dangerousamateur Posted March 8, 2014 Posted March 8, 2014 Working on my chlorate cell I find it very challenging to get my MMOs connected. The commom method seems to connect the MMO mesh directly to a piece of Ti and lead that out of the cell. However, I only have a very simple welding transformer equipment, and when I weld it with a welding rod, the welding rod will of course add metal to the thing - metal that will quickly corode and fail, and also contaminate my chlorate. Is there some thing like a welding electrode made of Ti? Do you have any method for this problem, doable without "heavy industry equipment"?
pyrojig Posted March 10, 2014 Posted March 10, 2014 Hey friend I too struggled with this prob. The right answer came after many failed attempts and much time wasted . I purchased a cheap spot welder ( from a Harbor Freight store) and presto!!!! Perfect strong welds that dont fail .If you dont have the $ for such a item ( i think mine was $160) then the next best option is find someone who does. You might try high school metal shops , or metal working shops ( business) . All other methods are prone to fail , or degrade after time in a cell. Even Ti bolts etc, these too will loose conductivity between surfaces ,compared to a weld nothing comes close.
Arthur Posted March 10, 2014 Posted March 10, 2014 Swede offered (and I think youtube offers ) a method of conversion for a microwave oven transformer to be rewound into an economy spot welder. Basically cut off the HV secondary and wind 3 - 5 turns of thick cable in the space -the fattest wire that will fit the number of turns needed for 2 - 2.5v open circuit. You are hoping for 500 - 1000A in 2 second bursts, yes the transformer will get hot, no it's not for industrial use.
taiwanluthiers Posted March 12, 2014 Posted March 12, 2014 The bolt must be made of CP grade 2 titanium, same as the strap. 6/4 (grade 5) bolts will fail immediately and contaminate your solution. Unfortunately just about all the bolts out there are 6/4 grade... so your option is to find a grade 2 Ti rod and use a die to make a threaded rod, then use a tap to tap holes into the strap... or use a hacksaw and slowly cut little strips of the strap material and use it as little Ti nails to secure it to the strap. That's what I had to do and it worked fine. You need to use a spot welder (that does not add materials but instead melts the original material) for this. There is a way to do this with a microwave transformer but it does involve rewinding the transformer.
dangerousamateur Posted March 12, 2014 Author Posted March 12, 2014 Instead of using one single thick "wire", is there any reason why I should not use a bunch of thinner but more easy to process copper wires and put the parallel? Lets pretend i've got the transformer finished. How do you design the electrodes that touch the victim to be welded?What if they melt first?
Arthur Posted March 12, 2014 Posted March 12, 2014 (edited) As long as you get the right number of turns into the small space available it matters not. Try using the sort of 2 - 8 AWG flex as used for car hi-fi -it's hundreds of strands per outer, but it will take up space and the insulation is not for HOT use. For instructions try youtube or Swede's blog. Using pure copper and the shortest lengths possible anything else will have higher resistivity and melt first. addedIf I put "DIY spot welder" into youtube I get PAGES of sensible turorials. Edited March 12, 2014 by Arthur
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