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Solar Tracker

This page logs my design/thoughts/progress of building the solar mounting and tracking device.

Design and initial construction.

Here are a number of pictures of how others have mounted their solar arrays, not all of them are pole mounted. A lot of these images were accumulated from the Redrok Energy website, I should have kept better track so that the proper credits could have been given, but the persons last names are part of some of the image names.

Click on the thumbnails to see a larger image :

As you can see from the last couple of images here is a simple portable solution that could be used for either a ground or (moveable) roof mount while still allow tracking of the sun.

Ok - first decision, I will be using a 6" schedule 40 pipe for the upright, it will be about 15' long with 1/3 of the length of it contained in the concrete base. Essentially the base will be a suitable depth (3' or more), with outside dimensions of 3' x 3' square, and a bunch of 1/2" rebar for reinforcement.

The main mount needs to be pretty heavy duty so that it can stay as stationary as possible when the wind blows, something like a 2" x 2" or 2" x 3" tubular steel with 3/16" or 1/4" wall thickness. Other than the adjustment for declination this mount does not move. It is held stationary to the post by putting some bolts through flanges that mount onto the post cap, the easiest way to do this is put a corresponding piece of tubing on top of the post cap. The lower retainer on the post (for declination) can be made with some smaller diameter tubing as it is typically in compression, and a couple of bolts to retain it. This way the 6" diameter post can be installed without any mounts/modifications, a simple straight post, this way you don't have to worry about post orientation when you do the concrete work.

All bolts/nuts/hardware used should be made of stainless steel so that they do not rust and make future changes/removal easy.

Here is a rough diagram of the post and post mount, none of the drawings are to scale:

As you can see the main supporting column for the polar mount should be pretty beefy as it is the major supporting structure. What I will refer to as the "frame/rack" is the portion (not shown) that the solar panels actually bolt onto. The distance between the pivot points can vary from 1' to 8', and my basic feeling is that the farther apart they are the more stable the mount 'should' be.

The 'frame' is probably made from similar tubing is rectangular or 'H' shaped and has flanges that will connect to the post mount at the pivot points. The frame can connect to the post mount using some sort of bronze bushings or even automotive style ball joints. The ball joints have the advantage of having a rubber boot to keep out the elements and in addition usually a zerk grease fitting! While the bronze bushings allow easy movement and can be replaced easily.

On top of this steel framework is the optional 'rack' which can be pieces of aluminum, either channel, tubing or something with 'Tee' slots. The solar panels will actually be mounted onto this rack, so it would be nice to be able to re-configure them ontop of the steel frame, and the rack is bolted somehow onto the frame. Optionally you can simply weld in some angle iron to bolt the solar panels directly to the framework, but this has the disadvantage of not being so modular.

If this solar polar mount is constructed heavy enough the solar array can be increased in size in the future, without having to change it, and simply modify the frame and re-configure the rack!!!

Here are 2 versions of a mounting frame, the height and width can vary greatly depending on the solar panel size and number of panels being mounted. The rectangular frame is probably the more stable and versatile plus it gives more clamping surface to hold the rack:

The rectangular frame can be 1-1/2" or 2" x 1/8" thick steel tubing while the H-frame may need to be a bit larger/heavier tubing/channel so that it is rigid and won't twist. The tubing size will depend ultimately on the size and number of panels that will be mounted onto it.

Initially I will only be installing 4 solar panels (180 watts each) and will be using a rectangular frame, it would be nice to make it large enough to mount additional panels. The reason for this is that I want to provide a large air gap between panels, by doing this it should reduce the 'sail' effect caused by the panels. If the panels are mounted so that there is little or no gap between them then it will act as a large sail and cause a 'racking' effect (back/forth shaking) of the entire unit during high winds, adding gaps between the panels should reduce this effect.

Here is the final version of the mounting frame, I decided to put an extra piece of tubing through the center of the frame. The reason for this is so that when I mount the panels I can have one end of the extruded aluminum extend to it for fastening. The image on the right shows how I plan on mounting the panels and the extruded mount locations. The aluminum extrusions are pretty pricey so this helps keep the costs down by using shorter lengths.

Since this is my first solar tracker and solar panel installation, I will just be making what I need to mount the panels, and not be too concerned with future additions. After all I may not really need/want additional panels, so I will build a beefy polar mount, while keeping the framework lightweight and sized appropriately.

The sensor will be located in the empty center square between the panels. Redrok suggests plastic Jiff jars, alternatives include:

Here are images of sensor mountings, all are from the Redrok Energy website.

The main thing is that the enclosure is weather tight, if you use glass it should have as little distortion as possible otherwise the sensitivity
of the sensor may be degraded. You can see in some of the above examples that the builder uses the side of the glass rather than the
bottom for pointing the sensor.

Myself I am a bit partial to the modified pagoda style sidewalk lighting enclosure (top right image)...

    I have been in contact with a somewhat local company West Virginia Solar and talked with Dan Bowes. Dan has been a huge help and phenomenal resource to bounce off my needs/concerns.

