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Thread: Gating Tubular Lost Foam Part

  1. #151
    Kelly, what is the clocking of the flange?
    If you think you can't do it, you're right!

  2. #152
    Quote Originally Posted by sandcrab View Post
    Kelly, what is the clocking of the flange?
    You can see it approximately here.

    http://www.alloyavenue.com/vb/showth...l=1#post202345


    If the tube is vertical and your looking at the flange the diagonal line through the center of the flange ears runs approximately through 2 & 8 O'clock. That's close enough but it can probably be in any position you like. The tube centerline dimensions on your samples are close but not precisely what I made the actual parts. . On my sample parts I clocked the flanges in line with the tube centerline. If you'd like a more precise answer, I can measure tonight.

    I wouldn't sweat it. It's just for grins and learning opportunity for me from all of you.

    Best,
    Kelly

  3. #153
    OK gotcha.
    If you think you can't do it, you're right!

  4. #154
    Unboxing the foamies:


  5. #155
    Quote Originally Posted by FrostOak View Post
    Unboxing the foamies:
    I like your letter opener.

    Best,
    Kelly

  6. #156
    Went with the test piece to work out my strategy for the two real attempts at casting this water neck. I think I set the bar pretty low for the other guys
    I took apart the test piece and re-glued it using different methods. I took one section and re-did the original hot-glue butt-joint. In another section I used white school glue. In another I butted them together and only smeared hot glue over the outer seam and inner seam, with none on the actual joining faces (my method of choice). Lastly I put a piece of scotch tape over the inner and outer seam.
    Next I wanted to try different surface finishes. My drywall mix had dried but I was able to re-hydrate it. I put the drywall on one section, some waterglass on another section. I left a section bare except for a piece of scotch tape, and I didn't know what to do with the 4th section so I smeared some graphite powder on it.
    I attempted to use a piece of the packing material that came with the pieces as a sprue, it was some squishy plasticy foam, like a sponge. I didn't really like how it was working out so I took it off and put a piece of pink foam as a sprue instead. On the sprue I put only a small amount of glue on the butting faces and then hot glued around the outside of the joint.
    Set up a fan to let it dry and went to prepare the sand. Started sifting the bugs and leaves out then a storm passed by. It only lasted about 10 minutes so I lit the fire and cast the part. I only have a small amount of sand for lost foam so I put bricks in the bucket to take up space and protect the plastic bucket. Tapped on them with a hammer to vibrate the sand and tried to make sure it filled the inner core. Left the sprue barely sticking out of the sand and had a soup can for the reservoir.
    Attached my nearly empty propane tank because who doesn't like the drama of nearly running out of gas during a melt? I know I love it. Set it to a blistering 10psi and within about 10 minutes I was down to 20psi in the tank and the regulator had dropped to about 7 psi.. The aluminum was liquid and I poured. I was a bit worried I didn't see 'the burp' until it came very delayed. But it was nearly raining, almost out of gas, the apparent bad pour was just par for the day. But as I pulled out the cooled casting I was surprised with a mostly intact water neck.
    Of course there were tons of defects, and the part wouldn't be functional as is, but it gave a lot of information which I am still pondering. Some of my methods that I was fairly confident in gave some trouble so I am going to have to rethink some things. I did try 4 different joinery techniques and 4 finishes so I wasn't looking for really looking for a complete success. After I digest everything I look forward to trying one of the real parts. Just wanted to say thanks Kelly for sending these and hope we all can learn something useful.
    The graphite powder, bare foam, and the waterglass all gave good finishes. I think the drywall mud was still wet since it left a dimpled surface
    finish. The tape gave a smooth finish but had some weird defects at the transition from foam to tape. Could be some clues there. There were some parts of the seam which had holes which I expected due to the incomplete gluing. A little surprised the smearing of glue on the outside of the seam gave as poor finish as it did but then again I didnt sand it smooth. The white glue and hot glue gave similar results and the tape-only joinery gave great results in some spots and very poor results in some spots. I think the hot glue smeared on the outside of the seam only was the leader by a small margin. The weirdest defect was a void in the sprue. It was very circular and I am so far at a loss to explain it.
    There were also some defects around the sprue joint like a hole or fold all the way through the tube. Also the end of the tube was a bit oval instead of circular. I believe this was from setting it in the sand and hammering the bucket and it became squished somehow. I've had this problem before with lost foam distorting in the sand. A sand vibrator may be on the to-do list.

    video

  7. #157
    Thanks for the video FrostOak. I should have sent that sample tube to you unassembled. Glad you were able to get some experimental mileage out of it. I'll be interested to see what you choose to apply to the parts. I'm thinking you were right about the dry way mud possibly being wet. I'm getting very good results with it. I was able to get a good afternoon in today and lot's to post but I'll post up a short one for now. Much more after the holiday weekend.

    Best,
    Kelly

  8. #158
    I can't compete with FrostOak for action flicks, but I did start on the test piece. I decided to gate it from the bottom. The sprue was hot glued to the pattern and the seam and a portion of the tube was coated with melted beeswax and then flashed with a heat gun to smooth. The joint compound was thinned to a brushable mixture, and then additionally thinned to coat the interior. I hung it on the fence to dry and then coated the exterior one more time.

    I tested my Chastain rotary vibrator on my bucket and from a full level it condensed the sand one inch with two plane vibration.





    This was a fail, but I attribute it to moisture in the closed elbow. I thought it had gotten enough air and heat yesterday on the fence.
    Last edited by sandcrab; 05-30-2017 at 12:13 AM.
    If you think you can't do it, you're right!

  9. #159
    I cast a few today. I'm getting pretty consistent results at 1540F metal temp. Here is an example. I used up the last of my blue foam patterns. I sanded them and made a better effort at surface preparation and you can see the contrast between the surface finish of the rest of the part and shellac on the interior of the Ford logo. I'm going to complete a couple of ink foam patterns tomorrow incorporating all lessons leaned.







    I've been promising a video of my turbine vibrator on my lost foam rig. Here it is. It motors pretty well, is fast, and very effective. You may want to turn down the volume when the vibe kicks in.

    https://www.youtube.com/watch?v=RuVpX9-CRTQ

    I also tried an experiment to characterize the metal propagation speed through foam. The test piece of foam was 1/4" by 1" and 13"long, similar to my water neck part I figure. Some pretty hefty thermal shock but was hoping the glass would hold out long enough to video the result. Not sure if it froze at the gate or lost head but looked to be frozen before the glass let go. This was 1540F with 356 alloy. The black lines are one inch each. I'll have another go on this later.

    https://www.youtube.com/watch?v=xUUl...ature=youtu.be

    Here's the resulting test coupon.



    Much more later.

    Best,
    Kellyy

  10. #160
    Moderator DavidF's Avatar
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    Nice work Kelly, they just keep getting better and better. Im getting ready to head out for a short vacation and will be making my attempt when i get back..
    A calm sea does not make a skilled sailor....

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