Silver Soldering A Model Boiler : Failure! | Model Boiler Build Part 7

sometimes at night i can still hear the torch but i love the smell of flux in the morning smells like failure because you see the internet experts all going to have their opinions but if you haven't been in this particular foxhole then you don't know you don't know [Music] sprocket sprocket i'm trying to do a thing here never mind this is going to be stupid anyway hello internet my name is quinn and this is blindix well this is not the video i thought i was going to make this week they say you learn the most from your failures and if that's true i'm going to learn a lot in this video yes it's silver soldering time for my boiler project and i'm going to tell you right now it failed now i'm going to show you all the things that i tried all the steps that i went through and my plans for recovering from this failure so i think you're still going to learn a lot if you're interested in silver soldering your own boiler but just understand that there is not yet a working boiler at the end of this road but there will be one at the end of this journey so let's go here's my shiny freshly fabricated copper boiler all ready for silver soldering now for silver soldering large model boilers like this there are basically two schools of thought on one extreme we have the alex weiss method which is to set up the entire thing fixture all the joints in place flux everything apply solder to every single joint and then heat up the entire boiler all at once on the other extreme we have the kozo oga method which is to go one joint at a time very meticulously one by one conventional wisdom says that shouldn't work because you risk re-melting old joints every time you heat up the next one but in fact kozo's method actually does seem to work for him very very well now in my case i'm going with the alex weiss method mostly because i learned about kozo's method halfway through this process and you'll see me change strategy here along the way this is actually my second large model boiler the first one was a much simpler pot boiler and i did have success on that one but i made lots of mistakes there as well now rest assured i make all new mistakes on this boiler so the first step is to dismantle everything so that i can flux the joints and clean everything up silver soldering is about three things clearances cleanliness flux and heat wait is that five things anyway it's about some very important things on the cleanliness front you will need a pickle bath so i've got sparex number two here which is a common pickling acid people also use 10 sulfuric acid for this asparagus is a little easier to get and a little cheaper and it works just fine so i've got enough here for two gallons which is enough for my boiler the general rule of thumb is you always want to add acid to water not water to acid i don't know if it matters for the sparx it's pretty mild stuff but nevertheless i will do it this way so pour that stuff in there and then just stir it up until it's nice and evenly mixed note that my stir stick is brass one thing about sparx is you're not supposed to put anything ferrous in it it will contaminate the acid next i set up my hearth now this is actually a really poor hearth setup and i'll explain why here in a moment next i cut a piece of round ceramic fiber board this ceramic board is great for silver soldering fixturing because it's immune to heat pretty much and you can cut it easily into different shapes you can score it and snap it or you can hack saw it or whatever so i'm making this round piece to fit inside the tube sheet and that's going to hold the tubes in place vertically when i flip the boiler over just to make sure that the tubes don't fall through if the silver solder happens to re-melt the silver solder that i'm using is harris safety silv 56 this is a cadmium free low temperature silver solder so it melts at about 1200 degrees perfect for this application and i'm using their accompanying white flux a quick sidebar on silver solder because i think a lot of people from outside the model engineering world aren't very familiar with this stuff or why we use it now all solder is technically a form of brazing it's a chemical bond between dissimilar metals but silver solder is closer to what you think of with brazing so it's a very high silver content form of solder that melts at a high temperature so it's typically got somewhere between 40 and 60 silver compared to electrical or plumbing solders which are considered soft solders and they typically melt at a much lower temperature now silver solder is important for boilers because not only is it very very strong it's actually stronger than the copper around it when properly used it also remains flexible so it can handle the expansion and contraction and shifting and so on that boilers do during their lives now don't confuse this with so-called high-temperature plumbing solders these have like seven percent silver in them and they are still considered soft solders and definitely not safe for boilers i'm preparing my silver solder now so i'm making rings to go around the tube sheet joints and then i also made little rings to go around all the tubes now a quicker way to do this is just to wrap a coil around one tube and then cut them into into rings but you know i did it the stupid way because at the time i didn't know about the other method and note that i'm also using one 32nd silver solder here which is already a mistake i should have been using 1 16 silver solder the little thicker stuff before silver soldering the complex parts all go in the pickle bath which is a chemical cleaning cleanliness is absolutely critical for silver soldering everything has to be spotlessly clean you can do chemical cleaning or mechanical cleaning so for the shell i just ran the drum sander in there and did a nice mechanical cleaning