My initial requirements were:

  • between 600-800 watts solar
  • must work within existing equipment: Xantrex XW-6048 inverter and Xantrex XW-SCC (MPPT solar controller)
  • be within my budget
The initial budget basically came from a $4000 tax credit for putting the wind turbine into service last year, so initial cost of acquiring panels were dependant on that sum. More will be needed for installing post, concrete, running conduit, wiring, mounting and tracker.
4/18/09   Dan Bowes got back to me and suggested that I get four Mitsubishi 180watt panels for a total of 720 watts. Each panel puts out 7.45 amps at 24.2 volts, I will be putting them in series for a total of 96.8 volts. The XW-SCC can handle up to 140 volts operating, and the XW-6048 needs 54+ volts to utilize so these panels seem to fit my needs.

These are polycrystalline and have a pleasing blue color, and they have a 25 yr warranty. Even though the monocrystalline panels have been proven to have more efficiency (in direct sunshine) it seems that the polycrystalline produce better over a variety of sun light/cloudy environments and that is what he recommends for our area.

One thing that I learned is that in cold temperatures solar electric panels actually produce *more* voltage than when warm. You have to compensate for this, which is why I'm staying < 100 volts total on the panels.

If I find that during cold winter months the voltage could possibly go over 140 volts then I will install a temperature cut-out device that is made by Apollo Solar. This device will drop a single panel out of the array at a temperature selectable temperature (around 32 degrees F), so that only the output of three panels will be connected to the XW-SCC, when temperature warms up it will automatically switch the panel back into the array - nice!

Here is info for the Apollo Solar low temperature overvoltage bypass.

So I basically blew the entire initial budget on the panels - but that was known right up front!
4/19/09   Research begins for mounting and solar tracker!
I just ordered up the solar sensor/controller component for the solar tracker from Redrok Energy.

They make a simple, accurate, low cost, single axis electronic solar tracker based on using green LEDs as photovoltaic light sensors. On their website they also have a plethora of options, 12 - 48 volts, 1 or 2 axis, reverse inhibit, parking, kits/complete. I just purchased the LEDSRMP48Vc3 unit which is perfect for my needs.

It is a single axis with reverse inhibit, parking, remote sensor, completed assembly and can run with anywhere between 10.5v to 93v, so have a lot of options in how it is connected to my battery bank, although I will probably use it at 24v.The dish actuator is wired directly to the controller and as the sensors detect the movement of the sun the controller engages the actuator, it is supposed to be accurate within about 2 degrees.

Since this is my first solar tracker I figure it's best to do just a single axis rather than concern myself with any additional complexities that a dual axis tracker may involve. In addition a dual axis may only give marginally more output from the array, so initially KISS.
I figured out my basic steel needs, the lengths below are extra long, so more than enough for fabrication:
  • 60' - 1/2" rebar (for concrete)
  • 12' - 6" schedule 40 pipe
  • 10" - 6-3/4 mechanical thick wall tubing (cap for pipe)
  • 12' - 2" x 4" x 3/16" tubing
  • 4' - 2" x 2" x 1/4" tubing
  • 40' - 1-1/2" x 1-1/2" x 1/8" tubing
  • 32' - 1" angle 1/8 " thick
  • 10' - 2" wide 1/4" flat stock
  • 16' - 1-1/2" wide 1/8" flat stock
I like to have extra in case of mistakes and to have extra left over.
4/25/09   Initially my attention shifted over to our old 12' C-band satellite antenna, I took it down about 5 years ago and it had just been sitting on the ground. I got the linear actuator removed from it. The actuator turned out to be a SuperJack XL.

I took off the motor cover and sprayed some WD-40 on the internal parts and cleaned it up a bit. Amazingly enough it still worked, and gave 23-1/2" of travel. I will be purchasing a new unit as the balls were rusted solid, but this will give me something to design with.

The rest of today is to begin the fabrication of the mounting frame. In laying out on paper the solar panels I calculated that the outside dimensions of the mounting frame (for my particular solar panels) should be 88".

I cut the 1-1/2" tubing with 45 degree ends, squared up the whole assembly on my garage floor, measured from corner to corner to ensure squareness and welded it all together. Next I cut a piece of the 2" x 4" tubing to fit the middle of the frame, I put this in with the outside edge flush with what will be the mounting face for the solar panels. I put the 2" x 4" on edge as it is strongest that way and should allow for more rotation. The remaining open ends of the 2" x 4" were capped off using some 1/8" steel plates.

All the welds on the mounting surface were ground flush.

I am hoping for a full 180 degrees of rotation of the frame to end up with a horizon to horizon tracker. This will give maximum panel output.
4/26/09   Work continues on the mounting frame and the main support column. I was able to salvage some bronze "Tee" thrust bushings from the old satellite dish mount and used them between the main column and the framework. They fit into a 5/8" hole and take 1/2" bolts through them, I may end up making some bushings out of delrin instead, but these will do for now.

