Building a Geodesic Dome Greenhouse Part 2

Here is the second video in the series of building a geodesic dome greenhouse.  It covers 3 different hub designs (and failures) along with the details of how they are assembled.  I’m trying not to make them too boring, but after all, its just a bunch of diagrams, cutting and welding.  At least you can see some sparks fly!  There’s a couple of bloopers at the end too!
 

Below is the transcript from the video:

In this video I will discuss the hub design for this dome and the next video in the series will detail the strut design.  This is 3V 3/8th dome so it will require a total of 46 hubs consisting of twenty-five 6-way, six 5-way and fifteen 4-way hubs that will be used along the base.  Because of the large span, this dome is going to need a hub that can withstand a great deal of compression force.  Plus, it must be able to withstand the downward force from heavy snow loads during the winter.

The first hub design had hanger bolts anchored into the end of each strut.  The end of each bolt would go through a hole in a piece of schedule 40 3-1/2” steel pipe which was used at the hub.  The strut was tightened to the hub with a washer and nut.  This is the first prototype using the hanger bolt method and a PVC hub.  The triangulation between each section was extremely strong.  When I created a full scale prototype, the leverage of a full length strut and removal of the triangulated pieces cause the hanger bolts to easily pull out of the end of the struts.

The second hub design was similar to the hanger bolt design, except a hole was drilled through the strut and a washer and nut was inserted.  This was to create enough surface area to prevent the bolt from pulling through the wood.  However, testing a full scale prototype proved to be too much force against the strut and the bolt acted as a level and split the wood.

The third hub design is completely different. The strut is sandwiched between two spokes.  Flat bar-stock is welded to the hub at the appropriate angles and a bolt is placed through the top spoke, through the strut and fastened with a nut under the bottom spoke. This full-scale prototype shows how 4 spokes of a 6 spoke hub would be assembled.  A load test shows it can support my body weight on only 4 spokes, plus none of the other struts are used to strengthen the legs.  There was some slight bending of the bolts from my bouncing but there was no hardware failure.  Regardless, the final design will use 3/8th inch bolts instead of 5/16th.

The central hub is made from 3 ½” galvanized rigid conduit which is about ¼” thick.  The conduit is cut into 3 ½” lengths.  The galvanized zinc is ground off wherever the spokes are to be welded.  Please note that working with galvanized material, especially using abrasion cutting equipment or welding should be done in a well-ventilated area.  Also, you should always wear gloves and safety glasses.

I made up a jig that will safely hold the bar stock to the drill press.  It allows me to consistently drill a pilot hole in the same location near the end of the stock.  Since I have 480 holes to drill, creating jigs and templates is crucial for building an accurate hub.  Once the pilot holes are drilled, I switch over to a stepped bit that will finish the hole at the proper size.  I then flip the piece over and gently remove any tear-out from the bottom of the hole.  Once the holes are in the end of the stock, I then cut it to the correct lengths.  I built a stop for my abrasion saw so I could cut each piece to the same length.  After cutting off the ends, I can go back to the drill press and drill a new set of holes for the next set of spokes.

Now it’s time to start assembling!  This template has markings on it so I know where the locations are for the 5 spoke or 6 spoke hubs.  I just place the hub over the template and draw a small mark on the hub.

This jig is used to accurately weld the spokes to the hub.  The hub is placed over the post and each spoke is held in place with a pin.  By using this jig, I can weld a complete hub in less than 15 minutes.

All the pieces are welded together with a standard MIG welder.  Another safety note:  Please weld in a well-ventilated area and free from items that can catch on fire.  Also wear the appropriate gear to avoid burns from the hot metal and use a welding helmet to prevent blindness.  Keep fire suppression equipment nearby at all times.  No one else should be in the area while using a welder.

When each hub is complete, any dirt and rust is removed by sandblasting and is then painted with cold-galvanizing paint to prevent future rusting.  I hope you enjoyed this video on making a hub for the geodesic dome.  The next video will show how the struts are made.  Thanks for watching!

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Expanded Shale for Hydroponics and Aquaponics

A little self promotion for my company....

