Advanced Tools for Making Collector Heat Absorbing Fins
-- aka The Mother of All Collector Fin Presses

Tom and friends are making many hundreds of square feet of this type of solar water heating collector, and have worked out this rather impressive press and other tools to cut, form, and install the collector fins. 
 
Directory:
  1. Pressing the fin grooves
     
  2. Clamping fins in place during attachment
     
  3. Shearing to length
     
  4. Finished fins

 

While these tools are great for improving speed and accuracy of making the fins, it is also quite feasible to use these simple tools if you are only doing a few collectors, and don't have Tom's machine shop at your disposal. 
 
 
  Update on Tom's Absorber Plates

Tom has decided to make absorber plates from his press available as a regular product from his UP Truck Center business.

He offers plates to fit 1/2 inch and 5/8 inch copper or PEX pipe.  Fin length can be customized from 24 to 34 inches.  He offers a "standard" fit as well as a 90% wrap fit.  The modified vice-grip that make it easier to clamp the fins tight to the tubes are also available.

The prices are very reasonable, and I can attest to the fact that the plate fit is very good.  I think this is a very good option for anyone who does not want to bother with making fins. 

 

All the details on ordering and using the fins on ordering fins from Tom...

 
 
The kind of tools that Tom made would be a great investment for a solar club or association to support collector making workshops -- dozens of collectors could be turned out by a team of people in a single workshop at a cost of around  $120 per collector -- this would result in a payback period of about 2 years!  -- even less if your state has an incentive or rebate program.
 
 
Thanks very much to Tom for making these descriptions available!

 

Groove Forming Press


Here are some pictures of the absorber molds I've made to stamp out the aluminum on my shop press. I plan on making a 320 Sq' collector array for my home this summer, several of these pool heaters, and also will need diffuser panels in the house. In addition, several guys I'm working with are designing systems as well.

 

 I started working with my new absorber material recently. I ordered a 3,000' coil of 8" x .018 "1100" grade aluminum. This is supposedly more conductive and malleable than the "6061" grade I believe the soffit aluminum is made with. It bends really nice, yet holds shape well too. I've enclosed a few pictures I've taken of the absorber and some more tooling.  With a cost per foot on the soffit running about $.62 a foot, the coil will get the absorber cost down around $.42 a foot, and will only need to be cut to length.

 

The press is a lot easier on my body, not to mention I can press out the panels in about 1/4 the time. I've quoted a coil of .018" aluminum, 8" wide and 3000' long.

 

 


This is the basic groove making tool.
It goes in the press shown in the picture below.

 

 


The tool used as the 2nd step in forming
the fin so that it wraps tightly around almost the full diameter
of the copper tube.


Another view.

 The pressing tools were modified many times to get the version that works so nicely now. I believe the first molds are pretty self explanatory, and get the initial shape to the aluminum. The second tool took some time to get right. I started with three hinges welded to each angle iron and found the press was stretching the hinges apart. I was also using a flat plate on top of the angles, but this caused a "scuffing action" as the top of the angles wanted to move out, and the bottom of the angles pressed the aluminum under the round rod.

I had some pipe left over from the wind turbine tower, and saw it would create a nice transition area that would naturally push the top of the angles down and outward at the same time (the bottom of the hinges press in an inward direction creating the "wrap effect" I'm getting on the absorber). The "hinge point" to the angles are two bolts in the center of the angles. They have springs on them to force the lower part of the angles outward at the beginning of the procedure to clear the widest part of the 3/4" rod (and aluminum absorber). The bolts at the top of the tool are running through a channel of 1/8" x 1" strap tacked to the pipe which suspends the angles to the pipe (and ultimately to the top of the press). As the tool encounters resistance, the top of the angles start to spread, hinging the bottom of the angles inward. I can run 2 absorbers a minute through the first tool and 3-4 absorbers a minute through the second tool ( I can do enough absorbers for 4 panels in a little over an hour).

 

Fin Installation Clamps

The picture below shows two of the clamps Tom made to hold the fin tightly against the tubing while the fin is being secured.  The tighter the fin fits over  the tube, the better the thermal connection between the fin and tube, and the better the performance of the collector -- very nice!


A couple of Vice Grip tools I made to get a better "squeeze" on
the absorber before installing my screws.

 

 

Aluminum Dispensing Roll and Shear

The picture shows the stand and "shear" I made to store, roll out, and cut the absorber material. I looked for an old heavy duty paper cutter, but couldn't find one. Fabricating a shear seemed like the best option. The cutting edge is a piece from an edge for a big steel shear that a friend of mine had purchased "new" at an auction but it wouldn't fit his machine. I cut out 75 absorber blanks (enough for 3 collectors) in about 5 minutes on this shear.

 

Finished Fins

Some pictures of the finished product.


A stack of the new material after pressing on my molds

Note how well formed Tom's fins are, and how the groove wraps nearly the full circumference of the tube -- this is the key to good thermal contact between the tube and the fin, which results in a high efficiency absorber.

 

 


A collector completed with the new
absorber material


Collectors on trailers for
school demonstration


 


Tom
March 28, 2009, and May 13, 2009
 

Tom will answer email questions -- you can reach him at: toms1 AT chartermi DOT net  (replace At with @, DOT with .)

 


 

Tom's Other Projects

Tom has sent in several great renewable energy projects ...

 

Gary March 31, 2009,  Added clamps and shear May 13, 2009