I got the main assembly assembled and mechanically I have about 210 degrees of rotation between the assemblies. However you really only want about 160 degrees of actual movement. The reason is the physics of mounting the actuator, once it goes past 0 degrees or 180 degrees it will not want to reverse direction, so keep about 10 degrees so the mechanism does not bind.

I got the old actuator mounted, and after some design decisions/construction I really only need an actuator with just over 16" of travel, so an 18" actuator is right in line and I really don't need additional movement that a 24" would provide.

The mount for the actuator is made from some 3/8" thick steel angle iron that I had lying around, spacing it above the top of the main column a little gives plenty of space so the tubing of the actuator does not contact the hinge point when fully extended. All of the other flanges were made from 2" x 1/4" flat stock.

The actuator mounts are shown here with heavy duty reinforcement, like I previously said I live in a high wind environment and taking all precautions. In addition I will be adding some 1/8" thick straps across the top and bottom of the frame work to help reinforce it, in the end you probably can jump on it (although I would not advise it) and barely move it.

I put the actuator through the whole range of movement and it moves easily and smoothly. When you mount the actuator you should position it so that when it is stationary (night time) the actuator is fully retracted. This lessens the possibility of corrosion and will put less strain on the actuator as it just sits there in one position for 12 hours, waiting for the sun to come back up.

If you have a controller that does not have parking capabilities then you might want to consider flipping the actuator so that it is fully retracted in the Westerly direction. My solar sensor/controller does have parking so at night time it will return itself fully to the Easterly direction. If in doubt put mounts on *both* sides of the framework!

Here is the entire assembly so far with the actuator in the fully retracted (parked) position, I still have to mount the main polar column to the post cap:

So far the only slop in the movement is from the rusty ball mounts of the actuator, hoping that the new unit will be tighter. Worst case is that I TIG weld the main actuator ball mount, after all because of the way that I have it mounted I really don't need it since the actuator moves in a simple straight line.

Right now I do not know if there is a disadvantage to having the actuator closer to the top of the framework, but I have a feeling that since I put my pivot points so far outwards that it should not be an issue. Had I made the main column shorter this could have been an issue. If you use the mounting from a satellite dish the actuator should be as centered as possible because of the small foot-print of the dish mount.

The outside of the framework is 88", while the length of the main polar column is about 60" long.
4/27/09   While driving into work today I was thinking about the movement of the framework and realized that I need to put in place some adjustable positive stops. I think that if I did not have the positive stops then there is the potential that the wind could push the framework past the 0 and 180 degree positions and when the actuator went to rotate the framework that it would tear itself up in the process.

These will have some double nutted 1/2" bolts through on each side so that the stops can be adjustable. I will be putting one of them on each side, centered on the cross piece on the main polar column. First I will complete polar column so I know exactly where to position the stops..

Today I also made another decision, I am not going to use aluminum extrusions for mounting the panels. On 5/5/09 I came up with a low cost solution that gives me the ability to easily and neatly bolt lengths of angle iron onto the framework, the solar panels will then be bolted onto these pieces of angle.
Pro Brand 24" Ball Screw Large Tube Satellite Dish Actuator (includes shipping)

Just happened to find this item on craigslist.com, while doing a google search!

  • 24 inch length
  • large diameter tube
  • Ball screw operation
  • 36 volt operation
  • 1500 Pounds of thrust
  • 40 pulses per inch
  • used for 12' - 16' sized dish

The ball screw versions have more thrust potential than an acme screw, and I was lucky to run across this item.
Got all of the stainless steel mounting bolts/nylock nuts/washers ordered from McMaster-Carr, they are *the* best place to buy small to large quantities of a whole array of things, at *the* best prices.

I am getting 1/2" stainless bolts/nuts/washers for the heavy mounting, and 5/16" stainless bolts/nuts/washers for the solar panels mounting onto the framework.The Parts List has the breakdown of items.

In addition to all the hardware I also am getting a 2" dia x 12" long piece of Delrin. I will be using this to make up the thrust bearings for mounting the solar tracker, they should last longer than the bronze bushings that I robbed from the old satellite mount.
4/30/09   I decided not to use the 1-1/2" angle iron, and instead use some 1" angle iron. This will be used for mounting the solar panels onto the framework of 1-1/2" tubing, and adjusted the steel requirements above to reflect it.

Over the next couple of days I will finish up all the welding and show updated pictures.
5/1/09   Had a couple of hours to work on the tracker, I used a couple pieces of 2" x 2" x 1/4" tubular steel for the mounts. On the polar column I cut out a space so that it was inset. Before welding I squared and trued it up as close as possible. All of the mounting tabs were made from 2" x 1/4" flat stock, and use 1/2" diameter bolts.

I decided to use some square tubing to make up the stops, and used some 1/2" bolts so they were adjustable. These stops will contact the cross piece of the polar column as it rotates in either direction.

The other piece of the 2" x 2" x 1/4" tubular steel was welded ontop of the post cap. I offset it from center a little bit and made some angled tabs so that the polar column could be almost vertical, this should help when I go to assemble the entire tracker ontop of the post. I used the salvaged bronze bushings from the old C-band dish for the bolts on this mount.