Bigelow Brook Farm is pleased to announce a new partnership with The Aquaponic Source as a distributor for our expanded shale product line. The Aquaponic Source (www.TheAquaponicSource.com) specializes in a wide array of products providing complete solutions for the North American home aquaponic gardener. Along with their on-line store, they also provide an active and free community site filled with a vast array of aquaponic discussion topics and information for both novice and experienced users at www.AquaponicsCommunity.com. “We are extremely excited to be working with Bigelow Brook Farm and offer expanded shale to the aquaponic and hydroponic gardening communities. Finally there is a US based grow media with optimal growing properties!” says Sylvia Bernstein, President of The Aquaponic Source. “We think this will become a core component in the rapidly expanding soil-less growing market in North America.”

For more information about Expanded Shale, please visit our web site at www.BigelowBrook.com or www.ExpandedShale.com.

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Teaser Video 8

Heres the latest teaser video for the geodesic dome greenhouse!  Enjoy!

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Butterfly

While I was filming my latest video, this butterfly landed on my hand.  In the past, I’ve received several questions about why I don’t put screens on the greenhouse vents…this is why!

(Sorry it’s blurry, this is a screen grab from the video and the camera wasn’t focused for the close up shot!)

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Geodesic Dome Greenhouse 6 Teaser

A quick preview of our next video.

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Cloning Tomatoes

Just a quick video on how I clone my tomato plants.  Only one plant was grown from seed in the greenhouse and everything else has been cloned.

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Building the Aquaponic Geodesic Dome Greenhouse in TWO Minutes!

This is a time-lapse video of the complete construction project for the geodesic dome. There are 1555 images taken over the last 1.5 years.  What you cant see is all the work thats done preparing the pieces in the shop or any of the construction work done inside.   Overall, Im overjoyed on how well everything came out!

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Building a Geodesic Dome Greenhouse Part 5

I finally finished up the 5th video in the series.  This one covers how the footings were done, and then a little problem with flooding in the foundation hole!

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Playing with Fire

Its been quite awhile since posting any info about the geodesic dome greenhouse.  This spring had more rain then usual and the site was too wet to run heavy equipment through.  Were hoping to start digging for the footings in next week or so.


Ive started to experiment with rocket mass heaters and have had very good luck with running a good clean burn.  It will be quite impressive to be able to heat the entire greenhouse without needing electricity to store heat in a thermal mass or run a blower for the burner.  More to come!

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Geodesic Dome Greenhouse Teaser

A quick preview of the next video!

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Building a Geodesic Dome Greenhouse Part 3

Finally got around to doing the third video in my series of building the geodesic dome.  This one covers how all the struts are made.  Its filmed in HD so you should be able to expand it to full-screen!  I hope you enjoy it!

Below is the transcript from the video....

Hello Everyone,
This is the third video in the series about building a geodesic dome greenhouse.  This time I will cover how to build the interconnecting struts which are made from red cedar.   I choose red cedar because it is rot resistant.  You could use treated lumber, which is substantially cheaper, but I was concerned about chemicals leaching into the water for my aquaponic system.

The site I used for the calculations is acidome.ru.  The entire site is in Russian, but Google Translate does a fairly good job converting the text.  The calculator lets you enter the diameter of the dome, choose the hub type and size, and even the dimensions of the struts.  It will then calculate the angles needed at each hub and also calculate all the various sized struts and labels them with the dimensions taking into consideration the size of the hubs.

The best feature is the ability to have the software calculate a flat base, since a 3V 3/8th dome is not flat.  One click and the struts are recalculated with the proper lengths!

With a 33 foot diameter 3V dome, each triangle will never be wider than 6 feet.  This will allow me to purchase the polycarbonate glazing in 6 by 24 foot sheets, helping to minimize the amount of scrap.

The struts are made from red cedar 2x4’s by 14 feet.  This will be enough material to cut 2 struts from each board with some scrap.  The end of each board is cut at a 12 degree angle so it will align with the hub.  Not every hub connection is exactly 12 degrees, but there is enough flex in the structure for the angles to average out properly.

Once the struts are cut to length, they are run through the table saw to add a slight bevel to them.  When the dome is fully assembled, the polycarbonate panels will rest fairly flat along the bevel.  This will also insure that the height of each strut is the same since it can vary slightly from the mill.

