The completed 8-can-pipe. Notice cat inspection and the associated feline brain power.

Prior to putting the components together I laid this out to show how the hot band would slip over the stopper and then the cold can with "PAM" would be tapped into the band, stopping at the wood insert. Notice that I had 4 pairs of can's with narrow bands joining the cans bottom-to-bottom. Now it is time to join these pairs of cans with wide bands, with the cans oriented top-to-top.

I only ran into troubles when I attempted to tap a set of cans into place, but I tapped against a band. They are just not stiff enough to take that abuse and that resulted in a split band. Always start with any can combination as shown above, and then connect groups of cans by tapping them together, with the band between the cans.

Although the "pipe" is meant to just be a ventilation duct, there is benefit to the pipe being able to at least maintain it's shape. As a test, I wrapped the 4 x 4 wood block in a towel and hung it at the mid-point of the cans as they were supported on each end by the chairs. There was very little deflecton so in the hot environment of a solar collector, just supporting it's own weight, which for aluminum is pretty light, I suspect these "pipes" made without glue, fasteners or tape will do quite well.

More details on cutting the bands and connecting the cans...

I made some supports and stops to help position the can in the most favorable locations. The "C" shaped stops under the Dremel allowed for a smooth surface along that cut side and the blocks on either side provided lateral support. The can is supported vertically so it is just within the range of the cutting wheel. I added a piece of coarse sandpaper to fine-tune that vertical support plus the bar code on the paper served as a visual guide while turning the can. The wide and narrow bands already cut are visible. I used a sanding disk to de-burr those bands prior to use.

The support for the joining operation is shown here. Shown is the end result of joining 4 pairs of cans (bottom-to-bottom) with narrow bands. On the left the circular disk is the detachable stop to help insure the can is inserted to the mid-point of the band. The bands were put into the oven at 400-degrees F. The bottoms of the cans had been sanded off and "PAM" was smeared along the area where the band was to be located. The cans were then put into the freezer. I would pull out a band and slip it over the round stopper, then take the cold can and place it on the support. Using the wood block and hammer I tapped the can into the band. This process of joining one can to one band may have taken 30 seconds.

I put the can/band combo back into the oven and waited a couple minutes for them to heat up. With the round stopper removed I pulled out the hot can/band and then the cold can was positioned to go into the other side of the band and tapped. The end result would be one of the four pairs as seen in the photo. Again this took perhaps 2 minutes for all 4 pairs to be completed. Besides working extremely well, the only issue was the tendency to "tap" too hard, somewhat compressing the can in an unfavorable way. The 8 cans, when lined up as four connected pairs are exactly the same length as the 8 cans when positioned tightly end-to-end.

Although tempted, I will not test the final 8-can-pipe to see if it is watertight, but by selecting cans without the dimples, and insuring the cans were inserted to the midpoint of the bands, I'm sure these will be water-tight. Next operation will be to grind out the tops of these cans so I can then repeat this process with the three wide bands and therefore complete the 8-can-long pipe.

Interesting observation....

I have been working on a system to better slice 'n dice my cans as well as a support to help improve the process of joining cans with these bands. Doing so had led me to the discovery that at least half the cans I had set aside had the same small dimple where I had the previously mentioned pinhole leak. I have done a better job of can selection by restricting the cans to non-dimpled versions.

Some of the cans will still be used for bands. By using a wood dowel I can work out some of the minor indentations but still, I'll try to limit the use of cans that are not in the best of shape, so to speak.

With many issues cropping up in December, work has been slow but it has been cold in that lab as well. Now if the sun were out and the collector was working, and I could cut a ventilation hole into the side of my house..................

Update: A COMPLETE SUCCESS !

Before I jumped into the freezer/oven technique I also checked my cat can stopper and discovered if I shaved off about 1/8th inch then that would help the two cans to butt against each other at the center of the band.

I cut a few more bands and opened the ends of a few cans. I tossed cans into the freezer and the bands into the oven (at about 350 degrees F). Being impatient the cans were not inside either oven or freezer for more than a couple minutes. Hey, they are aluminum! They are suppose to conduct heat (or lose it) FAST !

I pulled out the band from the oven, then grabbed the can from the freezer and slid the can into the band with very little trouble. I would guess there is about a 10 second window before the metals acclimated enough toward room temperature to make significant movement difficult without the possibility of twisitng the can. I tossed the can/band combo into the oven, let them heat up and then pulled them out and grabbed another can from the freezer. Rinse and repeat BUT I did not rinse with water.

I attached 5 cans in series, bottom-to-bottom and top-to-top. Very tight fits, and with the 4 bands between 5 cans, there were only 2 "pin hole" size openings where the cans buckled inward. So the final product is almost watertight, definitely structurally much more sound, and the oven/freezer angle buys at least 5 to 10 seconds to get the cans joined very well. Success!

TIME TO IMPROVISE !

