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Thread: Simple draft and full mold patterns

  1. #21
    cx: Since the flask in this case is just a 5 gal. pail I wanted to be able to bed more than one pattern and when the sand is fully aereated the
    pattern must be held submerged. If I let go of the first pattern to insert a second one in the same pail as soon as I hit the air #1 pops up . With
    the ring removable I just withdraw it, get another bucket, fill it, and bed the second pattern.
    If you think you can't do it, you're right!

  2. #22
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    Thanks sandcrab. I was visualizing the process and wondered if the withdrawal helped get the sand set. I want to try this but the only metal tubing i have is 1/4" copper that i don't want to give up. I do have some stiff plastic used for setting up automatic watering systems. I was thinking of drilling holes in a piece and setting it in place an inch above the bottom of a bucket. (think bailing wire and holes in the side of the bucket)

    sand is sure strange stuff. This is the same way that quicksand works only with water rather than air.

    cx
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  3. #23
    Look at Jeff's
    Fluidized sand bed..

    http://www.backyardmetalcasting.com/...asc&highlight=
    Heat them up, mold them out.

  4. #24
    cxevalo:

    You could use any rigid pipe since there is really no pressure to speak of. If you do not want to draw the air tube it could be made of PVC in the form of a cross in the bottom.

    Re read your post, in a dedicated mold any material could be used and it has the advantage of being self cleaning. Whenever you run the air the lightest material surfaces and can be skimmed off.
    If you think you can't do it, you're right!

  5. #25
    Following Gene T's project on both this forum and the General Foundry I decided to do a quick pattern and pour of that style rammer. Since we only need one rammer and probably won't wear it out a pattern is not really called for. This is an ideal reason to use lost foam.

    I'll say up front that I do not really care for this type of rammer and use a wooden one with a cylindrical end. The last photo shows it alongside the one I just made today, and another small one that I believe was a kitchen tool that I like for tight spots. The reason I do not like it is that at the start of the ramming after the first facing has been riddled into the flask the loose material falls into the depression formed by the pein and onto its backside. When working quickly this sand is thrown back out of the flask. With the longer end of the wooden rammer the material does not get to fall until the rammer is withdrawn . This type of tool is a simple wood turning project, just be sure to use kiln dried wood and seal it from the moisture.

    Any way I wanted to make a quick pattern and pour using lost foam and get some photos while doing it.

    These are the blanks I started with at 1:00 PM yesterday.



    I cut them out with the bandsaw and used HHWC suggestion of hot glue for the first time. More on that later.

    The pein end was sawn round and chucked in the lathe. I used a coarse sanding disk in a cordless to shape it and smoothed it with 120 grit sandpaper.



    Then I did the same with the handle but held it with a center.



    I sanded the wedge end on a belt sander and then made small cavities in the two end pieces to accept the handle. Here they are just put together prior to glueing.



    Then it was time to determine how much metal the casting would require. The block in the foreground is 25 cu.in. and weighs 11.5 gms. The weight of the pattern with the sprue added was 16.5 gms which would mean the pattern was about 36 cu.in. Since aluminum weighs .090 lbs/cu.in. by multiplying by the volume of the pattern I arrived at 3.24 lbs of aluminum. A 3/4 full no.8 crucible would be about right.



    By 3:00 PM it was time to coat the pattern with taping mud thinned 50/50 with water and air dried. This took the longest but I had other projects in the shop. I used two coats and while the second one was still wet I sprinkled with 120 mesh sand. That probably does not do much but it seems to strengthen the coating.



    At 11:00 AM on 9-8 I lit the furnace and activated the air bed in the 5 gallon pail to insert the pattern and then withdrew the air ring. A basin was formed with the sprue exposed so it would be surrounded by metal.



    At 11:40 I had at least 5 lbs at 1450* so I pulled, skimmed and poured. Sorry no action or video . With the length of the pattern and the choke through the handle there is a pause when the basin fills and then drains away. This is where the "Cush Head "sp? tool works to allow a volume of molten metal to be built up to vaporize the foam. I only had the little bit left to pig off in the background before putting the crucible back in the furnace and bricking the vent.



    I had 600* temp at 12:00 and when I came out after lunch the casting was registering below 200*.



    At 1:45 PM I pulled the casting and everything looked fine. the tip on the end of the wedge was so I could put the casting between centers to clean up. I mentioned the Hot Glue earlier. It is so strong that it withstands the sanding disk and tends to accentuate the joint. It also gets hot enough to melt the foam, so care must be taken if the glue is on the surface. I filled the scars with beeswax before coating. Here you can see the joint compound burned and flaking but still intact.



    I could have used this rammer as cast by just cutting off the sprue and sanding, but decided to machine it true and polish. The pour picked up little Hydrogen so was not as clean a casting as I would have liked but at 4 o'clock it looked like this.



    And at five here it is with the tools I spoke of at the start of this post :wink:.

    If you think you can't do it, you're right!

  6. #26
    I cut them out with the bandsaw and used HHWC suggestion of hot glue for the first time. More on that later.
    Boy you sure know how to make a guy's heart race :!:
    I just knew it wasn't comeing out and I would be to blame.

    I've never known hot glue to melt foam, but I do use a low watt "mini-gun".
    Some hot glues are higher tenp than others too.
    I got some hot glue chips off E-bay and they are very low temp but you would have to use a pot or make your own sticks.

    Very nice cast sandcrab 8)
    Why don't anyone make the round end sq ?
    I meen if yor flask is sq it would fit in the corrers just right.
    Heat them up, mold them out.

  7. #27
    Administrator Site Admin Anon's Avatar
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    Square is harder to turn on a lathe.

    Nice work, by the way.

    Typically, on a dual-temp glue gun, the higher temperature will melt foam if the gun is allowed to fully heat up. If you use it fast enough, unplug it periodically, or turn it down to low temp, it won't do that.
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  8. #28
    That is what the wedge end is for . In the corner the wedge gets anything the pein end can't.

    It is probably time for a new glue gun. I probably got it in the 70's.

    Also the weight after cutting and machining is 2 lbs. which just happens to be what the wood one weighs.

  9. #29
    Senior Member Jammer's Avatar
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    That is a nice looking rammer. 8)
    I was also inspired by GeneT and made one yesterday. After seeing yours I'm a little embarrassed to put it on here. Maybe I'll hide it in Home Grown tools. :lol:

  10. #30
    Wow! Nicely done! I wish I'd thought about adding a tit to the wedge for turning - that would have been real convenient. Thanks for the show-n-tell.

    GsT

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