Next I remove some of the material from the end of each strut using a dado blade mounted in the radial-arm saw.  This space will provide an area for the top tab of the hub to rest and provide enough clearance for the polycarbonate panels over the crown of the carriage bolt.

I built a jig to act as a stop and keep each strut aligned properly during drilling.  This allows for a consistently placed hole to be drilled near the end of each strut.  The placement of this hole is important so it will fit properly into the hub and provided an accurate length for the hub and strut combination.

And now, the perfect excuse to use one of my favorite tools!
The bottom of the head of a carriage bolt has a square neck so it can grab into wood to prevent it from turning.  To get it to fit into the metal tab, I would either have to drill the tab’s hole larger, compromising some of its strength, or turn down the neck of the bolt in the metal lathe.  I chose to turn each bolt and then will re-galvanize the area with cold-galvanizing paint.

Here is an example of how the final assembly will fit together.  The strut is sandwiched between the two hub tabs and then tightened into place using a lock washer and nut.

This top view displays how each strut can pivot slightly on each hub.  Since the angles of each triangle section aren’t the same from one section to the next, this allowed for me to make the same hub and allow the pivot against the bolt to make minor changes to the angles.

This side profile shows how the dado in the strut allows the polycarbonate glazing to clear the area without hitting the tab or bolt head.

Finally, this profile displays how the glazing will set flat into the beveled area that is cut along the top of each strut.

I assembled the base to verify that the calculations were correct and the pieces fit together.  So far, so good!

That’s all for now.  The next video I plan on detailing some of the site work.  Thanks for watching!

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Geodesic Dome Greenhouse ASSEMBLING THE DOME!

The structure is up!  Making great progress!







TRANSCRIPT:

Hello Everyone!

Once again you’re treated to an extra-long video about building the dome!

The structure went up in a day!  I started off the morning by laying out all the pieces around the perimeter knee-wall and bolting everything

together.  This helped to create a firm base to build on.

A fellow aquaponic grower and dome lover, Steve, volunteered to help erect the dome.  This was one job where having an extra set of hands was

extremely helpful.  We found it was easiest to connect two legs together with a hub, and then set them into the base unit.  When the bolts were placed

in the hubs, each section was able to stand on its own without any supports.  Once we figured out a system, the entire assembly process was relatively

smooth.

A couple of the bolts would get stuck going through the struts, but a little persuasion would get them in.  Once each triangle section was installed,

we would connect each one with a horizontal strut.  This simple action made the side wall rigid enough to support my weight of leaning against it.

It took a little bit of thought on how to assemble to the second level, but we decided the best way to assemble it was the same way as the first tier:

 Steve would support the assembly from the ladder and I would align it with the hub and run the bolt through it.

The horizontal strut was a bit trickier but I was able to lean a ladder against the dome and hold it into place.

The third tier went together just as smoothly.  The dome was self-supporting and there was no problem leaning against the structure to assemble the

struts.

By the end of the day, the dome was now visible from the road and a few of the neighbors would stop by to see how we were progressing. 

We finished late in the evening using flashlights….here is how it looked when it was completed.

Here’s a little time-lapsed segment of the dome being assembled.

On October 30th, we had a freak snowstorm that decimated the region.  We were without power for a week while the town and line crews cleaned up the

roads and utilities.  The project was put on hold…

Once we recovered from the storm and most of the snow melted, it was time to go back to work.  Even though the dome was standing on its own, I stilled

needed to adjust a few of the hubs and tighten the nuts.

The next part of the project was to build the walls for the shed area.  One of the biggest problems with working in the fall is the rain and snow,

along with the constant freeze and thaw cycles.  This turns any disturbed dirt in to mud.  I decided that it was best to build the walls up by the

house and set them in place with the tractor.

When building a prefab-type building, it’s critical to make sure each section is square and accurate.  Once each wall frame is squared up, I would

secure it with a few angle braces to keep it from racking.  After all of the studs were nailed in place, I would again check to make sure it was still

square and then install the sheathing.  Since the walls are placed so close to the ground, I installed treated plywood sheathing along the bottom 16

inches of the wall to help prevent rot and insect damage.

