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Thread: Casting thin shell bronze blocks

  1. #71
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by Sailor View Post
    Will someone be able to drive the pins out to replace bearings in 100 years if they need it?
    I'm thinking that the axles will be drilled through and through and made removable for assembly and maintenance.
    It really is quite difficult to build an ugly wooden boat.

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  2. #72
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by amish rob View Post
    They should be VERY discrete in the finished product, eh?

    Peace,
    Robert

    That would be the ideal, Rob, understated like you wouldn't believe..




    Quote Originally Posted by Sailor View Post
    Will someone be able to drive the pins out to replace bearings in 100 years if they need it?

    Dan, that would depend more on who's doing the driving than anything else. Probably not is my guess.

    This is how I'd do it. First, drill a small hole through the center of the pin, enlarge the hole with successively larger drill bits, making sure not to nick the shell. Give the block a good soaking in WD-40 and try an EZ-Out and light taps with a hammer and punch.


    Quote Originally Posted by Peerie Maa View Post
    I'm thinking that the axles will be drilled through and through and made removable for assembly and maintenance.
    The axle will be captured, Nick.

  3. #73
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by Jim Ledger View Post
    Dan, that would depend more on who's doing the driving than anything else. Probably not is my guess.

    This is how I'd do it. First, drill a small hole through the center of the pin, enlarge the hole with successively larger drill bits, making sure not to nick the shell. Give the block a good soaking in WD-40 and try an EZ-Out and light taps with a hammer and punch.




    The axle will be captured, Nick.
    So you are not planning to strip down, clean and repack the bearings? Just dropping them in a bucket of oil to soak?
    It really is quite difficult to build an ugly wooden boat.

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  4. #74
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by Jim Ledger View Post
    That would be the ideal, Rob, understated like you wouldn't believe..







    Dan, that would depend more on who's doing the driving than anything else. Probably not is my guess.

    This is how I'd do it. First, drill a small hole through the center of the pin, enlarge the hole with successively larger drill bits, making sure not to nick the shell. Give the block a good soaking in WD-40 and try an EZ-Out and light taps with a hammer and punch.




    The axle will be captured, Nick.
    Yeah. I was imaging the pins on my little pocket folder. I know there are pins in there, and I th8nkmthey are in this one spot, but I am not 100% sure.

    I canít wait to see them.

    Peace,
    Robert

  5. #75
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by Peerie Maa View Post
    So you are not planning to strip down, clean and repack the bearings? Just dropping them in a bucket of oil to soak?

    Unlike wood shelled blocks there's plenty of room in these blocks between the shell and sheave. Should I wish to pack the bearings with grease in the old-fashioned way it could be easily accomplished using a palette knife to force the grease into the bearings from one side while removing whatever old grease squeezes out the from other side. Being all metal, there's also the option of throwing the entire block into a bucket of lacquer thinner to clean out any crud, or use a parts cleaner.

  6. #76
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    Default Re: Casting thin shell bronze blocks

    What sort of bearings are you planning on?

    Jeff

  7. #77
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by jpatrick View Post
    What sort of bearings are you planning on?

    Jeff
    Hi, Jeff, I'll be using a set of roller bearing sheaves that I made a few years back, turning on stainless steel axles. Here's a link to the thread where all is explained...

    http://forum.woodenboat.com/showthre...ave&highlight=


  8. #78
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    Default Re: Casting thin shell bronze blocks

    Looking lovely... Great to see you back at play. Subscribing for updates. Thanks as always Jim!
    My Goat Island Skiff Project Photos:
    https://www.flickr.com/photos/999065...7648295059621/

  9. #79
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by BrianMCarney View Post
    Looking lovely... Great to see you back at play. Subscribing for updates. Thanks as always Jim!
    Updates imminent, Brian. The welder is back on line, the lift-out tongs for the smaller crucible are nearing completion, four new, smaller flasks made to better fit the project, the new pyrometer's ready.

    Jim

  10. #80
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    Default Re: Casting thin shell bronze blocks

    I'm gearing up to be able to do smaller melts to cast smaller pieces, like these block shells.

