This will document the construction of a Helios (see photos of completed Helios at http://www.solarfire.org/Helios,36 ) in Lytton Springs, Texas (just a bit less than 30 degrees N. Latitude). Since the first construction article for the Helios was written in French, I ran the article through a translation program, saved it, and printed it so I could convert the measurements for materials into American units of thicknesses, widths, and lengths that I could purchase at a local steel supply yard. (Discount Door and Metal L.L.C 2 at 1083 Highway 71 West, in Bastrop, Texas 78602) Then, I obtained a printed price list from them, and made a list of what I wanted, and hooked up my 12 foot long cattle trailer to my diesel truck and drove the 20 miles to the supply yard. Loading the 24 feet long 11 gauge (heavy duty) square tubing into the 12 foot trailer left me with a good bit angled up into the air over the bed of the truck. With luck, I managed to clear all the low hanging power and telephone lines on the way home. The first photo shows the material and prices I picked up on that trip. Then using the pictorial Helios construction plans put together by Marie Testud (GUIDE DE CONSTRUCTION FOUR HELIOS) I began using a hacksaw and a 14" metal chop saw to cut metal. To cut the 3" wide 1/8" thick material that the 12" mirror tiles are glued to, I used the chop saw to cut two at once. Put them on edge, measure carefully (These need to be square 3" by 3") and lower the grinding disk. Works great! Then clean up the edges on the bench grinder. The smaller pieces for the spider were cut in a bench vise using some old hacksaws, mostly to save on material, because the chop saw takes at least 1/8" of material for each cut. However, the chop saw does cut at pretty close to 90 degrees each time.

Mirrors were purchased from Lowes Home Center for $1.40 each. They were available in boxes of six tiles. I bought all they had (8 boxes) using a ten dollar discount coupon, plus my cash. Two days ago, they sent me another ten dollar discount coupon, so it is time to drive there and buy more mirrors, and some polyurethane adhesive. Lowes and Home Depot are our two large chain building supply and home repair stores. Eerik says in Canada, they use Lepage Bulldog industrial adhesive. A google search yields no availability in the U.S., but did say that Henkel purchased all or part of Lepage. Lowes has plenty of Henkel glue products..Gorilla glue might work, but I certainly don’t want the mirrors falling off the steel plate.

Nuts and bolts: I priced the metric threaded items, and decided to use a 1/4-20 size bolt which is a very common size here. The eight bolts pressing on the mirrors need to have threads from the top of the bolt to the bottom, so you have to order a TAP BOLT. I ordered 1/4-20 x 2" Tap Bolts grade A, Zinc for less than a nickel each from WholesaleBolts.com. They were ordered at 2 P.M., and showed up the next morning at 8:30 A.M. I also ordered some lock nuts, and shorter 5/8" grade Hex bolts (1/4-20) to attach the spiders to the tabs on the square tubing.

I’m welding these spiders using a Miller Synchrowave 250 TIG welder with Argon Gas and RG-60 welding rod. There was a label on the square tubing indicating it was made in Mexico. The square tubing looks very strong, and the 24 foot length is heavy. The 1/2 strap steel used for the spiders is not very strong, (I guess I should say it is very soft steel) but it is light weight, and I believe it is going to do the job. When welding it, I’ve noticed parts here and there that don’t seem to be real pure steel. (i.e. not like aircraft grade 4130.) Well, yesterday I added a few more spiders to the pile and today I need to cut out some more materials, and possibly get a few more made.

Thanks to my neighbor (Dave), I bought a trailer for a small boat and I hope to be able to modify it to hold the array so I can move it into the barn during a storm or hurricane. Also, the two tires hold air, and would simplify movement of the array so it can track the sun.

For the interior of the oven, I’ve stripped a discarded dishwasher of all electrical, rubber, and plastic parts and now have a steel box with a door and a large round hole. A round microwave clear glass turntable might work as a porthole to let the energy into the oven. (I now have two of those, for FREE, but I have no idea whether or not they will work, as the glass is thick.)