Post Note: If I were to build another solar tracker I would make one change, that would be the length of the 2" x 2" x 1/4" sections of steel tubing. The lengths that I used were about 20" long, a bit shorter would be better say about 15". The reason for this is as the frame work rotates around the polar mount at both extremes these ends begin to protrude above the mounting surface for the PV panels as they approach the stop blocks. If the panels are not laid out properly the mount could contact them. I ended up using some longer 2-1/2" stop bolts to keep this from happening, the worst case here is that I lost about 10 degrees of rotation - not a bit deal.

Finally I drilled and tapped a couple of holes in the sides of top cap so that I could lock it into position once in place ontop of the post. Here is a picture showing the assembled post mount and the main column, again all mounting bolts are 1/2" diameter.

I made up a couple of rod ends from some round tubing, these will be used for the declination adjustment. I will make the connecting rod after I get the tracker mounted.

Next I cut another piece of mechanical tubing to act as the lower mount for adjusting the declination of the tracker and welded on some tabs using the rod ends plus a washer to get the proper spacing. I use the washer to give me some wiggle room as I really don't want the rod ends too tight between the tabs.

Finally I made a couple more tabs and welded them to the lower part of the main column which the declination adjustment will be connected to.

Post Note: a couple of days later I realized that I welded these above tabs onto the wrong piece! They should have been put onto the bottom of the main polar support column!!! Minor rework!!!
5/2/09   We had our 15th annual Cheat River Festival this weekend, dodged a bullet with the rain and had great attendance.
5/3/09   Not much residual time this weekend but I was able to make up the delrin bushings. I previously bought a foot long of the 2" diameter rod, so I cut off a piece, drilled a 1/2" hole through and machined a shoulder, the main part of the bushing is about 1/4" thick. Here are the finished bushings:
5/4/09   Ordered up some needed items from Dan Bowes at West Virginia Solar, no pricing yet.
  • 1 - Midnite Solar MNPV3 combiner box
  • 2 - 15amp breakers for above
  • 4 - lay in ground lugs
  • 4 sets - MC cables
  • 1 - lightning/surge suppressor
  • 20' - #6 stranded copper ground wire
5/5/09   I had a thought today about mounting the angle iron onto the framework, I was dreading welding the angle iron onto the framework as it creates an area for water/snow to accumulate onto, eventually causing rust - so it's a better idea not to directly weld it on unless you really have to. For another thing I was concerned about having to clean/grind/paint it, not to mention that welding it directly on takes away any flexibility that I may need/want in the future.

So instead of welding the angle directly onto the framework instead I will be welding short 2" lengths of round pipe. I am pretty sure that I have heard them referred to as 'spuds', not exactly sure but that is what I am calling them. I can put mounting holes into one side of the angle iron and using a bolt/nut through the spud to hold the angle iron to the framework.

By welding these spuds onto the framework, the layout and positioning of the angle iron is easily reconfigurable, not to mention easier to apply paint onto as now the framework and the mounting angle iron can be done separately.

One alternative to using round pipe spuds, is to use 2" wide pieces of angle iron welded onto framework. I don't like that idea as much because it takes more headroom and there is more sharp edge/protrusions.

Another alternative is to drill holes into the tubing and weld in 'plugs' at both sides. These plugs are round pipe/tubing (same material as spuds) are welded on for two reasons 1) to seal the tubing from water/etc. 2) keep the tubing from collapsing when tightening bolt/nut. They would have been easier to do before I welded all the tubing to form the framework, and a bit harder to do at this point. So I am going with the spuds instead.

Here is a drawing showing a samples of what I am talking about (click on for larger image):

I plan on welding on these spuds at various positions along the framework, this way if I want to change things in the future this gives me a flexible and easy solution plus the angle iron can be mounted onto either side of the spud and pointed towards either direction! Worst case is that I weld 2 or 3 of them for every short section of angle iron that I want to mount.
Another order to McMaster-Carr, 3/8" diameter stainless bolts/washers/nuts will be used to mount the angle iron onto the spuds.
5/6/09   In reviewing some of the pictures that I posted I realized that I welded the tabs for the declination support onto the wrong piece! They should have been put onto the bottom of the main polar support column and instead they were put onto the center column on the framework.

This will not work as while the main polar column is fixed, the framework rotates following the sun. This error came to light when I went to calculate the various lengths of the support that I would need for the declination adjustment.

I knew that my main polar column was about 60", but I measured a distance from the center of rotation to the support tabs being 42". When I went to do the math it did not make sense as it should have been 1/2 the length of the main column. I am referring to the last picture on the date 5/1/09, and I put a notation there showing the error.

Minor rework... Good catch before painting.
    Picked up my Mitsubishi 180watt panels from West Virginia Solar tonight.

They are really nice looking solar panels!
5/7/09   Took a couple of days vacation so that I can get the post in the ground. For the most part unless you are going to mount your panels on your roof-top you have to go through the process of putting a post/rebar into the ground, whether or not you have a tracker, so this portion is applicable to you as well.

