Mike, the bending is not the problem so much as bending a tube inside a tube without the inner tube flattening out or kinking. Though, the more I think about it, the inner tube, being smaller than the outter tube will be less likely to kink than the outter purely by smaller diameter and tighter bend radius.
Moreover, I talked to a fellow this weekend that told me to try tightly wrapping the center tube with a heavy gauge, uninsulated wire then insert it into the outter tube, this will make up some difference in size and help to prevent kinking of the inner tube. I'm going to try this along with simply inserting the smaller tube inside the larger and bending. I had considered tube-in-tube-in-tube and running hot propolene glycol and water, in opposite directions, through it. I'm not sure that I'm still going to pursue that route except for experimentation purposes. Take care, Ken On 9/27/05, Mike Weaver <[EMAIL PROTECTED]> wrote: > Maybe I'm losing my mind but I swear I used to have a kit w/ different > head and a long bar that I used to bend copper pipe. I remember it as being > very cheap (under 100.00 USD) at someplace like Norther Tool or Harbor > Freight. Of cource I haven't done any plumbing in over 20 years - maybe > the don't make it any more. > > -Mike > > Kjell Löfgren wrote: > > > Ken, to avoid the tube bending business you can use a plate heat > > exchanger - more compact but if DIY you have to do some welding. Cut > > two equally sized pieces of *thin* stainless steel plate. Make about > > two dimples about 2 mm deep on every square 10 cm of the plate with a > > ball-peen(sp?) hammer (work on a wooden bench!). Weld the two plates > > together all around the edges with the sides with the raised dimples > > facing each other. > > Grind away the weld and cone out openings for the short pieces of > > pipes where the fluid goes in and out (on opposite corners). The short > > pipe pieces are welded in place. > > Carefully pressurize the unit with very low air pressure - less > > than 0.05 kg/cm2 - and test for leaks with soap water, remember to use > > clamps or something to hold the plates together or you end up with a > > pressurized 'football'! > > Make two or more of these units and submerge in whatever storage tank > > you use, you can connect them in series or in parallel as long as you > > avoid air pockets. > > The size of the plates is as big as needed but keep in mind that these > > DIY units are not meant to be used with internal pressure! Pressure > > can maybe be used inside the storage tank but the numbers of dimples > > have to be increased. > > Also beware of air pressure in large containers - even a small > > pressure can add up to large forces and even blow the container! > > > > Stainless steel rods for welding and a TIG welding equipment is also > > needed - a skilled TIG welding buddy will make things easier if you > > don't have the know-how. _______________________________________________ Biofuel mailing list Biofuel@sustainablelists.org http://sustainablelists.org/mailman/listinfo/biofuel_sustainablelists.org Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html Search the combined Biofuel and Biofuels-biz list archives (50,000 messages): http://www.mail-archive.com/biofuel@sustainablelists.org/