Making the 90 degree bends (about 500 of them) for the spiders. I’ve been hacksawing these in my basement using large vise and a couple of CFL lamps. Earliler, I had made some templates out of light cardboard from a cereal box. Next, I carefully cut out some "Go-By" pieces, and marked them using a ring of duct tape. These are my reference pieces for the three different sizes of legs for the spiders. Place the steel in the vise with the wide side up, so you get a 90 degree cut (no slants). After cutting a large stack, lay one of them on the anvil part of the vise, and determine which end is going to have the hole (save the perfectly perpendicular end for the weld joint.) and lay an old hacksaw blade over the end of the piece and use the hole in the end of it to locate the position of the center punch mark. Give it a good whack with a hammer, and inspect. If it isn’t in the center, turn the piece over and try again. (Put this piece in your pocket, so you know it has marks on both sides.) Set up your drill press with a slow speed and using a #7 wire drill size or a 13/64th fractional drill size drill the holes. I like to keep the drill bit cool by using a little acid brush dipped into used motor oil. The one bit should be able to drill 500 holes if it never gets overheated. (The steel cuts like butter.) A photo shows the nice spirals coming out of the hole. (Cool!)

After drilling a bunch of them, take them back to that big vise and clean the chips from around the hole with a large coarse file. Insert the metal piece into the vise so the end of the metal is exactly even with the lower edge of the jaw. (Otherwise, you can build those little boxes that Marie shows on her plans.) (see photo) Now, drop the large nuts (together these are 3/4" high) over the end of the steel and use a large adjustable (Cresent) wrench to twist the steel 90 degrees. Remove the steel from the vise, and insert it horizontally in preparation for the threading operation. First, examine the twist and see if everything is straight. If not, lightly hit it with the hammer, or twist it a bit more with the wrench. Run the tap in the hole, backing it out to remove the chips, and then going forward. Insert one of those 2" 1/4-20 bolts and see if you can put it in with your fingers. (No wrenches here!) If not, run the tap into the hole again. I have an old toothbrush that I use to clean the chips from the Tap each time I use it, and then put a drop of oil on it. This seems to reduce the number of times I have to re-insert the tap in the hole so I can easily turn the bolt with my fingers. BTW, when you buy taps, I would recommend getting at least three, because I’ve already had two break...maybe because I dropped them on the concrete floor?? There are different types of taps. One type has a long taper. The other type has a blunt end, probably for tapping holes in solid blocks. I’m using what I found in the drawer in my shop, but if you need to purchase them, the tapered type is what you should buy. After taking all these little pieces to the steel welding table, and creating a stack of spiders, you should return to the big vise again. Clamp a large C-Clamp (mine is a 7" labelled "malleable" - I think it came from Sears.) Put a spider into the C-Clamp, one leg at a time, held near the 90 degree bend. Examine the bolt to see if it is straight up and down, and if not, bend it with the large adjustable wrench. (Tweak it!) Also inspect all of the welding, and if something doesn’t look good enough, tag it for re-work. Feb 15, 2010 After welding enough spiders for two rows of mirrors, I decided to paint them so I could start gluing the mirrors to the frame. Since the raw steel is covered with a black grease or oil, I decided to construct a sandblasting booth using some canvas tarps. First, I removed all the bolts from the spiders (they were installed so I could "adjust" them using the C-Clamp.) and put them in a large pile on a metal grate, and then blasted them with the sand. Hopefully, the sand would hit more than one spider during its flight, so it wouldn’t take as long to sandblast the ones that were in the stack. The sandblasted spiders are very light-colored, and the part that gets attached to the mirror back has a "tooth" and almost feels like sandpaper. This really works the air compressor, so I did several, and then moved to the bench to paint them using a small brush. I’m using oil based premium RUST-OLEUM enamel that is supposed to provide excellent rust prevention when applied over bare metal. (The can says that for even longer lasting protection you can use a STOPS RUST primer.) After painting and sandblasting for most of a nice 70 degree F day, I had nine of them hanging up to dry. The second day, I got six more done, when a cold front arrived with a tremendous wind that blew down my sandblasting booth, rained on my sifted sand, and sent me looking for my jacket. It froze the water in buckets on the porch. Until it warms up, I can’t do any more painting outside. The strong wind got me to thinking about what would happen if I had a completed Helios sitting out there when the cold front arrived? I wonder if the wind would break the mirrors?

Feb. 17, 2010. The first nine mirrors are glued to the spiders and ready to be mounted. 60 watts/mirror X 9 mirrors = 540 watts. Time to build on the frame so I can start cooking something! The weather forecast looks good. Ice on the grass as I type this, warming into the 60’s this afternoon.