The excess sheathing is marked and cut off to the appropriate length and then nailed into the studs.

My good friend, Ford, helped me lift the walls and carry them to the greenhouse site.  Each section fit perfectly into place.  Ford was also kind

enough to hold the wall in place while I secured each section together.

After all the walls were in place, I finished installing the remaining sheathing.

Even though the dome structure probably could support the weight of the shed roof, I felt it was best to add a support beam across the length of the

shed and cantilever the rafters over the dome.  The rafters are attached to the dome, but they have almost no load bearing weight against it.

There are 35 rafters, all custom cut with the correct angle to match against the dome.  Any of the excess is then cut off, and the scrap is then used

as blocking between the rafters to keep them from racking.  The roof decking is then laid down, cut, and secured.

Once again, that’s the end of another segment.  I invite you to join our Facebook page at the link below for building updates prior to these video

releases.  Thanks for watching!

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Whitefly control

Heres a little video on how to make cheap flypaper traps.  White flies are a big nuisance in greenhouses!

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Dome video 7 Teaser

Another teaser video. Its moving along quickly! Most likely the dome part will go up within the next week!

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geodesic dome at night

One of the nice things about having the dome enclosed is that I can work in there at night without freezing in the wind! Still no heat, but were getting closer!

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Geodesic Dome Greenhouse Part 12 THE END

This is the final video about construction the aquaponic geodesic dome greenhouse. Dont worry, there are still more videos about the aquaponic system and other projects were working on!



Hi Everyone.  I’m Rob Torcellini from Bigelow Brook Farm.  This is the last video on the series on building the geodesic dome.  I wanted to thank you for watching all of these.  I’ve had a great time of the last year building this.  Learned a lot, made a few mistakes along the way, but overall, it came out pretty good!

I’m planning on do a short series of videos about how I set up the aquaponics system inside the dome.

I also had this camera shoot about 1500 photos of the entire project that will be in a time-lapsed video.

Again, thanks for watching and we’ll see you soon!


It’s starting to get a bit warm in here so it’s time to add some vents.  I started by building frames that would fit loosely inside various areas around the dome.  There will be a total of five vents and each section will be able to swing open and closed.

Next I removed the existing polycarbonate glazing and then attached the new frame to the dome with a couple of standard door hinges.  In order to get the glazing to fit back into its spot properly, I had to cut it down a bit so that it wouldn’t hit against the hinges or the surrounding polycarbonate when the vent was closed.

I simply held the polycarbonate into the new frame and screwed it into place with the washer-backed screws and the vent was done.  The remaining 4 vents installed the same way, but just a bit trickier for 2 of them since they were 15 feet off the ground.

All of the exterior joints needed to be sealed to help prevent the rain from leaking in between each joint.  I used a clear polyurethane tape which is used as a protective tape on the edge of aircraft wings and wind turbines.  If it’s good enough to hold on to a wing at 500 miles per hour in the rain, it just may be good enough on the dome.  It was easy to apply by just removing the backing and pressing it down with a j-roller.  Once it bonds with the polycarbonate, it’s basically impossible to remove.  After covering each joint I drove a washer backed screw through the tape and polycarbonate.

Wherever there is a vent opening, I applied the tape to the polycarbonate and cedar which created a channel for the water to drain from.  I’m not sure how well the tape will bond to the wood…only time will tell.

Applying the tape on the upper areas of the dome proved to be a bit trickier. I found it to be unnerving being up there with the risk of sliding over the side or dropping through a section of polycarbonate.  I’m happy to say there were no trips to the hospital for this project!

I wanted to use some of the logs that I cut down last year from the site in a couple of areas of the dome and for grow beds for the aquaponic system.  My neighbor stopped by with his WoodMeiser saw mill and milled roughly 1500 feet of white pine into 1 inch and half inch thick boards.  It was a great way to save some money instead of buying lumber and we got to use some logs that would have gone to waste.

Inside the dome I covered the walls with some of the half-inch pine boards.  Each piece is roughly fitted, measured for the proper angle, and cut to size.  Sometimes the pieces had to be cut a few times to fit properly.  It was a very tedious process cutting all the angles, but the end result looks great!

