Lost Foam Bracket

Discussion in 'Lost foam casting' started by oldironfarmer, Apr 27, 2018.

  1. oldironfarmer

    oldironfarmer Silver Banner Member

    I had a friend ask me whether I could repair his umbrella elevator bracket.

    IMG_3437.JPG

    I'm not sure what it is. Zamak, magnesium, but likely not aluminum. It is fractured several places and I don't want to try to weld it with aluminum, it already broke once.

    IMG_3438.JPG

    So I decided I need more practice on lost foam. I modified the design a little, making it much heavier.

    IMG_3439.JPG

    And I added his initials.

    IMG_3440.JPG

    Added a short sprue to the bottom and invested it in sheetrock mud.

    IMG_3441.JPG

    I'm brushing hot wax on the joints and the investment does not cover the slick wax very well. It does not seem to matter on the surface finish in those areas.

    It poured rather uneventfully and came out great.

    IMG_3444.JPG

    I had put the initials offcenter so they would not interfere with chucking it in a three jaw chuck to true up the bore.

    IMG_3445.JPG

    I was expecting a little shrinkage but the best I can tell the finished piece has the same dimensions as the foam pattern. Bore was 4.00" on the foam.

    I did err on the cavity for the rollers, made it right but then pushed it farther into the pattern than planned. Since one roller is cracked, I plan on making two smaller rollers which will fit.
     
    Al2O3 and Jason like this.
  2. Jason

    Jason Silver Banner Member

    Whip out the tig machine and lite up on that sucker! If it goes nuts, just film it for us!

    Your replacement looks spot on! The initials is a nice touch.
     
  3. Tobho Mott

    Tobho Mott Silver Banner Member

    Nice! Good job...

    Jeff
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Nice job OIF and good application for LF. Your friend should be very happy with that. I would have expected a 4" bore to shrink about 0.05".

    The wax is hydrophobic and tends to repel water. Polystyrene isn't great in this respect either but the surface finish tends to help coating adhesion. The consistency of the mud mix seems to make a difference too. If it's too wet and thin it tends not to cover wax as well. I usually get the wax areas to cover but most of my wax areas are small. They are easy to touch up. If you ever have a piece where surface finish is critical, be it wax or foam, coating with a surfactant will help the coatings lay down and be free of bubbles. Thinned ethylene glycol (antifreeze) or propylene glycol (dishwasher anti-spot) can help. I don't usually use it. Some professional coatings have surfactants in them. I haven't tried adding it to the mud. Seems like it might slow drying a bit.

    Are you using setting or non setting drywall mud (i.e. tape joint or top coat)? I seem to get less of the dark residue on the casting with the non-setting stuff and lower density foams. It doesn't seem to really make any difference on casting or surface quality though and comes off with wire brush or media blast. As a side benefit, the non-setting mud can be stored in a sealed container and maintains it's consistency with just a few whips of a stir stick.

    Best,
    Kelly
     
    oldironfarmer likes this.
  5. oldironfarmer

    oldironfarmer Silver Banner Member

    0.05" should have been noticeable. But maybe I made it larger than I thought.

    Thanks for mentioning surfactant. on the farm we use Dawn dishwashing liquid for surfactant. It's a lot cheaper than labeled surfactant and works well. It jogged my memory that sheetrock finishers put Dawn in their mud to make it smoother. I don't think it affects drying. Since I keep some in my shop for various purposes I dripped a bit in my mud mixture and got instant results on the wax. Full coverage. Thank you!!

    I'm using non-setting, which is all I've ever used mudding and taping. I have a 50# box left over from the last job I never got around to returning. I think it will keep me in foam mud for 130 years unless I go crazy. Then at least 65 years. I'm good.
     
  6. oldironfarmer

    oldironfarmer Silver Banner Member

    I'm going crazy.

    IMG_3480.JPG
     
  7. Jason

    Jason Silver Banner Member

    Wild man!
     
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Once you realize how quick and easy it is to put metal where you want it you start designing it into your builds. It is habit forming.

    Best,
    Kelly
     
  9. oldironfarmer

    oldironfarmer Silver Banner Member

    I'm definitely a student of the "Kelly School of Foam into Metal" and have studied in the "Thin Sheetrock Mud" curriculum. I'm building a shelf which will require 24 sets of bearing/bearing-cap type brackets. I only sprued them two to a tree to limit losses of patterns on the bad pours but have failed to get any bad pours so far.:rolleyes:
     
  10. oldironfarmer

    oldironfarmer Silver Banner Member

    I got a picture of the umbrella bracket in service. He was very pleased.

    IMG_3513.JPG

    The brackets I posted earlier are for a shelf I'm making for a local pharmacist. Six shelves, four pipe clamps per shelf. Let's see, 6 times 4 is 26?
    IMG_3532.JPG
     
    Tobho Mott, Al2O3 and Jason like this.
  11. Jason

    Jason Silver Banner Member

    Bracket on the umbrella looks great. That piece work on the bench looks like a PITA. Didn't you just start pouring hot metal? You look like an old pro at it.
     
  12. Petee716

    Petee716 Silver Banner Member

    You sure can't argue with the success rate but boy oh boy that's a lot of work.
    It's cool to see the umbrella clamp in service.

    Pete
     
  13. Tobho Mott

    Tobho Mott Silver Banner Member

    That is pretty cool, I must say. Good job!

    Jeff
     
  14. crazybillybob

    crazybillybob Silver Banner Member

    That looks like a ton of work. do you really mean pharmacist or is this for a local grow operation ;)
    The umbrella bracket looks great.
     
  15. oldironfarmer

    oldironfarmer Silver Banner Member

    Wonderful idea. I may stick with ammonia...

    Thanks, he loved the initials. I could have done a better job, and will next time.

    Thanks Jeff!

    :D It's so easy...

    Thanks!

    24 clamps to make a shelving unit with pipe for a friend who has done her pharmacy in Steampunk. I pressed her kids' and employees names into some of the brackets. I'm ready to machine them now and get her shelf done.

    February of 2017 is when I melted my first aluminum intentionally. Thanks for the kind words. I've struggled a little, especially having nobody to help other than YT. I could figure out some stuff I didn't want to do. I'm learning a lot around here. I was keeping my sand too wet for a long time but have about figured that out. Kelly's posts have convinced me I want to mud every lost foam pour.

    My only lost foam failures came from getting aggressively short with the sprues and having radiant heat from the crucible melt the foam before I started pouring. I learned. I use foil cones and no cush cup (don't know how) but I've had the two failures in about forty pours.

    I was glad they sent me a picture of the umbrella. I hadn't seen anything except the bracket when they brought it. He had tried to find a replacement part and had no luck.

    Thanks again!

    Apparently we're going to have a 420 vote. But it will not affect me very much. If it passes a friend plans to put in a shop.

    Thanks on the bracket.

    I'm learning more about lost foam. I made this clamp today to hold my dross spoon and as an upper stop for my furnace arch lift swivel (the yellow ring). I was a little surprised the spike to hold the spoon filled in nicely. It's about three inches long.

    IMG_3555.JPG

    It's on a 2-3/8" pipe. Here it is with the arch stowed.

    IMG_3557.JPG
     

Share This Page