on that and the little studs that support the plates went into a little bit of pickling acid as well after five minutes in the acid everything is thoroughly rinsed in clean water and then i apply flux to both sides of every joint so there's the tube sheets on both sides and then i can slide the tube sheets into place there and then those little studs you may recall hold them suspended in space in the right positions so i slide that down there now obviously some of the flux is going to get rubbed off in this process but it's okay it'll mostly still stay there the studs get dipped in flux and threaded in it's important that the silver solder flow all the way around those studs as well or they will be leaks the silver solder will follow the heat and also the flux to some degree so it's also important same thing on the bottom and then i'm also just flexing the outsides of the joints again when the flux melts it'll tend to run into the joints as well so that'll help now on the subject of fire tubes there are other methods people use for sealing those including swedging and flaring and rolling almost none of those methods are going to be approved though by a model club boiler inspector and they're not typically done by model engineers silver solder is a method of choice it's not to say some of those other methods don't work in certain situations tube rolling for example is used on model locomotives but it does require a lot of skill and very expensive specialized equipment to do that properly and again if you don't really know what you're doing you're probably not going to get certified doing that and if you use one of the simpler mechanical methods like swedging or flaring you do still have to use a caulking of some sort which is often soft solder and again that's not considered safe for long-term use in model boilers so silver soldering is by far the easiest way to get a result that is safe and will stand the test of time and that's how model engineers have been doing it for a long long time and i'm fairly new to this so i don't know enough to question established practice so i'm going to do it the way people say you should do it and then flux all the tube holes and the outsides of the tubes as well of course and remember that the tops of the tubes are slightly flared so that they will be held in place and then i put a little ring of silver solder around each tube and then slide the tubes into place and then the same process for the boiler bushings and remember i made a fixture plate to hold these at the right spacing and to keep them square to each other now this is again the alex weiss method which is different than the kozo method kozo would have soldered these bushings in place by themselves first and then did the next series of joints whereas alex has you do all of this stuff all at once in one giant heating the fixture plates are tied in with titanium wire as i described last time and then of course a ring of solder goes around those bushings as well and then those big rings of solder go around the tube sheets now the solder has only been applied to the top tube sheet for now because you always want to have gravity working in your favor when you do this now the big moment the actual heating if you do everything right the actual heating only takes a few minutes and it just works and you're done the prep is by far the most effort however i am not doing it right and i'm doing a whole bunch of stuff wrong here already so let's talk about that first of all i'm using oxyacetylene with a rosebud tip oxyacetylene is not a good choice for silver soldering large model boilers for the simple reason that what you need is not actually peak temperature which is where acetylene really excels what you need is volume of heat you need to heat the entire boiler up all at once acetylene is a poor choice for large volume heating jobs like this because of the one-seventh rule of acetylene or what's actually now more commonly used is the one-tenth rule it's a little more conservative the rule says it's not safe to extract more than 10 percent of the weight of the tank in an hour if you do what happens is you start drawing acetone out of the bottom of the tank acetone is added to acetylene to stabilize it so if you draw that acetone out the acetylene gets less stable and the tank starts to get dangerous so that's obviously very very bad acetylene is also expensive and you're going to need a lot of it to heat up a boiler this big it's hard to appreciate if you've never done this job how much heat a boiler like this can shed like it's incredible even acetylene has trouble adding heat to a four-inch copper boiler faster than that copper can shed it it really is quite amazing which brings me to the next big mistake i'm making here and that's my hearth this is woefully inadequate it's not enough to just have some fire brick around the boiler you have to really make a cocoon of fire brick or refractory brick is even better something to insulate the process and really keep that heat in otherwise again you're just wasting fuel and you'll never get that boiler hot enough fast enough because you have to get the boiler hot within about five minutes because the flux has an effectiveness window that the silver solder has to melt within if you sit there heating for too long the flux will spoil the last thing i'll call out here is you see me doing some heating from above on the tube sheets which is really not ideal one of the key tenets of silver soldering is that you have to heat the metal not the solder the metal has to melt the solder because the solder follows the heat just like electrical soldering you should never touch the heat source to the solder itself you're not going to get a good joint doing that however with the alex weiss method on a fire tube boiler you really don't have any choice for part of the tube sheets you can't reach the