Reinforcing 12 Inch deep pattern for green sand?

Discussion in 'Sand Casting' started by Mark's castings, Oct 9, 2021.

  1. Yep it's a truncated pyramid, doing otherwise would be an elaborate form of self abuse :D. So it's 10mm taper per side over 290mm vertical height: arctan(10/290)=1.9749 degrees draft. So the drag moves up the cope 10mm to give a wedge 10mm tall at that angle, the thickness change will be (TAN 1.9749) x 10mm = 0.345 mm thinner casting?.
     
    Last edited: Oct 11, 2021
  2. Melterskelter

    Melterskelter Gold Banner Member

    Phew! 2 deg draft should be just right.

    BTW, my math was wrong. Not leaning, the draft angle would have been half my miscalculation. And you are also right about the tangent rather than sin calculation, though at that small angle (.008 deg) the difference won’t appear for a few decimal places.

    Anxious to see this rammed up and cast.

    Denis
     
  3. Me too!
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    What's it for?

    Best,
    Kelly
     
  5. Petee716

    Petee716 Gold Banner Member

    I've never seen the hole in any other photos of this part. It was a clean hole, I dont remember if it was painted or not. They made this design for decades so I'm sure the process was optimized.

    Back to my previous post, I've also used the same arrangement when casting a bronze bell, except instead of holding the pattern in the cope when opening the rammed flask I used downward force to keep it on the drag so that it could be more carefully rapped and removed. The resulting cavity in the cope left me with a way to hold the bell in the lathe afterwards. 20200820_194401.jpg
     
    Melterskelter likes this.
  6. It's the spindle housing for a lapidary machine, the photo is of a 6 inch machine and I'm making an 8 inch version:

    cabbing machine 1.jpg
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Nice!

    Best,
    K
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    I do not want to slow your progress, but sort of logo identifying the maker seems to be needed for this project. Stylized letters??? “Marks Castings??? Something.

    Denis
     
    Last edited: Oct 12, 2021
  9. I think I'll attach a separately made label plate to the front of the housing. The first one is already has a buyer but I still haven't come up with a good name yet. They are known as "Cabbing" machines, maybe "Cabulator" in homage to the Turbo Encabulators. :rolleyes:
     
    Last edited: Oct 11, 2021
  10. Melterskelter

    Melterskelter Gold Banner Member

    Lap Dancer? :cool: In homage to who knows what.

    I kinda like “Silk” indicating both finish and smooth operation.

    But this definitely has to have a raised logo that gets hit with a buffing wheel so that it stands out from the mill-finish body. I guess that logo will have to be on the top cover, though, unless it is made using a loose piece as part of the pattern. Added: I just reread your post indicating a separate applied logo. Meh, loose piece cast it needs to be.



    Denis
     
    Last edited: Oct 12, 2021
  11. The top lid will be a small tray area, it may be possible to cast in a logo of some kind, maybe recessed rather than raised.
     
  12. While the third coat of epoxy cures and some minor patching gets done, I welded two 8" deep flasks from the cut off purlins. They can be split or joined as needed. I'll add some lifting lugs, handles and brackets and a pair of alignment pins on one box. The welds got a coat of primer to compensate for the ground off galvanizing as things rust overnight here in the wet season.

    pattern 3rd coat.jpg


    flask steel 8 inch 1.jpg
     
    Last edited: Oct 17, 2021
  13. Melterskelter

    Melterskelter Gold Banner Member

    One thing about rust—-it’s a good thing on the interior anyway. It helps sand retention. I have a few steel flasks and can see real benefit of the rusty rough inside surface caused by the moisture, heat, and acid production from casting iron in green sand.

    Accurately lifting and reassembling this deep and narrow-clearance mold should be something of a challenge, guide pins or no. A repurposed hydraulic cylinder or a pair of heavy duty drawer slides come to mind. Maybe a simple pair of pins will do. Just sounds tricky to me.

    Denis
     
  14. Those welded corners will be rusty pretty soon, maybe the thin galvanize finish will last a bit longer before it succumbs, that fully painted side had a bit of surface rust already.

    I'm definitely planning on some long guide pins, there are some heavy duty drawer slides in the workshop that could be used too. I had some advice about having the flasks clamped to a pneumatic vibrator table tuned to high frequency and low amplitude vibrations for ramming and aiding pattern removal for production use. It might be worth using a kerosene flame to soot the pattern with an oily soot layer inside and out before ramming the sand?.
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    Just talc and/or graphite should provide adequate parting. My main concern is just guiding very accurately for a 12 inch lift. I think you have an electric hoist of some sort. If that frees up your hands, just the pins may be ok. But, a hydraulic double-action cylinder with a ?power steering pump? and foot control would be awesome. It looks pretty easy to do.I’ve no experience with this, but I bet several others here have.

    Here is one vid of a simple setup that might be useful.

    Denis
     
  16. I'll have to come up with something to raise and lower the drag into position without getting a hernia, I do have four 100lb Firgelli linear screw jacks but I'll have to retrofit longer screws from all thread rod to get enough stroke, these are 10cm at the moment. The other alternative is a battery drill winch with 3/16"-4mm cable on a 4"/10cm drum.

    Classic-min_1600x.jpg

    linear_actuator_exploded_view_1728x.jpg
     
  17. Petee716

    Petee716 Gold Banner Member

    I set up some guides on my drag to help with a deep draw. They’re not real sturdy but helped give me a visual guide, not only for lateral alignment, but also to make sure I was level.
    491A138A-BCA0-4705-8245-9D974ECF9ABE.jpeg


    If you were just doing one of these I’d suggest setting up lifting timbers and getting an extra set of hands, but you appear to be doing several of these. This is what I came up with.

    8AFE3830-3A58-4648-AE91-62F2CB71818D.jpeg

    The basic idea was stolen from Denis, as was the replacement of the original cable with the strap. It makes for very smooth raising and lowering with no bumping or jarring of the load.

    Pete
     
    Mark's castings likes this.
  18. Hmmm.... a drill driven winch with a worm drive is do-able without too much of a stretch: I could cut a chunk of that three inch brass bar I cast and use a thread tap to cut a worm wheel on the lathe, I always wanted to try that. I have a 12 volt Bosch battery drill with chuck brake that could be hooked up permanently to drive it all. With some longer alignment pins on the cope to guide the drag into place it'd be the simplest way to handle the assembly of the mould. I'd been mulling various ways to drive a cable drum without relying on the drill to take the load on the brake.
     
  19. Melterskelter

    Melterskelter Gold Banner Member

    One nice thing about your long deep flask is that if you attach lifting eyes to the upper end of the flask well above the center of gravity, the flask will naturally tend to stay vertically oriented. Then all you have to do is guide it side to side as you power lift it. Using a hydraulic cylinder, if rigidly attached, would both lift and guide. But, I have really appreciated the smooth powerful lift of my strap lift similar to the one Pete shows. And, good guide pins with such a lift should just do it, particularly if both hands can be free. And you don’t really need your lift to traverse once the cope is lifted. You could just slide the drag laterally on the table and remove the pattern. Slide the drag back into place and lower the cope.

    Here is a link to my hoist build: http://forums.thehomefoundry.org/in...trol-foot-pedal-foundry-hoist-prototype.1016/

    You do not really need it to traverse and you do not need the wireless features. So, yours could be much simpler. A second person to run the drill motor or a foot control would be nice, though. The strap rather than cable is really desirable.

    Denis
     
  20. Interesting, how does the strap end up being better than cable?. I already have a hand cranked nylon strap winch I could fit a worm drive to, it would be even simpler to build.
     

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