Here I'm now focusing on the issue of joining the cans in such a manner as to eliminate the problems of melting glue and mechanical connectors that would no doubt cause corrosion. So lets make the connections out of the same cans that were being used originally.

There is a lot of information in this picture so examine it carefully!  In the center of the picture is the Dremel with the #409 cut-off wheel.The can that is laying on it's side is braced against a piece of wood (darker wood) behind, and another brace at the top of the can toward the Dremel. This way I can just pull the board and can toward me slightly and rotate the can while the cutter does it's job. Notice the band already cut to the right.

If you look at the two cans that have been joined by a band on the left side of the photo, the band is a bit narrower since it's joining two cans that are oriented bottom-to-bottom. If you look real close, you can actually see the impression from the cans beneath, about 1/4-inch inside the cuts. The attachment is much stronger than the glued versions, and will not be affected by the heat.

Referring to the band on the right again, notice the cans, one in the cut band, and one outside the band. I knew that if I were lucky enough to push the can into the band easily, then I needed something to stop the can from going beyond a halfway point. These are "Fancy Feast" cans (cat food) nicely cleaned by the kitties and then cut with the same #409 cut-off wheel. They "can" act as a stop.

Besides having a great connection, there are a few other observations to bring to light. I only put the can in the freezer and left the band at room temperature. Once both cans were in place, I saw that I have probably a 1/4-inch gap between the cans on the inside. They could have traveled another 1/8th inch each to butt-up against each other. So here's the next question. Would air flow over the gap be adversely affected enough to warrant more effort to get the cans against each other, or would the heat that will be generated on the band be extracted more efficiently with the gap?

Heat generated would no doubt transfer from the band and through the cans anyway, so I will try the following. Regardless of the plastic coating on the can, I will heat the band (or the band plus the already attached can) to 300 degrees F in my oven.  The other can (or the first can) will go to the freezer. If the expansion of the heated band, and contraction of the can is more pronounced, I may easily get the extra 1/8th inch (down to the cat food can stopper).

What makes the aluminum can such a good conductor will work against me as the cold can will heat up fast, while the hot band will also contract pretty fast. Lets see what can be accomplished !

MY FAN SYSTEM DOES NOT SUCK!!

I just had to use that line, since as I expected all along, the 1/2-inch PVC line from the collector was just too restrictive. The fan was just churning away inside the fan housing, but there was just not enough air flow to pull the heated air from the collector. No sense even hooking the circulation system to the collector since the air temp would easily top that 250 degree mark while the fan would be doing it's best to....suck....that air out.

So how did I get to that conclusion? Que more pictures!!!

The outlet is on the left, attached to the wood frame which is attached to the fan. Notice the attractive cover for the batteries? That prevents air from skirting beneath the expertly made intake housing shown on the right as well as having the heated air blowing directly onto the batteries on the way to the fan.

I realize anyone reading this will think the same as I did when looking at that small diameter PVC line. I believe I recited the phrase "Not a chance" on multiple occasions.

With the housing in place (but without showing the superb duct tape sealing work to further eliminate losses) the unit was complete. With no significant air losses, I could hold the unit up to my face and barely detect a current. All I had to do was pull the housing back a bit, thus allowing air to freely get to the fan intake side and there was more than enough current. SO, since this current configuration does NOT suck, I have to re-design the air circulation system so it WILL suck. Rest assured I had actually been working on this all along. More to come shortly.

Here is the beginning of my conversion of an LED "lantern" into a fan housing.  The previous experiment was also in it's early stages. I determined the 15 LEDs could operate well for 8 hours off eight rechargeable AA batteries. This was enough information to warrant the sacrifice of this wooden creation to become the basis for the fan housing I needed for the solar collector.

The 8 batteries are just a temporary substitution for the 12 V DC solar power that would drive the fan. First we have to verify that this system will work regardless of the power source. Look closely and you can see the batteries are held in place by the remains of a Radio Shack, radio controlled car. After about 10 years I finally found a real good use for that! I also found a solar battery charger but that only put out 7 V DC. Notice the red wire at the left side of the bottom battery. By just looping that around the appropriate connection (in this case all 8 batteries in series) I can get the total voltage I needed. Nothing here is permanent!

In my effort to not spend a bunch of cash, I looked for a fitting to expand from the measly 1/2-inch diameter PVC pipe entering the fan, and reducing to about the 2-inch "exhaust" end of the housing. For $1.88 I got the necessary fitting for the exhaust end. A funnel for pouring oil into your vehicle.

Sadly, the McDonald's cup really would not withstand the heat, but it's readily available at my place, and is a perfect size. Perhaps I'll hit a dollar store and find some cups that can be slightly modified. Regardless, you can see in this picture above the ridges have been ground off the funnel and it has been suitably ground to size. The open space between the wood frame and the indentations of what is left of the funnel, were blocked with duct tape. What else!  I have yet to build the "housing" to attempt to keep this fine preliminary experiment from leaking like a sieve. More to come.