In the shed area, I only filled the walls with one inch of foam to save a little money.  The rest of the wall cavities are filled with regular fiberglass insulation.  The boards on these walls installed much quicker since there are long and have square cuts!

The ice and water shield held up well through the winter but it was time to shingle the roof.  A friend of mine volunteered his crew to help out which was much appreciated.  Even for a professional builder, there was a lot of pondering on how to lay the shingles on the dome area.

On the south side of the greenhouse, I leveled and planted timothy grass.  Eventually, this area will used as a small orchard.  A local arborist was more than happy to get rid of their wood chips so I was able to spread this on the remaining areas that didn’t have any top soil.

The shed area and dome knee-wall is sided with cedar shakes.  They require little maintenance and they help to give a contemporary building a little New England feel.  I also added a small awning over the main entrance to make the building less….boring.

That’s about it.  There will still be more videos in the future.  If you have questions or comments, please leave them in the comments section below and I’ll try to address them in future videos.  Thanks for watching!

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Sequencing Indexing Valve

This is a sequencing / indexing valve that I designed a couple of years ago.  This uses a pinching mechanism to stop the flow of water.  It is able to pass solids and keep operating if there is a clog elsewhere in the plumbing.  I decided that it would be too expensive to develop and would show everyone how it works.

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Adding Automatic Vent Openers

I finally get to work on some of the more exciting things in the dome.  Automation!!!  I love being lazy!




A few years ago I made up some vent openers which use windshield wiper motors. They work well for the small greenhouse, but the frames have had some structural problems in strong winds.  For the dome greenhouse I’m using linear actuators to operate the vents.  The actuators have a lot more lifting strength and can withstand stronger wind forces.

To attach the actuator to the window frame, I took a piece of angle iron and made a cross brace.  The brace will fit about half-way up the vent.  I cut off a section from each end so that there were tabs that would be used for bolting the brace into the face of the vent frame.  I then welded a couple of tabs into the bracket which provided the connection linkage for the actuator.  After rounding over the edges and cleaning up some of the welds, the bracket was attached to the vent frame.

The rest of the braces are standard steel bar stock that are bent at slight angles.  There are four of them which go from the greenhouse struts to the back side of the actuator.  Because of the odd angles of the dome, a few of braces need to be bent as compound angles.  If this was a traditional vent the angles would have been much simpler bends.

I temporarily bolt the top brackets to the back side of the actuator and mark where the brackets connect into the dome’s strut.  It wasn’t necessary, but I set the actuator to be level when it was closed, simply for aesthetics.  I drilled out the first hole in the dome strut and attached the bracket.  Once the pieces start to hold themselves in place, it’s much easier to mark and attach the remaining brackets.

The bottom brackets are marked and installed the same way.  It’s just a bit more critical to make sure they are placed properly so that the vent is pulled completely closed when the actuator is fully retracted.  Once all four brackets are secured, the pyramid shape from the triangulation creates a sturdy mount for the actuator.

Now that it’s fully assembled, a quick test is in order.  All the pieces are cleaned and painted to give the system a nice new look!  Once the paint is dried, it’s a quick reassembly and then time to it get wired to the controller.

A regular two-conductor wire is used for each actuator and each vent opener has a line that runs back to the controller.  The actuators have built in limit switches which stop the motors automatically.  To open and close the vent, you just have to reverse the polarity of the power in the wire.

The thermostat controller is a prototype six-relay control unit that can be programmed to set each vent to open on independent temperatures.  The unit can be programmed to sample the temperature at predetermined intervals and also delay the change between relays so that all the vent motors aren’t running at the same time.  This keeps the unit from drawing too much power all at once.  Each relay can also be disabled and forced into an open or closed position.  There are more details about the thermostat in the description area of this video.

Thanks for watching.  Don’t forget to “thumbs up” this video if you want to see more like it in the future and feel free to leave comments too.

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Videos on YouTube and Vimeo

We have had numerous problems with our YouTube videos being blocked in several countries. We created an account on Vimeo that should work. (www.vimeo.com/web4deb). The majority of our videos can still be found on YouTube at www.youtube.com/web4deb. Thanks!

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Rocket Mass Heater preview

Heres the teaser video for the rocket mass heater.  More details to follow!

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