Started out today by using my tractor/back hoe and dug out a hole about 3-1/2' x 3-1/2' wide and 3-1/2' deep. Next trenched out all the way from the pit to the corner of the house where the conduit will enter. Basically you want to try to shoot for a minimum of 5-6" of cement covering all of the rebar, now this doesn't always work out as planned, and in my case a tree trunk from an old crab-apple tree was slightly protruding into one location in the pit, but it's a good plan to start with.

Next I cut up four pieces of rebar 120" long and formed them into squares. Then I welded up the rebar to make a cage with 2 going vertical and 2 going horizontal. Now the plan was that this rebar was going to hold the weight of the 6" pipe so I put some pretty hefty tack welds onto all locations. My personal choice is to weld the rebar, others use twisted wire, but for me I have found that the twisted wire can give too much movement, and prefer to weld the rebar instead, plus with a MIG welder it is sooo easy.

With the post elevated a bit I slid the rebar cage over the pipe and marked out spots where I wanted to drill through the pipe for inserting rebar, and drilled six holes all of them 5/8" diameter. (You have to drill 5/8" holes for the 1/2" rebar to fit through.) The rebar through the pipe keeps the pipe from twisting when the winds blow against the panels - you absolutely need them, I would figure a minimum would be two pieces of rebar through the pipe, so I used three.

Then cut three more pieces of rebar passed them through the holes in the pipe and welded the ends to the rebar cage. Here are a couple of pictures of the rebar cage welded up:

I was working alone today so made full welds on all the rebar connections, mainly because I have to use my tractor to position the pipe and then raise it up by hand, so the rebar was going to hold the full weight of the pipe. Got the post fairly well balanced and going out to drop into hole:

The pipe got inserted into the pit and elevated actually fairly easily, due to the herky-jerky motion of getting it positioned in the pit one of the rebar welds broke but that is not a big deal and is why I put pretty solid welds onto the rebar in the first case. You can see the remnants of the crab-apple tree in the lower left position of the hole - a chain saw removed the protruding top so it did not get in the way of the form.

Got the conduit laid, I ran 1-1/2" for the PV power to the solar charge controller, and another line for power to the sensor/controller as a separate circuit, and used some twine to hold them into position.. The solar tracker is about 75' from the corner of the house.

Here in WV nothing is flat, especially when you live on a ridge top, when I made up the form I used a 2" x 10" on the downhill side and a 2" x 4" on the uphill side, not perfectly level and the downhill side has about 1/2" of pitch to it to help rain/snow runoff. The sides of the form taper, all that is left now is to pin the form to the ground and pour concrete (tomorrow).

I was able to square up the pipe using some 4" x 4" posts that were already in the ground around the site, as initially we were going to put a small shelter for some of our farm animals (sheep, goats, llamas) but the location for the solar panels was perfect and so took prioritiy.. Initially I was just going to cut them out so that I could have easier access to the pit with the tractor, but decided (good decision) to leave them to help in squaring/holding the post so that it was plumb.

5/8/09   Today I had some spare time so I went out and bought 5' of 3/8" black pipe, this is the material that I will be making the spuds out of. I chopped it into lengths of about 2-1/8" on my band saw, put them into the lathe to square up the ends and the final length of them was 2". I made up about 24 of them so that I would have some extras. A bit time consuming but should work out ok in the long run.

My buddy Paul Schreiner from PS Composites came by to help out with the concrete job. In years back Paul used to do concrete work professionally and I always welcome his help where fiberglass and concrete are involved.

With the size of the pit I calculated that it would use about 1-1/2 yards total of concrete and decided to order up an extra yard so that I could pour a slab out near our back deck - something that I have been putting off a couple of years.

Paul used his concrete vibrator to remove the air bubbles from the base, and it works fantastically. We ended up using my tractor bucket to move the remaining yard of concrete from the truck to out around the back - I don't know what I would do without my tractor!!

We lucked out on the weather as it did not rain all day even though there was a 60% chance, and it did not rain till late evening so I did not have to put a cover of plastic on the concrete.

Before the concrete completely setup, I put in the obligatory paw prints from our two dogs (Sparky and Ranger) on one corner.
5/9/09   Took apart the concrete form from the base and happy with the result, it had a strange white shimmer today. One thing that I wish that I did was to sand and paint the post *before* pouring concrete. It's not a big thing but having the conduit in the way makes it a bit harder. Perhaps I will just do a quick sand job and brush on some Rustoleum rather than trying to spray it.

For the remainder of the day I wanted to finish up welding on the solar tracker.

First thing that I did was to make up a template of the bolt pattern on the solar panels using some angle iron. I bolted it onto the back of one of the panels - and with the panels carefully covered I spot welded the angle iron together.