    I was using the crucible on the right exclusively. It can hold thirty pounds...theoretically, if you care to pick up such a brimming teacup. The disadvantage of the large crucible is that you need to pick it up with lift-out tongs and then set it into a pouring shank for the pour. Lotsa moves there, and all the while the metal is cooling off.

    For smaller pours, using the crucible on the left, the two functions of lifting and pouring can be done with one tool. This is quicker to do and safer as there's less handling of the crucible.

    For this purpose I made the set of tongs in the foreground. I can pick up the crucible, pivot a quarter turn and pour and return the crucible to the furnace with very few motions. This will result in a quicker, more controlled pour.

    The design for the tongs is unusual. It was taken from the internet and modified to use what was laying around the shop.



  11. #81
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    Default Re: Casting thin shell bronze blocks

    http://www.wish.com/search/crucible#...bff56308a58176

    I saw these online and thought they may be of some use to those of you who do casting. The site has several different types available.
    Money may not buy happiness, but it can buy a boat that will pull right up next to it!

  12. #82
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    Default Re: Casting thin shell bronze blocks

    As I mentioned over on the Catboat thread I have done a couple castings last fall with mixed results. I made a small bucket furnace that was more designed with melting aluminum with charcoal in mind. I thought if I upgraded the liner to refractory cement and use coal instead of charcoal to get the temps up a bit more it might be good enough for Bronze. Well even after I got rid of the hairdryer as bellows and upgraded with my real bellows from my smithy I still couldn't keep the temps up long enough to have the bronze hot enough to pour. I could melt it but I would run out of fuel and had to open up the furnace to reload more coal, and that would drop the temp, and bellow the temp up and sweat and repeat... LOL. Here's a short clip showing the original setup with the hairdryer.


  13. #83
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    Default Re: Casting thin shell bronze blocks

    Two hours later I moved to this...



    And after a couple more hours of sweating this was the result.
    Attached Images Attached Images

  14. #84
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    Default Re: Casting thin shell bronze blocks

    So I found a design online for a propane burner for this kind of furnaces and made one up.

    furnace burner.jpg

    This was the ticket! It had my small crucible of bronze melted in 25-30 minutes from cold and I didn't sweat a drop doing it! LOL


  15. #85
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    Default Re: Casting thin shell bronze blocks

    The great thing about casting bronze is you can remelt your failures!

    recycling.jpg

    This is the two piece model of my torpedo cleat. I saw something similar in an old ebay auction and decided I could make something a little nicer and this is what I came up with. You'll notice how it changed as I carved it out of wood from the drawing I originally sketched up.

    idea.jpg
    C-model.jpg
    c-model1.jpg

    I also carved out recesses so I can cast in bronze bolt into the casting as seen here after the model has been removed from the one mold half.

    C-model mold.jpg

  16. #86
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    Default Re: Casting thin shell bronze blocks

    And finally the result of my second attempt....

    sucess2.jpg
    sucess.jpg
    prepolish.jpg

    I was pleased with these results but there are some bad sand inclusions in this one because I wasn't careful enough with keeping my pouring channels clean of loose sand. So I will use this one to practice polishing and I will cast another one in the spring. I've learned a lot in these two castings and I know I have a lot more to learn.

    I don't mean to hijack your thread Jim but I thought I'd share. I made my green sand with playsand and kitty litter. It works well but could be finer. I noticed your sand was really fine Jim. Is that premade commercial sand or did you make it yourself? It's also very dark, is it oil based?
    Last edited by wainair; 02-17-2018 at 11:55 AM.

  17. #87
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    Default Re: Casting thin shell bronze blocks

    My apologies, Wainair, but I didn't see your post until now when I reopened this old thread. I'm impressed with your efforts, including the gas burner, which will open up a new range of casting possibilities. That's a nice cleat pattern and I would like to see the finished product. To answer you question, the sand I'm using is Petrobond, which starts out an orange color but turns black with use. Every so often I retemper the sand by adding a few tablespoons of thirty weight, non-detergent motor oil.


    I've recently resumed my efforts on the bronze block project, having made a run of four shell castings followed by a second run of four. I have four flasks of the right size and sufficient sand to fill them, which limits the number of castings that can be made with any melt. Of the first four only one was acceptable, the rest had major holes in them. This was disappointing but not unusual due to the thinness of the shells and the need to work out the gating of the mold to insure a quick fill. The second attempt did much better with three perfect shells and one with two small holes that will be easily repaired.

