Interesting Video on Bronze Sand Casting, Down Coping

Discussion in 'Sand Casting' started by Melterskelter, Jun 28, 2020.

  1. Melterskelter

    Melterskelter Silver

    Here is an interesting video on making bronze floor castings for a classic sailboat restoration. The foundry portion of the video begins around seventeen minutes.

    This foundry is located about 80 miles from me, though, I just learned of the foundry today.

    At first I was surprised to see the down coping that was done, but then I realized the floors had to have angulation in the wings that would prevent draft being included in the outside of the pattern. That is, the boat tapers to a point both fore and aft so the wings have to accommodate that taper. Natural draft occurs on the side of the wings oriented toward the bow or stern. But on the side of the wings oriented toward amidships reverse draft is required. So they down coped to get around that problem. They also had trouble with drop out of sand in the large, poorly supported sand in the mold when they separated the cope from the drag. This happened despite placing some bars in the sand (see about 20m 30 sec into the vid).
    I had a similar problem early on with my 30" square which I solved with "ceiling bolts" as seen in post 2. The wood panels were soon replaced with more durable metal sheets.

    I also noted use of some bars to help support the drag sand. Overall, I enjoyed watching the vid and thought the down coping was nicely shown.

    I was wondering why the guy was using a bar to tamp maybe 50 silver dollar-sized depression on the flat face of the cope.

    I'd be interested in hearing comments.

    Tobho Mott likes this.
  2. I watched that from start to finish, it's been a while since I watched one of their videos...then I realized I spent the weekend pouring bronze boat parts and now I'm watching videos about pouring bronze boat parts.
  3. Jason

    Jason Gold Banner Member

    HOW MANY of those do they have to cast???????o_O Without listening to the entire thing... What was the point? Certainly not for ballast at that location.
  4. I think he said 18 of them each with their own unique pattern, $11K of bronze ingots...must be one per rib or one every two ribs.
  5. Jason

    Jason Gold Banner Member

    18? I don't know the specifics or how special this boat is... Sounds like they ARE making this their ballast?? I'm no boat builder, but I've been a sailor my entire life and if this is their ballast, these guys are wayy out there. I did see someone with a bone in a nose.:rolleyes: Now I am going to have to watch the whole thing.
    11grand I can believe, that stack on my workbench ran me a grand.
  6. Melterskelter

    Melterskelter Silver

    The rationale for the use of bronze, the spacing of the floors, engineering considerations, and pattern making technique are all discussed in the first portion of the video. A lot of thought and some decent engineering resulted in the scantlings
    of the floors. This design did not use bronze because of it weight as a ballast. Actually, the fact that the bronze is strong enough to be used in relatively thin section allows for room for ballast.

  7. crazybillybob

    crazybillybob Silver Banner Member

    Floors tie the frames (vertical load members of the hull) to the Keel. Their main job is to hold everything together. Making them in bronze is a corrosion resistance and it doesn't accelerate wood rot (ie no iron sickness), and as a side bonus they cut down the amount of ballast needed,but a boat that size made from wood is still going to need a bunch of ballast. Hopefully the keel takes care of 90% of it.
  8. Petee716

    Petee716 Silver Banner Member

    The context of the project is interesting enough to make it an enjoyable video, but the explanation of material selection, rationale and method of production, as well as the demonstration and explaination of the casting process makes this one a real winner. One of the best I've seen.
    Melterskelter likes this.
  9. Melterskelter

    Melterskelter Silver

    Ok, so why is he thumping those 2” dents into the sand face?:)

  10. oldironfarmer

    oldironfarmer Silver

    I thought it was interesting they tried to wet the cope failure to help it stick. I wonder if that ever works? Obviously it didn't here because they flipped the flask anyway.

    The foundryman explains why welded plate would have been inferior. I think I would have gone with welded plate and I'll bet the builders wish they had after they finished with the pattern work.

    All the work put into the patterns and casting is going to be a real shame if heavy weather takes it down.
  11. Petee716

    Petee716 Silver Banner Member

    Keys maybe? Although I cant see why.
  12. Melterskelter

    Melterskelter Silver

    Yes, those were my thoughts exactly. They seem too small to really be effective as keys on that large mold. Plus he has guide pins. So, I am sure he had his reasons, but what were they? Hmmm.

  13. Jason

    Jason Gold Banner Member

    No doubt it's the best choice for the job, but geez, who needs a boat to last THAT long? Spend the money of stuff you see, like booze and the entourage of bikini babes on the deck! >>Carbon fiber sails, TEAK up the yinyang!! If any of you are into sailing, check out this website. The guy is a first class liberal dick, but it's a pretty good rag.
  14. HT1

    HT1 Silver

    one of you guys owes me 45 minutes of my life back!!!

    i'm only going to talk about the MOLDING . but i will preface it "with i would not let that foundry cast ingots for me!!!"

    the screw driver handle poked in the Molds are a poor attempt at Mold alignment buttons, they normally are not used on green sand, and you need 4 one at each corner.

