Vertical Boiler Project  4/17/11

Warning!!! The following articles are NOT plans for building a model boiler. There are no drawings or engineered specifications posted on these pages for a reason. These articles only serve as a record of my experience in building a vertical boiler. Please DO NOT try to use these articles as a guide to build you own boiler. They simply aren’t written for that purpose. Thank you...

Posted on April 17, 2011

       Hello folks!! It’s time to see if my new rivet tooling is going to work or not. I have been really anxious about this phase of the build as I can easily damage my work if I am not careful !!! Although it wouldn’t be the first time I had ruined an intricate part by being impatient :0P

       This week I made a cradle for the boiler to be riveted as seen below. The rivet dolly bar is held by the vise while a set of 4 x 4 blocks will hold the boiler shell in position.....

       At this point I am ready to rivet on my first end however I must first prep the mating surfaces for a solder caulk that will be applied once the rivets are in place. I would almost bet that the rivet job would hold tight without a solder caulk but I am going to hedge my bet by sealing the joint anyway.
       To make sure the solder will stick I am applying a non-acid soldering paste to the mating surfaces before the riveting is started....

       And now for the rivets!!! I tested out a few virgin rivets on some scrap copper to make sure I have the process down and found that the copper was too hard to properly form the buck-end. For that reason I decided to anneal the rivets to soften them as I did with my copper end plates (seen below). The 3/16” rivets were also cut down from their original length of 3/4” to about 9/16” long (before annealing). This will ensure that there is the proper amount of material to form the dome shaped head you commonly see on a rivet.
       The actual formula used to determine rivet protrusion length is:

                                     D X 8/5 = Length of rivet protrusion

       The value “D” is the diameter of the rivet so in my case:

                                         0.1875 X 1.6 = 0.3” protruding

       Since my boiler plate/shell will be a total of 0.265” to rivet through I can add the 0.3” for a total of 0.565” total length (9/16”)......

       And now for the first set of rivets!!! I had previously drilled out four of the end plate holes to properly align the assembly. These will be the first ones to get set into place....

       I positioned the boiler shell on the wooden cradle and fitted the first rivet into the dolly insert as seen below. The drawing up tool was then used on the plates to close up any gap between the plates. I used my 16 oz ball peen hammer to drive the tool into the plates (not shown)...

       The next step was to use the “setting” tool (#1 forming tool) to squash the rivet post, setting it into place. I used four smart blows from the hammer to set the rivet as seen below. At this point I decided to set all of four of the end plate rivets before moving onto the next forming step to help prevent the plates from shifting....

       The next step was to use the #2 forming tool. I used a bit more force with this tool to properly from the cone shape. I would say about six blows with the hammer. You will notice that the rivet sort of folds over itself just under the cone....

       And now for the final step!! I used the #3 forming tool to dome over the rivet to give it that classic look (below). This forming took even more force, about eight blows with the hammer!!

       After the four rivets were finished off I took some measurements to see if the plate had shifted during the riveting process. To my surprise the whole end plate shifted about 1/16” inward at each rivet which seems to indicate that I am either not hitting the rivets squarely or the dolly is flexing in the vise. I am guessing that it is possible that the vise itself flexes ever so slightly allowing the dolly bar to “dip” at each strike which induces a shift :o/
       At this point I am not too concerned with the shift as long as it does not progress past the first set of rivets...

       I decided  to drill and install another four rivets at 45° from the original four. This time the shift was negligible so my worries are over....

       I now had to mass produce the rivets for the rest of the project so I made a cutting jig (seen below) to shorten the rivets evenly. A slot was cut in the dolly bar to allow me to cut the rivets on my bandsaw at the right length. The rivet fits into a hole drilled into the end of the bar and protrudes past the slot. An access hole was drilled at the end of the slot to eject the cut off end. All in all it worked quite well :0)
       You will notice the beveled edge under the rivet head. This is to make it easier to remove the shortened rivet after it is cut...

       I cut all of the 56 remaining rivets needed for the job and then annealed them for installation...

       I continued the riveting process by installing the next eight rivets in between the existing rivets. My thoughts are that I will reduce any warpage of the plates if I keep spacing the rivets out evenly...

       At this point I am half way there!!! I drilled out the remaining holes and deburred the inside face.....

       After about an hour of pounding I had finished the one end of the boiler as seen below. Not too shabby for my first go around :0)

       Now it is quite possible that this joint would be leak free as-is considering that I riveted the heck out of it !!! However I will have a hard time fixing any leaks should they occur when I am boiler testing. To ensure the joint is sealed I will be adding a “soft” silver solder “caulk” to simply seal the joint.
       The solder I am using is a 1% Tin, 97.5% Lead and 1.5% Silver solder that has a melting temperature of 588° F. This is about a 160° hotter than a standard soft solder which will help keep this solder solid during the consecutive soldering steps needed to seal the boiler tubes and bushings. This type of solder has a tensile strength of about 1750 PSI @ 300° F which is suitable for caulking joints....

       To seal the joint I prepared the boiler by re-cleaning the inside joint and re-applying some non-acid paste flux. I then laid a ring of solder wire into the valley of the joint to evenly distribute the solder (seen below).

       I supported the boiler on a scrap piece of pipe and proceeded to heat the shell with my Map-Pro torch. Once the shell reached 588° the solder flowed beautifully into the seam :0)

       I inspected the solder for any gaps after the shell had cooled down and none were to be found....

       I could now start on the other side of the boiler shell and rivet in the second end plate as I had done before. I used the same method and order of operations as before with the exception of adding a solder ring to the inside of the boiler in preparation for sealing the second side...

       I had placed the solder ring at the previously riveted side of the boiler and held it into place with some strategically placed tape (not shown). Once the end plate was riveted into place I removed the tape and set the ring into the valley of the joint as before..

       Using my torch I heated the shell to seal the joint and finish the job !!!

       I am now ready to install the boiler tubes and bushings to complete the pressure vessel of this build !!! It won’t be long before I can hydro-test the boiler and see if my work is up to par :0)

       Please join me again for the next episode of the vertical boiler project. Till then be safe my friends and always remember - safety first !!!!!

Don Giandomenico

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