My plan is to use this template for welding all the spuds onto the frame so that when done the solar panels can be mounted directly to it with all the mounting holes are predrilled. Here is the template positioned on the frame so that I could weld the spuds the holes seen in the template should exactly match up with the mounting holes on the panels:

I also made up one piece of angle iron with the holes drilled in their exact positions as another template and made up 6 lengths of 1" angle iron so that they all were exact duplicates. As it turned out both of the templates were a real time saver, not to mention that all the holes should be dead-on for mounting the panels. Now any one of them can be used in any of the positions.

I also made up 2 lengths of 1-1/2" angle iron, these had to span from the center column to the outside tubing and 1" was a little too weak for these pieces. The larger 1-1/2" angle iron was much more rigid, but I had to trim the ends down to 1" where the angle went over the framework tubing so that the mounting surface would match the rest of the 1" angle iron. In hind site I probably should have used the 1-1/2" angle iron all around, but using the shorter lengths of 1" angle saved both money and weight.

One other thing that I was careful of is that all the angle iron pointed downward, this should help to keep them clear of rain and snow. Here is a picture showing some of the spuds and angle iron mounted to them:

In the long run using the spuds for bolting the angle iron leaves a nice clean look.

Next on the list is the ungrateful job of deburring all parts, sanding and paint!
5/10/09   First thing I did was cut off the mis-placed mounting tabs for the declination support and got them welded onto the bottom of the main polar column. I remeasured the distance from the center of rotation and came up with 31-1/2", much more inline now that they are located in the right position!

Spent the better part of 3/4 day grinding the cap, polar column and framework, I still have the 8 pieces of angle iron PV panel mounts to do, but pretty good progress. My large 220v compressor was running most of the time as air grinders take a lot of CFM, it would have taken longer had I been using a smaller 110v compressor. This is back-wrecking grueling work as you are stooped over most of the time, be sure to wear respirator for grinding/painting!

I decided that for this project I was going to spray the primer but brush on the final coat(s) of paint. I have all the HVLP equipment to spray the paint but this time I wanted a nice thick coating of paint on the outside of the solar tracker/post so decided to brush on the final coats. It's tough to get a good heavy coat of paint by spraying without creating a lot of runs/drips.

Pretty typical prep using acetone to wipe down all surfaces and then spray the primer. It was windy outside so did it inside my garage.

I bought a quart of Rustoleum 'Royal Blue' which is an oil based exterior paint, and after finished with the primer coat used a couple of disposable bristle paint brushes that I have for fiberglass work and applied a good heavy coat onto all parts of the solar tracker (minus one side of the framework).

When done I also wiped down the 6" post and gave it a good coat as well. In the end I have at least 1/2 the original quart of paint left over. I used some twine to hold the PVC conduit runs away from the post so that I could get paint applied behind them. I did not even sand the post, just used some acetone on a rag and wiped it down as well as possible.

Pretty much the whole day spent grinding/prep/painting, but should have a pretty durable finish. Over the next couple of nights this week I will flip the framework over and apply a coat of Rustoleum paint to it, as well as work on the angle iron parts, they are a bit harder to sand/grind which is why I wanted them separate from the main framework in the first place.
Electrical wiring supplies:
  • $122.00 - 200' THWN-2 #6 (100' red, 100' black)
  • $10.68 - 12' Liqui-Tite 3/4" flexible pvc
  • $3.68 - 90 degree fitting for 3/4" pvc
  • $8.11 - 1-1/2" pvc LB
  • $4.03 - 3/4" pvc LB
  • $7.50 - ground rod
  • $32.00 - 240' TFFN #16 (120' red, 120' black) battery bank feed to RedRok solar sensor/controller/actuator
5/12/09   Very happy with the brushed on Rustoleum paint, it leveled off really nicely and looks great. I will probably give everything a 2nd coat.

I went to my local Lowes to see what sort of exterior lighting that they may have, I was hoping to find something suitable to contain the sensor/controller. I was not happy with any of the sidewalk lighting, didn't care for how most of them were made, even the spot lights.

In walking around the store I found another section "outdoor lighting" this area had stuff like illuminated exit signs - and then I saw it! It was a Utilitech #045028 - they referred to it as a floodlight, but it was a domed enclosure for a standard 100watt light bulb, and it also had a protective cover and weather proof box - PERFECT!

The picture does not show it but it also comes with a waterproof electrical box that it mounts to.

The instructions with the light state that it can hang upside-down or sideways, and I knew that I would have to do some slight modification to it. Once home I drilled a couple of weep holes on both sides of the base, but above the rubber gasket that seals the glass dome to the inside of the base. This way when water gets into this area it can easily escape, since it will be mounted somewhat vertical.

The rest of the day was spent in grinding the 8 pieces of angle iron to remove any rust/scale. I also drilled in an additional three holes along the length so that I could use some zip-ties to hold wiring to the angle, as well as a couple of holes to mount the box used for the sensor. By the end of the day I got all the pieces painted with two coats of paint.
5/15/09   Got all of the angle iron mounted onto the framework using the 3/8" stainless steel bolts/nuts.