    But they did clearly show me that the first mold was rammed entirely too soft , which was evident in the finished casting as flashing on the corners of cope and drag on the part ( sometimes called rat tails)
    they did a good job on the heat control, if the metal had been over heated at all, the first part would have looked like it had barnicles., but seriously they had a Pneumatic floor rammer, and made poor use of it ( I suspect there was some students involved, and they where not getting enough instruction the ramming was haphazard at best)

    The drop of the green sand core, was absolutely evident, before the mold was opened, the cope popped up on one side as they opened it , bothe sides must come up together!!!

    Pauls repair technique (the double roll) is the techunique that should have been started with , you do not try to lift the green sand core, you roll the entire mold and lift the drag, so that big hunk of sand( green sand core) never hangs unsupported.

    as to wetting the green sand for repairs: Pretty common , though I would have added a mold wash and torched the face of the mold to drie back moisture and closed it just before pouring ( this requires a big crew that knows what they are doing,) Again I think there was one molder in the room and a bunch of students

    he did not start with the Double roll technique because the cope was not flat, another PP technique, copes are always FLAT especially if there is any chance you will be double rolling which again should have been the first technique used.

    YOU NEVER SET A MOLD WITH THE PATTERN INSIDE ON IT"S SIDE, all kinds of bad stuff can happen , if there was any detail on the pattern, like letters, they would have been damaged, no doubt at all BAD technique

    Vents, for the thousandth time proper vents do not fill with metal .

    Now one thing I did like (well appreciate, not like) exothermic riser sleeves where used , but did not go entirely through the cope , but the mold was only filled to the top of the exothermic riser sleeves. this is really important, if they had filled higher then the exothermic riser sleeves, the top of the riser would have solidified first and stopped the Piping . but if you are going to use that technique, why not just used closed exothermic riser sleeves, they feed 30% more then open sleeves ($$$ is the only reason, and a piss poor one in this case one box of 24 would have been perfect)

    anyone that was inpressed with that coping down, needs to make a propeller , the only trick to coping down is knowing exactly where the parting line is on the pattern, in that case it was silly simple , a propeller is a much better practice piece

    V/r HT1

    P.S. the next time I make mug parts, I use a follow board and coping down, I'll make a video and post it so you all can see it
    Jason likes this.
  15. Melterskelter

    Melterskelter Silver

    I'll be sure to let him know that when I go down to see his foundry and operation.;) He seems like a very pleasant guy who would be a good teacher and eager to share his 20 years of experience. Though I don't cast bronze, I suspect there are some things to learn from him.

    By the way, I'd do the double turn technique to solve my problem with a large block of suspended sand in the middle of my mold except that the mold is symmetric, so one side has to be lifted with that block of sand hanging relatively unsupported. Gave me a few more grey hairs til I figured it out.

  16. HT1

    HT1 Silver

    I cant visualize your issue, post A picture and I will try to help

    V/r HT1
    P.S. the village idiot will be happy to share his lifetime of experience, at least then you know it is coming from an idiot. Like I said, I think there where too many student/apprentices involved, you note the Big floor rammer came out in the hands of the "boss" way too late in the ramming . pretty good sign, that there are alot of inexperienced people about . the fact that a hand rammer was used when not one but two Pneumatic rammers where available prettymuch guarantees something wierd was going on. Maybe the Compresor was down
  17. Jason

    Jason Gold Banner Member

    See if he wants to buy a couple thousand pounds of bronze bolts and nuts off of Lou. He can cast his keel out of the stuff.
  18. Melterskelter

    Melterskelter Silver

    The problem was outlined in my sand casting thread concerning my 30” square. It was solved using a suspension system. If you have a suggestion for a better solution, please do. The suspenders work very well, however. Not a problem with dropout in 12 molding sessions since dreaming them up and starting to use them.

    I use a pneumatic rammer every molding session. Saves a huge amount of time ramming up those 300 and 400 pound molds. Works a treat.

  19. Reading this discussion makes it clear how much experience and skill is involved in making a good green sand mould. Resin bound sand is easy by comparison: most of those green sand mould making issues just go away. The trouble is that it uses sand once, without lots of processing like burning and washing the sand. I need to learn about green sand for one off castings like all those iron stove parts.
  20. Jason

    Jason Gold Banner Member

    Exactly Mark.. It was way faster for a dummy like me to get up to speed with ceramic shell. The only thing I did in the sandbox as a kid was try to eat the cat turds!

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