    Here's the result of the second pour as cast with the sprue and runners still attached to the shells. I need twenty and I'm about halfway there.



  18. #88
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    Default Re: Casting thin shell bronze blocks

    The casting of the shells continues. With each pour the recipe gets tweaked in one way or another. A few days ago my wife Tracey, pointed out a small detail in the gating that proved to be quite consequential, and since then the success rate has improved dramatically. Yesterday was four pours for four good castings. The overall quality of the castings is going up as well, so much so that previously acceptable castings will be remelted.

    Timewise, it takes forty five minutes to make one mold. The actual pouring takes two and a half hours from lighting the furnace to the last pour and involves melting seven kilograms of metal. Most of the metal goes into the sprue and feeding channels, which get cut off and remelted.

    Each mold is poured separately, the metal heated, poured into one mold, more metal added to the melt and another pour done when the melt reaches a sufficient temperature. Because the shells are thin the metal needs to be hot in order to completely fill the mold without freezing. Pouring two molds at once gives the metal a chance to lose enough heat that the second mold is chancy.

    Here's the third pour, the metal for the fourth is in the furnace, the two previous pours are cooling on the side





    Last edited by Jim Ledger; 07-12-2020 at 10:09 AM.

  19. #89
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    Default Re: Casting thin shell bronze blocks

    I ended up with twenty-five decent half shell castings. I eventually found a gating setup and pouring temperature that worked almost every time. As the quality of the castings improved and they became faster to mold it became apparent that some of the early attempts should be redone. Melting and recasting raised the general quality of the batch. There are more shells than I need in case of mistakes and, hopefully, to end up with a few spares.


    This is going to be the general arrangement of the double blocks, two half shells with an eighth inch plate in between. The ends will be drilled through and pinned with bronze rod.

    You can see a little suction print on the top of the casting where the boss cooled slowly and pulled metal from the outside inward, making a shallow crater. It's a cosmetic defect and can be filled with bronze weld and faired.



  20. #90
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    Default Re: Casting thin shell bronze blocks

    I have just read right through the whole thread. Hadn't looked at the date and it gave me a jolt to see Peter's posts.
    BTW Jim, his last build, has been bought by a friend of Peter's and is on it's way to a new home not too far away.
    http://forum.woodenboat.com/showthre...56#post6236956

  21. #91
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    Default Re: Casting thin shell bronze blocks

    I am curious Jim if you intend to cage the rollers to prevent them from rubbing each other. All the old (Merriman bros, Wilcox) stuff I copied had some sort of "cage" (roller bearings rub against each other in opposite directions without that) I can't remember which is which and I may be including South Coast blocks in my mind. Some used a sort of star shaped piece centered in a groove in the rollers and some used a more conventional roller cage with wee pins on the ends of the rollers.
    What you have are beautiful, and like the rest of this mob I am envious!

  22. #92
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by skuthorp View Post
    I have just read right through the whole thread. Hadn't looked at the date and it gave me a jolt to see Peter's posts.
    BTW Jim, his last build, has been bought by a friend of Peter's and is on it's way to a new home not too far away.
    http://forum.woodenboat.com/showthre...56#post6236956
    Peter was very kind and generous with encouragement when I started bronze casting. I found his efforts in this area quite impressive and there's no doubt that the high bar he set for his own work gave me something better to aim for than I would have found going it alone. Anyone who's seen the winch he cast will know what I mean. It was an incredible piece of pattern making and casting and he delighted in sharing it here. He is missed.

    I'm very pleased that Tom has acquired his boat. It's fitting that someone we all know has stepped in to continue the story, and I wish him well.

    Jim

  23. #93
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by Canoeyawl View Post
    I am curious Jim if you intend to cage the rollers to prevent them from rubbing each other. All the old (Merriman bros, Wilcox) stuff I copied had some sort of "cage" (roller bearings rub against each other in opposite directions without that) I can't remember which is which and I may be including South Coast blocks in my mind. Some used a sort of star shaped piece centered in a groove in the rollers and some used a more conventional roller cage with wee pins on the ends of the rollers.
    What you have are beautiful, and like the rest of this mob I am envious!