Put the cap onto the post and drilled a couple of 1/2" holes through the post to positively fix the cap onto the post. Next using a step ladder I muscled the main polar column up onto the mount and got it bolted.

Where I live the latitude is just over 39 degrees, so according to what I have read:

  • summer months -15 degrees from latitude
  • spring/fall months - latitude
  • winter months + 15 degrees to latitude

Initially this confused me and seemed backwards as I was thinking relative to vertical, however the calculation is actually taken from the horizontal plane! So according to the numbers at my location:

  • summer months 24 degrees from horizontal
  • spring/fall months 39 from horizontal
  • winter months 54 degrees from horizontal

I used an adjustable level that I have and set the polar column up for each of the degrees shown above and measured out the three lengths that were needed for the declination support, and show them in the image below. These numbers do not have to be exact, close is good enough so they are rounded to the nearest fraction to make life easier.

This is what I came up with:

These 3 different lengths are what I need (assuming that the collar stays in one position) for the declination support/brace. So now I should be able to fabricate this brace ahead of time. I will make the support so that it can expand/collapse to fit all 3 lengths required. Another way to do it would be to use a fixed length support rod and move the collar up/down the post for proper panel positioning. My feeling is to leave it in a single position this way it will not scratch up the paint on the post and I don't have to worry if the retaining bolt on the collar was tightened sufficiently.

I happened to have some 3/4" stainless steel bar and some 3/4" black pipe. I welded up the rod ends that I had previously made and drilled a couple of holes in the assembly to obtain the three various lengths of the declination support. Here is a picture of the final support:

I realized that getting the framework up onto the post (by myself) was going to be quite a chore. So I decided to put my floor engine hoist into my wife's pickup bed, I used some nylon ratchet straps to hold it into place, used some nylon webbing to pick up the framework, and backed the truck up to the post.

It actually worked out pretty well and after a bit of maneuvering the truck position I finally got it put on! It was almost too easy...

5/19/09   On the cap that goes over the top of the post I have drilled/tapped two 1/2"-13 holes. In addition I also drilled through the post 1/2" holes so the bolts could go through and essentially lock the cap on top of the post.

There should be three holes through the cap, as currently if you grab the framework and shake it there is a slight movement of the cap. This motion gets amplified by the time that you get 4' out from the post, so the cap must not move at all!

So one additional hole should be put in to positively lock this cap into position. Before I mount the panels this weekend I will put this additional drilled/tapped hole in place.
5/22/09   Today I again used the engine hoist in my wife's pickup truck bed and lifted the framework off from the post cap.

I ended up drilling/taping two additional holes in the cap and repositioned it on top of the post. I transferred the new hole locations on to the post, removed the cap and drilled the post with 1/2" bit. Now there is 4 holes each at 90 degrees in the cap mount.

Reversed the operation and put the framework back onto the cap, no there is not even a wiggle.
5/23/09   This afternoon I got Dan Bowes from West Virginia Solar to come on by and help me put the PV panels onto the tracker.

Together there was three of us and I have to admit that putting the panels up is *not* a one man job, it could be done with two but worked out very well with the three of us. We used the bucket of my tractor to position one person on the top side of the tracker while one person lifted the panel to the bucket person, and the last person was on the underside of the tracker installing the bolts/nuts.

There were some lessons learned and are as follows:

  • Use 1-1/2" angle iron, not 1". The 1" angle iron does not give enough wrench clearance and made installation tougher.
  • No need to use stainless washers.
  • Dan advised that it would have been easier to use lock-tite rather than nylon-lock nuts.
  • Use 3 or 4 bolts to hold the cap onto the post
But in the end the panels did get up.
5/24/09   I am still awaiting the arrival of the combiner box, breakers and other misc parts, but decided to get all the wires pulled through the conduit and rig the PV panels up temporarily.

Using a long length of twine, a small plastic bag tied to the end and a shop vacume I got the twine sucked through the conduit and pulled the wires through.

Got the wires routed to the DC distribution box breaker, then to the Xantrex XW-SCC solar charge controller. The output of the charge controller goes to another breaker, then to the buss bars where everything is connected to the battery bank.

Next I got all the PV panel connection done (all in series), taped up all the MC connectors and using zip ties got the wires all neatly tied down to the tracker framework.

I temporarily rigged up the THHN wires to the MC connectors on the panels. Simply remove some insulation and pushed the wire into the male/female MC ends and taped them together. Once the breakers were turned on the panels were immmediately began making about 600 watts once the tracker was turned into the sun manually.

Once I get the combiner box/etc I will permanently wire up the PV panels, but at least for now they are operational.
5/28/09   The rain broke long enough for me to get a couple of pictures of the PV panels mounted on the solar tracker.

This picture shows the underside of the panels - the orange electrical chord has been replaced with some good waterproof 16/2 cable:

By virtue that the panels had the positive and negative connections at opposite ends made for a nice neat wiring installation. I just made sure that the panel was oriented properly for the shortest run to the next panel.