Feb 19, 2010 Yesterday, I welded the tabs onto the 1 1/2" square tubing that will hold the spiders/mirrors in the array. This is heavy-duty tubing with 1/8" walls, and the tabs may not have been required, but putting them on is extra security. Doing 54 of anything takes time, and it took me almost all day to get these aligned and welded. I also glued three more mirrors to their spiders. Now, I will rig up a step-ladder to hold the ends of these tubes to I can run them through the drill press and drill the 54 holes to be tapped. Also, If the humidity drops a bit, I need to sand blast some more spiders so I can paint them, watch the paint dry, and then attach the mirrors.

Feb 21, 2010 Those six 1 1/2" square tubes have end plates that get welded on, and then have a threaded rod or a threaded hole in each one. The photo below shows how I cut the little squares that will be welded to the ends of the tubes. When I cut the 3" squares out of 1/8" plate for the spiders, some of them were not exactly square, and were placed in a "reject" pile, so I cut some of these into four pieces using my chop saw. Since they were small, it was hard to figure out how to hold them. I ended up using the two C-Clamps, as shown in the photo.

Instead of using a threaded rod, I found some short 1/2" bolts with nuts, so I welded the bolts to six of the end pieces (squares), then drilled a 1/2" hole in six pieces, inserted a old bolt, attached the square, then the nuts, and welded them in place. The 100 Amp current from the welding machine messed up the threads a bit, so I ran a 1/2" NC (13) tap into the nuts to clean them up. The photo below shows the nuts and bolts attached to the end plates. Also shown is a stack of freshly welded spiders that are in the process of being sandblasted. It was a nice warm day (80 F or 26 C) just ahead of another cold front, so I spent the rest of the day sandblasting and painting spiders. I got 11 done, and hanging on wires around the shop, before I retired for the evening news. Between the zinc fumes from welding the galvanized nuts/bolts, and the dust from sandblasting, I feel like I have been in a nasty dust storm! Plus all the sand in the hair and ears and shoes and...everywhere.

Feb 25, 2010 It snowed here and has been really cold for South Texas! I stayed in the basement and attached the mirrors to the painted spiders. 26 of them are now completed. I’m using Gorilla Glue that I bought at the local Wal*Mart store. It needs water to cure, so I sprinkled a bit of water on the back of the mirror, and dabbed some of the glue in the little square I outlined in pencil on the back-side of the mirror. See photo below. The directions say to let the glue stand for a few minutes, as it takes about ten or twelve minutes for the reaction to begin. At that time, it expands 4X. Meanwhile, I take a rag and wet the piece of sandblasted steel that the mirror will be attached to, and then lay the metal spider carefully over the glue, and weigh it down with various hunks of steel. Watch it carefully, because when the glue expands, it often moves the spider around on the back of the mirror. The excess oozes out around the edge of the steel, and eventually you learn not to put too much glue on the glass. The amount shown in the photo on the left seems to work for me. If it does slide around, you just shove it back into position. In fact, in the photo above, on the right side, you can see that the spider needs to be slid up a bit. (That happened while I was taking the photo!) So far, all of the finished assemblies are correct, but the process needs watching. It is easy for a sleeve of the jacket to brush the spider when you reach up to switch off the light.

March 5, 2010 I’ve been working on the frame that holds the mirrors. Both ends were fastened to the six bars, and they were mounted into the frame, and once everything was tested to make sure it turned freely, the frame was fastened securely together. Unfortunately, one corner got screwed up, and needs to be re-done. The boat trailer now has the tail lights and poles (for holding the boat in place) removed. This afternoon, the location for the square tubing was determined, so perhaps by next week, the frame holding the array will be mounted on the trailer. At the hitch end of the trailer, a two-wheeled cart has had a 1 7/8" ball attached above the axle, and this will allow the trailer/with concentrator to be pulled into the barn during storms. It will also allow the concentrator to be easily rotated to follow the sun.