    Thank you, Jake, that's very kind.

    The sheaves have a thread of their own. They've been waiting patiently in a box for a while now. Hopefully it won't be much longer before they get put to use.

    http://forum.woodenboat.com/showthre...ave&highlight=


    Here's a picture from the thread showing the piece that keeps the rollers apart from one another, as well as the steps taken to make it from a bronze disc. The sheaves were copied from an old Merriman sheave as best I could.



  24. #94
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    Default Re: Casting thin shell bronze blocks

    Yup, that's the deal! They work with a resounding clicking.

    Again, very nice!

  25. #95
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    Default Re: Casting thin shell bronze blocks

    Thanks, Jake.


    Here we have the makings of a double block. The board underneath has a recess carved to fit a half shell, inside facing up. The aluminum rectangle holds the piece in place. With a shell clamped up the whole board can be run through the bandsaw, against a fence, to trim the two legs to proper length. For a double block the legs are cut the entire width of the sheave recess, for a single they would be cut halfway.

    After cutting the legs to length, still clamped in the jig, the legs were marked with a punch and drilled for the pins. Having drilled one half shell all three pieces were temporarily tack welded together. The whole unit was then reclamped in the jig, drilled holes uppermost. Using the drilled holes as a guide the holes were continued through the center plate and then through the lower half shell.

    The result of which is shown here...


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    Default Re: Casting thin shell bronze blocks

    Here's a view of the tack welded double block after being removed from the jig. An axle has been cut and two sheaves have been skewered in place...just to see how it looks.



  27. #97
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    Default Re: Casting thin shell bronze blocks

    That recessed area to hold the shell in place is genius. How do you come up with these ideas?
    I was born on a wooden boat that I built myself.

  28. #98
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by Rich Jones View Post
    That recessed area to hold the shell in place is genius. How do you come up with these ideas?
    That's a handy jig, Rich, no doubt about that. Genius, though, really? Inspired perhaps, but at the time it just seemed a sensible thing to do. It does come in handy, as the shape of these things makes them difficult to hold, especially when they need drilling through. There's not a whole lot of room for error there.

    If I recall, as it was a year or two ago, I used a lot of lipstick to get the fit right. It's a good example of the lipstick technique. Smear up the back of the shell with lipstick, apply the shell to the board, and gouge out everywhere that shows any red. Repeat. Lipstick, as a transfer medium, works best with metal parts, hinges, hardware and so on. Just yesterday I used a similar variation, using a piece of rusty angle iron to highlight the high spots on a concrete beam for removal with a mason hammer. It actually saves labor as well as insuring a good fit because you remove only the high material. Chalk and carbon paper also get a lot of use, depending on the material and situation.

  29. #99
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    Default Re: Casting thin shell bronze blocks

    Jim,

    Does continued re-melting of the bronze have any discernible effect on the metal? I seem to recall from a materials class years ago that repeated melting tended to purify some metals as the impurities are skimmed off time and again?

    JRM

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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by willin woodworks View Post
    Jim,

    Does continued re-melting of the bronze have any discernible effect on the metal? I seem to recall from a materials class years ago that repeated melting tended to purify some metals as the impurities are skimmed off time and again?

    JRM
    Some bronzes change composition with repeated remelting, I think some of the elements with lower melting points burn off. Silicon bronze, however, stays pretty much the same, and for this reason it's a good metal to use when learning to cast. The impurities, called dross, floats to the top where it can be skimmed off before pouring. I believe that a large portion of the dross is made up of oxides that form on the surface, you know, that nice patina. Melt up a bunch of old boat fittings and you'll get a whole lot of dross, fresh ingot metal, not so much.

    Jim

  31. #101
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    Default Re: Casting thin shell bronze blocks

    So far I've managed to make some rather nice paperweights. Without any way to attach a line to one or both ends it's all just window dressing.

    To that end I've started to make a pattern for a toggle that will attach to the top end of the block. A hole will be bored through the toggle for a shackle.