As the actuator extends the angle between it and the framework becomes shallow, thus allowing for some movement of the array. If no movement is desired you need to mount the actuator more at a 90 degree angle. As it is the movement is not excessive and would rather have more walking clearance under the array.

Here is the array from a couple of different distances, click on the thumbnail to see larger picture:

6/13/09   This morning I was finally able to install the combiner box and button up all the wiring, rather than using the temporary wiring like I have been. Locally I was not able to find a 1" pvc offset so I made my own by using a heat gun and softened up the 1" pvc to create about a 1-1/2" offset, it was pretty easy to do and came out looking looking pretty good.

In the mounting board for the combiner box I predrilled 2 mounting holes and transferred them to the post. Then I drilled the post holes using a .250" drill bit, and then tapped the holes for a 5/16-18 bolts. Once the board was up I mounted the combiner box to it and completed the wiring. They don't recommend mounting anything on the side holes, but that is the only place that the lightening arrestor would fit, I used an O-ring to help seal it up so it should be ok.

Before I cut the lengths of flexible tubing to size I cycled the array completely around to ensure that I had enough slack. The open end where the MC cables and ground cables go into I squirted a bunch of silicone caulk to seal the end up and used zip ties to keep everything neat and held in place.

Next I used a simple square box and mounted it directly to the post again using a 5/16" bolt. Before mounting I put in a hole in the side for the 1/2" Liqui-tite 90 degree connector. When I finally receive the solar sensor/controller from Redrok I will install a couple of switches inside this box to manually control the array during wind storms.

Here are a couple of photos:

I still have to get some long zip ties to tie down the flexible tubing to the post.

I'm a bit disappointed with Duane from Redrok, it's been over 45 days since I placed the order and he still has not shipped it to me. I talked with him a couple of times on the phone and apparently he has been working on something else and again assured me that the unit will be shipped...
6/19/09   Well I finally received the solar sensor/controller from RedRock...

I fabricated up a mounting plate which is made from some 16 gauge steel, for two manual switches so that in the event of a big wind storm I can stop the solar tracker and manually set the angle to minimize the effect that the wind would have on it.

Here is a picture of the two manual switches, on for fast/normal using a momentary DPDP switch, and the other using a 'normal' DPDT switch so that I can move it East/Off/West.

This will be mounted at the post so I can manuall controll the array position.

6/28/09   I finally got the chance to go to my local Lowes store and found the receptacle cover that I have been needing, it is a Tay Mac MM410G multi-purpose weatherproof receptacle cover. This will be used to cover the manual array control switches out on the post

7/3/09   Had some extra time today so I thought that I would work on the RedRock sensor/controller. First thing that I had to do was to make the wires to connect between the sensor and the controller. In hind sight it would have been easier had I just bought the non-remote sensor version, but at the time I was not sure and thought that I may need to be able to remotely mount the sensor.

I took a length of wire ribbon that I got from an old computer cable and soldered up the connector ends, not real difficult but took some time working with a magnifying glass but got a short length of cable and wired up the connector ends.

Next thing was to see about to mount the device onto some #6 all thread. It's a bit problematic in trying to mount the sensor, RedRock had pictures of sensors for dual-axis controllers and in the middle of the board is a mounting hole. The problem is in the single axis sensor they cut through this hole - not very well thought out...

After studying the problem for a while I decided to cut a small length of sheet metal and bend it into a 'U' shape and essentially lock onto one of the wire connector ends. After a couple of tries I finally got one that holds onto the connector real well and got it put onto the end of the all-thread:

BTW: the Red LED should be pointing to the East, and the Green to the West, the documentation was not real clear on this but on the board are some *very* tiny E and W letters.

Next task was to mount the controller board, there was only a single hole in the PCB and it was too small for the #6 all-thread so I had to use some alternate mounting. In looking around my shop I saw a plastic parts tray and chopped out a small section using a die grinder and drilled a mounting hole through one part.

I had no epoxy so I decided to whip up a small batch of fiberglass resin, and put in a bunch of chopped fibers and lots of catalyst (for the size of the batch) and essentially 'glued' the board onto the plastic. Here is the complete assembly almost ready to mount onto the array:

7/5/09   Ok so the plastic tray was not such a great idea, the plastic was brittle and when tightening down the nuts to hold the tray onto the all-thread it cracked. So I cut off the lower portion and decided to glass it directly onto the all-thread. Again mixed up a hot batch and filled it with a bunch of chopped fibers and got it positioned where I wanted it during the process.

Here are front/back pictures:

Got the manual switches wired up and the sensor put up on the array, drilled some more weep holes in the base so that it can drain off in all angles. Here is what it looks like inside the glass container without the protective cover:

Here is the electrical diagram showing the way in which I wired up the manual switches:

11/1/09   I had noticed that the tracker was not properly tracking the sun, it tended to be 15 degrees ahead of it. I figure that there were some sort of reflections inside the globe that were causing this.

So to resolve this situation I spray painted the inside of the glass (but not the very end of the dome) with some blue paint that I had laying around.

This completely fixed the tracking mis-alignment and now it very accurately is tracking the sun.

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