insides of them so this is what i was doing but more on that here in a little bit but basically you just heat the whole boiler until all the silver solder flashes shiny and chrome make sure to witness those joints to ensure their passage into valhalla what a lovely day but when you're done the boiler will look a frightful mess it'll be charred and black and flux residue everywhere so let it cool down most of the way and then back into the pickle bath it goes for another five minutes and then drain all that acid out of the inside of it there and then you can rinse it off in clean water and the pickle is really quite amazing it'll remove all that ugliness from the torch all of that black char and everything just wipes right off flux residue is dissolved it'll come out kind of a dull pink color because you're basically doing a very fine etch on the copper not enough to remove any real material you don't have to worry about safety from pickling many many times but the boiler will clean up very nicely after this and then you can buff it back to its original shine from here if you want after the first big heating it actually looked pretty good this is basically what you want your joints to look like there's a ring of solder around each tube and all the way around the outside there's a little fillet and there's no obvious flaws there the underside is a little messier i did struggle with the underside because it's hard to get the torch down inside the firebox there so it's messy but we'll see if those joints are any good and then i had some issues with some of the studs here one of them fell out and one of them looks like it didn't get silver solder all the way through but we can hopefully address those issues i am going to file these studs off now because we shouldn't need them anymore and that's really what they should look like you can see the solder penetrated all the way through and then the stud can be filed smooth and it's like they were never there well nervous moment time for the first pressure test so i put loctite 545 on all the plugs and plug off all of the bushings and then i put my hydrostatic test pump on one of the bushings one of the top bushings is left open so the air has somewhere to go and i pump the boiler full and then when the water is right up to the top then i put that last plug in the goal is to get all the air out of it at all possible and well i didn't even make it that far the boiler is not even watertight now that's actually okay i've read a lot of boiler built logs in the last six months and i can tell you that the boiler not being watertight right off the bat is not uncommon and certainly doesn't mean the boiler is no good now this moment right here is where a generous viewer had sent me kozo's book the pencey a3 switcher which has his incredible treatise on silver soldering in the back of it and i learned his method and it sounds great so i switched to using his method so you can see i've got a proper hearth now fully encasing the boiler and i've got the sievert propane torch that everybody recommends for this including kozo and this is an incredible torch now it's swedish made there is a us distributor for it called best materials but otherwise they're a little bit hard to get in the u.s but definitely worth the effort to get one it does not use oxygen just regular old barbecue propane tank and it's plenty hot enough for silver soldering you really don't need an oxygenated flame for this which is nice because it also means you can wear regular safety glasses you don't need the shade 5 in for red protection like you do for oxyacetylene now osha does technically recommend shade 2 glasses for regular propane torches but you know make your own judgments on that so at this point i've switched to kososan's method and i'm heating one joint at a time making little repairs on the leeks i'm heating the top tube sheet joint here because there was a leak there the green flames that you see incidentally are the pickling acid burning off i didn't do a very good job of getting all the acid out of the inside of the boiler but that's harmless enough i am wearing a respirator i always do for torch operations because you never know what kind of weird gases are coming off of it now the whole boiler will be black from the propane torch because it is a very dirty flame since there's no oxygenation but that's okay once again the pickling acid takes all of that off with that sievert torch and a proper hearth setup heating up that joint only takes one or two minutes which is about what you want any faster than a minute probably too fast you're probably stressing the joints and longer than five minutes and you've probably spoiled the flux another pressure test verified that that top joint was fixed so i switched to the bottom joint now this one was a much more of a mess there was some silver solder in there that hadn't flowed properly so i got in there with some sanding and grinding tools and did my best to clean out the crud usually after that grinding you can actually see the flaw so there you can see that's the pinhole right there after a little bit of sanding not always sometimes a perfect looking joint will still leak but it builds confidence when you can actually find the flaw like that for every repair you attempt you always have to pickle beforehand and then reflux and then reapply solder everything's always got to be clean so here's another view of the process here so the repair area is pointed downwards so gravity is working in my favor and that sievert torch is doing its magic and you can see the silver solder flashes into the joint when it gets to just the right temperature as soon as you see that silver solder flow you move the torch away and job done and you can see how the flux has cleaned the area all the pink area there is where the flux did its magic the flux keeps the torch from dirtying the