March 9, 2010 The bracket that is going to hold the two square tubes that the array will sit on has been finished and even painted. I welded two pieces of angle together that fit around the tube, and then welded four threaded rods to the sides of the angles (that now form a U). There is a good weld, but the whole weight of the array will be "teeter-tottered" across the rear of the trailer, and if the weld should break, the array would fall to the ground. Hence the large clamp. (Now I’m worried that the two 1 1/2" 1/8" walled square tubing might bend!) Here is a photo of the bracket or clamp.

I also managed to sandblast and paint five more spiders today. Over 80 degrees F is good painting weather! As soon as the frame for the array is mounted on the trailer, a photograph will be inserted here. Stay tuned!

The paragraph below consists of a number of questions I have... What are the failure modes of constructed arrays? How much do you tweak the bolts pressing against the mirrors? How much latitude is allowed in the placement of the bolts in the fingers of finished spiders on the backs of mirrors? (I’ve been putting them back in the C-Clamp using some cork to prevent marring the paint, and tweaking them with a hammer covered with parts from on old leather glove.) I guess the mirrors in the center of the array would be focused closer than mirrors at the ends of the array and thus those bolts would get "tweaked" tighter on the mirror backs? Are locking bolts necessary on the bolts, as shown in the construction guide in French, or do the bolts stay where you put them? Do the mirrors change focus? Do the edges of the mirrors needs to be sealed to prevent the backing from de-laminating? All these questions...

A couple of things I have noticed in the plans: Maybe the two-inch long bolts are a bit long? (I won’t know for sure until I tweak them down and bend the mirrors...maybe some could be shorter?) Also, if you do use the six hunks of 1 1/2" square tubing to hold the mirror arrays, then you would want to cut the 12 squares that get welded to the end of them to be 1 1/2" square. (If you use the light 1" square tubing, then the pieces for the end would be 1" square, obviously.) When purchasing steel, the 3/4" wide piece probably wasn’t necessary, because the one inch wide piece could just be cut 3/4" long. No big deal. Just something to think about when you are hack sawing and tapping the almost 600 pieces.

Potential applications for my Helios: Baking. (I wonder how to best control the temperature in the oven?) I guessing a big thermometer, and once temperature is reached, a set of 18 mirrors is moved away from the oven? Or, maybe put some thermal mass into the oven, and once the temperature is reached, remove the heat source from the oven?

We typically make 32 Pita Breads at once, using a pair of black cast irons pans and a Anderson Champion TLUD-ND (Top Loaded Up draft-natural draft) gasifier out on the patio. This requires a 500 degree F. temperature for about 90 minutes. It took a while, but we have this "down to a science", and it works every time. However, cooking a chicken or turkey in a pressure cooker over the gasifier makes for good stew, but doesn’t compete with an oven-baked fowl.

Water heating: My existing solar water heater doesn’t get water warm enough in the Winter, but will produce all the hot water we can use during Spring, Summer, and Fall. (During the Winter months, we use a timer/switch on a second hot water heater to only heat the water when needed. Immediately before using the water, we turn the switch off, so the water isn’t heated as it is withdrawn from the tank. The lower heating element has been disconnected, so only the upper element is being used. There is an incredible stratification of water within the tank. Only the water in the top of the tank is hot. The rest is cold.) The water storage tanks are located in our basement, so a 115 Volt TACO 006 pump on a hand operated switch moves the hot water down into the top of the tank, and pumps cool water from the bottom of the tank outside to the solar collectors. Of course, even the Helios won’t work if it rains for a month! When the Helios is completed with 54 mirrors, I intend to hook the two tanks in series, and pump much hotter water into both of them. There should be no shortage of very hot water. (Hopefully)

Kiln drying Mesquite Chunks: Kill the little yellow worms! These worms can destroy a nice hunk of mesquite by boring round holes in every square inch of it. It ruins a nice hunk of hardwood! My spouse is a woodworker, and has a site at http://www.woodworks-by-donna.com/ She doesn’t want any wormy wood anywhere near her precious wood storage bin! According to Wikipedia, most softwood lumber kilns operate below 240 °F (116 °C) temperature. Hardwood lumber kiln drying schedules typically keep the dry bulb temperature below 180 °F (82 °C). Difficult-to-dry species might not exceed 140 degrees F. This might be a good use for the oven when it is not used under full power for baking. I’m thinking a chimney might provide natural draft to keep the air moving. Most of the wood we use for wood working projects is small chunks, for pens, pins, or band saw boxes.