPasture
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.

blocking

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.