area during the process and ensures a good joint another pickle and rinse and another pressure test and i found another leak this time on a boiler bushing so once again i've got a good heart set up here i've got the right torch and i'm heating the metal around the bushing not on the bushing itself to make sure the metal melts the solder and once again that looks like a good joint and after pickling that's looking very fine indeed so at this point things are going quite well and fixing one joint on each heating just like kozo says and the boiler is getting better every time so at this point now i'm down to the tubes everything else is sound and so on this pressure test i'm actually starting to build some pressure now which is looking pretty good some marking problem areas with red sharpie and continuing to build pressure now at at its peak i got to about 110 psi and i had one remaining seeping tube things were really looking good i fixed a couple other tubes already as you can see from the extra silver solder around and i've got this one last tube that's seeping got one little pin hole right there and otherwise the boiler's holding 110 psi just 10 psi short of my goal i was getting excited so i made this last repair and well this is where it all started to go wrong after fixing that tube i had created two new leaks and i thought well that's odd but you can see here how this old joint which was perfect is now cracked and that was leaking so i fixed that tube and then i had another leak and then i had another leak and then i decided to go nuclear and i reapplied solder to several leaking tubes refluxed the whole tube sheet reheated the whole thing reflowed all of the solder which took quite a bit of heat because once silver solder has flowed once it takes more heat to get it to flow a second time because it oxidizes and it kind of cures if you will and basically the entire tube she got covered in silver solder because of all the repairs i'd made and reflowing everything kind of spreads it out real thin and doing that fixed four leaks so i thought okay i'm back on the road to success again at this point i theorized that repairing a tube was heating the adjacent tubes excessively and causing those joints to fail so i tried a different strategy i did a general heating with the propane got the whole thing pretty close to silver solder temperature and then switched to my small acetylene brazing tip and then just got in there like surgically this torch is like a scalpel so i can get in there and apply heat just where i need it and the idea was the whole thing is close to silver solder temp and i just need to add a little bit of heat right in the area around that joint to melt the one joint i'm trying to repair this however just doesn't work because copper is as i said so incredibly good at shedding heat it actually sheds the heat faster than the acetylene can put the heat in at least with this small brazing tip so short of a big rosebud the acetylene just cannot get the heat into that thing fast enough so in this case i had to switch back to the propane to finish the job and once again heated up the whole tube sheet and once again i created a couple of new tube failures i tried all different methods of shielding the other tubes and i tried cooling them down as slowly as possible with insulation and all sorts of things i couldn't find any way to repair a tube that didn't cause another tube to fail so uh this boiler was just about done just before i gave up i decided to try the last refuge of the boilermaking scoundrel and that's the tube swagers so i've got a swager and a flaring tool here so the tubes that are leaking i tried swaging them the squeezy style worked well on the top the lower tube sheet i couldn't reach with the squeezy style so i had to use the hammering style which requires supporting the tube from underneath so i don't bend the tube sheets in this process and it does risk bending the tube internally but a little bit of that is okay probably and that does actually work to some degree i did fix a couple of tube leaks doing that i don't know how safe those repairs are but it did fix some leaks however there was a couple that couldn't be fixed and you can see that all the hammering and heating and everything is distorted the tubes and the tube sheets and i just could never get ahead of the leaks and at this point i'm in about six weeks of time spent just trying to fix leaks every evening after work and every weekend and i just couldn't get ahead of it so at some point you got to call it i decided to cut this boiler apart and start over i want to cut this apart in a way that preserves the joints so i can inspect them from the inside and see what went wrong so i'm going to start by cutting the firebox off this will actually be reusable on the next boiler the firebox is where most of the machining time was in the shell so it'll be definitely worth saving this so i'm going to do my best to cut this off cleanly and squarely here on the horizontal band saw and bittersweet yahtzee that leaves just a pressure vessel and the pressure vessel is symmetrical now which is what i want for the next boiler because as you recall it was quite difficult to silver solder up inside the firebox now to get the tube sheets out i decided to drill them out i considered trying to pan them out on the lathe or setting up the rotary table and milling them out the problem is that the shell is not very round from all of my hammering and heating and so on and copper is really ornery to mill and i wasn't looking forward to that these tube sheets are pretty thick so i just set it up on the drill press and chain drilled it out i did one lap with a quarter inch drill and then a smaller drill for some of the tighter areas and then i finished up with a cold chisel to knock out all the remaining material there this went very quickly this only took