Sand Mold Casting Problems

Discussion in 'Home Foundry & Casting Projects' started by jimsshop1, May 10, 2018.

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  1. May 23, 2018 #21

    jimsshop1

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    Steamman70

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    After two attempts at casting a brass ring I got a good one. The first one failed because I did not have large enough gates and the melt cooled before it got all the way around the mold You could see the rolls in the ends where it cooled like lava. Second mold I had the gates as deep as the ring and much wider. I also made a 2" cup riser like Mark suggested and an 1-1/4" vent riser 180 degrees from the pouring gate. I also poked 1/8" vent holes at 4 evenly spaced marks in the ring pattern. I had the brass actually boiling when I took it out of the furnace and poured immediately. Wow was it hot! When the brass flowed up the vent like a volcano I new I had a complete ring cast. But as I watched it cool I was amazed how much it shrunk in the risers again like Mark said. I was afraid it would shrink all way down to the ring and leave a bad spot there. It finally stopped and hardened in the spout. When I broke the sand off I had a good brass ring 9- 1/2" in dia , 1-1/4" thick with thickheavy gates,4, 1/8" tits about an inch long sticking up where I poked the holes. So it went well and hopefully it will machine well. I forgot my camera but will take pics Thursday when I go back to work. Thanks Mark and myfordboy for all the wonderful helpful youtube posts.

    Jim in Pa
     
  2. May 25, 2018 #22

    jimsshop1

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    Steamman70

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    No one seems interested in this thread but I said I would post a picture of the cast Brass ring so here it is partially machined I still have about a 1/4" to take off the inside to get close to my flywheel size. Partially machined Brass Ring .JPG
     
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  3. May 25, 2018 #23

    jimsshop1

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    Steamman70

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    Hi Gordon,

    Did you ever finish your engine?

    Thanks,

    Jim
     
  4. May 26, 2018 #24

    Cogsy

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    It's interesting to me - I've never really cast anything that's turned out useable yet, but I plan to keep trying.
     
  5. May 26, 2018 #25

    Pierkemo

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    How is your furnace look like?
    I'm an absolute beginner, i will make an oven fot 1.8 Liter crouse.
    Can you give me some indicators??
    Thanks,
    Pierre
     
  6. May 26, 2018 #26

    Gordon

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    I have everything made and assembled but not spit and polished. I am running the engine with an electric motor per Gingery's suggestion to seat the rings. Actually I have been sidetracked the last couple of weeks but I hope to get back at it this week.
     
  7. May 26, 2018 #27

    maker

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    Take a picture.
    It sounds like a draft problem on your pattern.

     
  8. May 26, 2018 #28

    jimsshop1

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    Steamman70

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    Flywheel is finished. I had plenty of draft on all parts as per instructions in the book.
     
  9. May 26, 2018 #29

    jimsshop1

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  10. May 26, 2018 #30

    Pierkemo

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    Hello Jimsschop1, i'am living in Belgium.
    I think you have also a good burner, and short melt times.
    How big is your crusible?
    Thank you,
    Pierre
     
  11. May 26, 2018 #31

    jimsshop1

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    Steamman70

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    I will take some photos later and post them along with some measurements for you. Welcome to the best model engine forum.

    Jim
     
  12. May 27, 2018 #32

    Cogsy

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    Are you using cast iron rings? If so, the best way to 'seat' them is to try and start it. The extra force (in the right position) from combustion forces produces the best seal quite quickly. If run too long without combustion forces it may be impossible to ever get the rings to seal properly.
     
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  13. May 27, 2018 #33

    kadora

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    I agree with Cogsy the best way to seat rings and valves is to run engine.
     
  14. May 27, 2018 #34

    Gordon

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    I am turning it with the electric motor but have the fuel and ignition also working. It is starting to sputter but the compression is still to low for a good firing. I am using CI rings. It is improving but I have only been running it for less than an hour. Gingery says he ran it that way for as long as 40 hours.
     
  15. May 27, 2018 #35

    stragenmitsuko

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    I've learned over the years when casting ali , there's scrap and there's Scrap .
    Best results I ever got was using old scuba tanks as material to melt .
    Cut them into rings on the bandsaw , then crushed the rings on a hydrualic press to make
    them fit the crucible . Sadly I only had two , and can't get any more .

    I've also been told alloy car wheels make great castings .
    So that will be my next attempt .

    I've had far less luck with the "usual" aluminium scrap .
    It caused a lot of hydrogen inclusions , pitting , altough I degassed the crucible 2 sometimes 3 times .

    Pat
     
  16. May 28, 2018 #36

    jimsshop1

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    Al my ali has been billet or precast
     
  17. May 28, 2018 #37

    jimsshop1

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    Steamman70

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    Pierre,
    I made the furnace from 1/8" rolled steel. It is 13" high and 13" around. The top is 2" high hinged to the bottom and with wool type fire proof insulation. There is also insulation in the bottom under the plate riser the crucible sets on. The burner is made from a 2" tee bushed down to a 1" pipe 10" long. There is an .068 orifice in the tee. I have 2 crucibles I made. 1 is a 3" pipe 5" long and the other is a 4" pipe 9" long. Both have 1/4" steel plate welded in the bottom. I had access to a rolls set at work to roll the plate and my own welder for the rest. I am very pleased with the speed this melts ali and brass and how little propane is used. If you have more questions, please ask. Have a nice day.

    Jim in Pa
     

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  18. May 28, 2018 #38

    Rocket Man

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    I have 2 of those 9" flywheels I made 15 years ago then lost interest in the project. Remember the physics of casting, small areas like spokes cool & contract first sucking liquid material form the still liquid sections of the part like the center hub & outer part of the wheel. Hub & wheel both need large risers that will not freeze off as the hub & wheel cool first. As hub & wheel cool and contract it needs to suck in liquid metal from the larger risers. The flywheel has to freeze in stages and liquid needs to come from other areas of the part as it freezes in, 1, 2, 3, order. Good sand, good draft, good vents, make a big difference. My flywheels still may become a project some day but not likely.
     
  19. May 28, 2018 #39

    jimsshop1

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    Steamman70

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    Flywheel turned out great. Only took 2 tries after I figured out exactly what you just said. The first one stopped flowing half way because my exit riser was too small and the path from the pour riser to the mold was too small also. I also think the liquid was not hot enough. The second pour was really, really hot! I think it was boiling when I poured it. Very scary when you think what could go wrong in less than a second!
     

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    Last edited: May 28, 2018
  20. May 28, 2018 #40

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    Have you thought about using the Williams "saved wax" sand casting technique? It produces highly accurate product. It will even show fingerprints in the casting if they are not removed prior to casting.
     

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