    The toggles will be pierced through with a hole with the same cross section as the top leg, so that when the shell halves are assembled the toggle will be captured. The toggle will have limited movement due to its loose fit, but little movement is needed.

    The thin pieces of wood shown will be refined to the cross section shape of the top leg. They are for use directly on the pattern and also to make a core box for making sand cores for the casting mold.

    Several patterns will be needed, for single and double block, and to orient the shackle in line with the block or across. Later on we'll have to make a few beckets as well for the bottom end of the blocks.



  32. #102

    Default Re: Casting thin shell bronze blocks

    Jim,
    Just saw this thread, What a Great Job! and an Incredible amount of work.
    How well does that lifting/pouring tongs work for you, I have been thinking of making a set like that since I had seen them on the internet, seems much safer being able to pour with the tongs.

  33. #103
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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by ShorelineJohn View Post
    Jim,
    Just saw this thread, What a Great Job! and an Incredible amount of work.
    How well does that lifting/pouring tongs work for you, I have been thinking of making a set like that since I had seen them on the internet, seems much safer being able to pour with the tongs.

    Thanks, John. The work on this particular project has been spread out over a number of years. I believe I made the sheaves in 2014, the shells more recently. As these things often go the work was sporadic, and usually accomplished during a few hours in the evenings with the occasional episode of intense activity. This befits the experimental nature of the project as problems had to be solved with no solution apparent at the time. Had I known at the beginning how to proceed I could have done the work in a more forthright manner. So, although it was a lot of work all told, I have managed to fool myself into thinking that it really wasn't. This self deception is a valuable skill to learn for anyone interested in doing long term, ultimately foolish, endeavors. It's not for everybody.

    The lifting/pouring tongs you mention are the second pair I've made. The first was an individual set of lifting tongs made for a much larger crucible, as the pieces I needed to make early on were larger. These tongs were used to lift the crucible out of the furnace and to set it into a separate pouring shank. When the need arose to pour a lot of small parts, the half shells, I made this set of combined lifting/ pouring tongs, fit to a smaller crucible. I also made four smaller flasks in which to mold the parts for multiple castings in one heat. I used a pattern that I found online, I forget where, with a few modifications to suit the materials on hand. I'm very pleased with the result as the crucible is much lighter and quicker to handle than the larger set. I can pick yp the crucible and pour in a matter of seconds and return the crucible back to the furnace quickly. This keeps the pour hot and reduces the chance of mishap as there are far fewer motions involved.

    If you're interested I could take some pictures of the tongs showing the various details.




    Meanwhile...here are the pattern pieces from the previous post undergoing some refinement. They end up being quarter rounds, just like you could buy off the shelf, but sized to just fit the pattern, which means you have to make them yourself. Keep in mind, that these will define negative space in the finished castings, holes going through.




  34. #104
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    Default Re: Casting thin shell bronze blocks

    Jim, in post #98, you mention using carbon paper for checking fit - are you still able to source it, in the current post-typewriter world ?




    Rick

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    Default Re: Casting thin shell bronze blocks

    Quote Originally Posted by hawkeye54 View Post
    Jim, in post #98, you mention using carbon paper for checking fit - are you still able to source it, in the current post-typewriter world ?

    Rick

    Hi, Rick. Believe it or not carbon paper is readily available. A hundred sheet pack costs about twenty five bucks, up from fifteen last time I bought some. That'll last a couple of years, depending on your use. The sheets can be used over and over until they're quite dog-eared. There's some hobby paper out there but I just use the typewriter paper.


    Feeling my way into this pattern now. The quarter round stuff was a good starting point. Sometimes it's good to have something in hand to wrap the thoughts around, make a little tracing maybe, give yourself a sense of scale. I need some kind of starting point. A little sketch is useful but the real design will be done on the actual piece. I suppose it could be done on a 3D printer, but how would you know how the piece feels in hand, or looks when you turn it this way and that?

    Here's a little mortise for the quarter round, there's another on the opposite face. Blocking in the important feature will define the limits of the chunk to be carved.

    I should mention that this pattern will be a split, two piece pattern, split symmetrically. To that end the block has been glued down the middle with a piece of newspaper sandwiched in. This will allow the pattern to be split once it's made. The quarter round is glued up the same way.



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