maybe 20 minutes to run the drill press around there and it preserved all the joints for inspection so mission accomplished here i think the core took a little bit of persuasion to get out of there because some of those tubes were a little bent from my ham-fisted swaging efforts but out comes the core which bears a striking resemblance to some piece of a nuclear reactor the first look at the insides of the tube joints is very educational so in general those joints are excellent that's exactly what the tube joints are supposed to look like the solder flowed through there's a nice fillet on the backsides of all of them everything looks great except look very closely and you can see these hairline cracks if it weren't for those cracks these joints would be perfect so at some point in their lives these joints were good and then these cracks formed so probably that's when things started to go downhill with my repair efforts is i was starting to crack those joints on the back and those are not going to be fixable from outside the boiler once you get those cracks on the backs of the joints you're done the tube sheet joints look good it's hard to show on camera with the copper carnage that's in there but silver solder flowed all the way through no issues there not surprising the tube sheet joints are pretty easy to do now i struggled to keep the boiler bushings from leaking on the top and you can see why on this one i got very poor penetration of silver solder almost none made it down there so that was never gonna seal on the other one it's a little better i did get some silver solder through the joint but you can see a gap there and that gap is right where there was a leak that i was fighting so again that was probably never going to be fixable from above so cutting this thing apart really was the right move at this point it probably was not fixable now i'm going to cut one of the tube sheets off here just to get a better look at some of those internal joints the horizontal band saw made mostly quick work of that but towards the center there it was really starting to trap the blade so i switched to the hacksaw and a little bit of persuasion with extreme prejudice and off it comes so now we can see all of the joints and yeah the story is the same in here these joints were all perfect at some point in their life but they pretty much all have fine hairline cracks in them that were never going to be fixable one crazy thing here on this tube you can see there's a massive waterfall of silver solder on this particular tube not exactly sure what happened there but clearly that was again one of my ham-fisted repair efforts i must have opened up that joint at some point and silver solder just ran down there like water so uh yeah i i was using a lot of silver solder trying to repair this thing and well now i know where it all went all the repair efforts and deconstruction have left basically all the components badly distorted as you can see on many axes so nothing except the firebox is going to get reused in the next boiler but none of this copper will go to waste it'll all be useful for something it'll go in the stockpile the old shell is too out of round to reuse what i will probably do is split it lengthwise and anneal it and unroll it and make a nice big piece of copper plate out of it which will be very useful for future projects failure is only failure if you don't learn from it if you do learn from it then it's just a step along the way so given what i've learned here the rebuild will be different for starters i'm going to simplify the geometry it will be fewer tubes of larger diameter so it'll have comparable surface area but be a much simpler structure to build and i'll be building the tube sheet and fire tube core as a separate assembly with high temperature silver solder and then i can heat the joints from below as is good practice and i can possibly even pressure test the core separately then i can slide the whole thing into the shell solder that up with lower temperature silver solder and those tube sheet joints are easy to do from the outside so i think all of that will greatly increase my chances of success the next time around now the bigger failure i show on my channel the more unsolicited advice i get from commenters who've never actually done this job so all i ask is that you please be humble and understand that just because you you know work on air conditioning cores or you've built brake systems for cars that seem to have similar structures to this it doesn't mean you actually understand all the challenges here and on that note i want to really thank and shout out to the chasky home machinist forum the boilermaking experts over there gave me a lot of great advice and were really supportive and helped me make a plan for moving forward on this project so i'll link to them below big thanks also to my patrons who got to see all six weeks of the ups and downs on this in gory detail and provided much emotional support and if you'd like to be one of those patrons you can use that card there at the end of the video and help out the channel i got a lot of copper to buy now and the patrons are really what keep this channel going thanks for watching and i'll see you next time you

Channel: Blondihacks

Views: 50,386

Rating: 4.966506 out of 5

Keywords: blondihacks, machining, machinist, abom79, this old tony, vintage machinery, steam, electronics, making, maker, hacking, hacker, lathe, mill, woodworking, workshop, shop, model engineering, engineer, engineering, live steam, machine shop, metal lathe, vertical mill, metalworking, metal shop, how to, do it yourself, do it yourself (hobby), mini mill, mini lathe, tutorial, silver soldering, boiler making, keith appleton, model steam boiler, silver solder, copper boiler making, model steam engine

Id: RpDQvTnvXcs

Length: 25min 59sec (1559 seconds)

Published: Sat Aug 21 2021